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Hong Young Yan

Academia Sinica, Academia Sinica, Faculty Member

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Address: Taipei, T'ai-pei, Taiwan

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Papers by Hong Young Yan

Regional Specialization for Control of Ocular Movements in the Compound Eyes of a Stomatopod Crustacean

Journal of Experimental Biology, 1992

1. Regional specialization within the triple compound eyes of the gonodactyloid stomatopod Gonoda... more 1. Regional specialization within the triple compound eyes of the gonodactyloid stomatopod Gonodactylus oerstedii (Hansen) was studied by examining how ocular tracking of a small target was affected after occluding vision in particular ommatidial regions with black enamel paint. 2. Complete occlusion of one eye did not prevent the other eye from tracking, indicating that the two eyes act somewhat independently. However, following such treatment, the angular extent over which the seeing eye moved while tracking was reduced. 3. An eye was able to continue tracking a moving target even after occlusion of the anterior tip or after painting over all of its posterior surface except the anterior tip (restricting the visual field to a patch about 40° in diameter). Similarly, occlusion of only the midband, the medial half or the lateral half of an eye did not prevent tracking. 4. Tracking was also possible, although with decreased amplitude, when either the dorsal or the ventral hemisphere w...

An automated positive reward method for measuring acoustic sensitivity in fish

Behavior Research Methods, Instruments, &amp Computers, 1991

The Cone Opsin Repertoire of Osteoglossomorph Fishes: Gene Loss in Mormyrid Electric Fish and a Long Wavelength-Sensitive Cone Opsin That Survived 3R

Molecular Biology and Evolution, 2018

Vertebrates have four classes of cone opsin genes derived from two rounds of genome duplication. ... more Vertebrates have four classes of cone opsin genes derived from two rounds of genome duplication. These are short wavelength sensitive 1(SWS1), short wavelength sensitive 2(SWS2), medium wavelength sensitive (RH2), and long wavelength sensitive (LWS). Teleosts had another genome duplication at their origin and it is believed that only one of each cone opsin survived the ancestral teleost duplication event. We tested this by examining the retinal cones of a basal teleost group, the osteoglossomorphs. Surprisingly, this lineage has lost the typical vertebrate green-sensitive RH2 opsin gene and, instead, has a duplicate of the LWS opsin that is green sensitive. This parallels the situation in mammalian evolution in which the RH2 opsin gene was lost in basal mammals and a green-sensitive opsin re-evolved in Old World, and independently in some New World, primates from an LWS opsin gene. Another group of fish, the characins, possess green-sensitive LWS cones. Phylogenetic analysis shows that the evolution of green-sensitive LWS opsins in these two teleost groups derives from a common ancestral LWS opsin that acquired green sensitivity. Additionally, the nocturnally active African weakly electric fish (Mormyroideae), which are osteoglossomorphs, show a loss of the SWS1 opsin gene. In comparison with the independently evolved nocturnally active South American weakly electric fish (Gymnotiformes) with a functionally monochromatic LWS opsin cone retina, the presence of SWS2, LWS, and LWS2 cone opsins in mormyrids suggests the possibility of color vision.

The Role of Gas-Holding Structures in Fish Hearing: An Acoustically Evoked Potentials Approach

The Senses of Fish, 2004

Fish varies greatly in their sensitivity to underwater acoustic signals. Over the past century, s... more Fish varies greatly in their sensitivity to underwater acoustic signals. Over the past century, scientists have designed many methods to investigate auditory capacity of fish. Behavioral training paradigms (with either punishment or reward as incentives to the tested subjects) and various electrophysiological methods have been used to obtain audiograms, i.e., the auditory sensitivity curves of fish. Each method has its practical limitations: behavioral methods take long training time while the electrophysiological methods are invasive. This chapter first describes a novel, non-invasive electrophysiological recording method, i.e., the auditory brainstem response (ABR), which was first developed in my laboratory with the purpose of obtaining audiograms within short time for a comprehensive study on fish hearing ability. The setup of the system as well as technical details involved in using the ABR system are discussed in-depth with inputs from various users over the past 5 years since the debut of the ABR method. The second part of this chapter is focused on understanding how gas-holding structures (e.g., gasbladder, suprabranchial chamber, otic gasbladder) play a role in overall hearing ability of fish. The gas-holding structure, e.g., gasbladder, is generally regarded as an underwater resonant bubble. It is assumed that the resonant frequency created by the passing sound wave to gas-holding structure could aid in overall hearing ability of fish. This chapter reviews the work carried out by the ABR method in the author's laboratory investigating how gas-holding structure plays a role in hearing ability of fish. The audiograms are obtained with the use of the ABR method before and after gas removal from: 1) gasbladder of goldfish, toadfish, and blue gourami; 2) suprabranchial chambers of blue gourami, kissing gourami, dwarf gourami; and 3) otic gasbladder of a mormyrid weakly electric fish. The general conclusion is that those fish (e.g., goldfish, gourami, mormyrid) that have direct coupling between gas-holding structure and the inner ear benefits greatly from such a coupling to have better hearing ability. While the gasbladder of toadfish, albeit large in size and is placed in close proximity to the inner ear does not contribute to the overall hearing ability. The finding is in general agreement with how a fish is either classified as a hearing specialist (with coupling device between ear and gas-holding structure) or a hearing generalist (without such a coupling device). This study also reveals the possible existence of different populations of sensory hair cells in specialist species.

The Giant Mottled Eel, Anguilla marmorata, Uses Blue-Shifted Rod Photoreceptors during Upstream Migration

PLoS ONE, 2014

Catadromous fishes migrate between ocean and freshwater during particular phases of their life cy... more Catadromous fishes migrate between ocean and freshwater during particular phases of their life cycle. The dramatic environmental changes shape their physiological features, e.g. visual sensitivity, olfactory ability, and salinity tolerance. Anguilla marmorata, a catadromous eel, migrates upstream on dark nights, following the lunar cycle. Such behavior may be correlated with ontogenetic changes in sensory systems. Therefore, this study was designed to identify changes in spectral sensitivity and opsin gene expression of A. marmorata during upstream migration. Microspectrophotometry analysis revealed that the tropical eel possesses a duplex retina with rod and cone photoreceptors. The l max of rod cells are 493, 489, and 489 nm in glass, yellow, and wild eels, while those of cone cells are 508, and 517 nm in yellow, and wild eels, respectively. Unlike European and American eels, Asian eels exhibited a blue-shifted pattern of rod photoreceptors during upstream migration. Quantitative gene expression analyses of four cloned opsin genes (Rh1f, Rh1d, Rh2, and SWS2) revealed that Rh1f expression is dominant at all three stages, while Rh1d is expressed only in older yellow eel. Furthermore, sequence comparison and protein modeling studies implied that a blue shift in Rh1d opsin may be induced by two known (N83, S292) and four putative (S124, V189, V286, I290) tuning sites adjacent to the retinal binding sites. Finally, expression of blue-shifted Rh1d opsin resulted in a spectral shift in rod photoreceptors. Our observations indicate that the giant mottled eel is color-blind, and its blue-shifted scotopic vision may influence its upstream migration behavior and habitat choice.

A comparative study on the visual adaptations of four species of moray eel

Vision Research, 2011

The goal of this study was to investigate how the eyes of different species of moray eel evolved ... more The goal of this study was to investigate how the eyes of different species of moray eel evolved to cope with limitations to vision imposed on them by the photic environments in which they reside. The comparative retinal histological structures and visual pigment characteristics including opsin gene sequences, of four species of moray eel inhabiting diverse habitats (i.e., shallow-water species, Rhinomuraena quaesita and Gymnothorax favagineus, and deep-sea species, Gymnothorax reticularis and Strophidon sathete) were examined. The histological sections showed that retinal layer structures of R. quaestia are significantly different from those of the other three species which likely reflects the effects of distribution depth on the structures. The maximal absorbance wavelength (k max) of photoreceptor cells, as measured by microspectrophotometry (MSP), showed a close correlation between the k max and the intensity/spectral quality of the light environment where each species lives. The spectra-shift, between shallow and deepsea species, observed in the rods cells results from amino acid substitution in Rh1 gene, while that in cones most likely results from differential expression of multiple Rh2 genes.

Adaptive evolution of cone opsin genes in two colorful cyprinids, Opsariichthys pachycephalus and Candidia barbatus

Vision Research, 2008

Opsariichthys pachycephalus and Candidia barbatus are two phylogenetically related freshwater cyp... more Opsariichthys pachycephalus and Candidia barbatus are two phylogenetically related freshwater cyprinids that both exhibit colorful, yet quite different nuptial coloration. This study was designed to test the hypothesis that differences in nuptial coloration between two species could reflect differences in color perception ability and the opsin genes that coded for it. Genes encoding the visual pigments of these two species were cloned and sequenced, k max of cone photoreceptors and the reflectance spectra of their body coloration were measured to test the hypothesis. The 14-nm spectral shift between green-light-sensitive photoreceptors of these two cyprinids is found to correlate well with differences in their reflective spectra. The spectral shift could result from differential expression of opsin genes and the interactive effects of the amino acid replacements in various minor sites. These results support our hypothesis that nuptial coloration is tied to color perception ability and opsin genes.

Adaptation of visual spectra and opsin genes in seabreams

Vision Research, 2009

Three species of seabreams, Acanthopagrus berda, Acanthopagrus schlegelii and Pagrus major, livin... more Three species of seabreams, Acanthopagrus berda, Acanthopagrus schlegelii and Pagrus major, living at different depths, were chosen to investigate how visual spectra and opsin genes evolve in response to various photic environments. The kmax of photoreceptors and opsin genes were measured and cloned from these species. Eight to twelve nm spectral shifts in the rod and blue cone cells were observed between the deep-sea, P. major, and shallow-sea species, A. berda and A. schlegelii. Furthermore, the deep-sea P. major has lost its red light vision. Six opsin genes, Rh1, Rh2A, Rh2B, SWS1, SWS2 and LWS, were identified from all three seabream species, with the LWS genes of P. major having undergone pseudogenization. These data indicate that the photic environment of habitats select for the physiology of visual spectra and coding of opsin genes.

A comparative study of hearing ability in fishes: the auditory brainstem response approach

Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 1998

Auditory brainstem response (ABR) techniques, an electrophysiological far-®eld recording method w... more Auditory brainstem response (ABR) techniques, an electrophysiological far-®eld recording method widely used in clinical evaluation of human hearing, were adapted for ®shes to overcome the major limitations of traditional behavioral and electrophysiological methods (e.g., invasive surgery, lengthy training of ®shes, etc.) used for ®sh hearing research. Responses to clicks and tone bursts of dierent frequencies and amplitudes were recorded with cutaneous electrodes. To evaluate the eectiveness of this method, the auditory sensitivity of a hearing specialist (gold®sh, Carassius auratus) and a hearing generalist (oscar, Astronotus ocellatus) was investigated and compared to audiograms obtained through psychophysical methods. The ABRs could be obtained between 100 Hz and 2000 Hz (oscar), and up to 5000 Hz (gold®sh). The ABR audiograms are similar to those obtained by behavioral methods in both species. The ABR audiogram of curarized (i.e., Flaxediltreated) gold®sh did not dier signi®cantly from two previously published behavioral curves but was lower than that obtained from uncurarized ®sh. In the oscar, ABR audiometry resulted in lower thresholds and a larger bandwidth than observed in behavioral tests. Comparison between methods revealed the advantages of this technique: rapid evaluation of hearing in untrained ®shes, and no limitations on repeated testing of animals.

Variability in the role of the gasbladder in fish audition

Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2000

The teleost gasbladder is believed to aid in fish audition by transferring pressure components of... more The teleost gasbladder is believed to aid in fish audition by transferring pressure components of incoming sound to the inner ears. This idea is primarily based on both anatomical observations of the mechanical connection between the gasbladder and the ear, followed by physiological experiments by various researchers. The gasbladder movement has been modeled mathematically as a pulsating bubble. This study is extending the previous work on fish with a physical coupling of the gasbladder and ear by investigating hearing in two species (the blue gourami Trichogaster trichopterus, and the oyster toadfish Opsanus tau) without a mechanical linkage. An otophysan specialist (the goldfish Carassius auratus) with mechanical coupling, is used as the control. Audiograms were obtained with acoustically evoked potentials (e.g., auditory brainstem response) from intact fish and from the same individuals with their gasbladders deflated. In blue gourami and oyster toadfish, removal of gas did not significantly change thresholds, and evoked potentials had similar waveforms. In goldfish thresholds increased by 33-55 dB (frequency dependent) after deflation, and major changes in evoked potentials were observed. These results suggest that the gasbladder may not serve an auditory enhancement function in teleost fishes that lack mechanical coupling between the gasbladder and the inner ear.

The Hearing Sensitivity of the Little Skate, Raja erinacea: A Comparison of Two Methods

Environmental Biology of Fishes, 2003

We determined the hearing sensitivity of the little skate, Raja erinacea using two methods: Behav... more We determined the hearing sensitivity of the little skate, Raja erinacea using two methods: Behavioral conditioning and the auditory brainstem response (ABR). This marks the first time that the hearing in any member of the Rajiformes has been examined and the first time that the ABR method has been used with an elasmobranch. We obtained audiograms of R. erinacea using each method and were found to be statistically similar. The best hearing sensitivity for R. erinacea was between 100 and 300 Hz. We compared the audiograms to audiograms obtained from other species of elasmobranchs. This analysis showed that R. erinacea, a bottom-dwelling elasmobranch, has less sensitive hearing than the lemon shark, Negaprion brevirostris, and the bull shark, Carcharhinus leucas, a free-swimming, raptorial elasmobranch. However, R. erinacea showed sensitivity comparable to that of the horn shark, Heterodontus francisi, another bottom-dwelling elasmobranch; both species feed primarily on benthic prey. These findings are in agreement with Corwin's hypothesis (1978) that hearing sensitivity is correlated with feeding behavior. An examination of the macula neglecta of R. erinacea found a total count of 10 000 hair cells, which is within the range of other bottom-dwelling elasmobranchs.

Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response (ABR) approach

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So ... more It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So far there is no proof for the detection of underwater sound above 400 Hz via a physiological approach. The controversy of whether cephalopods have a sound detection ability above 400 Hz was tested using the auditory brainstem response (ABR) approach, which has been successfully applied in fish, crustaceans, amphibians, reptiles and birds. Using ABR we found that auditory evoked potentials can be obtained in the frequency range 400 to 1500 Hz (Sepiotheutis lessoniana) and 400 to 1000 Hz (Octopus vulgaris), respectively. The thresholds of S. lessoniana were generally lower than those of O. vulgaris.

Subject Index Vol. 46, 1995

Brain, Behavior and Evolution, 1995

Sensitivity of Crayfish Procambarus clarkii Antennules to Hydrodynamic Stimuli is Reduced during Diazinon Exposure

Yan (2011) Sensitivity of crayfish Procambarus clarkii antennules to hydrodynamic stimuli is redu... more Yan (2011) Sensitivity of crayfish Procambarus clarkii antennules to hydrodynamic stimuli is reduced during diazinon exposure. Zoological Studies 50(2): 145-154. In this study, the susceptibility of crustacean antennular mechanosensitivity to a pesticide was examined. We investigated the sensitivity of crayfish Procambarus clarkii Girard antennules to sinusoidal stimuli during a short-term exposure to different concentrations of diazinon. Electrophysiological recordings from the antennules showed that neural activities in the crayfish antennules were still present 2 h after exposure to diazinon, although at decreased rates. In addition, responses to hydrodynamic stimuli indicated that the mechanosensitivity of crayfish antennules was reduced after exposure to concentrations of as low as 0.5 mg/L. The reduction in mechanosensitivity was larger and more rapid in the lateral flagellum than the medial flagellum. Observations from dye experiments showed that ambient water was more readily absorbed at the lateral flagellum than the medial flagellum probably because of differences in the setal structures of the 2 flagella. We discuss the results in relation to the possible immediate sublethal effects of diazinon on the ability of animals to search for and detect chemical and hydrodynamic cues that are important in feeding, mating, and prey/predator detection. Such information is important considering the rapid degradation of diazinon in the natural environment. http://zoolstud.sinica.edu.tw/Journals/50.2/145.pdf

Androgens Increase lws Opsin Expression and Red Sensitivity in Male Three-Spined Sticklebacks

PLoS ONE, 2014

Hearing in Marine Fish and Its Application in Fisheries

Capture Processes and Conservation Challenges, 2010

The acousticolateralis system of fi sh is composed of two major structures-the inner ear and the ... more The acousticolateralis system of fi sh is composed of two major structures-the inner ear and the lateral line. The inner ear is responsible for the balance and detection of acoustic signals, whereas the lateral line detects water-borne vibration signals (Hawkins 1986). These mechanosensory functions are crucial for the survival of fi sh. In terms of anatomical structure, the functional units of the inner ear are sensory hair cells and are used to detect underwater acoustical signals, whereas the neuromasts of the lateral line detect waterborne lowfrequency vibrations caused by physical as well as biological forces. The sensation of water-borne sound and vibration offers fi sh a dual detection system to measure mechanical disturbances of their environment. In turn, fi sh can listen to sounds produced by either conspecifi cs or heterospecifi cs, and they can take corresponding actions such as retreating or escalating agonistic behavior or being attracted to the source if the sounds are courtship signals. Likewise, sensation from the lateral line informs recipients of the presence of obstacles, predators or prey. In conjunction with their eyes, the lateral line system also participates in the schooling behavior of fi sh (Pitcher 1979). The successful operation of fi sheries whether at the commercial or subsistence level requires proper designs of fi shing gears and methods. In light of how the auditory functions of ears and the sensation abilities of lateral line modulate the behaviors of fi sh, it would be useful to understand the physiological processes involved in the acousticolateralis system and to make the best use of the knowledge in the designs of fi shing gear and operation. This chapter reviews the fundamental knowledge of physical properties of sound and discusses the physiological characteristics of the ear. Methodologies involved in understanding fi sh hearing in terms of frequency range and hearing threshold are reviewed along with a discussion on how exposure to noise will impact the overall hearing abilities of targeted fi shes. The last section of this chapter provides a few examples of practical applications of acoustic signals in fi sheries either to attract or to expel fi sh. 3.2 PROPERTIES OF UNDERWATER SOUND AND VIBRATION An understanding of two major properties of sound in terms of sound pressure and water particle motion (displacement, velocity, and acceleration) is necessary to understand the responses of the ear and the lateral line system. The propagations of sound pressure and particle motion are complicated because of large differences in the attenuation level related to the type of sound source, its frequency, and the distance from the stimulus. 3.2.1 Sound Source and Sound Field Sound propagation speed in air (340 m/s) and water (1500 m/s) are different because the acoustic impedance values (ρ c) of sound (where ρ represents the density of medium and c is the velocity of sound) in the two media are different due to differences in

The Relative Distribution of Otoliths as a Means of Larval Fish Identification

Zoological Studies, 2002

A recently developed auditory brainstem response (ABR) protocol has indicated that acoustically e... more A recently developed auditory brainstem response (ABR) protocol has indicated that acoustically evoked brainwaves in fishes are species-specific. These brainwaves reflect the spatial distribution of auditory nuclei and the 3 auditory end organs along the ascending auditory neuronal pathways. Species-specific brainwaves suggest the hypothesis that the distribution of otoliths, which are closely coupled with sensory hair cells whose evoked response forms the 1st wave of the ABR, should also be species-specific. Eight species of marine fish larvae (belonging to 8 genera and 4 families) collected from Taiwan and Texas, USA were cleared in trypsin and examined microscopically with double polarization filters. Three indices (inter-utricular ratio, IUR; inter-saccular ratio, ISR; and inter-lagena ratio, ILR) were developed to measure the ratio of inter-otolithic to inter-orbital distances. IUR and ISR succeeded in separating species, but ILR was not as useful because of late development of...

Threatened Fishes of the World: Oncorhynchus masou formosanus (Jordan Oshima, 1919) (Salmonidae)

Environmental Biology of Fishes

Common name: Formosan landlocked salmon (E), Cherry blossom hooked snout salmon (Taiwan). Conserv... more Common name: Formosan landlocked salmon (E), Cherry blossom hooked snout salmon (Taiwan). Conservation status: Critically endangered (Taiwan Ministry of Interior). Identification: Maximum total length 57 cm. D 15 (13-16), A 12 (11-15), Pectoral 12 (11-14), Pelvic 9 (8-10), scales 121 (116-139) in lateral line, cycloid scale. One adipose fin behind dorsal fin. Gill raker 19 (16-21). Branchiostegal rays 12 (9-14); vertebrae 62 (60-63); pyloric caeca 46 (24-62). No basibranchial tooth. Body length/head length 4.20; body length/body height 3.48; head length/snout length 4.41; head length/diameter of eye 3.43; head length/inter orbital width 4.12 (Tang 1959). The adult has 8-12 parr marks as elliptical cloud-like markings along the flank, its back is green shot through with black, and its belly is a silver-white. Along its back are 11 to 31 black spots. During the mating season the lower jaw of the male hooks upwards and is the most obvious secondary sexual characteristics. Drawing by Hong Y. Yan based on a photo in Wang (1994). Distribution: This is an endemic salmonid in Taiwan and the most southernly distributed (N 24 • 10-25) landlocked salmon in the northern hemisphere. The mitochondrial DNA analysis Numachi et al. 1990) suggests that Oncorhynchus masou migrated from Japan Sea through Tsushima Strait into Taiwan areas some 10 to 80 millions years ago. Upon the retreat of glaciers, some members remained in the upper streams of Tachia River and through geographical isolation evolved from an anadromous into a landlocked species. This species is considered a glacier relic and is recognized as a sister subspecies to Japanese salmon, Oncorhynchus masou. Before 1940s it was widely distributed in tributary streams (namely Chichiawan, Wuling, Yousheng, Nanhu, Hofan, and Suchiehlan creeks) with elevation higher than 1500 m of the upstream areas of Tachia River in central Taiwan. Between 1950s to 1970s, the range was reduced to Suchiehlan, Wuling, Chichiawan and an unnamed tributary of Chichiawan creeks. Now they can only be found in lower stretch of Wuling Creek (within the boundary of a newly established Shei-Pa National Park), Chichiawan and an unnamed tributary of Chichiawan creeks. The majority of the population is confined to a seven-kilometer stretch of Chichiawan Creek within the Wuling area. Abundance: Total number is less than 1000 according to a field survey conducted in 1991. Restocking of wild population through captive breeding program has been going on since 1986. Habitat and ecology: The majority of this fish prefers to stay in backwater pools and plunge pools created by silt trapping dams. This species can not tolerate water temperature above 17 • C. Microhabitat use is season-and size-dependent. During summer time, adult fish prefer to stay in areas upstream where higher diversity of microhabitats can be found far away from silt trapping dam. Young individuals prefer slow flow and wider section of the stream where natural shelters are abundant. During winter time due to reduction of water level, adult fish move to plunge pool underneath trapping dams while young fish aggregate in lateral scour pools formed by drifted woods, tree roots and boulder along the creek. Stomach content analysis reveals that aquatic insects (Trichoptera, Ephemeroptera, Disperta) accounts for 74% of food while terrestrial insects (Hymenoptera, Coleoptera, Hemiptera, Diptera) accounts for 22% of food. Some Arachonidae, Diploapoda, Crustacea, and Anura are also found in the stomachs. This species is considered an insectivorous fish. Reproduction: The spawners are considered hiding lithophils, prefer to build nests with gravels ranging in diameters from 0.2 to 25.6 cm. Females build the nests by using tail and sideway body movement to clear silt away from bottom and create elliptical shaped nests. The average size of nest range is about 0.3 m 2 (0.2-1.8 m 2) with a long axis 0.7 m (0.2-1.2 m) and a short axis 0.5 m (0.2-0.85 m). Water depth is 0.25 m (0.1-0.6 m). Water current speed at the surface of nest is 0.09 ms −1 (not to exceed 0.6 ms −1) and at the bottom of nest is 0.06 ms −1 (not to exceed 0.45 ms −1). However, due to skewed sex ratio in the population (1 female: 0.65 male), mating between 1 female and two or three males have been observed. Eggs are laid from mid-to late October and within 20-30 days later they reach eyed-embryo state. The water temperature in the spawning ground is 11-15 • C. In general it takes 30-60 days (after fertilization) to hatch (around late November). From tagging experiment it was determined that two-year-old fish are the dominant spawners. The life expectancy is 4-5 years. Threat: The Der Jee Dam was built in the middle section of Tachai River in 1974 to control flooding and provide irrigation in the low land areas of central Taiwan. In order to prolong the life span of this dam, a series of silt trapping dams were built along the upper reach of Tachai River where most of natural habitats of this fish can be found. Within its existing habitat, albeit very small (with only a stretch of about 7 km), there are 11 silt trapping dams along the stream which further result in habitat fragmentation and isolation. Furthermore, illegal logging and uncontrolled land development such as operation of orchards and vegetable farms at high elevation, coupling with hurricanes, leads to extensive soil erosion of slopes along tributaries. This leads to severe siltation of spawning and nursery grounds. Illegal logging also exposed stream bank areas to direct sunlight and raise water temperature in preferred shallow habitats. This leads to significant reduction of microhabitats. Conservation action: This fish was first declared as a 'natural treasure' by Japanese government in 1938 when Taiwan was under Japan's colonial rule. The protection decree specifically declared: (1) prohibition of any introduction of exotic fish species into natural habitats of this fish; (2) fishing moratorium from 1 May to 31 December; (3) no logging and change of landscape within 300 m radius of Chichiawan Stream. After departure of Japanese in 1945 this fish received very little attention and in the ensuring years the population declined dramatically due to illegal fishing and deterioration of its natural habitats. It was not until 1976 the wild population started gaining notice of concerned biologists. First attempt was made to use artificial propagation to restock the dwindling population. This fish was first declared as an endangered species in 1984 by the Taiwanese government after the enactment of endangered species act. Since then many scientists have participated in the field study of this species. The establishment of the Shei-Pa National Park legally gives park rangers authority to protect the species and its natural habitats. Conservation recommendation: The removal of all silt trapping dams should be the first priority in the recovery plan. The removal of these dams will increase genetic diversities of once segregated populations. However, this action will inevitably shorten the life span of the Der Jee Dam with great economic loss and is not likely to be considered a viable option to various government agencies. It is recommended that a good number of fish produced from breeding programs should be located in hatchery to maintain a spare breeding stock in case disaster happened to its natural population. The breeding program should also mix spawners from different populations to enhance genetic diversity of restocked populations. The alternative plan is to buy back vegetable farms and orchards and to conduct an extensive and a long term reforestation project to reduce soil erosion. The successful soil conservation can lead to removal of silt trapping dams within a decade which in turn will allow genetic exchanges among fragmented populations.

Effects of Boat Engine Noise on the Auditory Sensitivity of the Fathead Minnow, Pimephales promelas

Environmental Biology of Fishes

Fishes are constantly exposed to various sources of noise in their underwater acoustic environmen... more Fishes are constantly exposed to various sources of noise in their underwater acoustic environment. Many of these sounds are from anthropogenic sources, especially engines of boats. Noise generated from a small boat with a 55 horsepower outboard motor was played back to fathead minnows, Pimephales promelas, for 2 h at 142 dB (re: 1 µPa), and auditory thresholds were measured using the auditory brainstem response (ABR) technique. The results demonstrate that boat engine noise significantly elevate a fish's auditory threshold at 1 kHz (7.8 dB), 1.5 kHz (13.5 dB), and 2.0 kHz (10.5 dB), the most sensitive hearing range of this species. Such a short duration of noise exposure leads to significant changes in hearing capability and implies that man-made noise generated from boat engines can have far reaching environmental impacts on fishes.

Plasticity of opsin gene expression in the adult red shiner (Cyprinella lutrensis) in response to turbid habitats

PLOS ONE

Vision is very important to fish as it is required for foraging food, fighting competitors, fleei... more Vision is very important to fish as it is required for foraging food, fighting competitors, fleeing from predators, and finding potential mates. Vertebrates express opsin genes in photoreceptor cells to receive visual signals, and the variety of light levels in aquatic habits has driven fish to evolve multiple opsin genes with expression profiles that are highly plastic. In this study, red shiners (Cyprinella lutrensis) were exposed to four water turbidity treatments and their opsin genes were cloned to elucidate how opsin gene expression could be modulated by ambient light conditions. Opsin gene cloning revealed that these fish have single RH1, SWS1, SWS2 and LWS genes and two RH2 genes. Phylogenetic analysis also indicated that these two RH2 opsin genes-RH2A and RH2B-are in-paralogous. Using quantitative PCR, we found evidence that opsin expression is plastic in adults. Elevated proportional expression of LWS in the cone under ambient light and turbid treatment indicated that the red shiner's visual spectrum displays a red shift in response to increased turbidity.

Regional Specialization for Control of Ocular Movements in the Compound Eyes of a Stomatopod Crustacean

Journal of Experimental Biology, 1992

1. Regional specialization within the triple compound eyes of the gonodactyloid stomatopod Gonoda... more 1. Regional specialization within the triple compound eyes of the gonodactyloid stomatopod Gonodactylus oerstedii (Hansen) was studied by examining how ocular tracking of a small target was affected after occluding vision in particular ommatidial regions with black enamel paint. 2. Complete occlusion of one eye did not prevent the other eye from tracking, indicating that the two eyes act somewhat independently. However, following such treatment, the angular extent over which the seeing eye moved while tracking was reduced. 3. An eye was able to continue tracking a moving target even after occlusion of the anterior tip or after painting over all of its posterior surface except the anterior tip (restricting the visual field to a patch about 40° in diameter). Similarly, occlusion of only the midband, the medial half or the lateral half of an eye did not prevent tracking. 4. Tracking was also possible, although with decreased amplitude, when either the dorsal or the ventral hemisphere w...

An automated positive reward method for measuring acoustic sensitivity in fish

Behavior Research Methods, Instruments, &amp Computers, 1991

The Cone Opsin Repertoire of Osteoglossomorph Fishes: Gene Loss in Mormyrid Electric Fish and a Long Wavelength-Sensitive Cone Opsin That Survived 3R

Molecular Biology and Evolution, 2018

Vertebrates have four classes of cone opsin genes derived from two rounds of genome duplication. ... more Vertebrates have four classes of cone opsin genes derived from two rounds of genome duplication. These are short wavelength sensitive 1(SWS1), short wavelength sensitive 2(SWS2), medium wavelength sensitive (RH2), and long wavelength sensitive (LWS). Teleosts had another genome duplication at their origin and it is believed that only one of each cone opsin survived the ancestral teleost duplication event. We tested this by examining the retinal cones of a basal teleost group, the osteoglossomorphs. Surprisingly, this lineage has lost the typical vertebrate green-sensitive RH2 opsin gene and, instead, has a duplicate of the LWS opsin that is green sensitive. This parallels the situation in mammalian evolution in which the RH2 opsin gene was lost in basal mammals and a green-sensitive opsin re-evolved in Old World, and independently in some New World, primates from an LWS opsin gene. Another group of fish, the characins, possess green-sensitive LWS cones. Phylogenetic analysis shows that the evolution of green-sensitive LWS opsins in these two teleost groups derives from a common ancestral LWS opsin that acquired green sensitivity. Additionally, the nocturnally active African weakly electric fish (Mormyroideae), which are osteoglossomorphs, show a loss of the SWS1 opsin gene. In comparison with the independently evolved nocturnally active South American weakly electric fish (Gymnotiformes) with a functionally monochromatic LWS opsin cone retina, the presence of SWS2, LWS, and LWS2 cone opsins in mormyrids suggests the possibility of color vision.

The Role of Gas-Holding Structures in Fish Hearing: An Acoustically Evoked Potentials Approach

The Senses of Fish, 2004

Fish varies greatly in their sensitivity to underwater acoustic signals. Over the past century, s... more Fish varies greatly in their sensitivity to underwater acoustic signals. Over the past century, scientists have designed many methods to investigate auditory capacity of fish. Behavioral training paradigms (with either punishment or reward as incentives to the tested subjects) and various electrophysiological methods have been used to obtain audiograms, i.e., the auditory sensitivity curves of fish. Each method has its practical limitations: behavioral methods take long training time while the electrophysiological methods are invasive. This chapter first describes a novel, non-invasive electrophysiological recording method, i.e., the auditory brainstem response (ABR), which was first developed in my laboratory with the purpose of obtaining audiograms within short time for a comprehensive study on fish hearing ability. The setup of the system as well as technical details involved in using the ABR system are discussed in-depth with inputs from various users over the past 5 years since the debut of the ABR method. The second part of this chapter is focused on understanding how gas-holding structures (e.g., gasbladder, suprabranchial chamber, otic gasbladder) play a role in overall hearing ability of fish. The gas-holding structure, e.g., gasbladder, is generally regarded as an underwater resonant bubble. It is assumed that the resonant frequency created by the passing sound wave to gas-holding structure could aid in overall hearing ability of fish. This chapter reviews the work carried out by the ABR method in the author's laboratory investigating how gas-holding structure plays a role in hearing ability of fish. The audiograms are obtained with the use of the ABR method before and after gas removal from: 1) gasbladder of goldfish, toadfish, and blue gourami; 2) suprabranchial chambers of blue gourami, kissing gourami, dwarf gourami; and 3) otic gasbladder of a mormyrid weakly electric fish. The general conclusion is that those fish (e.g., goldfish, gourami, mormyrid) that have direct coupling between gas-holding structure and the inner ear benefits greatly from such a coupling to have better hearing ability. While the gasbladder of toadfish, albeit large in size and is placed in close proximity to the inner ear does not contribute to the overall hearing ability. The finding is in general agreement with how a fish is either classified as a hearing specialist (with coupling device between ear and gas-holding structure) or a hearing generalist (without such a coupling device). This study also reveals the possible existence of different populations of sensory hair cells in specialist species.

The Giant Mottled Eel, Anguilla marmorata, Uses Blue-Shifted Rod Photoreceptors during Upstream Migration

PLoS ONE, 2014

Catadromous fishes migrate between ocean and freshwater during particular phases of their life cy... more Catadromous fishes migrate between ocean and freshwater during particular phases of their life cycle. The dramatic environmental changes shape their physiological features, e.g. visual sensitivity, olfactory ability, and salinity tolerance. Anguilla marmorata, a catadromous eel, migrates upstream on dark nights, following the lunar cycle. Such behavior may be correlated with ontogenetic changes in sensory systems. Therefore, this study was designed to identify changes in spectral sensitivity and opsin gene expression of A. marmorata during upstream migration. Microspectrophotometry analysis revealed that the tropical eel possesses a duplex retina with rod and cone photoreceptors. The l max of rod cells are 493, 489, and 489 nm in glass, yellow, and wild eels, while those of cone cells are 508, and 517 nm in yellow, and wild eels, respectively. Unlike European and American eels, Asian eels exhibited a blue-shifted pattern of rod photoreceptors during upstream migration. Quantitative gene expression analyses of four cloned opsin genes (Rh1f, Rh1d, Rh2, and SWS2) revealed that Rh1f expression is dominant at all three stages, while Rh1d is expressed only in older yellow eel. Furthermore, sequence comparison and protein modeling studies implied that a blue shift in Rh1d opsin may be induced by two known (N83, S292) and four putative (S124, V189, V286, I290) tuning sites adjacent to the retinal binding sites. Finally, expression of blue-shifted Rh1d opsin resulted in a spectral shift in rod photoreceptors. Our observations indicate that the giant mottled eel is color-blind, and its blue-shifted scotopic vision may influence its upstream migration behavior and habitat choice.

A comparative study on the visual adaptations of four species of moray eel

Vision Research, 2011

The goal of this study was to investigate how the eyes of different species of moray eel evolved ... more The goal of this study was to investigate how the eyes of different species of moray eel evolved to cope with limitations to vision imposed on them by the photic environments in which they reside. The comparative retinal histological structures and visual pigment characteristics including opsin gene sequences, of four species of moray eel inhabiting diverse habitats (i.e., shallow-water species, Rhinomuraena quaesita and Gymnothorax favagineus, and deep-sea species, Gymnothorax reticularis and Strophidon sathete) were examined. The histological sections showed that retinal layer structures of R. quaestia are significantly different from those of the other three species which likely reflects the effects of distribution depth on the structures. The maximal absorbance wavelength (k max) of photoreceptor cells, as measured by microspectrophotometry (MSP), showed a close correlation between the k max and the intensity/spectral quality of the light environment where each species lives. The spectra-shift, between shallow and deepsea species, observed in the rods cells results from amino acid substitution in Rh1 gene, while that in cones most likely results from differential expression of multiple Rh2 genes.

Adaptive evolution of cone opsin genes in two colorful cyprinids, Opsariichthys pachycephalus and Candidia barbatus

Vision Research, 2008

Opsariichthys pachycephalus and Candidia barbatus are two phylogenetically related freshwater cyp... more Opsariichthys pachycephalus and Candidia barbatus are two phylogenetically related freshwater cyprinids that both exhibit colorful, yet quite different nuptial coloration. This study was designed to test the hypothesis that differences in nuptial coloration between two species could reflect differences in color perception ability and the opsin genes that coded for it. Genes encoding the visual pigments of these two species were cloned and sequenced, k max of cone photoreceptors and the reflectance spectra of their body coloration were measured to test the hypothesis. The 14-nm spectral shift between green-light-sensitive photoreceptors of these two cyprinids is found to correlate well with differences in their reflective spectra. The spectral shift could result from differential expression of opsin genes and the interactive effects of the amino acid replacements in various minor sites. These results support our hypothesis that nuptial coloration is tied to color perception ability and opsin genes.

Adaptation of visual spectra and opsin genes in seabreams

Vision Research, 2009

Three species of seabreams, Acanthopagrus berda, Acanthopagrus schlegelii and Pagrus major, livin... more Three species of seabreams, Acanthopagrus berda, Acanthopagrus schlegelii and Pagrus major, living at different depths, were chosen to investigate how visual spectra and opsin genes evolve in response to various photic environments. The kmax of photoreceptors and opsin genes were measured and cloned from these species. Eight to twelve nm spectral shifts in the rod and blue cone cells were observed between the deep-sea, P. major, and shallow-sea species, A. berda and A. schlegelii. Furthermore, the deep-sea P. major has lost its red light vision. Six opsin genes, Rh1, Rh2A, Rh2B, SWS1, SWS2 and LWS, were identified from all three seabream species, with the LWS genes of P. major having undergone pseudogenization. These data indicate that the photic environment of habitats select for the physiology of visual spectra and coding of opsin genes.

A comparative study of hearing ability in fishes: the auditory brainstem response approach

Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 1998

Auditory brainstem response (ABR) techniques, an electrophysiological far-®eld recording method w... more Auditory brainstem response (ABR) techniques, an electrophysiological far-®eld recording method widely used in clinical evaluation of human hearing, were adapted for ®shes to overcome the major limitations of traditional behavioral and electrophysiological methods (e.g., invasive surgery, lengthy training of ®shes, etc.) used for ®sh hearing research. Responses to clicks and tone bursts of dierent frequencies and amplitudes were recorded with cutaneous electrodes. To evaluate the eectiveness of this method, the auditory sensitivity of a hearing specialist (gold®sh, Carassius auratus) and a hearing generalist (oscar, Astronotus ocellatus) was investigated and compared to audiograms obtained through psychophysical methods. The ABRs could be obtained between 100 Hz and 2000 Hz (oscar), and up to 5000 Hz (gold®sh). The ABR audiograms are similar to those obtained by behavioral methods in both species. The ABR audiogram of curarized (i.e., Flaxediltreated) gold®sh did not dier signi®cantly from two previously published behavioral curves but was lower than that obtained from uncurarized ®sh. In the oscar, ABR audiometry resulted in lower thresholds and a larger bandwidth than observed in behavioral tests. Comparison between methods revealed the advantages of this technique: rapid evaluation of hearing in untrained ®shes, and no limitations on repeated testing of animals.

Variability in the role of the gasbladder in fish audition

Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2000

The teleost gasbladder is believed to aid in fish audition by transferring pressure components of... more The teleost gasbladder is believed to aid in fish audition by transferring pressure components of incoming sound to the inner ears. This idea is primarily based on both anatomical observations of the mechanical connection between the gasbladder and the ear, followed by physiological experiments by various researchers. The gasbladder movement has been modeled mathematically as a pulsating bubble. This study is extending the previous work on fish with a physical coupling of the gasbladder and ear by investigating hearing in two species (the blue gourami Trichogaster trichopterus, and the oyster toadfish Opsanus tau) without a mechanical linkage. An otophysan specialist (the goldfish Carassius auratus) with mechanical coupling, is used as the control. Audiograms were obtained with acoustically evoked potentials (e.g., auditory brainstem response) from intact fish and from the same individuals with their gasbladders deflated. In blue gourami and oyster toadfish, removal of gas did not significantly change thresholds, and evoked potentials had similar waveforms. In goldfish thresholds increased by 33-55 dB (frequency dependent) after deflation, and major changes in evoked potentials were observed. These results suggest that the gasbladder may not serve an auditory enhancement function in teleost fishes that lack mechanical coupling between the gasbladder and the inner ear.

The Hearing Sensitivity of the Little Skate, Raja erinacea: A Comparison of Two Methods

Environmental Biology of Fishes, 2003

We determined the hearing sensitivity of the little skate, Raja erinacea using two methods: Behav... more We determined the hearing sensitivity of the little skate, Raja erinacea using two methods: Behavioral conditioning and the auditory brainstem response (ABR). This marks the first time that the hearing in any member of the Rajiformes has been examined and the first time that the ABR method has been used with an elasmobranch. We obtained audiograms of R. erinacea using each method and were found to be statistically similar. The best hearing sensitivity for R. erinacea was between 100 and 300 Hz. We compared the audiograms to audiograms obtained from other species of elasmobranchs. This analysis showed that R. erinacea, a bottom-dwelling elasmobranch, has less sensitive hearing than the lemon shark, Negaprion brevirostris, and the bull shark, Carcharhinus leucas, a free-swimming, raptorial elasmobranch. However, R. erinacea showed sensitivity comparable to that of the horn shark, Heterodontus francisi, another bottom-dwelling elasmobranch; both species feed primarily on benthic prey. These findings are in agreement with Corwin's hypothesis (1978) that hearing sensitivity is correlated with feeding behavior. An examination of the macula neglecta of R. erinacea found a total count of 10 000 hair cells, which is within the range of other bottom-dwelling elasmobranchs.

Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response (ABR) approach

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So ... more It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So far there is no proof for the detection of underwater sound above 400 Hz via a physiological approach. The controversy of whether cephalopods have a sound detection ability above 400 Hz was tested using the auditory brainstem response (ABR) approach, which has been successfully applied in fish, crustaceans, amphibians, reptiles and birds. Using ABR we found that auditory evoked potentials can be obtained in the frequency range 400 to 1500 Hz (Sepiotheutis lessoniana) and 400 to 1000 Hz (Octopus vulgaris), respectively. The thresholds of S. lessoniana were generally lower than those of O. vulgaris.

Subject Index Vol. 46, 1995

Brain, Behavior and Evolution, 1995

Sensitivity of Crayfish Procambarus clarkii Antennules to Hydrodynamic Stimuli is Reduced during Diazinon Exposure

Yan (2011) Sensitivity of crayfish Procambarus clarkii antennules to hydrodynamic stimuli is redu... more Yan (2011) Sensitivity of crayfish Procambarus clarkii antennules to hydrodynamic stimuli is reduced during diazinon exposure. Zoological Studies 50(2): 145-154. In this study, the susceptibility of crustacean antennular mechanosensitivity to a pesticide was examined. We investigated the sensitivity of crayfish Procambarus clarkii Girard antennules to sinusoidal stimuli during a short-term exposure to different concentrations of diazinon. Electrophysiological recordings from the antennules showed that neural activities in the crayfish antennules were still present 2 h after exposure to diazinon, although at decreased rates. In addition, responses to hydrodynamic stimuli indicated that the mechanosensitivity of crayfish antennules was reduced after exposure to concentrations of as low as 0.5 mg/L. The reduction in mechanosensitivity was larger and more rapid in the lateral flagellum than the medial flagellum. Observations from dye experiments showed that ambient water was more readily absorbed at the lateral flagellum than the medial flagellum probably because of differences in the setal structures of the 2 flagella. We discuss the results in relation to the possible immediate sublethal effects of diazinon on the ability of animals to search for and detect chemical and hydrodynamic cues that are important in feeding, mating, and prey/predator detection. Such information is important considering the rapid degradation of diazinon in the natural environment. http://zoolstud.sinica.edu.tw/Journals/50.2/145.pdf

Androgens Increase lws Opsin Expression and Red Sensitivity in Male Three-Spined Sticklebacks

PLoS ONE, 2014

Hearing in Marine Fish and Its Application in Fisheries

Capture Processes and Conservation Challenges, 2010

The acousticolateralis system of fi sh is composed of two major structures-the inner ear and the ... more The acousticolateralis system of fi sh is composed of two major structures-the inner ear and the lateral line. The inner ear is responsible for the balance and detection of acoustic signals, whereas the lateral line detects water-borne vibration signals (Hawkins 1986). These mechanosensory functions are crucial for the survival of fi sh. In terms of anatomical structure, the functional units of the inner ear are sensory hair cells and are used to detect underwater acoustical signals, whereas the neuromasts of the lateral line detect waterborne lowfrequency vibrations caused by physical as well as biological forces. The sensation of water-borne sound and vibration offers fi sh a dual detection system to measure mechanical disturbances of their environment. In turn, fi sh can listen to sounds produced by either conspecifi cs or heterospecifi cs, and they can take corresponding actions such as retreating or escalating agonistic behavior or being attracted to the source if the sounds are courtship signals. Likewise, sensation from the lateral line informs recipients of the presence of obstacles, predators or prey. In conjunction with their eyes, the lateral line system also participates in the schooling behavior of fi sh (Pitcher 1979). The successful operation of fi sheries whether at the commercial or subsistence level requires proper designs of fi shing gears and methods. In light of how the auditory functions of ears and the sensation abilities of lateral line modulate the behaviors of fi sh, it would be useful to understand the physiological processes involved in the acousticolateralis system and to make the best use of the knowledge in the designs of fi shing gear and operation. This chapter reviews the fundamental knowledge of physical properties of sound and discusses the physiological characteristics of the ear. Methodologies involved in understanding fi sh hearing in terms of frequency range and hearing threshold are reviewed along with a discussion on how exposure to noise will impact the overall hearing abilities of targeted fi shes. The last section of this chapter provides a few examples of practical applications of acoustic signals in fi sheries either to attract or to expel fi sh. 3.2 PROPERTIES OF UNDERWATER SOUND AND VIBRATION An understanding of two major properties of sound in terms of sound pressure and water particle motion (displacement, velocity, and acceleration) is necessary to understand the responses of the ear and the lateral line system. The propagations of sound pressure and particle motion are complicated because of large differences in the attenuation level related to the type of sound source, its frequency, and the distance from the stimulus. 3.2.1 Sound Source and Sound Field Sound propagation speed in air (340 m/s) and water (1500 m/s) are different because the acoustic impedance values (ρ c) of sound (where ρ represents the density of medium and c is the velocity of sound) in the two media are different due to differences in

The Relative Distribution of Otoliths as a Means of Larval Fish Identification

Zoological Studies, 2002

A recently developed auditory brainstem response (ABR) protocol has indicated that acoustically e... more A recently developed auditory brainstem response (ABR) protocol has indicated that acoustically evoked brainwaves in fishes are species-specific. These brainwaves reflect the spatial distribution of auditory nuclei and the 3 auditory end organs along the ascending auditory neuronal pathways. Species-specific brainwaves suggest the hypothesis that the distribution of otoliths, which are closely coupled with sensory hair cells whose evoked response forms the 1st wave of the ABR, should also be species-specific. Eight species of marine fish larvae (belonging to 8 genera and 4 families) collected from Taiwan and Texas, USA were cleared in trypsin and examined microscopically with double polarization filters. Three indices (inter-utricular ratio, IUR; inter-saccular ratio, ISR; and inter-lagena ratio, ILR) were developed to measure the ratio of inter-otolithic to inter-orbital distances. IUR and ISR succeeded in separating species, but ILR was not as useful because of late development of...

Threatened Fishes of the World: Oncorhynchus masou formosanus (Jordan Oshima, 1919) (Salmonidae)

Environmental Biology of Fishes

Common name: Formosan landlocked salmon (E), Cherry blossom hooked snout salmon (Taiwan). Conserv... more Common name: Formosan landlocked salmon (E), Cherry blossom hooked snout salmon (Taiwan). Conservation status: Critically endangered (Taiwan Ministry of Interior). Identification: Maximum total length 57 cm. D 15 (13-16), A 12 (11-15), Pectoral 12 (11-14), Pelvic 9 (8-10), scales 121 (116-139) in lateral line, cycloid scale. One adipose fin behind dorsal fin. Gill raker 19 (16-21). Branchiostegal rays 12 (9-14); vertebrae 62 (60-63); pyloric caeca 46 (24-62). No basibranchial tooth. Body length/head length 4.20; body length/body height 3.48; head length/snout length 4.41; head length/diameter of eye 3.43; head length/inter orbital width 4.12 (Tang 1959). The adult has 8-12 parr marks as elliptical cloud-like markings along the flank, its back is green shot through with black, and its belly is a silver-white. Along its back are 11 to 31 black spots. During the mating season the lower jaw of the male hooks upwards and is the most obvious secondary sexual characteristics. Drawing by Hong Y. Yan based on a photo in Wang (1994). Distribution: This is an endemic salmonid in Taiwan and the most southernly distributed (N 24 • 10-25) landlocked salmon in the northern hemisphere. The mitochondrial DNA analysis Numachi et al. 1990) suggests that Oncorhynchus masou migrated from Japan Sea through Tsushima Strait into Taiwan areas some 10 to 80 millions years ago. Upon the retreat of glaciers, some members remained in the upper streams of Tachia River and through geographical isolation evolved from an anadromous into a landlocked species. This species is considered a glacier relic and is recognized as a sister subspecies to Japanese salmon, Oncorhynchus masou. Before 1940s it was widely distributed in tributary streams (namely Chichiawan, Wuling, Yousheng, Nanhu, Hofan, and Suchiehlan creeks) with elevation higher than 1500 m of the upstream areas of Tachia River in central Taiwan. Between 1950s to 1970s, the range was reduced to Suchiehlan, Wuling, Chichiawan and an unnamed tributary of Chichiawan creeks. Now they can only be found in lower stretch of Wuling Creek (within the boundary of a newly established Shei-Pa National Park), Chichiawan and an unnamed tributary of Chichiawan creeks. The majority of the population is confined to a seven-kilometer stretch of Chichiawan Creek within the Wuling area. Abundance: Total number is less than 1000 according to a field survey conducted in 1991. Restocking of wild population through captive breeding program has been going on since 1986. Habitat and ecology: The majority of this fish prefers to stay in backwater pools and plunge pools created by silt trapping dams. This species can not tolerate water temperature above 17 • C. Microhabitat use is season-and size-dependent. During summer time, adult fish prefer to stay in areas upstream where higher diversity of microhabitats can be found far away from silt trapping dam. Young individuals prefer slow flow and wider section of the stream where natural shelters are abundant. During winter time due to reduction of water level, adult fish move to plunge pool underneath trapping dams while young fish aggregate in lateral scour pools formed by drifted woods, tree roots and boulder along the creek. Stomach content analysis reveals that aquatic insects (Trichoptera, Ephemeroptera, Disperta) accounts for 74% of food while terrestrial insects (Hymenoptera, Coleoptera, Hemiptera, Diptera) accounts for 22% of food. Some Arachonidae, Diploapoda, Crustacea, and Anura are also found in the stomachs. This species is considered an insectivorous fish. Reproduction: The spawners are considered hiding lithophils, prefer to build nests with gravels ranging in diameters from 0.2 to 25.6 cm. Females build the nests by using tail and sideway body movement to clear silt away from bottom and create elliptical shaped nests. The average size of nest range is about 0.3 m 2 (0.2-1.8 m 2) with a long axis 0.7 m (0.2-1.2 m) and a short axis 0.5 m (0.2-0.85 m). Water depth is 0.25 m (0.1-0.6 m). Water current speed at the surface of nest is 0.09 ms −1 (not to exceed 0.6 ms −1) and at the bottom of nest is 0.06 ms −1 (not to exceed 0.45 ms −1). However, due to skewed sex ratio in the population (1 female: 0.65 male), mating between 1 female and two or three males have been observed. Eggs are laid from mid-to late October and within 20-30 days later they reach eyed-embryo state. The water temperature in the spawning ground is 11-15 • C. In general it takes 30-60 days (after fertilization) to hatch (around late November). From tagging experiment it was determined that two-year-old fish are the dominant spawners. The life expectancy is 4-5 years. Threat: The Der Jee Dam was built in the middle section of Tachai River in 1974 to control flooding and provide irrigation in the low land areas of central Taiwan. In order to prolong the life span of this dam, a series of silt trapping dams were built along the upper reach of Tachai River where most of natural habitats of this fish can be found. Within its existing habitat, albeit very small (with only a stretch of about 7 km), there are 11 silt trapping dams along the stream which further result in habitat fragmentation and isolation. Furthermore, illegal logging and uncontrolled land development such as operation of orchards and vegetable farms at high elevation, coupling with hurricanes, leads to extensive soil erosion of slopes along tributaries. This leads to severe siltation of spawning and nursery grounds. Illegal logging also exposed stream bank areas to direct sunlight and raise water temperature in preferred shallow habitats. This leads to significant reduction of microhabitats. Conservation action: This fish was first declared as a 'natural treasure' by Japanese government in 1938 when Taiwan was under Japan's colonial rule. The protection decree specifically declared: (1) prohibition of any introduction of exotic fish species into natural habitats of this fish; (2) fishing moratorium from 1 May to 31 December; (3) no logging and change of landscape within 300 m radius of Chichiawan Stream. After departure of Japanese in 1945 this fish received very little attention and in the ensuring years the population declined dramatically due to illegal fishing and deterioration of its natural habitats. It was not until 1976 the wild population started gaining notice of concerned biologists. First attempt was made to use artificial propagation to restock the dwindling population. This fish was first declared as an endangered species in 1984 by the Taiwanese government after the enactment of endangered species act. Since then many scientists have participated in the field study of this species. The establishment of the Shei-Pa National Park legally gives park rangers authority to protect the species and its natural habitats. Conservation recommendation: The removal of all silt trapping dams should be the first priority in the recovery plan. The removal of these dams will increase genetic diversities of once segregated populations. However, this action will inevitably shorten the life span of the Der Jee Dam with great economic loss and is not likely to be considered a viable option to various government agencies. It is recommended that a good number of fish produced from breeding programs should be located in hatchery to maintain a spare breeding stock in case disaster happened to its natural population. The breeding program should also mix spawners from different populations to enhance genetic diversity of restocked populations. The alternative plan is to buy back vegetable farms and orchards and to conduct an extensive and a long term reforestation project to reduce soil erosion. The successful soil conservation can lead to removal of silt trapping dams within a decade which in turn will allow genetic exchanges among fragmented populations.

Effects of Boat Engine Noise on the Auditory Sensitivity of the Fathead Minnow, Pimephales promelas

Environmental Biology of Fishes

Fishes are constantly exposed to various sources of noise in their underwater acoustic environmen... more Fishes are constantly exposed to various sources of noise in their underwater acoustic environment. Many of these sounds are from anthropogenic sources, especially engines of boats. Noise generated from a small boat with a 55 horsepower outboard motor was played back to fathead minnows, Pimephales promelas, for 2 h at 142 dB (re: 1 µPa), and auditory thresholds were measured using the auditory brainstem response (ABR) technique. The results demonstrate that boat engine noise significantly elevate a fish's auditory threshold at 1 kHz (7.8 dB), 1.5 kHz (13.5 dB), and 2.0 kHz (10.5 dB), the most sensitive hearing range of this species. Such a short duration of noise exposure leads to significant changes in hearing capability and implies that man-made noise generated from boat engines can have far reaching environmental impacts on fishes.

Plasticity of opsin gene expression in the adult red shiner (Cyprinella lutrensis) in response to turbid habitats

PLOS ONE

Vision is very important to fish as it is required for foraging food, fighting competitors, fleei... more Vision is very important to fish as it is required for foraging food, fighting competitors, fleeing from predators, and finding potential mates. Vertebrates express opsin genes in photoreceptor cells to receive visual signals, and the variety of light levels in aquatic habits has driven fish to evolve multiple opsin genes with expression profiles that are highly plastic. In this study, red shiners (Cyprinella lutrensis) were exposed to four water turbidity treatments and their opsin genes were cloned to elucidate how opsin gene expression could be modulated by ambient light conditions. Opsin gene cloning revealed that these fish have single RH1, SWS1, SWS2 and LWS genes and two RH2 genes. Phylogenetic analysis also indicated that these two RH2 opsin genes-RH2A and RH2B-are in-paralogous. Using quantitative PCR, we found evidence that opsin expression is plastic in adults. Elevated proportional expression of LWS in the cone under ambient light and turbid treatment indicated that the red shiner's visual spectrum displays a red shift in response to increased turbidity.