Characidae

DNA barcoding can be an effective tool for fast and accurate species-level identification based on sequencing of the mitochondrial cytochrome c oxidase subunit (COI) gene. The diversity of this fragment can be used to estimate the richness of the respective species. In this study, we explored the use of DNA barcoding in a group of ornamental freshwater fish of the genus Hyphessobrycon. We sequenced the COI from 10 species of Hyphessobrycon belonging to the ''Rosy Tetra Clade'' collected from the Amazon and Negro River basins and combined our results with published data. The average conspecific and congeneric Kimura 2-parameter distances were 2.3% and 19.3%, respectively. Six of the 10 species were easily distinguishable by DNA barcoding (H. bentosi, H. copelandi, H. eques, H. epicharis, H. pulchrippinis, and H. sweglesi), whereas the remaining species (H. erythrostigma, H. pyrrhonotus, H. rosaceus and H. socolofi) lacked reciprocal monophyly. Although the COI gene was not fully diagnostic, the discovery of distinct evolutionary units in certain Hyphessobrycon species under the same specific epithet as well as haplotype sharing between different species suggest that DNA barcoding is useful for species identification in this speciose genus.

Copper oxide nanoparticles (nCuO) are widely used in boat antifouling paints and are released into the environment, potentially inducing toxicity to aquatic organisms. The present study aimed to understand the effects of nCuO and dissolved copper (Cu) on two ornamental Amazon fish species: dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi). Fish were exposed to 50% of the LC for nCuO (dwarf cichlid 58.31μgL and cardinal tetra 69.6μgL) and Cu (dwarf cichlid 20μgL and cardinal tetra 22.9μgL) for 24, 48, 72 and 96h. Following exposure, aerobic metabolic rate (ṀO), gill osmoregulatory physiology and mitochondrial function, oxidative stress markers, and morphological damage were evaluated. Our results revealed species specificity in metabolic stress responses. An increase of ṀO was noted in cardinal tetra exposed to Cu, but not nCuO, whereas ṀO in dwarf cichlid showed little change with either treatment. In contrast, mitochondria from dwarf cichlid exhibit...

This study evaluated the effect of dietary supplementation with L-tryptophan (L-TRP), a serotonin precursor, on the aggressiveness of juvenile matrinxã Brycon amazonicus. Fish were kept in individual aquaria for 7 days receiving the diets: D1 (control: 0.47% of TRP), D2 (0.94% of TRP), D3 (1.88% of TRP), and D4 (3.76% of TRP). After this, they were grouped with an intruder fish to establish a resident-intruder relationship during periods of 20 min. Blood cortisol, glucose, chloride, sodium and calcium; hemoglobin, hematocrit, red blood cell count and volume; liver glycogen and lipids were measured. Territoriality had significant effect on the aggressiveness of matrinxã (the residents were more aggressive than intruders, P \ 0.001) and tryptophan significantly affected their behavior. Fish fed with the D2 diet presented a longer latency until the first attack (P = 0.0069) and bit the intruder fewer times (P = 0.0136) during the period of observation, compared to the control group. The frequency of bites and chases after the first attack was not affected by the dietary supplementation of TRP. Physiological variables were not significantly affected by the diet, except for a moderate increase in cortisol level in fish fed with D2 diet after the fight, indicating slight activation of the hypothalamus-pituitary-interrenal axis. The results show that juvenile matrinxã have aggressive and territorial behavior and that a diet containing 9.4 g TRP kg -1 alter their aggressiveness, without affecting the stress-related physiological parameters.

A new species of characid is described from the upper rio Machado, a tributary of the rio Madeira basin, Rondônia, Brazil. Hyphessobrycon lucenorum can be distinguished from all congeners by the unique combination of the presence of a conspicuous rounded humeral blotch and a broad and diffuse longitudinal stripe. The new species is included within the Hyphessobrycon agulha group. The high number of endemic species of fishes occurring in the headwater tributaries of three river systems (rio Madeira, rio Tapajós, and rio Paraguai) draining the watershed defined by the Chapada dos Parecis is discussed.

The genus Hyphessobrycon is included within the subfamily Tetragonopterinae. The species are generally small, do not exceed 70mm of standard length, are economically important as ornamental fish, with 128 valid species distributed from Southern Mexico to Rio La Plata in Argentina. The collections of fish were made with seines, in a single biotope, along shore in backwaters and working downstream. Measurements of the specimens were taken point to point with digital calipers. Observations of bone and cartilage structures were made on cleared and stained (C&S) specimens. The morphometric relationships between species were explored using a principal component analysis (PCA)using 21 variables. We described a new species, Hyphessobrycon chocoensis, from the Telembi River drainage of the Pacific versant of Colombia. The new species, Hyphessobrycon chocoensis, is distinguished from congeners not of the "flammeus" species group by: having a diffuse humeral spot, in lacking a dark s...

O manejo de peixes em cativeiro proporciona situações de estresse que influenciam diretamente na sanidade dos animais. Nessa situação, o estresse acarreta em uma maior movimentação dos peixes, resultando em perda de muco, escamas e quebra das nadadeiras. Outras reações negativas causadas por atividades de manejo ocorrem a níveis fisiológicos e bioquímicos, causando muitas vezes mortalidade. Neste contexto, o presente trabalho avaliou a influência de concentrações de eugenol na anestesia e tempo de recuperação do rosacéu Hyphessobrycon sp. O trabalho foi realizado no laboratório de aquicultura tropical, UFRA, Belém, PA. Um total de 42 peixes com peso médio de 0,36 ± 0,10 g e comprimento total médio de 2,28 ± 2,12 cm foram submetidos a sete concentrações de eugenol, 10, 20, 30, 40, 50, 60 e 70 mg L⁻¹, sendo monitorados até alcançarem o estágio de anestesia cirúrgica. Após essa etapa, os peixes foram transferidos para aquários com água sem a presença de eugenol para avaliação da recuperação. A temperatura média tanto na fase de indução a anestesia quanto na fase de recuperação foi de 30 ± 0,27 °C. Os peixes alcançaram o estágio de anestesia cirúrgica em todas as concentrações avaliadas. Em geral, as maiores concentrações proporcionaram os menores tempo de indução a anestesia, sendo que não ocorreram diferenças estatísticas entre os tempos de indução das concentrações de 30 a 70 mg L -1 . As concentrações entre 20 a 40 mg L -1 apresentaram tempos de indução a anestesia similares entre si. A concentração de 10 mg L -1 apresentou o maior tempo de indução a anestesia quando comparado com as demais concentrações, e esse foi de 226 ± 28 segundos. O tempo de recuperação do estágio de anestesia cirúrgica dos peixes submetidos a concentração de 10, 20, 30 e 40 mg L -1 de eugenol foi similar estatisticamente e variou de 41 ± 8 a 66 ± 16 segundos, respectivamente. As maiores concentrações (50, 60, 70 mg L -1 ) apresentaram um aumento no tempo de recuperação dos peixes, sendo que esses foram estatisticamente semelhantes entre as concentrações de 60 e 70 mg L -1 de eugenol. Não ocorreram diferenças significativas entre o tempo de recuperação dos peixes submetidos às concentrações de 10, 20, 30 e 40 mg L -1 , os quais foram menores e variaram de 41 ± 8 a 66 ± 16 segundos, respectivamente. Com os resultados encontrados nesse trabalho, recomenda-se que peixes ornamentais de pequeno porte, como o rosacéu, sejam anestesiados com segurança na concentração de 10 mg L -1 , pois apresentou um tempo de anestesia cirúrgica e recuperação dentro da faixa recomendada para peixes.

Hyphessobrycon taphorni and H. eschwartzae (Teleostei: Characidae) two new species of fish in the basin of Madre de Dios river, Peru. Hyphessobrycon with 129 valid species, is a genus of fish that has a great diversity of species in the Neotropical ichthyofauna, reaches its greatest diversity in the Amazon basin with about 70% of these species, is highly desired by hobbyists because of their beauty and color, and are still meeting new species. We analyzed specimens from the Departamento de Ictiología, Museo de Historia Natural de la Universidad Mayor de San Marcos, Lima, Perú (MUSM); and measurements of the specimens were taken point to point with digital calipers. Observations of bone and cartilage structures were made on cleared and stained (C&S) samples. The morphometric relationships between species using 21 variables were explored using a principal component analysis (PCA). Here we describe two new species, Hyphessobrycon taphorni and H. eschwartzae from the Madre de Dios River drainage, Peru. Hyphessobrycon taphorni sp. n. can be distinguished by the number of dorsal-fin rays (iii, 8), by the number of: pored lateral-line scales (4-5), teeth in the outer premaxillary row (1-2), teeth in the inner premaxillary row (7-8), by: the caudal-peduncle length (11.4-16.4% SL), number of lateral scales (28-29, except from H. loretoensis which has 29-30) and absence of a humeral spot (vs. present), it differs from H. loretoensis by the number of: scales between the lateral line and the anal fin origin (4 vs. 3) and maxillary teeth (2 vs. 3-4), and it differs from H. agulha by the number of branched pectoral-fin rays (11-12 vs. 9-10). Hyphessobrycon eschwartzae sp. n. is distinguished by the number of: simple anal-fin rays (iv), teeth on the dentary (13-15), teeth in the inner premaxillary row (6), teeth in the outer premaxillary row (3, except from H. heterorhabdus and H. loretoensis which have 3-4); it differs from H. loretoensis by the number of: pored lateral-line scales (7 vs. 9-10), scales between the lateral line and the dorsal-fin origin (5 vs. 3-4); it differs from H. agulha in the number of lateral scales (30-31 vs. 33-34), by the number of: predorsal scales (9 vs. 10), maxillary teeth (4 vs. 0-1); in having in life a red lateral stripe above the dark lateral stripe that extends from the posterior part of the opercle to the caudal peduncle (vs. absent) and by the presence of bony hooks in mature males only on the anal fin (vs. hooks on all fins, including the caudal). Rev. Biol. Trop. 61 (2): 859-873. Epub 2013 June 01.

Intensification of aquaculture production systems exposes fish to numerous stressors, which may negatively affect their growth and limit profitability of aquaculture systems. This study determined effects of increasing levels of dietary mannanoligosaccharides on growth and intestine morphology of pacu. Fish (44.04 g) were randomly distributed into 32 tanks (500 L; 10 fishes per tank) and fed during 63 days with a commercial diet supplemented with 0.0; 0.2; 0.4; 0.6; 0.8; 1.0; 1.5 and 2.0% dietary mannanoligosaccharides. Growth parameters did not differ (P>0.05) between fish fed control diet and mannanoligosaccharide supplemented diets. Intestinal villi perimeter was performed in fish fed control diet, 0.4 and 1.5% dietary mannanoligosaccharides and also showed no differences (P>0.05) between treatments. Dietary supplementation of mannanoligosaccharides unclear did not have effects on pacu. Studies on the characterization of intestinal microbiota together with experiment that reproduce commercial fish production systems rearing conditions are necessary to determine the effective use of this dietary supplement for the species.

This study focused on intra and interspecific variations in the diet of small species in the Pelotas River, upper Uruguay River ecoregion. We tested the hypothesis that five small characids coexist via resource partitioning. Samplings were performed quarterly between August 2013 and May 2014 at 14 sites in the Pelotas River basin, using gillnets of different mesh sizes, seines, cast nets and electrofishing. In this study, the contents of 1,253 stomachs were analysed from Astyanax dissensus, A. paris, A. saguazu, A. xiru and Bryconamericus patriciae. The main food resources consumed were aquatic insects, leaves, seeds and detritus. There were significant seasonal intra and interspecific variations in the use of food resources by the five species. Permutational analysis of multivariate dispersions results indicated significant differences in individual intraspecific variability between the sampled periods, with the highest values found in November and February because of an increase i...

With the aim of creating an inventory of the metazoan gill parasites of Salminus hilarii in the Taquari River, state of São Paulo, Brazil, five species of monogeneans (Anacanthorus contortus, A. bicuspidatus, Annulotrematoides parisellei, Jainus iocensis and Tereancistrum arcuatus) are reported the first time for this host. A total of 28 fish were sampled quarterly between April 2011 and January 2012, with 10 hosts in a lentic ecosystem and 18 in a lotic ecosystem. Quantitative ecological descriptors (prevalence, intensity of infestation and abundance) were calculated for the purpose to comparing the two ecosystems sampled (lentic and lotic ecosystems). However, no quantitative difference between the lentic and lotic ecosystems was observed. The present study has made available a checklist for species of the genus Anacanthorus and their hosts and geographical distribution in the Neotropical region up to the present time.

As part of a biological inventory of the Rio Lacantún basin in the Biosphere Reserve of Montes Azules from Chiapas State (southeastern, Mexico), the following monogenoid ectoparasites infecting the external surface of the anal opening and the gill lamellae of the freshwater fish Astyanax aeneus (Characidae) in ten streams were found: Cacatuocotyle chajuli sp. nov. (anus), Cacatuocotyle exiguum sp. nov., and Cacatuocotyle sp. (gill lamellae). C. chajuli is differentiated from its single congener, Cacatuocotyle paranaensis (Boeger et al. Syst Parasitol 36:75-78, 1997), from the gills of Characidium lanei (Characidae) from Paraná Brazil, in having a noticeably V-shaped haptoral bar and larger hooks and anchors. C. exiguum differs from these two latter species in the size of its anchors. Illustrations and data on morphological and biometric variability of individual specimens of C. chajuli and C. exiguum from different streams are provided. The present data support the statement about three species of Astyanax, which harbor the richest monogenoidean diversity in the Neotropics with a total of 18 species reported up to now. Occurrences of species of Cacatuocotyle on different sites of infection on three distant host species [including a Neotropical cichlid (Cichlidae) species] suggest that these monogenoideans switching to new hosts can result in the availability of potential hosts within the same habitat instead of showing signs of preferential switching between closely related hosts or on their respective microhabitats.

Intensive fish production systems are characterized by 100% artificial feeding, so any dietary imbalances or deficiencies may lead to diseases outbreaks and economic losses. This study was set out to determine the effects of increasing levels of dietary vitamin E on growth and hematology of juvenile pacu. Fishes were fed for 90 days, twice a day until apparent satiation with semi-purified diets containing 0.0; 25; 50; 150; 300 or 600 mg.kg-1 diet DL-α-tocopheryl acetate in a completely randomized design trial (n=4); biometrical and hematological data were collected and analyzed. Fishes fed with vit E diet (150 mg.kg-1) showed higher (p<0.05) weight gain and specific growth. Hematocrit, erythroblast number and total plasma protein were increased (p<0.05) in fishes fed diet with no vit E diet. Vitamin E supplementation in artificial diets for pacu is essential for growth and maintenance of normal erythropoiesis.

A molecular phylogeny of Planaltina, including the three previously described species and an undescribed species, is presented. The monophyly of the genus, included in Diapomini, is strongly supported. Its sister group, the remaining Diapomini, includes only species without modified caudal-fin squamation in the present analysis (species of Diapoma with caudal organs were not sampled). Creagrutus is sister to Planaltina plus remaining Diapomini instead of Planaltina being sister to Creagrutus plus Diapomini, as a previous analysis had suggested. Species of Planaltina form two clades: P. britskii plus the new species, with low support (< 50%); and P. myersi plus P. glandipedis, with higher support. Planaltina is rediagnosed from all Characidae based on the morphology of the caudal organ, the absence of a humeral spot and the presence of a complete lateral line. Comments on the caudal-fin squamation of Diapoma and Lepidocharax burnsi, on the type-series of L. burnsi and on the geogr...

Erythrocharax altipinnis is described from the Serra do Cachimbo, Pará, Brazil. The new taxon is distinguished from all of the Characidae genera by having the pelvic bones firmly attached through the isquiatic processes; a nearly triangular hiatus in the musculature covering the anterior chamber of the swim bladder between the first and second pleural ribs (pseudotympanum); the pedunculate, notably expanded and distally compressed teeth in both jaws; circumorbital series represented by antorbital and four infraorbital bones with laterosensory canals not enclosed; a single tooth row in the premaxillary with the teeth perfectly aligned and similar in shape and cusp number; the first three branched dorsal-fin rays distinctly elongate in males; a bright red adipose and caudal fins in life; a conspicuous dark midlateral stripe extending from the opercle to the tip of the median caudal-fin rays; and by the absence of a humeral spot. The phylogenetic position of the new taxon is discussed using morphological and molecular datasets, with conflicting results of both approaches discussed. Additionally, a summarized discussion on the current problems in the Characidae taxonomy is presented and the principal biases in the morphological dataset are also discussed.

Brycon orthotaenia is an important fish for commercial and sport fishing and may reach 7 kg in body weight; it is endangered in some regions of Brazil's São Francisco River Basin. Breeders were subjected to spawning induction to analyse the early development; oocytes and semen were obtained by manual extrusion and fertilization was carried out using the dry method. After fertilization, eggs were kept in incubators at 24 • C. Egg samples were collected every 10 min until hatching in order to monitor embryonic development and were analysed and photographed. Larvae samples were collected daily until the seventh day to analyse the larvae development; larvae were fixed in Bouin's fluid and subjected to routine histological and histochemical techniques for glycoprotein and glyco-conjugated detection. Oocyte extrusion occurred 6 h after the second hormone dose at 26 • C. The recently extruded oocytes were spherical, dark green and non-adhesive, with a diameter of 1479.67 ± 53.18 and 3094.60 ± 80.34 m after hydration. The blastopore closure occurred within 7 h 30 min of fertilization and the fertilization rate was 50.0 ± 5.5 % at 24 • C. Embryonic development was completed within 21 h 30 min of fertilization. Complete yolk sac resorption and mouth opening occurred on the third day after hatching, at which time an adhesive organ with mucosubstances was observed. On the third day, an olfactory chamber with cilia and intense cannibalism amongst the larvae was observed. The complete differentiation of the digestive system occurred on the fifth day and the nervous and sensorial systems differentiation occurred on the sixth to seventh days.

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 h LC 50 of neem leaf extract for juveniles P. lineatus was estimated as 4.8 g L − 1 ; the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L − 1 or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L − 1 and 5.0 g L − 1 neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L − 1 . Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species.

Fish biodiversity of aquatic ecosystems is highly threatened by different economic activities driven by human populations, and its description is increasingly a priority. For the Cauca-Magdalena River system we have described 14 species, and the purpose of this paper was to describe three new species belonging to the same genus Hemibrycon from the Nare and Guatapé River drainages of the middle Magdalena River, Colombia. The description was based on a series of 200 specimens, and the use of morphometric, meristic and osteological characters, as well as fish distribution and morphogeometric analytical methods. We have found that Hemibrycon fasciatus n. sp. (n = 54) differs from other species of Hemibrycon (that also have a vertical humeral spot) in having: melanophores outlining the posterior margins of the scales along sides of body; humeral spot extending onto posterior margin of opercle; a dark lateral stripe, formed by deep pigment that is continuous with the peduncular spot; the ...

The relationship between growth rate and environmental space is an unresolved issue in teleosts. While it is known from aquaculture studies that stocking density has a negative relationship to growth, the underlying mechanisms have not been elucidated, primarily because the growth rate of populations rather than individual fish were the subject of all previous studies. Here we investigate this problem in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling form (surface fish) and several blind cave-dwelling (cavefish) forms. Surface fish and cavefish are distinguished by living in spatially contrasting environments and therefore are excellent models to study the effects of environmental size on growth. Multiple controlled growth experiments with individual fish raised in confined or unconfined spaces showed that environmental size has a major impact on growth rate in surface fish, a trait we have termed space dependent growth (SDG). In contrast, SDG has regressed to different degrees in the Pachó n and Tinaja populations of cavefish. Mating experiments between surface and Pachó n cavefish show that SDG is inherited as a dominant trait and is controlled by multiple genetic factors. Despite its regression in blind cavefish, SDG is not affected when sighted surface fish are raised in darkness, indicating that vision is not required to perceive and react to environmental space. Analysis of plasma cortisol levels showed that an elevation above basal levels occurred soon after surface fish were exposed to confined space. This initial cortisol peak was absent in Pachó n cavefish, suggesting that the effects of confined space on growth may be mediated partly through a stress response. We conclude that Astyanax reacts to confined spaces by exhibiting SDG, which has a genetic component and shows evolutionary regression during adaptation of cavefish to confined environments.

Sixteen polymorphic, dinucleotide microsatellite loci were developed for Rhoadsia altipinna, a small characid fish from impacted rivers in south western Ecuador. None of the loci were in linkage disequilibrium or deviated significantly from Hardy–Weinberg equilibrium after sequential Bonferroni correction. Variability was relatively high with allelic richness ranging between 2 and 22 alleles per locus (average = 9.125), observed heterozygosity ranging between 0.125 and 0.958 (average = 0.695), and expected heterozygosity ranging between 0.120 and 0.952 (average = 0.736)

Cholinesterase (ChE) activity was measured in Astyanax bifasciatus maintained in controlled conditions. Muscle ChE activity of individuals collected in field conditions in two seasons was compared among specimens collected in seven streams (forest and rural) of the lower Iguaçu river basin in association with physical, chemical, pesticides and biological factors. Significant differences in muscle ChE activity between control fish and fish collected in streams in both seasons were found, with higher activity in natural conditions. This the first time that differences in muscle ChE activity have been found among fish collected from different streams, suggesting synergism among multiple factors (e.g. temperature, pH, animal weight) and ecological attributes (richness and abundance) as influencing the variation in biomarkers. It is necessary to evaluate the quality of aquatic environments for a more accurate biomonitoring approach.

Brycon gouldingi is an endemic species from Tocantins-Araguaia basin, used as a food source by riverine communities and relevant to aquaculture. Information about the initial morphology of B. gouldingi, a recently described species, is absent. In the present study, we analysed the fertilization and the embryonic development of this species based on light and scanning electron microscopy. After collection of adult specimens in Mortes River - Mato Grosso, Brazil, adaptation to captivity and induced spawning at Buriti Fishculture, Nova Mutum - Mato Grosso, Brazil, in December 2007 and January 2008, samples were collected at pre-defined periods from egg extrusion up to larval hatching, which occurred at 13.9 ± 0.06 h post-fertilization (hpf) in average. At the moment of extrusion, the eggs were slightly ovoid bearing a single micropyle per oocyte with a funnel-shaped micropyle canal and vestibule covered with longitudinal folds, typical of the genus Brycon. The embryonic development of ...

Monogeneans are the parasites mostly found on the body surface and gills of fish and can cause large losses in farmed fish. Some studies demonstrate elevated parasitic levels causing hematological alterations. But few of them relate the effects of parasitism on the hematology and histopathology of native freshwater farmed fish. This study evaluated the host-parasite relationship in pacu (Piaractus mesopotamicus) parasitized by the monogenean Anacanthorus penilabiatus. Hematological and parasitological assessments were obtained in 60 fish captured in a fish farm located in Dourados, State of Mato Grosso do Sul, Central Brazil. Fish were analyzed in different categories of parasite number: class I (n=13; 0-200 parasites), class II (n=17; 201-1200 parasites); class III (n=7; 1201-2200 parasites); and class IV (n=23; more than 2200 parasites per host). The highest levels of parasitism caused significant decrease (p<0.05) in the hematocrit, red blood cells (RBC), mean hemoglobin conce...

Si bien la Huasteca es una región de amplia biodiversidad y cultura, hoy en día es un territorio altamente vulnerable a la degradación ambiental, causada principalmente por las actividades humanas que se relacionan directa e indirectamente con el uso y extracción del agua, lo cual pone en peligro no sólo al pez ciego de las cavernas, sino a todos los organismos acuáticos de una de las cuencas de mayor importancia y con mayor número de especies de peces en México, por su alto porcentaje de endemismos que se derivan de factores como: a) su ubicación geográfica de transición, entre la región Neotropical y la región Neártica, b) la adaptación de varios grupos marinos a las corrientes de agua dulce, y c) la gran diversidad geológica de la región (geodiversidad).

RESUMEN. Se presenta una descripción histológica de los núcleos neuronales en las distintas regiones del cerebro del pez tetra cola roja Aphyocharax anisitsi. Se muestra, además, la morfología externa del cerebro que se estudió cuan-tificando la longitud y el área de los principales lóbulos (bulbos olfatorios, hemisferios telencefálicos, lóbulos ópticos y cerebelo). Se realizó un ANOVA para determinar posibles diferencias significativas entre dichas estructuras. Se fija-ron diez individuos en solución de Bouin y se disecaron los cerebros para describir la anatomía externa y la captura digital de imágenes. Para estudiar la topología interna se procesaron los cerebros para un protocolo histológico de para-fina con cortes en micrótomo y tinción de Nissl. Los resultados indicaron la presencia de los lóbulos típicos descriptos para otras especies de teleósteos. El análisis morfométrico mostró los lóbulos ópticos de mayor área y longitud y los bulbos olfatorios de menor tamaño. Dichos resultados sugieren predominio del sistema visual. El cerebelo presentó mayor longitud total que los hemisferios telencefálicos sin diferencias respecto al área. En lo que concierne a la topo-logía interna, se observó a los núcleos asociados al cerebro anterior, medio y posterior. Los núcleos hallados en las dis-tintas regiones no presentaron diferencias respecto de aquellos descriptos para otros miembros del Superorden Ostariophysi como el pez cebra (Danio rerio) o el neón cardenal (Paracheirodon axelrodi).
SUMMARY. In this work a histological description of the neuronal nuclei present in the different regions of bloodfin tetra fish Aphyocharax anisitsi brain is presented. In addition, its external morphology studied quantifying the length and area of the main lobes (olfactory bulbs, telencephalic hemisphere, optic lobes and cerebellum) is shown. An ANOVA was performed to determine any possible significant differences among said structures. Ten individuals were fixed in Bouin's solution and brains dissected to describe the external anatomy and digital image capture. In order to study the internal topology brains were processed for a paraffin histological protocol with microtome sections and Nissl stain. Results indicated the presence of the typical lobes described for other teleost species. The morphometrical analy

The unparalleled diversity of tropical ecosystems like the Amazon Basin has been traditionally explained using spatial models within the context of climatic and geological history. Yet, it is adaptive genetic diversity that defines how species evolve and interact within an ecosystem. Here, we combine genome scans, population genetics and sequence-based phylogeographic analyses to examine spatial and ecological arrangements of selected and neutrally evolving regions of the genome of an Amazonian fish, Triportheus albus. Using a sampling design encompassing five major Amazonian rivers, three hydrochemical settings, 352 nuclear markers and two mitochondrial DNA genes, we assess the influence of environmental gradients as biodiversity drivers in Amazonia. We identify strong divergent natural selection with gene flow and isolation by environment across craton (black and clear colour)-and Andean (white colour)-derived water types. Furthermore, we find that heightened selection and population genetic structure present at the interface of these water types appears more powerful in generating diversity than the spatial arrangement of river systems and vicariant biogeographic history. The results from our study challenge assumptions about the origin and distribution of adaptive and neutral genetic diversity in tropical ecosystems. In addition, they have important implications for measures of biodiversity and evolutionary potential in one of the world's most diverse and iconic ecosystems.

Aphyocharax anisitsi is recorded for the first time from the upper Bermejo River, Argentina, in the provinces of Salta and Jujuy. This represents a range extension of the known distribution of approximately 600 km. Also, collection specimens of A. dentatus from this area are cited for first time.

The retina is the light-sensitive tissue of the eye that facilitates vision. Mutations within genes affecting eye development and retinal function cause a host of degenerative visual diseases, including retinitis pigmentosa and anophthalmia/microphthalmia. The characin fish Astyanax mexicanus includes both eyed (surface fish) and eyeless (cavefish) morphs that initially develop eyes with normal retina; however, early in development, the eyes of cavefish degenerate. Since both surface and cave morphs are members of the same species, they serve as excellent evolutionary mutant models with which to identify genes causing retinal degeneration. In this study, we crossed the eyed and eyeless forms of A. mexicanus and quantified the thickness of individual retinal layers among 115 F(2) hybrid progeny. We used next generation sequencing (RAD-seq) and microsatellite mapping to construct a dense genetic map of the Astyanax genome, scan for quantitative trait loci (QTL) affecting retinal thick...

A new species of Rhinopetitia is described from the Rio Teles Pires, a major tributary of the Rio Tapajós. The new taxon is distinguished from its only congener, Rhinopetitia myersi, by having all premaxillary teeth in both rows with seven to nine cusps, maxillary teeth with seven or eight cusps, a distinct dark midlateral stripe on the body and a round humeral blotch (v. outer series of premaxillary teeth with three cusps and inner series of premaxillary teeth with three to five cusps, maxillary teeth with three to five cusps, the absence of a dark midlateral stripe and humeral blotch). Putative characters suggesting a close relationship between Rhinopetitia, Bryconacidnus, Ceratobranchia, Monotocheirodon, Odontostoechus, Othonocheirodus and Rhinobrycon are presented. This putative clade is included in the Stevardiinae, a monophyletic group within the Characidae.

Background: Surface populations of Astyanax mexicanus, living in rivers like their common ancestors, school, while several, independently derived cave populations of the same species have lost schooling behavior. Results: We quantify schooling behavior in individual A. mexicanus and identify quantitative trait loci (QTL) for this trait. We find that the evolutionary modulation of schooling has both vision-dependent and-independent components. We also quantify differences in the lateral line and vision between cavefish and surface fish and relate these differences to the evolutionary loss of schooling behavior. We provide evidence that a monoamine neurotransmitter may have played a role in the evolution of schooling behavior. Conclusions: We find that vision is essential for schooling tendency in A. mexicanus, while the lateral line has a small effect on this behavior. Schooling behavior in A. mexicanus has evolved both through changes in sensory systems and through changes in genetic loci that likely act downstream of sensory inputs.

Hyphessobrycon with 129 valid species, is a genus of fish that has a great diversity of species in the Neotropical ichthyofauna, reaches its greatest diversity in the Amazon basin with about 70% of these species, is highly desired by hobbyists because of their beauty and color, and are still meeting new species. We analyzed specimens from the Departamento de Ictiología, Museo de Historia Natural de la Universidad Mayor de San Marcos, Lima, Perú (MUSM); and measurements of the specimens were taken point to point with digital calipers. Observations of bone and cartilage structures were made on cleared and stained (C&S) samples. The morphometric relationships between species using 21 variables were explored using a principal component analysis (PCA). Here we describe two new species, Hyphessobrycon taphorni and H. eschwartzae from the Madre de Dios River drainage, Peru. Hyphessobrycon taphorni sp. n. can be distinguished by the number of dorsal-fin rays (iii, 8), by the number of: pore...

SUMMARY Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or trapped in a gill net. These sounds are generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder. The piranha swimbladder is thought to play an important role in sound production as an impedance-matching device and as a resonator. However, the vibratory capacities of the cranial and caudal sacs and the exact role of both sacs in sound production remain poorly understood. In this study, three sounds were each associated to a specific behaviour. The first sound (type 1) was produced during frontal display; it had numerous pulses and lasted 140!±17 ms, with a fundamental frequency of 120±4 Hz. It corresponded to the sound made by hand-held fishes. The second sound (type 2) was produced during circling an...

The study evaluated the sublethal effects of the herbicides glyphosate (Roundup) and diuron (Hexaron) and the mixture of them, used extremely in agriculture, through biomarkers in fish. The glutathione S-transferase activity increased (74%) and catalase activity decreased (37%) at the higher exposure concentration of Hexaron in comparison to the control group, suggesting an activation of this metabolism route. Membrane damage was observed at the higher exposure of Roundup and in the mixture group compared to the control group, which can be related to the nuclear alterations observed in these exposed groups. The cholinesterase activity was also inhibited (37%) in mixture group compared to the control group and no gill morphology damage was found. The results suggested a potential synergic effect in some analysed parameters.

We investigated differentiation processes in the Neotropical fish Astyanax that represents a model system for examining adaptation to caves, including regressive evolution. In particular, we analyzed microsatellite and mitochondrial data of seven cave and seven surface populations from Mexico to test whether the evolution of the cave fish represents a case of parallel evolution. Our data revealed that Astyanax invaded northern Mexico across the Trans-Mexican Volcanic Belt at least three times and that populations of all three invasions adapted to subterranean habitats. Significant differentiation was found between the cave and surface populations. We did not observe gene flow between the strongly eye and pigment reduced old cave populations (Sabinos, Tinaja, Pachon) and the surface fish, even when syntopically occurring like in Yerbaniz cave. Little gene flow, if any, was found between cave populations, which are variable in eye and pigmentation (Micos, Chica, Caballo Moro caves), and surface fish. This suggests that the variability is due to their more recent origin rather than to hybridization. Finally, admixture of the young Chica cave fish population with nuclear markers from older cave fish demonstrates that gene flow between populations that independently colonized caves occurs. Thus, all criteria of parallel speciation are fulfilled. Moreover, the microsatellite data provide evidence that two co-occurring groups with small sunken eyes and externally visible eyes, respectively, differentiated within the partly lightened Caballo Moro karst window cave and might represent an example for incipient sympatric speciation.

The characid fish species Astyanax mexicanus offers a classic comparative model for the evolution of sensory systems. Populations of this species evolved in caves and became blind while others remained in streams (i.e. surface fish) and retained a functional visual system. The flow-sensitive lateral line receptors, called superficial neuromasts, are more numerous in cavefish than in surface fish, but it is unclear whether individual neuromasts differ in sensitivity between these populations. The aims of this study were to determine whether the neuromasts in cavefish impart enhanced sensitivity relative to surface fish and to test whether this aids their ability to sense flow in the absence of visual input. Sensitivity was assessed by modeling the mechanics and hydrodynamics of a flow stimulus. This model required that we measure the dimensions of the transparent cupula of a neuromast, which was visualized with fluorescent microspheres. We found that neuromasts within the eye orbit and in the suborbital region were larger and consequently about twice as sensitive in small adult cavefish as in surface fish. Behavioral experiments found that these cavefish, but not surface fish, were attracted to a 35 Hz flow stimulus. These results support the hypothesis that the large superficial neuromasts of small cavefish aid in flow sensing. We conclude that the morphology of the lateral line could have evolved in cavefish to permit foraging in a cave environment.

The genus Hyphessobrycon is included within the subfamily Tetragonopterinae. The species are generally small, do not exceed 70mm of standard length, are economically important as ornamental fish, with 128 valid species distributed from Southern Mexico to Rio La Plata in Argentina. The collections of fish were made with seines, in a single biotope, along shore in backwaters and working downstream. Measurements of the specimens were taken point to point with digital calipers. Observations of bone and cartilage structures were made on cleared and stained (C&S) specimens. The morphometric relationships between species were explored using a principal component analysis (PCA)using 21 variables. We described a new species, Hyphessobrycon chocoensis, from the Telembi River drainage of the Pacific versant of Colombia. The new species, Hyphessobrycon chocoensis, is distinguished from congeners not of the "flammeus" species group by: having a diffuse humeral spot, in lacking a dark s...

Some species of the genus Characidium have heteromorphic ZZ/ZW sex chromosomes with a totally heterochromatic W chromosome. Methods for chromosome microdissection associated with chromosome painting have become important tools for cytogenetic studies in Neotropical fish. In Characidium cf. fasciatum, the Z chromosome contains a pericentromeric heterochromatin block, whereas the W chromosome is completely heterochromatic. Therefore, a probe was produced from the W chromosome through microdissection and degenerate oligonucleotideprimed polymerase chain reaction amplification. FISH was performed using the W probe on the chromosomes of specimens of this species. This revealed expressive marks in the pericentromeric region of the Z chromosome as well as a completely painted W chromosome. When applying the same probe on chromosome preparations of C. cf. gomesi and Characidium sp., a pattern similar to C. cf. fasciatum was found, while C. cf. zebra, C. cf. lagosantense and Crenuchus spilurus species showed no hybridization signals. Structural changes in the chromosomes of an ancestral sexual system in the group that includes the species C. cf. gomesi, C. cf. fasciatum and Characidium sp., could have contributed to the process of speciation and could represent a causal mechanism of chromosomal diversification in this group. The heterochromatinization process possibly began in homomorphic and homologous chromosomes of an ancestral form, and this process could have given rise to the current patterns found in the species with sex chromosome heteromorphism.

Caldasia 36(2): xx-xx. 204 ABSTRACT Hemibrycon brevispini is a Neotropical characid fish endemic in La Venada Creek, a headwater tributary of the Quindío River of Colombia (Cauca River drainage). It is mainly a diurnal insectivore with a diet dominated by benthic dipterans (Chironomidae, Simuliidae, Psychodidae, Culicidae, Calliphoridae, Dixidae and Muscidae), hymenopterans (Formicidae and Vespidae) and ephemeropterans (Baetidae), as well as allochthonous prey and items eaten accidentally. Microhabitats of mountain streams with lower water velocity tend to have more riparian vegetation and the associated terrestrial arthropods that are consumed by H. brevispini. It has three peaks in reproduction: December, April and August. Average fecundity was 776 mature oocytes per female.

A freshwater fish Roeboides loftini n.sp. is described from the Río Coclé del Norte drainage of the Atlantic versant of Panamá. The new species differs from other species of the Roeboides guatemalensis-group by the number of perforated scales on the lateral line (83-100), body depth (31.8-36.1%), predorsal distance (49.1-51.9%) and the shape of the humeral spot. Rev. Biol. Trop. 59 (4): 1663-1667. Epub 2011 December 01.

Phenotypic variation is important for evolutionary processes because it can allow local adaptation, promote genetic segregation, and ultimately give rise to speciation. Lacustrine systems provide a unique opportunity to study the mechanisms by which sister species can co-occur by means of ecological segregation. The fish genus Astyanax is characterized by high levels of phenotypic variability, providing an excellent model for the study of local specialization. Here, we analyze the morphological specializations through geometric morphometrics of two sympatric species described as different genera: Bramocharax caballeroi endemic to Lake Catemaco, and the widely distributed Astyanax aeneus. Additionally, we assess the correlation between phenotypic and genetic structure, and the phylogenetic signal of morphological variation. We examined body size and shape variation in 196 individuals and analyzed mitochondrial cytochrome b sequences in 298 individuals. Our results confirm the striking morphological divergence among the sympatric characids. Differences between them were mainly found in the body depth and profile and orientation of the head, where B. caballeroi in contrast with the A. aeneus, presented a fusiform body and an upward mouth. Moreover, different growth trajectories were observed among morphotypes, suggesting that a heterochronic process could be involved in the diversification of our study system. Morphological differences did not correspond with the molecular differentiation, suggesting high levels of homoplasy among the lineages of B. caballeroi morphs. J. Morphol. 000:000-000,

Background: With nearly 1,100 species, the fish family Characidae represents more than half of the species of Characiformes, and is a key component of Neotropical freshwater ecosystems. The composition, phylogeny, and classification of Characidae is currently uncertain, despite significant efforts based on analysis of morphological and molecular data. No consensus about the monophyly of this group or its position within the order Characiformes has been reached, challenged by the fact that many key studies to date have non-overlapping taxonomic representation and focus only on subsets of this diversity. Results: In the present study we propose a new definition of the family Characidae and a hypothesis of relationships for the Characiformes based on phylogenetic analysis of DNA sequences of two mitochondrial and three nuclear genes (4,680 base pairs). The sequences were obtained from 211 samples representing 166 genera distributed among all 18 recognized families in the order Characiformes, all 14 recognized subfamilies in the Characidae, plus 56 of the genera so far considered incertae sedis in the Characidae. The phylogeny obtained is robust, with most lineages significantly supported by posterior probabilities in Bayesian analysis, and high bootstrap values from maximum likelihood and parsimony analyses.

Background and aims. We analyzed a small and wide geographically distributed Neotropical freshwater fish, the Piabina argentea from the Upper Paraná Basin, to check the hypothesis that this species is composed of more than one biological unit, since it has a limited dispersion, through the DNA barcode technique. Materials and methods. Partial mitochondrial COI and CytB gene sequences were obtained for 58 specimens drawn from 13 localities. Results. Phylogenetic analysis revealed six major clusters of P. argentea. Kimura-two-parameter (K2P) genetic divergences among these six P. argentea clusters ranged from 2 to 5.6% and from 2.3 to 5.4% for COI and CytB genes, respectively, and these values were on average approximately nine times greater than intra-cluster K2P divergences. The fixation index (F ST ) among clusters showed very high values and the haplotype network analysis displayed seven unconnected units. Conclusion. These results reinforce the hypothesis that the widely distributed P. argentea species concept as currently conceived actually represents more than one species (possibly six). These results demonstrate the efficacy of DNA barcoding for the discovery of hidden diversity in Neotropical freshwater fishes, and we conclude that barcoding is a useful tool for alpha taxonomy.