EELS

The PCB contamination of fish from the Gironde Estuary (France) was investigated. PCB distribution differed between lean, low-fat and high-fat species. A process of biomagnification was observed in the Gironde estuarine fish assemblage. Health concerns about fish flesh contamination were revealed.

The Elopomorpha (eels and relatives) is a morphologically diverse group of predominantly marine teleost fishes comprising about 1000 species placed in 25 families. It is one of the three major living teleost lineages along with the Osteoglossomorpha and Clupeocephala. Among a few morphological synapomorphies that have been offered as evidence for the monophyly of the Elopomorpha, the remarkable leptocephalus larvae stand out. Several studies aiming at reconstructing the elopomorph phylogeny using morphological or molecular characters led to inconsistent results. In this study, we have tested previous hypotheses regarding inter-and intra-relationships of the Elopomorpha using a multi-locus dataset composed of three nuclear and three mitochondrial genes. Our analyses were based on likelihood phylogenetic reconstruction methods using different character-weighting data matrices and gene partition schemes to assess reliability of our findings. Our results confirm the respective monophyly of the Elopomorpha, Osteoglossomorpha and Clupeocephala. The majority of our analyses identify the Elopomorpha as the sister group of a clade containing the rest of the Teleostei. Within the Elopomorpha, the Elopiformes is the sister group of the remaining taxa. The Albuliformes sensu Forey et al. (1996) and the Notacanthiformes are never sister-taxa in our phylogenetic trees, in contradiction with the recent mitogenomic hypothesis and current classification. Our results place the Notacanthiformes as the sister group of the Anguilliformes, including Saccopharyngiformes. Among anguilliforms, the families Congridae and Muraenesocidae are not monophyletic. The recently discovered anguilliform ''living fossil'' family Protanguillidae is not the sister group of the remaining Anguilliformes, instead, the sister group of the Synaphobranchidae. Based on the results presented here, we propose a revised classification for the Elopomorpha, comprised of four orders, including a resurrected Notacanthiformes but surrendering the Saccopharyngiformes. Within Anguilliformes, we recognized four monophyletic suborders named Protanguilloidei, Muraenoidei, Anguilloidei, and Congroidei.

The one-stripe spiny eel, Macrognathus aral (Bloch and Schneider), has been gaining importance not only as a food fish but also as an aquarium fish for its body shape and behaviour. The overall M:F ratio recorded 1:0.27, both the males and females were mostly mature in May-August. The peak values of gonado somatic ratio (GSR) attained during May for males (1.3) and August forfemales (12.4) indicating that the fish have only one breeding season during summer. The range of ova diameter was found to vary from 0.3 to 1.4 mm, the absolute fecundity ranged from 250 (21.6 cm/27.4 g) to 5220.1 (27.2 cm/66.3 g) while relative fecundity ranged from 9.1 to 128.9. The 50% maturity is attained in length group of 10.1-14 cm for males and 14.1-18 cm for females. The species is a moderately fecund, isochronal spawner and having a restricted breeding season. The relationship between fecundity and body weight and length has also been discussed.

Naobranchia Hesse, 1863 is a genus of the family Lernaeopodidae. This report presents an illustrated description of the adult female and male of a new species of this genus collected from the gill filaments of Muraenesox bagio (Hamilton) (pike conger) caught off the coast of Richards Bay, KwaZulu-Natal, South Africa. Its morphological features were examined using light and scanning electron microscopy. Characteristic features of the female Naobranchia kabatana n. sp. include egg-sacs situated along most the length of the trunk, cephalothorax and trunk of about equal lengths, and eggsacs, lacking distinct sclerotised bands, which meet at the posterior end of the body and usually obscure the abdomen and caudal rami in ovigerous specimens. The male has no division into the cephalothorax and trunk, resulting in an unsegmented body with a prominent genito-abdominal papilla in a subterminal position.

Fish species possess many specific characteristics that support their use in ecotoxicology. Widely used in clinical research, peripheral blood mononuclear cells (PBMCs) can reasonably be exploited as relevant target cells in the assessment of environmental chemical toxicity. The current article focuses on the methods necessary to isolate, characterize, and culture fish PBMCs. These procedures were successfully applied on an endangered species, the European eel (Anguilla anguilla L.), and on an economically important and worldwide exported species, the Asian catfish (Pangasianodon hypophthalmus S.). Proteomic approaches can be useful to screen xenobiotic exposure at the protein expression level, giving the opportunity to develop early warning signals thanks to molecular signatures of toxicity. To date, a major limitation of proteomic analyses is that most protein expression profiles often reveal the same predominant and frequently differentially expressed families of proteins regardless of the experimental stressing conditions. The current study describes a methodology to get a postnuclear fraction of high quality isolated from fish PBMCs in order to perform subsequent subproteomic analyses. Applied on samples from eel, the subproteomic analysis (two-dimensional differential in-gel electrophoresis) allowed the identification by liquid chromatography-tandem mass spectrometry and searches in the full NCBInr (National Center for Biotechnology Information nonredundant) database of 66 proteins representing 36 different proteins validated through Peptide and Protein Prophet of Scaffold software.

Anguilliformes are an ecologically diverse group of predominantly marine fishes whose members are easily recognized by their extremely elongate bodies, and universal lack of pelvic fins. Recent studies based on mitochondrial loci, including full mitogenomes, have called into question the monophyly of both the Anguilliformes, which appear to be paraphyletic without the inclusion of the Saccopharyngiformes (gulper eels and allies), as well as other more commonly known eel families (e.g., Congridae, Serrivomeridae). However, no study to date has investigated anguilliform interrelationships using nuclear loci. Here we present a new phylogenetic hypothesis for the Anguilliformes based on five markers (the nuclear loci Early Growth Hormone 3, Myosin Heavy Polypeptide 6 and Recombinase Activating Gene 1, as well as the mitochondrial genes Cytochrome b and Cytochrome Oxidase I). Our sampling spans 148 species and includes 19 of the 20 extant families of anguilliforms and saccopharyngiforms. Maximum likelihood analysis reveals that saccopharyngiform eels are deeply nested within the anguilliforms, and supports the non-monophyly of Congridae and Nettastomatidae, as well as that of Derichthyidae and Chlopsidae. Our analyses suggest that Protanguilla may be the sister group of the Synaphobranchidae, though the recent hypothesis that this species is the sister group to all other anguilliforms cannot be rejected. The molecular phylogeny, time-calibrated using a Bayesian relaxed clock approach and seven fossil calibration points, reveals a Late Cretaceous origin of this expanded anguilliform clade (stem age $116 Ma, crown age $99 Ma). Most major (family level) lineages originated between the end of the Cretaceous and Early Eocene, suggesting that anguilliform radiation may have been facilitated by the recovery of marine ecosystems following the KP extinction.

Eel aquaculture is capture based and thus dependent on the fishery for juvenile glass eels. This fishery typically takes place in estuaries where salinity varies and ammonia levels can be elevated. Also, during capture and transport glass eels are kept at high densities and ammonia from endogenous production can increase to toxic levels. Ammonia is known to have detrimental effects on fish growth and survival. In the present study, the salinity dependence of ammonia sensitivity in glass eels acclimated to either seawater or freshwater was determined, and the possible role of branchial sodium/potassium adenosine triphosphatase (Na ϩ /K ϩ -ATPase) was investigated. Freshwater-acclimated glass eels were found to be more sensitive to ammonia with a lethal concentration to 50% of the test organisms (LC50) value for 96 h of 3.30 mM for total ammonia nitrogen (TAN) and 117 M for un-ionized ammonia (UIA), versus values of 4.95 mM and 138 M, respectively, for seawater-acclimated animals. Freshwater glass eels also had significantly lower body TAN levels than seawater-acclimated glass eels, although body accumulation profiles during exposure were similar. The higher branchial Na ϩ /K ϩ -ATPase activities in seawater glass eels might explain this difference in sensitivity; however, activities decreased significantly with increasing ammonia levels. There was also no salinity dependence of net ammonia flux rates (0.388 mol of TAN/g/h). Holding glass eels at high densities characteristic of transport conditions resulted in elevated ammonia concentrations to approximately 3 mM, which coincidently approaches to the freshwater LC50 value and may therefore contribute to mortality.

European eel migrate from freshwater or coastal habitats throughout Europe to their spawning grounds in the Sargasso Sea. However, their route (, 6000 km) and orientation mechanisms are unknown. Several attempts have been made to prove the existence of magnetoreception in Anguilla sp., but none of these studies have demonstrated magnetic compass orientation in earth-strength magnetic field intensities. We tested eels in four altered magnetic field conditions where magnetic North was set at geographic North, South, East, or West. Eels oriented in a manner that was related to the tank in which they were housed before the test. At lower temperature (under 12uC), their orientation relative to magnetic North corresponded to the direction of their displacement from the holding tank. At higher temperatures (12-17uC), eels showed bimodal orientation along an axis perpendicular to the axis of their displacement. These temperature-related shifts in orientation may be linked to the changes in behavior that occur between the warm season (during which eels are foraging) and the colder fall and winter (during which eels undertake their migrations). These observations support the conclusion that 1. eels have a magnetic compass, and 2. they use this sense to orient in a direction that they have registered moments before they are displaced. The adaptive advantage of having a magnetic compass and learning the direction in which they have been displaced becomes clear when set in the context of the eel's seaward migration. For example, if their migration is halted or blocked, as it is the case when environmental conditions become unfavorable or when they encounter a barrier, eels would be able to resume their movements along their old bearing when conditions become favorable again or when they pass by the barrier.

Mastacembelocleidus gen. n. (Monogenoidea: Dactylogyridae) is proposed to include two species collected and redescribed from spiny eels (Mastacembelidae) in India and Iraq: Mastacembelocleidus bam (Tripathi, 1959) comb. n. (syn. Ancyrocephalus bam Tripathi, 1959) from the gills of Macrognathus pancalus (new host record) and Macrognathus aculeatus (Synbranchiformes: Mastacembelidae) from Lucknow, India; and Mastacembelocleidus heteranchorus (Kulkarni, 1969) comb. n. (syn. Urocleidus heteranchorus Kulkarni, 1969) from the gills of Mastacembelus armatus from Lucknow, India, and Mastacembelus mastacembelus (new host record) from the environs of Erbil, Iraq (new locality record). Urocleidus rhyncobdelli Jain, 1959, Haliotrema tandani Agrawal et Singh, 1982 and Urocleidus raipurensis Dubey, Gupta et Agarwal, 1992 are considered junior subjective synonyms of M. bam.

The effects of aqueous extracts from a cyanobacteria species, Anabaena spiroides, on fish (Odontesthes argentinensis), crab (Callinectes sapidus), and purified eel acetylcholinesterase (AChE) activity were studied. In vitro concentrations of A. spiroides aqueous extract that inhibited 50% of enzyme activity (IC50) were 23.0, 17.2, and 45.0 mg/L of lyophilized cyanobacteria for eel, fish, and crab AChE, respectively. Eel AChE inhibition follows pseudo-first-order kinetics, the same expected for organophosphorus pesticides. Inhibition of purified eel AChE using mixtures of bioxidized malathion and aqueous extract of A. spiroides showed a competitive feature (p Ͻ 0.05), suggesting that the toxin(s) could be structurally similar to an organophosphorus pesticide and that toxins present in the aqueous extract inhibit the active site of the enzyme. The inhibition recovery assays using 2-PAM (0.3 mM) showed that (1) bioxidized malathion inhibited 27.0 Ϯ 1.1% of crab and 36.5 Ϯ 0.1% of eel AChE activities; (2) with bioxidized malathion ϩ 2-PAM the registered inhibition was 13.2 Ϯ 2.1% and 3.7 Ϯ 0.5% in crab and eel AChE, respectively; (3) the aqueous extract from A. spiroides inhibited 17.4 Ϯ 2.2% and 59.9 Ϯ 0.5% of crab and eel AChE activity, respectively; and (4) aqueous extract ϩ 2-PAM inhibited 22.3 Ϯ 2.6 and 61.5 Ϯ 0.2% of crab and eel AChEs. The absence of enzyme activity recovery after 2-PAM exposure could imply that the enzyme aging process was extremely quick.

Eel virus European X (EVEX) was first isolated from diseased European eel Anguilla anguilla in Japan at the end of seventies. The virus was tentatively classified into the Rhabdoviridae family on the basis of morphology and serological cross reactivity. This family of viruses is organized into six genera and currently comprises approximately 200 members, many of which are still unassigned because of the lack of molecular data. This work presents the morphological, biochemical and genetic characterizations of EVEX, and proposes a taxonomic classification for this virus. We provide its complete genome sequence, plus a comprehensive sequence comparison between isolates from different geographical origins. The genome encodes the five classical structural proteins plus an overlapping open reading frame in the phosphoprotein gene, coding for a putative C protein. Phylogenic relationship with other rhabdoviruses indicates that EVEX is most closely related to the Vesiculovirus genus and shares the highest identity with trout rhabdovirus 903/87.

In euryhaline teleosts, osmoregulation is a fundamental and dynamic process that is essential for the maintenance of ion and water balance, especially when fish migrate between fresh water (FW) and sea water (SW) environments. The European eel has proved to be an excellent model species to study the molecular and physiological adaptations associated with this osmoregulatory plasticity. The life cycle of the European eel includes two migratory periods, the second being the migration of FW eels back to the Sargasso Sea for reproduction. Various anatomical and physiological changes allow the successful transition to SW. The aim of this study was to use a microarray approach to screen the osmoregulatory tissues of the eel for changes in gene expression following acclimation to SW. Tissues were sampled from fish at selected intervals over a 5-mo period following FW/SW transfer, and RNA was isolated. Suppressive subtractive hybridization was used for enrichment of differentially expressed genes. Microarrays comprising 6,144 cDNAs from brain, gill, intestine, and kidney libraries were hybridized with appropriate targets and analyzed; 229 differentially expressed clones with unique sequences were identified. These clones represented the sequences for 95 known genes, with the remaining sequences (59%) being unknown. The results of the microarray analysis were validated by quantification of 28 differentially expressed genes by Northern blotting. A number of the differentially expressed genes were already known to be involved in osmoregulation, but the functional roles of many others, not normally associated with ion or water transport, remain to be characterized.

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Reef fishes disperse primarily as oceanic "pelagic" larvae, and debate continues over the extent of this dispersal, with recent evidence for geographically restricted (closed) populations in some species. In contrast, moray eels have the longest pelagic larval stages among reef fishes, possibly providing opportunities to disperse over great distances. We test this prediction by measuring mitochondrial DNA (mtDNA) and nuclear DNA variation in 2 species of moray eels, Gymnothorax undulatus (N = 165) and G. flavimarginatus (N = 124), sampled at 14-15 locations across the Indo-Pacific. The mtDNA data comprise 632 bp of cytochrome b and 596 bp of cytochrome oxidase I. Nuclear markers include 2 recombination-activating loci (421 bp of RAG-1 and 754 bp of RAG-2). Analyses of molecular variance and Mantel tests indicate little or no genetic differentiation, and no isolation by distance, across 22 000 km of the Indo-Pacific. We estimate that mitochondrial genetic variation coalesce...

In mammals, growth hormone (GH) is under a dual hypothalamic control exerted by growth hormone-releasing hormone (GHRH) and somatostatin (SRIH). We investigated GH release in a pleuronectiform teleost, the turbot (Psetta maxima), using a serum-free primary culture of dispersed pituitary cells. Cells released GH for up to 12 days in culture, indicating that turbot somatotropes do not require releasing hormone for their regulation. SRIH dose-dependently inhibited GH release up to a maximal inhibitory effect of 95%. None of the potential stimulators tested induced any change in basal GH release. Also, neither forskolin, an activator of adenylate cyclase, nor phorbol ester (TPA), an activator of protein kinase C, were able to modify GH release, suggesting that spontaneous basal release already represents the maximal secretory capacity of turbot somatotropes. In contrast, forskolin and TPA were able to increase GH release in the presence of SRIH. In this condition (coincubation with SRIH), pituitary adenylate cyclase-activating polypeptide (PACAP) stimulated GH release, whereas none of the other neuropeptides tested (GHRHs; sea bream or salmon or chicken II GnRHs; TRH; CRH) had any significant effect. These data indicate that inhibitory control by SRIH may be the basic control of GH production in teleosts and lower vertebrates, while PACAP may represent the ancestral growth hormone-releasing factor in teleosts, a role taken over in higher vertebrates by GHRH.

Ouabain circulating in blood inhibits Na-K-ATPase in the gills of seawater eels at a concentration similar to that necessary for inhibition in vitro. By contrast, a much higher concentration is required when ouabain is applied to the exterior of the gill. Inhibition by external ouabain occurs only when the drug gains access to the circulation of the fish, as evidenced by simultaneous inhibition of Na-K-ATPase in the kidney. These results suggest that the Na-K-ATPase of gill chloride cells faces inward, lining intracytoplasmic tubular channels continuous with the extracellular fluid.

Thyroid-stimulating hormone (TSH) is composed of a specific β subunit and an α subunit that is shared with the two pituitary gonadotropins. The three β subunits derive from a common ancestral gene through two genome duplications (1R and 2R) that took place before the radiation of vertebrates. Analysis of genomic data from phylogenetically relevant species allowed us to identify an additional Tshβ subunit-related gene that was generated through 2R. This gene, named Tshβ2, present in cartilaginous fish, little skate and elephant shark, and in early lobe-finned fish, coelacanth and lungfish, was lost in ray-finned fish and tetrapods. The absence of a second type of TSH receptor (Tshr) gene in these species suggests that both TSHs act through the same receptor. A novel Tshβ sister gene, named Tshβ3, was generated through the third genomic duplication (3R) that occurred early in the teleost lineage. Tshβ3 is present in most teleost groups but was lostin tedraodontiforms. The 3R also gene...

Living anguilliform eels represent a distinct clade of elongated teleostean fishes inhabiting a wide range of habitats. Locomotion of these fishes is highly influenced by the elongated body shape, the anatomy of the vertebral column, and the corresponding soft tissues represented by the musculotendinous system. Up to now, the evolution of axial elongation in eels has been inferred from living taxa only, whereas the reconstruction of evolutionary patterns and functional ecology in extinct eels still is scarce. Rare but excellently preserved fossil eels from the Late Cretaceous and Cenozoic were investigated here to gain a better understanding of locomotory system evolution in anguilliforms and, consequently, their habitat occupations in deep time. The number of vertebrae in correlation with the body length separates extinct and extant anguilliforms. Even if the phylogenetic signal cannot entirely be excluded, the analyses performed here reveal a continuous shortening of the vertebral...

The sperm of European eel shows a high density and the time of spermatozoa motility is very short after activation with sea water. These characteristics make difficult the sperm handling and its quality assessment. Several diluents were previously described for the Japanese eel obtaining over 3 weeks’ conservation times under refrigeration, but they rendered bad results in the European species. In the present study, several diluents were developed taking as basis the P1 medium, and using different dilution ratios (1 : 50, 1 : 100) and two pH (6.5, 8.5). The effect of the addition of bovine serum albumin (BSA, 2% w/v) was also evaluated. At 24 h, undiluted samples already showed significant lower motility and viability than sperm samples diluted in the different media. The results for diluents with pH 6.5 and 8.5 were different. Spermatozoa diluted in media at pH 6.5 cannot be activated at 24 h, while samples diluted in the diluents with pH 8.5 and added with BSA did not show significant differences with respect to the fresh sperm motility until 48 h. The viability (percentage of alive cells) did not show differences until 1 week, independent of the dilution ratio. After 1 week, the motility was approximately 30% in the media containing BSA, which presented no differences for head size of the spermatozoa (perimeter and area) until 72 h and 1 week, respectively. In conclusion, the combination of one medium having similar physico-chemical characteristics to the seminal plasma, including pH 8.5, and supplemented with BSA can be used in different dilution ratios for the sperm’s short-term storage, preserving its motility capacity.

Heterosporis saurida is an intracellular microsporidian that infects lizardfish Saurida undosquamis. Although some attempts have been introduced to clarify microsporidian host−pathogen interactions, development of novel strategies to combat fish diseases is still needed. Here we present an in vitro cultivation model for fish microsporidia based on an eel kidney cell line (EK-1), which is susceptible to infection by H. saurida. Spores were isolated from infected lizardfish and used to inoculate EK-1 cells. H. saurida were propagated in the eel kidney EK-1 cell line and detected by immunofluorescence. Developmental stages of H. saurida were seen in EK-1 cells by transmission electron microscopy. Identity of the parasite was confirmed by partial se quencing of the 16S rDNA gene. Our cell culture model provides a valuable means to explore molecular and immunological events and will facilitate development of effective treatment strategies.

The aim of the present study was to assess the environmental quality of Orbetello lagoon (Tyrrhenian coast, Italy), using a biomonitoring method based on measuring organochlorinated pollutants in the Anguilla anguilla, chosen as sentinel organism, and remote sensing data obtained by elaboration of Landsat 7 Enhanced Thematic Mapper (ETM) data of 2002. Polychlorinated biphenyls and organochlorine pesticides were determined by gas chromatography/mass spectrometry in muscle of European eels captured in seven sites having different levels of pollution in Orbetello lagoon. Remote sensing data and chemical analysis showed the Albegna river as a probable vehicle of pesticides (hexachlorocyclohexanes).

The expression of the recombinant diphtheria toxin mutant CRM197 in bacteria other than Corynebacterium diphtheriae has proven to be difficult. Here we propose a new and alternative procedure for the production of full-length CRM197 in Escherichia coli. The present study relates specifically to the expression of an artificial sequence and to a method for the isolation and purification of the corresponding protein. In particular, a synthetic gene coding for CRM197, bearing a short histidine tag and optimized for E. coli codon usage, was cloned in the pET9a vector. Accordingly, the over-expression of the protein was simply induced with arabinose in E. coli BL21AI. The recombinant protein was insoluble and always found inside protein aggregates, which were solubilised using urea. Surprisingly, the expression of CRM197, devoid of the short tag, always failed. Following a refolding step, the his-tagged CRM197 was purified by affinity and gel-filtration chromatography and the purity of the final preparation reached 95%. Interestingly, the recombinant protein features DNase activity, indicating that the presence of the tag is not affecting its biochemical properties. However, the removal of the synthetic tag could be easily obtained by incubating the target protein with a proper quantity of a commercial enterokinase.

This review focuses on recent developments in the molecular biology of ion and water transporter genes in fish and the potential role of their products in osmoregulation in both freshwater and seawater environments. In particular details of isoforms of various ATPases, co-transporters, exchangers and ion channels in the eel as well as other teleost species are described. Many of the teleost transporter isoforms discovered so far, appear to occur as twin or duplicate copies compared to their homologous counterparts in higher vertebrates, although these duplicate isoforms often have distinct tissue-specific and developmental stage-dependent expression patterns. The possible meaning of this information will be examined in relation to the fish genome duplication debate. ᮊ

The eel pathogen Vibrio vulnificus biotype 2 comprises at least three serovars, with serovar E being the only one involved in both epizootics of eel vibriosis and sporadic cases of human infections. The virulent strains of this serovar (VSE) have only been recovered from clinical (mainly eel tissue) sources. The main objective of this work was to design and validate a new protocol for VSE-specific isolation from environmental samples. The key element of the new protocol is the broth used for the first step (saline eel serum broth [SEB]), which contains eel serum as a nutritive and selective component. This approach takes advantage of the ability of VSE cells to grow in eel serum and thus to separate themselves from the pool of competitors. The growth yield in SEB after 8 h of incubation was 1,000 times higher for VSE strains than for their putative competitors (including biotype 1 strains of the species). The selective and differential agar Vibrio vulnificus medium (VVM) was selected from five selective media for the second step because it gave the highest plating efficiency not only for the VSE group but also for other V. vulnificus groups, including biotype 3. The entire protocol was validated by field studies, with alkaline peptone water plus VVM as a control. V. vulnificus was isolated by both protocols, but serovar E was only recovered by the new method described here. All selected serovar E isolates were identified as VSE since they were virulent for both eels and iron-overloaded mice and resisted the bactericidal action of eel and iron-overloaded human sera. In conclusion, this new protocol is a suitable method for the isolation of VSE strains from environmental samples and is recommended for epidemiological studies of the pathogenic serovar E.

A detailed analysis of the optical properties of filled tetrahedral semiconductors Li 3 AlN 2 and Li 3 GaN 2 has been performed, using the full potential linearized augmented plane wave method within the density functional theory. The real and imaginary parts of the dielectric function e(x), the optical absorption coefficient I(x), the reflectivity R(x), and the electron energy loss function are calculated within the random phase approximation. The interband transitions responsible for the structures in the spectra are specified. Looking at optical matrix element, we note that the major peaks are dominated by transition from metal s, N 2p states to N 2p, Ga 3d states. The theoretical calculated optical properties and electron energy loss spectrum yield a static dielectric constant of 5.34 and a plasmon energy of 19.47 eV for Li 3 GaN 2 . In the Li 3 AlN 2 compound, the static dielectric constant decreases to 4.75 and yields a plasmon energy of 18.5 eV. The effect of spin-orbit coupling on the optical properties is also investigated and found to be quite small, especially in the low-energy region. In order to check the reliability of our calculations, analogous results obtained for Be 3 N 2 in the same structure [space group Ia3(206)] are included in this work.

Publisher Summary In most excitable membranes the rapid depolarization associated with an action potential is the result of a large, transient increase in membrane conductance to sodium ions. This chapter discusses some of the recent progress that has been made toward the biochemical characterization of the sodium-channel protein. The ultimate goal of biochemical studies of the excitable-membrane sodium channel is an understanding of the relationship between the structure of the channel at the molecular level and the functional aspects of its voltage-dependent gating properties. Preliminary evidence from reconstitution studies suggests that most, if not all, of the channel protein is purified as a unit, thus raising hopes for the study of the physiological properties of purified sodium-channel protein reconstituted into defined lipid bilayers. Ultimately, electrophysiological, biophysical, and biochemical avenues of investigation should merge, and explanations of ion selectivity, channel gating, and voltage dependence will be founded on a defined molecular architecture for this most important protein.

1. A computer model for swim-bladder gas filling has been developed. Phenomenological descriptions of the Root effect (pH-dependent O2 capacity of fish haemoglobin), of the lactic acid production in the gas gland and of the geometry of the rete mirabile are incorporated in the general counter-current equations to give a comprehensive model of gas filling. 2. It is known that pH along the rete is not constant, as supposed in an earlier gas-filling model. It is also known that the Root shift reaction has a different half-time model. It is also known that the Root shift reaction has a different half-time depending on whether the haemoglobin absorbs or releases O2. These particular effects are accounted for in the present model. 3. The model gives gas filling rate and maximum swim-bladder pressure for CO2, O2 and N2. The partial pressure of these gases as well as the concentration of lactic acid and the pH along the rete are also calculated. 4. The model reproduces quite accurately expe...

We have been able to separate optic fibers in the eye of the eel Anguilla rostrata into two distinct classes on the basis of spatial summation properties. X fibers, the first class, are like X ganglion cells in the cat: they have null positions for contrast reversal sine gratings; they respond at the modulation frequency; and many have a strong surround mechanism. X fibers, the second class, respond with an "on-off" response to local stimulation, to diffuse light modulation, to coarse drifting gratings, and to contrast reversal gratings. We have put forward a model for the receptive field of X fibers which involves two subunits, with rectification before the subunits add their signals. This model accounts for many of the quirks of X fibers.

1 The abbreviations used are: AFP, antifreeze protein; wlwAFP, wild type-linker-wild type AFP; wlxAFP, wild type-linker-knockout AFP; wsswAFP, disulfide-linked wild type AFP homodimer; FPLC, fast performance liquid chromatography; HPLC, high performance liquid chromatography; DTT, dithiothreitol.

Acetylcholinesterase (ChE) sensor based on Prussian blue (PB) modified electrode was developed and tested for the detection of organophosphorus and carbamic pesticides. The signal of the sensor was generated in PB mediated oxidation of thiocholine recorded at+200 mv in DC mode. ChE from electric eel was immobilized by cross-linking with glutaraldehyde in the presence of bovine serum albumin (BSA) on the surface of screen-printed carbon electrode covered with PB and Nafion. The content of the surface layer (specific enzyme activity, Nafion and BSA amounts) was optimized to establish high and reliable response toward the substrate and ChE inhibitors. The ChE/PB sensor makes it possible to detect Aldicarb, Paraoxon and Parathion-Methyl with limits of detection 30, 10 and 5 ppb, respectively (incubation 10 min). The feasibility of practical application of the ChE/PB sensor developed for the monitoring of degradation of the pesticides in wine fermentation was shown. To diminish matrix interferences, the electrolysis of the grape juice with Al anode and evaporation of ethanol were suggested, however the procedures decrease the sensitivity of pesticide detection and stability of the sample tested.

The expression of the recombinant diphtheria toxin mutant CRM197 in bacteria other than Corynebacterium diphtheriae has proven to be difficult. Here we propose a new and alternative procedure for the production of full-length CRM197 in Escherichia coli. The present study relates specifically to the expression of an artificial sequence and to a method for the isolation and purification of the corresponding protein. In particular, a synthetic gene coding for CRM197, bearing a short histidine tag and optimized for E. coli codon usage, was cloned in the pET9a vector. Accordingly, the over-expression of the protein was simply induced with arabinose in E. coli BL21AI. The recombinant protein was insoluble and always found inside protein aggregates, which were solubilised using urea. Surprisingly, the expression of CRM197, devoid of the short tag, always failed. Following a refolding step, the his-tagged CRM197 was purified by affinity and gel-filtration chromatography and the purity of the final preparation reached 95%. Interestingly, the recombinant protein features DNase activity, indicating that the presence of the tag is not affecting its biochemical properties. However, the removal of the synthetic tag could be easily obtained by incubating the target protein with a proper quantity of a commercial enterokinase.

We investigated the regulation of the pharyngeal and upper esophageal reXexes during swallowing in eel. By retrograde tracing from the muscles, the motoneurons of the upper esophageal sphincter (UES) were located caudally within the mid-region of the glossopharyngealvagal motor complex (mGVC). In contrast, the motoneurons innervating the pharyngeal wall were localized medially within mGVC. Sensory pharyngeal Wbers in the vagal nerve terminated in the caudal region of the viscerosensory column (cVSC). Using the isolated brain, we recorded 51 spontaneously active neurons within mGVC. These neurons could be divided into rhythmically (n = 8) and continuously (n = 43) Wring units. The rhythmically Wring neurons seemed to be restricted medially, whereas the continuously Wring neurons were found caudally within mGVC. The rhythmically Wring neurons were activated by the stimulation of the cVSC. In contrast, the stimulation of the cVSC inhibited Wring of most, but not all the continuously Wring neurons. The inhibitory eVect was blocked by prazosin in 17 out of 38 neurons. Yohimbine also blocked the cVSC-induced inhibition in Wve of prazosin-sensitive neurons. We suggest that the neurons in cVSC inhibit the continuously Wring motoneurons to relax the UES and stimulate the rhythmically Wring neurons to constrict the pharynx simultaneously.

This study was conducted to record the histological features of the gastrointestinal tract of wild Indonesian shortfin eel, Anguilla bicolor bicolor (McClelland, 1844), captured in Peninsular Malaysia. The gastrointestinal tract was segmented into the oesophagus, stomach, and intestine. Then, the oesophagus was divided into five (first to fifth), the stomach into two (cardiac and pyloric), and the intestine into four segments (anterior, intermediate, posterior, and rectum) for histological examinations. The stomach had significantly taller villi and thicker inner circular muscles compared to the intestine and oesophagus. The lamina propria was thickest in stomach, significantly when compared with oesophagus, but not with the intestine. However, the intestine showed significantly thicker outer longitudinal muscle while gastric glands were observed only in the stomach. The histological features were closely associated with the functions of the different segments of the gastrointestinal tract. In conclusion, the histological features of the gastrointestinal tract of A. b. bicolor are consistent with the feeding habit of a carnivorous fish.

The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N ¼ 159) and from the neighboring Faroe Islands (N ¼ 29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female  American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid  pure European eel) and three individuals identified as second-generation backcrosses originating from American eel  F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization.

Mastacembelocleidus gen. n. (Monogenoidea: Dactylogyridae) is proposed to include two species collected and redescribed from spiny eels (Mastacembelidae) in India and Iraq: Mastacembelocleidus bam (Tripathi, 1959) comb. n. (syn. Ancyrocephalus bam Tripathi, 1959) from the gills of Macrognathus pancalus (new host record) and Macrognathus aculeatus (Synbranchiformes: Mastacembelidae) from Lucknow, India; and Mastacembelocleidus heteranchorus (Kulkarni, 1969) comb. n. (syn. Urocleidus heteranchorus Kulkarni, 1969) from the gills of Mastacembelus armatus from Lucknow, India, and Mastacembelus mastacembelus (new host record) from the environs of Erbil, Iraq (new locality record). Urocleidus rhyncobdelli Jain, 1959, Haliotrema tandani Agrawal et Singh, 1982 and Urocleidus raipurensis Dubey, Gupta et Agarwal, 1992 are considered junior subjective synonyms of M. bam.