Second world record for Barathronus roulei Nielsen, 2019 (Ophidiiformes, Bythitidae), from the Porcupine Bank (Northeast Atlantic).

Barathronus is a genus of blind cusk eels comprising 11 valid species. In this paper, we report the second specimen ever documented of Barathronus roulei (Bythitidae) obtained from the Porcupine Bank by R.V. Vizconde de Eza using a bottom trawl at a depth of 1349 m. Morphological description and illustrations, including a radiograph, are provided. In addition, three new sequences corresponding to three different genes, cytochrome c oxidase subunit I (COI)-DNA barcoding, 16S ribosomal RNA (16S), and recombination activating protein 1 (RAG1), have been added to the molecular repositories, representing the first sequences for the species.

Hidden in the depths, discovery of a new spiny sucker eel of the genus Lipogenys Goode and Bean 1895 (Teleostei, Notacanthiformes, Notacanthidae) in the eastern North Atlantic Ocean.

This study describes Lipogenys hyalinumvelum, a new species of the genus Lipogenys found on the Portuguese coast on the northeastern Atlantic during a crustacean survey. Information on the classification history and known distribution of the genus Lipogenys is provided. Dichotomous keys to the genera of Notacanthidae and the species of Lipogenys, based on morphology, are provided. The specimens were analysed using both morphological and molecular methods, including DNA sequencing of the COI and 16S genes. The distinct genetic characteristics support the recognition of the present specimens as a new species. The hyaline color of the flap at the posterior edge of the operculum is a characteristic that differentiates L. hyalinumvelum from Lipogenys gillii and provides the etymology of the species name.

Description of a new moray eel (Anguilliformes: Muraenidae) from the Philippines, with a preliminary assessment of genetic and morphological variations of the Uropterygius concolor species complex.

Uropterygius concolor Rüppell, the type species of the genus Uropterygius, is a small, uniformly brown moray considered to be widely distributed in the Indo-Pacific region. However, a recent study indicated that the real U. concolor is currently known only from the type locality in the Red Sea, and species recorded outside the Red Sea may represent a species complex that comprises several species. In this study, we assess the genetic and morphological variations of this species complex based on available data. Analyses of cytochrome c oxidase subunit I sequences revealed at least six distinct genetic lineages recognized under 'U. concolor'. After carefully comparing the morphologies, one of the lineages is described herein as a new species, Uropterygius mactanensis sp. nov., based on 21 specimens collected from Mactan Island, Cebu, Philippines. Another distinct lineage is considered to be a possibly undescribed species based on diagnostic morphological characters. Although the taxonomic status of junior synonyms of U. concolor and some lineages still remain unresolved, this study provides informative morphological characters (i.e., tail length, trunk length, vertebrae number, and arrangement of teeth) that can be used in future studies on this species complex.

A new Congrid eel, Rhynchoconger smithi sp. nov. (Anguilliformes: Congridae), from the Bay of Bengal, India.

A new Conger eel species is described based on four specimens collected from Petuaghat fishing harbour, West Bengal, India. The combination of morphological characters and molecular data are discordant with the seven congeners currently recognized. Rhynchoconger smithi sp. nov. can be distinguished by having head smaller than trunk; pre-anal length more than three times in total length; a small eye, diameter 2.0-2.2 in snout length; rictus ending at a vertical through posterior margin of pupil; ethmovomerine teeth patch small, with 58-74 blunt teeth arranged in seven to eight irregular rows; vomerine teeth patch small, with 18-28 granular teeth arranged in four to six irregular rows, distinctly separated by narrow spaces from the ethmovomerine and maxillary teeth; three supraorbital pores and one supra-temporal pore; and 159+ to 164 total vertebrae. Moreover, R. smithi differs significantly from four congeners, R. nitens, R. flavus, R. ectenurus and R. gracilior, with Kimura two-parameter (K2P) distances 14.6%-20.3%.

A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae) from the Bay of Bengal, India.

A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae), Cirrhimuraena indica sp. nov., is described based on eight specimens collected from the Paradip (Odisha) and Petuaghat harbours (West Bengal) along the Bay of Bengal. The species is distinct in having the upper jaw fringed with 16-17 cirri before posterior nostril and 4-5 in between the anterior and posterior nostrils on the side; dorsal fin originates above the level of gill opening, predorsal length is 9.3-10.9 in total length; the head is relatively large, the length is 9.3-9.8 in total length; no infraorbital pores are observed between the nostrils; teeth are numerous, small, conical and in bands on each jaw; pores are present before the gill opening 10-11 and before anus 47-48; pectoral-fin length is 2.4-2.8 in head length; predorsal vertebrae are 8-10, pre-anal vertebrae 43-47 and total vertebrae 164-169. In the maximum likelihood tree analysis for COI gene, the new species belongs to the same clade as the other congener of Cirrhimuraena chinensis and is separated from the species morphologically and genetically.

A review of the genus Strophidon (Anguilliformes: Muraenidae), with description of a new species.

Strophidon McClelland is a muraenid genus with characteristic appearance of a very elongated body, a large mouth cleft and anteriorly placed eyes. The nomenclature and taxonomic history of species within Strophidon are contentious and its members are easily misidentified. In the present study, species of the genus Strophidon are revised based on morphological and molecular data, and five species are considered valid, including S. dawydoffi Prokofiev, S. dorsalis (Seale), S. sathete (Hamilton), S. ui Tanaka and a new species, S. tetraporus. Strophidon tetraporus sp. nov. is described based on 15 specimens from Indonesia, the Philippines, Taiwan and Vietnam with the unique characteristic of the constant presence of the fourth infraorbital pore among species of Strophidon. The intraspecific variation of vertebral formula within S. dorsalis is discussed based on molecular data. Muraena macrurus Bleeker and Thyrsoidea longissima Kaup are synonyms of S. sathete that can be distinguished from the most similar congener S. ui by a longer tail, smaller eyes and more inner maxillary and inner dentary teeth. A key to identify species of Strophidon is provided. The distribution and maximum size of each species are also re-evaluated.

Cytological analysis of integumentary and muscular adaptations in three sand-dwelling marine teleosts, Ammodytes tobianus (Ammodytidae), Gorgasia preclara (Congridae) and Heteroconger hassi (Congridae) (Teleostei; Actinopterygii).

Sandy bottoms are a ubiquitous environment found from sea bottoms to intertidal and freshwater zones. They are inhabited by many invertebrates and vertebrates which have developed morphological and physiological adaptations to sustain life under these particular conditions. Sandy habitats exhibit three potential constraints: abrasion, hypoxia and mechanical resistance. Here, three teleost species living in sandy environments were investigated: Ammodytes tobianus (Ammodytidae), Gorgasia preclara and Heteroconger hassi (Congridae). These teleost fishes were studied for their integument and muscular systems, which are potentially subject to sand abrasion and hypoxia, respectively. Based on histochemistry and transmission electron microscopy, we found the complex mucus system of G. preclara and H. hassi consists of two types of goblet cells and one type of sacciform cell. The secretions of both species are made of complex polysaccharides. In contrast, the scaly integument of A. tobianus has only a few goblet cells and no sacciform cells. We also highlighted, by immunohistochemistry, that the epidermal cell proliferation was much higher for this latter species, potentially resulting from the high rate of sand abrasion when A. tobianus buries itself quickly in the substrate. For all species, the major muscle fibre type was revealed by histoenzymology and corresponds to fast glycolytic fibres followed by intermediate fibres with slow fibres in the lowest proportion. Ammodytes tobianus possesses the highest fast fibre proportion (about 87% for A. tobianus and 75-78% for both garden eels). Our results provide new insights into the previously poorly studied teleost species, such as G. preclara, and allow us to highlight the complex skin histology of both garden eel species. Furthermore, the previously unknown muscle typing of these three species was determined.

Can an eel be a flatfish? Observations on enigmatic asymmetrical heterenchelyids from the Guinea coast of West Africa.

Morphological asymmetry is described in the heterenchelyid mud eel Pythonichthys cf. macrurus from inshore coastal waters of Guinea, West Africa. The intensity of asymmetry differs between two examined specimens, with the more extreme case exhibiting strong asymmetry in both external and internal features, including unilateral depigmentation, reductive degeneration and embedding of a blind-side eye, skewed jaws with reduced dentition and tooth loss. The extent and nature of asymmetry suggests that this individual probably lived primarily on its left lateral side, not unlike sinistral pleuronectiform flatfishes.

Evolution of the locomotory system in eels (Teleostei: Elopomorpha).

BACKGROUND: 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. RESULTS: 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 column with a simultaneous increase in vertebral numbers in conjunction with short lateral tendons throughout the order. These anatomical changes contradict previous hypotheses based on extant eels solely. CONCLUSIONS: The body curvatures of extant anguilliforms are highly flexible and can be clearly distinguished from extinct species. Anatomical changes of the vertebral column and musculotendinous system through time and between extinct and extant anguilliforms correlate with changes of the body plan and swimming performance and reveal significant shifts in habitat adaptation and thus behaviour. Evolutionary changes in the skeletal system of eels established here also imply that environmental shifts were triggered by abiotic rather than biotic factors (e.g., K/P boundary mass extinction event).

Molecular phylogenetics reveals convergent evolution in lower Congo River spiny eels.

BACKGROUND: The lower Congo River (LCR) is a region of exceptional species diversity and endemism in the Congo basin, including numerous species of spiny eels (genus Mastacembelus). Four of these exhibit distinctive phenotypes characterized by greatly reduced optic globes deeply embedded into the head (cryptophthalmia) and reduced (or absent) melanin pigmentation, among other characteristics. A strikingly similar cryptophthalmic phenotype is also found in members of a number of unrelated fish families, strongly suggesting the possibility of convergent evolution. However, little is known about the evolutionary processes that shaped diversification in LCR Mastacembelus, their biogeographic origins, or when colonization of the LCR occurred. METHODS: We sequenced mitochondrial and nuclear genes from Mastacembelus species collected in the lower Congo River, and compared them with other African species and Asian representatives as outgroups. We analyzed the sequence data using Maximum Likelihood and Bayesian phylogenetic inference. RESULTS: Bayesian and Maximum Likelihood phylogenetic analyses, and Bayesian coalescent methods for species tree reconstruction, reveal that endemic LCR spiny eels derive from two independent origins, clearly demonstrating convergent evolution of the cryptophthalmic phenotype. Mastacembelus crassus, M. aviceps, and M. simbi form a clade, allied to species found in southern, eastern and central Africa. Unexpectedly, M. brichardi and brachyrhinus fall within a clade otherwise endemic to Lake Tanganikya (LT) ca. 1500 km east of the LCR. Divergence dating suggests the ages of these two clades of LCR endemics differ markedly. The age of the crassus group is estimated at ~4 Myr while colonization of the LCR by the brichardi-brachyrhinus progenitor was considerably more recent, dated at ~0.5 Myr. CONCLUSIONS: The phylogenetic framework of spiny eels presented here, the first to include LCR species, demonstrates that cryptophthalmia and associated traits evolved at least twice in Mastacembelus: once in M. brichardi and at least once in the M. crassus clade. Timing of diversification is broadly consistent with the onset of modern high-energy flow conditions in the LCR and with previous studies of endemic cichlids. The close genetic relationship between M. brichardi and M. brachyrhinus is particularly notable given the extreme difference in phenotype between these species, and additional work is needed to better understand the evolutionary history of diversification in this clade. The findings presented here demonstrate strong, multi-trait convergence in LCR spiny eels, suggesting that extreme selective pressures have shaped numerous phenotypic attributes of the endemic species of this region.

Phylogenetic analysis of molecular and morphological data highlights uncertainty in the relationships of fossil and living species of Elopomorpha (Actinopterygii: Teleostei).

Elopomorpha is one of the three main clades of living teleost fishes and includes a range of disparate lineages including eels, tarpons, bonefishes, and halosaurs. Elopomorphs were among the first groups of fishes investigated using Hennigian phylogenetic methods and continue to be the object of intense phylogenetic scrutiny due to their economic significance, diversity, and crucial evolutionary status as the sister group of all other teleosts. While portions of the phylogenetic backbone for Elopomorpha are consistent between studies, the relationships among Albula, Pterothrissus, Notacanthiformes, and Anguilliformes remain contentious and difficult to evaluate. This lack of phylogenetic resolution is problematic as fossil lineages are often described and placed taxonomically based on an assumed sister group relationship between Albula and Pterothrissus. In addition, phylogenetic studies using morphological data that sample elopomorph fossil lineages often do not include notacanthiform or anguilliform lineages, potentially introducing a bias toward interpreting fossils as members of the common stem of Pterothrissus and Albula. Here we provide a phylogenetic analysis of DNA sequences sampled from multiple nuclear genes that include representative taxa from Albula, Pterothrissus, Notacanthiformes and Anguilliformes. We integrate our molecular dataset with a morphological character matrix that spans both living and fossil elopomorph lineages. Our results reveal substantial uncertainty in the placement of Pterothrissus as well as all sampled fossil lineages, questioning the stability of the taxonomy of fossil Elopomorpha. However, despite topological uncertainty, our integration of fossil lineages into a Bayesian time calibrated framework provides divergence time estimates for the clade that are consistent with previously published age estimates based on the elopomorph fossil record and molecular estimates resulting from traditional node-dating methods.

Imperfect morphological convergence: variable changes in cranial structures underlie transitions to durophagy in moray eels.

Convergence is central to the study of evolution because it demonstrates the power of natural selection to deterministically shape phenotypic diversity. However, the conditions under which a common morphology repeatedly evolves may be restrictive. Many factors, such as differing genetic and environmental backgrounds and many-to-one mapping of form to function, contribute to variability in responses to selection. Nevertheless, lineages may evolve similar, even if not identical, forms given a shared selective regime, providing opportunities to examine the relative importance of natural selection, constraint, and contingency. Here, we show that following 10 transitions to durophagy (eating hard-shelled prey) in moray eels (Muraenidae), cranial morphology repeatedly evolved toward a novel region of morphological space indicative of enhanced feeding performance on hard prey. Disparity among the resulting 15 durophagous species, however, is greater than disparity among ancestors that fed on large evasive prey, contradicting the pattern expected under convergence. This elevated disparity is a consequence of lineage-specific responses to durophagy, in which independent transitions vary in the suites of traits exhibiting the largest changes. Our results reveal a pattern of imperfect convergence, which suggests shared selection may actually promote diversification because lineages often differ in their phenotypic responses to similar selective demands.

Histological features of the gastrointestinal tract of wild Indonesian shortfin eel, Anguilla bicolor bicolor (McClelland, 1844), captured in Peninsular Malaysia.

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.

Precaudal Vertebrae in the Postcranial Region of Moray Eels Form Ventral Processes.

Fish vertebrae are primarily morphologically classified into precaudal vertebrae jointed to the ribs and caudal vertebrae with hemal spines, through which the caudal artery and veins pass. Moray eels (family Muraenidae) capture prey by directly biting, combining oral and pharyngeal jaw. During feeding motions, they exhibit various head manipulations, such as neurocranial elevation, ventral flexion, and horizontal shaking, with their postcranial region acting like the neck of amniotes. However, the bone morphology supporting these movements remains unclear. In this study, the vertebral morphologies of the Kidako moray (Gymnothorax kidako), starry moray (Echidna nebulosa), pink-lipped moray (Echidna rhodochilus), tidepool snake moray (Uropterygius micropterus), and Seychelles moray (Anarchias seychellensis) were investigated using X-ray computed tomography. These five species exhibited longitudinal ventral processes in the second to approximately 12th precaudal vertebrae with canals for blood vessels, structurally similar to hemal spines. In addition, the morphology of the precaudal vertebrae in three Anguilliformes species closely related to moray eels and two Gasterosteiformes species, including a seahorse that flexes its head ventrally as a feeding motion, was compared with that of moray eels. However, no remarkable ventral processes were observed in their precaudal vertebrae in the postcranial region, suggesting that these structural features in the postcranial vertebrae were preserved in Muraenidae but not necessarily required for the fish to bend its head ventrally. Although the functional significance of the ventral process has yet to be determined, our findings highlight a novel aspect of fish vertebral morphology.

The morphology of the branchial skeleton of heterocongrines (Anguilliformes: Congridae) and its relation to their diet.

Members of the subfamily Heterocongrinae (Congridae) are a peculiar group of anguilliform eels that construct sandy borrows, form large colonies, and are popularly recognized as garden eels. They live with most of their bodies inside self-constructed borrows exposing their heads and trunk to feed on zooplankton, preferably copepods, that are brought passively by currents. As plankton feeders there was a suspicion that their branchial skeleton would have structures that could aid in the filtering process, such as highly developed or modified branchial rakers, which are observed in other suspension-feeding fishes, such as anchovies and sardines. Branchial rakers, however, were considered to be absent across Anguilliformes (except for Protanguilla). Nonetheless, specimens that were examined using clearing and staining and computed tomography showed, in all cases, branchial rakers associated with their gill arches. Heterocongrines have branchial rakers across their first to fourth branchial arches. These rakers are conical and apparently unossified, but further studies are necessary to attest its degree of ossification or its complete absence. Their pharyngeal tooth plates are reduced, a condition that may reflect their preference for smaller food items. Additionally, they may use crossflow filtering to feed, although detailed studies are necessary to clarify if hydrosol sieving may also aid in food capture. Furthermore, the present study proposes that the presence of branchial rakers should be better investigated in Anguilliformes with similar feeding habits as heterocongrines, considering that these structures may be more widespread within the group than previously considered.

A candidate of organum vasculosum of the lamina terminalis with neuronal connections to neurosecretory preoptic nucleus in eels.

Systemic angiotensin II (Ang II) is a dipsogen in terrestrial vertebrates and seawater teleosts. In eels, Ang II acts on the area postrema, a sensory circumventricular organ (CVO) and elicits water intake but other sensory CVOs have not yet been found in the eel forebrain. To identify sensory CVOs in the forebrain, eels were peripherally injected with Evans blue, which immediately binds to albumin, or a rabbit IgG protein. Extravasation of these proteins, which cannot cross the blood­brain barrier (BBB), was observed in the brain parenchyma of the anteroventral preoptic recess (PR) walls. Fenestrated capillaries were observed in the parenchymal margin of the ventral wall of the PR, confirming a deficit of the BBB in the eel forebrain. Immunostaining for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) detected neurons in the lateral region of the anterior parvocellular preoptic nucleus (PPa), which were strongly stained by BBB-impermeable N-hydroxysulfosuccinimide. In the periventricular region of the PPa, many neurons incorporated biotinylated dextran amine conjugated to fluorescein, a retrograde axonal tracer, injected into the magnocellular preoptic nucleus (PM), indicating neuronal connections from the PPa to the PM. The mammalian paraventricular and supraoptic nuclei, homologous to the teleost PM, receive principal neuronal projections from the organum vasculosum of the lamina terminalis (OVLT). These results strongly suggest that the periventricular subpopulation of the PPa, which is most likely to be a component of the OVLT, serves as a functional window of access for systemic signal molecules such as Ang II.

Comparative proteomics analysis of degenerative eye lenses of nocturnal rice eel and catfish as compared to diurnal zebrafish.

PURPOSE: The aim of this study was to determine the lens crystallin diversity of degenerative eyes from the rice eel (Monopterus albus) and walking catfish (Clarias batrachus) as compared to that of zebrafish (Danio rerio) by using comparative proteomics methodologies. We endeavored to investigate the evolution of vertebrate lenses particularly concerning the functional loss of lenses in degenerative eyes of rice eels and catfishes living under an environment of perpetual darkness. METHODS: Fish lenses were collected and homogenized to extract total soluble proteins. The protein mixtures were separated by one- and two-dimensional gel electrophoresis (1D or 2D gel), plus the newer gel-free shotgun proteomic strategy, followed by in-gel digestion and subjection of the digested protein bands or spots to liquid chromatography coupled with tandem mass spectrometry. The proteomics data were analyzed and compared based on the proteomics databank of zebrafish. The soluble lens protein solutions of three piscine species were also processed by gel-filtration chromatography and 1D sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the comparison and validation of various crystallin families, e.g., α-, ß-, and γ-crystallins. RESULTS: In zebrafish eye lenses, γ-crystallin constituted about 71% and α- and ß-crystallins comprised 30% of total lens proteins. In rice eel lenses, very little or almost no α-crystallins were detected and ß- and γ-crystallins comprised more than 98% of total lens proteins. In catfish lenses, α- and ß-crystallins comprised about 40% and γ-crystallin constitutes 60% of total lens proteins. It was of interest to find that α-crystallin was totally absent in the rice eel in contrast to the presence, albeit with very low amounts, of α-crystallin in similarly nocturnal catfish. The ratio of α-crystallin subunits (αA/αB) was found to be about 20:1 for the catfish lens, in great contrast to the ratio of about 3:1 found for most mammalian lenses. In contrast, ß- and γ-crystallins were more abundant in lenses of these three piscine species, similar to mammalian lenses. By proteomics analysis, the most abundant ß-crystallins were found to comprise a diverse group of ßA1a, ßA1-2, ßA2a, ßA2-2, ßA4, ßB1, ßB2, and ßB3 subunit crystallins; the monomeric γ-crystallin class contains γB, γD, γM2, γM3, γM5, γM7, γN-A, γN-B, γS1, and γS2 crystallins. CONCLUSIONS: In cave or nocturnal animals, the eye is sometimes reduced or eliminated because of adaptation to life in visual darkness. The comparative proteomics analysis of degenerative and normal lenses forms a firm molecular basis to investigate further the evolution of piscine lenses in the future. The total numbers of α-, ß-, and γ-crystallins in the three fish species as revealed by the current proteomics methodology clearly indicate the complexity and diversity of crystallin species present in the piscine class of vertebrates. The unexpected finding that α-crystallin is absent in the degenerative eye lenses of rice eel may have some bearing on the chaperone function of α-crystallin in regard to its protective role of preventing protein aggregation in diurnal vertebrate lenses to maintain functional transparency.

The eel heart: multilevel insights into functional organ plasticity.

The remarkable functional homogeneity of the heart as an organ requires a well-coordinated myocardial heterogeneity. An example is represented by the selective sensitivity of the different cardiac cells to physical (i.e. shear stress and/or stretch) or chemical stimuli (e.g. catecholamines, angiotensin II, natriuretic peptides, etc.), and the cell-specific synthesis and release of these substances. The biological significance of the cardiac heterogeneity has recently received great attention in attempts to dissect the complexity of the mechanisms that control the cardiac form and function. A useful approach in this regard is to identify natural models of cardiac plasticity. Among fishes, eels (genus Anguilla), for their adaptive and acclimatory abilities, represent a group of animals so far largely used to explore the structural and ultrastructural myoarchitecture organization, as well as the complex molecular networks involved in the modulation of the heart function, such as those converting environmental signals into physiological responses. However, an overview on the existing current knowledge of eel cardiac form and function is not yet available. In this context, this review will illustrate major features of eel cardiac organization and pumping performance. Aspects of autocrine-paracrine modulation and the influence of factors such as body growth, exercise, hypoxia and temperature will highlight the power of the eel heart as an experimental model useful to decipher how the cardiac morpho-functional heterogeneities may support the uniformity of the whole-organ mechanics.

Raptorial jaws in the throat help moray eels swallow large prey.

Most bony fishes rely on suction mechanisms to capture and transport prey. Once captured, prey are carried by water movement inside the oral cavity to a second set of jaws in the throat, the pharyngeal jaws, which manipulate the prey and assist in swallowing. Moray eels display much less effective suction-feeding abilities. Given this reduction in a feeding mechanism that is widespread and highly conserved in aquatic vertebrates, it is not known how moray eels swallow large fish and cephalopods. Here we show that the moray eel (Muraena retifera) overcomes reduced suction capacity by launching raptorial pharyngeal jaws out of its throat and into its oral cavity, where the jaws grasp the struggling prey animal and transport it back to the throat and into the oesophagus. This is the first described case of a vertebrate using a second set of jaws to both restrain and transport prey, and is the only alternative to the hydraulic prey transport reported in teleost fishes. The extreme mobility of the moray pharyngeal jaws is made possible by elongation of the muscles that control the jaws, coupled with reduction of adjacent gill-arch structures. The discovery that pharyngeal jaws can reach up from behind the skull to grasp prey in the oral jaws reveals a major innovation that may have contributed to the success of moray eels as apex predators hunting within the complex matrix of coral reefs. This alternative prey transport mode is mechanically similar to the ratcheting mechanisms used in snakes--a group of terrestrial vertebrates that share striking morphological, behavioural and ecological convergence with moray eels.

First record of the moray eel Gymnothorax reticularis, Bloch, 1795 in the Mediterranean Sea, with a note on its taxonomy and distribution.

The first Red-Sea Indo-Pacific alien moray eel in the Eastern Mediterranean is reported here. A single specimen ot Gymnothorax reticularis was captured by a commercial bottom-trawl vessel off the northern coast of Israel. Morphological and anatomical similarities with the single known Red-Sea specimen raise an old taxonomic dilemma.