Moray Species Research Articles

Directional asymmetry in gonad length indicates moray eels (Teleostei, Anguilliformes, Muraenidae) are “right-gonadal”

Directional asymmetry indicates a unidirectional deviation from perfect bilateral symmetry, which was rarely examined in the inner organs of the teleost (Teleostei) compared to external traits. This study examines the directional asymmetry in the gonad length of 20 species of moray eels (Muraenidae) and two outgroup species with 2959 individuals. We tested three hypotheses: (1) moray eel species did not exhibit directional asymmetry in the gonad length; (2) the directional asymmetry pattern was the same for all selected species; (3) the directional asymmetry was not related to the major habitat types, depth and size classes, and taxonomic closeness of the species. Moray eels were generally “right-gonadal”, the right gonad length being constantly and significantly longer than the left one in all studied Muraenidae species. The degree of asymmetry varied among species and was not significantly related to taxonomic closeness. The habitat types, depth, and size classes had intermingled effects on observed asymmetry without a clear correspondence. The directional asymmetry in the gonad length is a unique and widely occurring phenomenon in the Family Muraenidae, which was likely a by-product in the evolutionary history without significant disadvantage in survival.

Green morays (Gymnothorax funebris) have sedentary ways in mangrove bays, but also ontogenetic forays to reef enclaves

Surprisingly, little is known about basic life history of the largest moray eel species in the Caribbean region, the green moray eel (Gymnothorax funebris). Sixteen eels were captured from the mangrove fringe in multiple bays on St. Croix, USVI, implanted with coded acoustic transmitters, and their movements were tracked for up to 11 months using an array of 37 stationary acoustic receivers. They exhibited high site fidelity in the bays during their residence, using the same general parts of individual bays and did not switch bays except for one individual. There was no relationship between eel size (mean TL = 83 cm, range = 54–126 cm) and home range size (mean area of 95% KUD = 5.8 ha ± 0.7 SE). Most individuals were more frequently detected at night than during the day suggesting greater nocturnal activity. Several of the larger eels (mean TL = 93 cm ± 5.9 SE) showed clear and permanent emigration tracks out of the mangrove estuary to coral reef habitats offshore. For some individuals, these habitat shifts were preceded by exploratory movements away from the eel’s typical home range the night before emigration. All final emigration events took place nocturnally, happened during a single night, and occurred during months from December to May. Mean emigration speed was 3.4 km/h. This study is the first documentation of an ontogenetic habitat shift in moray eels, as well as the first determination of home range size for this species and their site fidelity in mangrove habitats.

Descriptions of neurocranium morphology in 34 species of moray eels (Muraenidae) found in Taiwan.

Taiwan is one of the richest in the world in terms of eel fauna. In this study, we examined the osteological and morphological characteristics of eels in the family Muraenidae. Furthermore, we focused on the neurocranium of 34 muraenid species in the genera Echidna (2), Enchelycore (3), Gymnomuraena (1), Gymnothorax (25), Scuticaria (1), Strophidon (1), and Uropterygius (1), which are caught in Taiwanese waters. This paper shows the results of a comparative study on osteological characters of the neurocranium including the ratio of nine length characters and 20 diagnostic characters for 34 eel species in the family Muraenidae. The subfamily Uropterygiinae is distinguished from the subfamily Muraeninae in having the lowest value on the depth of mid pre-orbit due to the termination of the ethmoidal crest toward premaxilla. Moreover, aside from Gymnomuraena zebra, the species of subfamily Uropterygiinae have the lowest orbit length. These results in neurocranial comparative morphology between the species are consistent with their previous classification based on molecular results. These morphological and osteological characters may be valuable for taxonomic purposes and might be used as the basis for further studies on the status of genera in Muraenidae.

New Moray Eel Species of Strophidon genus (Muraenidae) from Vietnam

A new species, Strophidon dawydoffi sp. n., from Nha Trang Bay (South China Sea, Vietnam) was described. The new species is well distinguished from the cooccurring S. sathete species by a thinner and elongated body, tail lobiform-extended at the end, external absence of vertical fins, a much smaller number of preanal vertebrae, elongated vertebral centra in the middle portion of the caudal region of the vertebral column, the structure of neural arches and parapophyses, variegated coloring of the body and oral cavity, a larger number of teeth in the inner rows on maxillare and dentale, and two or three rows of papillae on the lips. Differences in the number of infraorbital pores and in the shape of the snout between S. sathete specimens are associated with individual variability.

Effects of Diet and Intraspecific Scaling on the Viscera of Muraenid Fishes

Diet has a strong influence on the morphology and physiology of vertebrates. Members of numerous fish clades have provided excellent comparative models for examining the effects of diet, primarily carnivory vs. herbivory, on organ systems. In this study, we comparatively examined the effects of carnivory, specifically independent evolutions of piscivory and durophagy, on body dimensions, organ topology, and organ proportions between nine moray species (Muraenidae). We found that organ placement via the anteroposterior organ positions differed between members in the two diet categories, although general organ topology is conserved. The stomach (31 – 55%) and intestine (68 – 76%) consistently occupied the majority of the body cavity irrespective of diet. Diet was shown to influence overall body dimensions and relative organ proportions across all moray species. Durophagous morays have shorter head lengths and body depths, and shorter heart, liver, gall bladder, and spleen lengths compared to piscivorous species. There was also greater variation in organ lengths among durophagous species than within piscivorous species. We attribute this greater variation in organ lengths to the multiple independent origins of durophagy within Muraenidae. Our single intraspecific comparison of the California moray, Gymnothorax mordax, a piscivorous species, revealed that all organs scale isometrically with body cavity length over ontogeny. The stomach grows proportionally with body cavity length and is the second longest organ in G. mordax at all ontogenetic stages, with the longest being the intestine. This suggests that morays can consume large quantities of prey or relatively large individual prey throughout their life history. In addition to scaling patterns of G. mordax, our study is the first to investigate the effects of diet and the intraspecific scaling patterns on the viscera of members of the Muraenidae, a clade of obligate carnivores that inhabit most marine ecosystems.

Review of the moray eels (Anguilliformes: Muraenidae) of the Red Sea, with description of a new species.

Thirty-eight species of moray eels (Muraenidae) from the Red Sea are reported in an updated review. A species account is provided for each species, along with a full synonymy of all nominal species described from the Red Sea. One species is new to science, G. pharaonis, and two species are new for the Red Sea, Gymnothorax phasmatodes (Smith) and Scuticaria tigrina (Lesson). Gymnothorax pharaonis n. sp. is a common species that has long been misidentified as G. undulatus (Lacepède), although it more closely resembles G. margaritophorus Bleeker, to which it is closely related phylogenetically. It is characterized by the following combination of characters: total vertebrae 123-128; body slender, depth at anus 17-28 in TL; maxillary teeth biserial, dentary and vomerine teeth in a single row; color brown with irregular dendritic pale markings, not interconnected or chain-like, with oblique, conspicuous, parallel streaks posteriorly in dorsal fin. The new record of the distinctive whitish G. phasmatodes is based on an underwater photograph taken at Jeddah, Saudi Arabia. The new record of Scuticaria tigrina is based on a specimen collected from Jeddah, Saudi Arabia, and underwater photographs taken from the northern part of the Red Sea. Based on an integrative taxonomical approach by a combination of morphological and phylogenetic analyses and re-examination of holotype specimens, Gymnothorax cinerascens (Rüppell) is resurrected as a valid species, and it is shown that previous records of G. hepaticus (Rüppell), with which it has previously been synonymized, should refer to G. cinerascens. The true G. hepaticus is redescribed based on examination of the holotype and additional specimens collected during the course of this study. The two species are distinguished by the color of the jaws, the position of the median intermaxillary teeth, and a slight difference in the preanal length. They are also clearly distinct genetically. The Red Sea record of Gymnothorax atolli (Pietschmann) is based on an error, possibly a misidentification of G. griseus (Lacepède). A key to the species of Red Sea moray eels and a phylogenetic tree of presently known lineages of Indo-Pacific moray eels are provided including recently collected Red Sea specimens.

<i>Gymnothorax zonipectis</i> Seale, 1906 (Anguilliformes: Muraenidae) - an addition to the Eel Fauna of Andaman and Nicobar Islands and India

A moray eel species, Gymnothorax zonipectis Seale, 1906, is reported for the first time from India based on photographic evidence from Neil Island, Andaman and Nicobar Islands, and expands its geographical distribution further westward. The description, habitat ecology and distributional range of the eel also provided establishing its first record from India. An annotated checklist of moray eels from these islands is also appended.

PRE-SPAWNING SNOUT-GRIPPING BEHAVIORS OF GYMNOTHORAX PICTUS AND GYMNOTHORAX THYRSOIDEUS (MURAENIDAE) IN CAPTIVITY

The main focus of this study has been on the distinctive pre-spawning snout-gripping behaviors and mate choice of two moray species (Gymnothorax pictus and G. thyrsoideus). The behavior of snout-gripping means that the male grips the female’s snout with its jaws. It is the most distinctive behavior to confirm the success of mating pair formation naturally and was rarely described on moray eels or other coral reef fishes. The reproductive behaviors of the two moray species were also first observed and photographed in the laboratory aquaria. Over 22 reproductive events including 9 spawning events by 28 adult individuals of G. pictus were recorded. Eight sequential behaviors were recorded in the successful spawning events of G. pictus searching, courting, inviting, snout-gripping, rushing toward the water surface, turning around, spawning, separating and settling to the bottom. G. thyrsoideus also exhibited similar pre-spawning behaviors as G. pictus, but showed more aggressive behaviors between the males than G. pictus. Courtships and mating affairs occurred about 23 times by 32 adult individuals of G. thyrsoideus, but without spawning. Both species mated mainly between a female and a male at night (8:00PM-2:00AM). It only took a shorter time for G. pictus to go from snout-gripping to spawning (3-7 seconds), but a longer time for G. thyrsoideus to go from snout-gripping to separating (35-43 seconds).

A new species of the genus Diaphenchelys (Anguilliformes: Muraenidae) from Thailand

A new species of moray eel, Diaphenchelys dalmatian is described based on five specimens [289.8–503.0 mm total length (TL)] collected from the western coast of peninsular Thailand and the Gulf of Thailand. It can be easily distinguished from Diaphenchelys pelonates McCosker and Randall 2007, another species of the genus Diaphenchelys McCosker and Randall 2007, by its coloration (ground color white with brown dalmatian-like spots vs. brown with pale vermiculate pattern). The present new species also differs from D. pelonates in its longer tail (62.0–64.6% TL vs. 59.6–61.5%), fewer infraorbital pores along upper lip (three vs. four), fewer mandibular pores (five vs. six or seven), and fewer vertebral counts (preanal vertebrae 43–46 vs. 55–58; total 126–131 vs. 153–155). Diaphenchelys is closely similar to the genus Strophidon McClelland 1844 in the shape of neurocranium, the elongate body, low vertical fins, eye location, jaw shape, and presence of inner mandibular teeth. However, both differ in the vertebral counts (126–155 in Diaphenchelys vs. 164–208 in Strophidon) and coloration (prominent pattern vs. uniform).

Scaling of dentition and prey size in the California moray (Gymnothorax mordax)

Scaling patterns of tooth morphology can provide insights on prey capture strategy and dietary patterns as species grow through ontogeny. We report the scaling of dentition and diet and how it relates to body size in the California moray, Gymnothorax mordax. We sampled lengths, widths, and curvature for teeth lining five distinct regions of the oral jaws across 21 G. mordax individuals ranging from 383 to 1110mm total length. Absolute tooth length in relation to moray size shows positive allometry only for the outer maxillary teeth, while teeth lining the inner maxilla display positive allometry in tooth base width. All other regions exhibit isometric growth in both length and width relative to moray size. Similar to previous descriptions of other moray species, the longest teeth in the oral jaws are the median intermaxillary teeth. This series of three teeth are depressible and rooted in the center of the ethmovomer, the bone that forms the roof of the rostrum. We hypothesize that caudal mobility of the median intermaxillary teeth aids in prey transport by enabling the pharyngeal jaws to remove pierced prey without requiring full abduction of the oral jaws. The predominantly isometric tooth growth in G. mordax suggests that the oral teeth grow proportionately as individuals increase in size. Stomach contents from the field suggest that G. mordax is highly piscivorous. While a strong positively allometric relationship between vertical gape and head length supports the expectation that moray increase relative prey size over ontogeny, we found no relationship between prey standard length and moray size. This suggests that while larger individuals are capable of consuming larger prey, individual G. mordax are opportunistic predators that do not specialize on prey of a specific size over ontogeny.

A moray’s many knots: knot tying behaviour around bait in two species of Gymnothorax moray eel

Being able to tie their body into a knot is beneficial to some moray eels and other cylindrical vertebrates for various reasons, although not all morays’ tie knots. Knot tying can generate leverage for feeding activity by moving the knot up the body, and this leverage may be affected by knot type. Three types of knots are known to have been used by morays’ and this study further elucidates this behaviour and ability. Baited Remote Underwater Videos (BRUVs) were used to compare knot tying between the moray eels Gymnothorax prasinus and Gymnothorax prionodon in the Solitary Islands region, eastern Australia. Gymnothorax prasinus tied more knots overall and more types of knot than G. prionodon (five types vs one type, respectively). Both tied the overhand knot and this was the most common knot used by G. prasinus. The figure of eight knot was used two times more than the double overhand knot, being relatively wider and likely easier to move up the body. Gymnothorax prasinus also tied two undescribed knots, now called the ‘moray knot’ and the ‘morays banana knot’, which have more crossings and are bulkier, increasing potential for generating leverage. However, their uncommon use indicates costs may outweigh benefits of these more complex knots. Lower habitat complexity in deeper waters may influence differences in knot tying as G. prasinus were only recorded shallower than 40 m and G. prionodon mainly deeper. These findings further reveal the utility and complexity of knot tying in moray species and cylindrical vertebrates generally.

Freshwater habitat use by a moray eel species, Gymnothorax polyuranodon, in Fiji shown by otolith microchemistry

Freshwater eels of the Anguillidae are diadromous because they migrate between ocean and freshwater environments, but other anguilliform fishes are generally considered to be strictly marine species. A few marine eels of the Muraenidae and Ophichthidae have occasionally been found in freshwater or estuaries, indicating that anguillids are not the only anguilliform eels that can use freshwater in some parts of the world. The moray eel Gymnothorax polyuranodon is one species that is known to be present in freshwater in the Indo-Pacific, but its life history is unknown. One way to evaluate what types of habitats are used by fishes is to determine the ratio of strontium (Sr) to calcium (Ca) in their otoliths, because this can show if they have used freshwater or saltwater environments. To evaluate the patterns of freshwater use by this unusual species of marine eel, the otolith Sr/Ca ratios of four G. polyuranodon (275–344 mm) caught in a freshwater stream of Fiji were analyzed. The consistently low Sr/Ca values (0–4) indicated upstream movement after settlement and freshwater or estuarine residence of all four individuals. These eels did not appear to have entered freshwater just for a short time period, which is consistent with other reports that this species is present in estuarine and freshwater habitats. This suggests that G. polyuranodon may be a catadromous species of marine eel. The similarities and differences between the life histories of anguillid eels and the few marine eels that have evolved the ability to invade freshwater habitats is discussed in relation to the evolutionary origin of diadromy in anguilliform fishes that originated in the marine environment.

Ninth East China Sea Conference 2013: International Conference on the Marine Biodiversity and Environmental Fisheries Science of the East China Sea in Keelung, Taiwan

Five rare moray species: ＂Anarchias cantonensis＂ (Schultz), ＂Gymnothorax dorsalis＂ Seale, G. ＂intesi＂ (Fourmanoir and Rivaton), ＂G. phasmatodes＂ (Smith) and ＂G. sagmacephalus＂ (Bohlke) belonging to subfamilies Uropterygiinae and Muraeninae are reported for the first time off Taiwan. Diagnoses of these five species of moray eels including their fresh coloration and dentitions are provided. A redescription of ＂G. sagmacephalus＂ is provided since its description was based on the unique holotype was incomplete, especially due to its damaged tail tip. We add twelve additional specimens, give the statistics of morphological measurements and vertebral formulae for this species, and expand its geographical distribution from Japan to Taiwan.

OLFACTION AND VISUAL DETECTION OF FOOD AND RELEVANT MORPHOMETRIC CHARACTERS IN SOME SPECIES OF MORAY EELS (MURAENIDAE)

ABSTRACT Studies on moray eels (Muraenidae) in the Gulf of Aqaba have shown that species of the genera Siderea and Echidna dwell mainly in shallow, subtidal sandy habitats, whereas species of Gymnothorax and Lycodontis are frequently found in deeper, rocky or coral reef dwellings. Experiments with food items showed that species of the first group are macrosmatic, detecting their prey by olfaction, whereas the second group are microsmatic, hunting primarily by vision. These two foraging types were also found to differ in ratios of mouth length and eye diameter to total body length and of longest-tooth length to mouth length. The macrosmatic morays have smaller eyes, and shorter mouths and teeth. These differences probably reflect partitioning of habitat and food niches among the various moray eel species.

Evolutionary history of elongation and maximum body length in moray eels (Anguilliformes: Muraenidae)

Body shape and size are important axes of organismal diversification. The elongate body form has evolved repeatedly in disparate vertebrate clades, and is associated with a variety of maximum body lengths. We used a time-calibrated phylogeny for 40 species of moray eels to analyse the evolution of elongation and the morphological mechanisms underlying variation in body shape and maximum body length. We find that body elongation in morays evolves independently of elongation of the vertebral column. In contrast, maximum body length evolves by a different mechanism: through region-specific increases in vertebral number, elongation of individual vertebral centra, and postembryonic somatic growth. We reconstruct an ancestral moray eel and provide evidence for accelerated morphological evolution in three highly elongate species that are associated with a burrowing lifestyle. We compare these patterns with those described for other vertebrates, and show that body shape and body length may evolve independently of each other and (in the case of shape) of the vertebral column. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, ••, ••‐••. ADDITIONAL KEYWORDS: axial skeleton ‐ morphological evolution ‐ pleomerism ‐ size ‐ vertebrae ‐ vertebral aspect ratio.

A checklist of the moray eels of the world (Teleostei: Anguilliformes: Muraenidae)

A checklist of the currently recognized species of moray eels (Muraenidae) is presented. One hundred ninety seven speciesare considered to be valid, in 15 genera, and two subfamilies. The account for each valid species contains bibliographicinformation for that species and all synonyms, including primary type specimens and type locality. Also given for eachspecies is the number of vertebrae, the mean vertebral formula (MVF), the general geographic distribution, and any ex-planatory remarks that may be needed. A list of nominal genera and species is given, with the current status of each. Separate lists are provided for names that cannot be assigned to known species (incertae sedis) and those that are unavailable.

ADDITIONS TO THE TAIWAN MARINE EEL FAUNA WITH FIRST RECORDS OF THREE RARE MORAY EELS (ANGUILLIFORMES: MURAENIDAE)

The specimens of three new records of moray eels (Anguilliformes: Muraenidae) were identified for the first time off the eastern (Changbin) and southern (Kenting) coast of Taiwan. They were Enchelynassa canina (Quoy and Gaimard), Gymnothorax elegans Bliss and Gymnothorax fuscomaculatus (Schultz). The monotypic genus Enchelynassa which had only one species in the genus was also a newly recorded genus to Taiwan. In this paper, we reported the three rare moray species, included diagnostic characters and the fresh coloration on whole body, head, dorsal and ventral sides; as well as their dentitions; and the key to the relative species.

Comparative phylogeography of four Indo-Pacific moray eel species (Muraenidae) reveals comparable ocean-wide genetic connectivity despite five-fold differences in available adult habitat

Most coral reef fishes have non-migratory adults and depend on a pelagic larval stage for dispersal. Species with long pelagic larval duration (PLD) can have tremendous dispersal potential and thus display little geographic-genetic differentiation among reef habitats. Restricted adult niche breadth due to habitat specialization can have the opposite effect of fragmenting populations and increasing geographic-genetic differentiation. If long PLD suffices to ensure widespread gene flow among reef populations, we predict similar geographic-genetic homogene- ity within species whose adults differ in niche breadth. We tested this hypothesis using a compar- ative phylogeographic study of 4 sympatric moray eel species that differ in the amount of available habitat within their reported ranges. We generated molecular genetic data for Echidna nebulosa (N = 79) and Gymnomuraena zebra (N = 67) to measure geographic-genetic structure within these species, whose adult habitat is very restricted for moray eels, and compared these results to iden- tical measurements previously published for habitat generalists Gymnothorax undulatus and Gymnothorax flavimarginatus. These 4 species share an ocean-wide distribution with adults occu- pying the same reefs; however, adults of E. nebulosa and G. zebra are restricted to shallow waters and occupy only 20% of the area occupied by the Gymnothorax species. Mitochondrial (632 bp of cytochrome b and 596 bp of cytochrome oxidase I) genomic sequences revealed high genetic vari- ation (h = 0.995 to 0.998) and low geographic-genetic differentiation (pairwise ΦST < 0.07 and not significant) for each species across 22 000 km of the Indo-Pacific. Nuclear genomic sequences (420 bp of RAG-1 and 746 bp of RAG-2) demonstrated 16 to 25 haplotypes per marker within each species with minimal geographic-genetic differentiation among populations. This suggests that in cosmopolitan and highly dispersive species such as morays, larval life history can ensure wide- spread gene flow despite a 5-fold difference in the habitat breadth occupied by adult populations.

Spatial distribution of ciguateric fish in the Republic of Kiribati

Ciguatera is food poisoning caused by human consumption of reef fish contaminated with ciguatoxins (CTXs). The expanding international trade of tropical fish species from ciguatera-endemic regions has resulted in increased global incidence of ciguatera, and more than 50000 people are estimated to suffer from ciguatera each year worldwide. The Republic of Kiribati is located in the Pacific Ocean; two of its islands, Marakei and Tarawa, have been suggested as high-risk areas for ciguatera. The toxicities of coral reef fish collected from these islands, including herbivorous, omnivorous and carnivorous fish (24% [n=41], 8% [n=13] and 68% [n=117], respectively), were analyzed using the mouse neuroblastoma assay (MNA) after CTX extraction. The MNA results indicated that 156 fish specimens, or 91% of the fish samples, were ciguatoxic (CTX levels >0.01ngg−1). Groupers and moray eels were generally more toxic by an order of magnitude than other fish species. All of the collected individuals of eight species (n=3–19) were toxic. Toxicity varied within species and among locations by up to 10000-fold. Cephalapholis argus and Gymnothorax spp. collected from Tarawa Island were significantly less toxic than those from Marakei Island, although all individuals were toxic based on the 0.01ngg−1 threshold. CTX concentrations in the livers of individuals of two moray eel species (Gymnothorax spp., n=6) were nine times greater than those in muscle, and toxicity in liver and muscle showed a strong positive correlation with body weight. The present study provides quantitative information on the ciguatoxicity and distribution of toxicity in fish for use in fisheries management and public health.

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

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