Sea Snake Research Articles

First record of potential Batesian mimicry in an elasmobranch: juvenile zebra sharks mimic banded sea snakes?

Various forms of mimicry have been recorded in a large number of marine fishes; however, there have been no records of mimicry for any elasmobranch species. We propose that the distinctly banded neonates of the zebra shark (Stegostoma fasciatum) are Batesian mimics of banded sea snakes (Elapidae). Observations of banded juveniles of S. fasciatum swimming close to the surface strongly resemble banded sea snakes in colour and body form as well as the undulatory swimming movements. Sea snakes are venomous and are known to defend themselves against predators. Although several shark species prey on them, most species appear to avoid sea snakes as prey items. Juvenile S. fasciatum possess a very long, single-lobed caudal fin that remarkably resembles the broad, paddle-like tail of sea snakes. This may be an adaptation enabling this species to mimic sea snakes, at least in the earliest life stages. There is a need for empirical testing of the hypothesis that juvenile S. fasciatum is a true example of Batesian mimicry, but here we provide evidence that suggests this may be the first example of mimicry in an elasmobranch species.

Cytotoxicity of Southeast Asian snake venoms

Cytotoxicity of venoms from eleven medically important snakes found in Southeast Asia (Naja kaouthia, Naja siamensis, Naja sumatrana, Ophiophagus hannah, Bungarus candidus, Bungarus fasciatus, Enhydrina schistosa, Calloselasma rhodostoma, Trimeresurus purpureomaculatus and Tropidolaemus sumatranus) was determined, based on the MTS cytotoxicity assay, which determines the survival of viable cells in monolayer MDCK and Vero cell cultures upon exposure to the snake venoms. Snake venom toxicity was expressed as the venom dose that killed 50% of the cells (CTC50) under the assay conditions. Venoms of C. rhodostoma (2.6 µg/mL, 1.4 µg/mL) and O. hannah were the most cytotoxic (3.8 µg/mL, 1.7 µg/mL) whereas N. siamensis venom showed the least cytotoxicity (51.9 µg/mL, 45.7 µg/mL) against Vero and MDCK cells, respectively. All the viper venoms showed higher cytotoxic potency towards both Vero and MDCK cell lines, in comparison to krait and cobra venoms. E. schistosa did not cause cytotoxicity towards MDCK or Vero cells at the tested concentrations. The cytotoxicity correlates well with the known differences in the composition of venoms from cobras, kraits, vipers and sea snakes.

Status of the Annulated Sea Snake, Hydrophis cyanocinctus, in the Hara Protected Area of the Persian Gulf

Data on the Annulated Sea Snake (Hydrophis cyanocinctus) were collected during more than one year of field study in the Hara Protected Area, the largest mangrove forest in the Persian Gulf. Mean snoutvent length (SVL) was 117 cm and the largest snake was a female with a SVL of 155 cm and a weight of 1019 g. The Annulated Sea Snake is the dominant sea snake in the area. The species is more active in the warm season (April to November). Local fishing activities are considered the main threat for the species in this area.

Rediscovery of the Rare Sea Snake Hydrophis parviceps Smith 1935: Identification and Conservation Status

Smith's small-headed sea snake, Hydrophis parviceps, was originally described in 1935 from a single type specimen collected in southern Vietnam. Since this time there has been only one further record for the species—a specimen collected near the type locality in 1960 that has since been lost. Through field surveys in southern Vietnam in 2001, we obtained three additional specimens of this poorly known sea snake from fisheries bycatch. In the current paper, we present morphological and molecular data for the three new specimens and the holotype, and redescribe H. parviceps based on data synthesized for all five specimens known to date. We also discuss the conservation status of the species based on its vulnerability to fisheries bycatch mortality and seemingly low abundance within a very restricted geographic distribution.

The first record of the sea snake Chitulia inornata Gray, 1849 from the Arabian Sea with notes on the composition of the genus Chitulia Gray, 1849 (Serpentes: Hydrophiidae)

The first record of the sea snake Chitulia inornata from the Arabian Sea and its distribution data are reported. The species composition of the genus Chitulia is analyzed. A revised key to the species of the genus Chitulia is provided.

海蛇ロボットの推進力特性に関する研究

海蛇ロボットの推進力特性に関する研究

Metal concentrations in selected tissues and main prey species of the annulated sea snake (Hydrophis cyanocinctus) in the Hara Protected Area, northeastern coast of the Persian Gulf, Iran

This study is the first detailed ecotoxicological study of the annulated sea snake, Hydrophis cyanocinctus. Concentrations of lead, cadmium, nickel and vanadium were evaluated in muscle, liver, kidney, skin and blood of the annulated sea snake (H. cyanocinctus) and in the whole bodies of its main prey species (Periophthalmus waltoni and Boleophthalmus dussumieri) in the Hara Protected Area, the Persian Gulf. The mean concentrations of lead and vanadium were highest in the kidney, which identified the kidney as a target organ for metals in sea snakes as it is in other reptilian groups. Mean concentrations of cadmium and nickel were highest in the liver and skin, respectively. Mean cadmium concentrations were significantly higher in the liver compared to prey species, which indicated that prey items may be a source of cadmium for the annulated sea snake in the study area. Data presented here may be considered as a baseline for further ecotoxicological studies in sea snakes.

Abundance of Sea Kraits Correlates with Precipitation

Recent studies have shown that sea kraits (Laticauda spp.) – amphibious sea snakes – dehydrate without a source of fresh water, drink only fresh water or very dilute brackish water, and have a spatial distribution of abundance that correlates with freshwater sites in Taiwan. The spatial distribution correlates with sites where there is a source of fresh water in addition to local precipitation. Here we report six years of longitudinal data on the abundance of sea kraits related to precipitation at sites where these snakes are normally abundant in the coastal waters of Lanyu (Orchid Island), Taiwan. The number of observed sea kraits varies from year-to-year and correlates positively with previous 6-mo cumulative rainfall, which serves as an inverse index of drought. Grouped data for snake counts indicate that mean abundance in wet years is nearly 3-fold greater than in dry years, and this difference is significant. These data corroborate previous findings and suggest that freshwater dependence influences the abundance or activity of sea kraits on both spatial and temporal scales. The increasing evidence for freshwater dependence in these and other marine species have important implications for the possible impact of climate change on sea snake distributions.

Observations on the anterior testicular ducts in snakes with emphasis on sea snakes and ultrastructure in the yellow‐bellied sea snake, Pelamis platurus

The anterior testicular ducts of squamates transport sperm from the seminiferous tubules to the ductus deferens. These ducts consist of the rete testis, ductuli efferentes, and ductus epididymis. Many histological and a few ultrastructural studies of the squamate reproductive tract exist, but none concern the Hydrophiidae, the sea snakes and sea kraits. In this study, we describe the anterior testicular ducts of six species of hydrophiid snakes as well as representatives from the Elapidae, Homolapsidae, Leptotyphlopidae, and Uropeltidae. In addition, we examine the ultrastructure of these ducts in the yellow-bellied Sea Snake, Pelamis platurus, only the third such study on snakes. The anterior testicular ducts are similar in histology in all species examined. The rete testis is simple squamous or cuboidal epithelium and transports sperm from the seminiferous tubules to the ductuli efferentes in the extratesticular epididymal sheath. The ductuli efferentes are branched, convoluted tubules composed of simple cuboidal, ciliated epithelium, and many species possess periodic acid-Schiff+ granules in the cytoplasm. The ductus epididymis at the light microscopy level appears composed of pseudostratified columnar epithelium. At the ultrastructural level, the rete testis and ductuli efferentes of P. platurus possess numerous small coated vesicles and lack secretory vacuoles. Apocrine blebs in the ductuli efferentes, however, indicate secretory activity, possibly by a constitutive pathway. Ultrastructure reveals three types of cells in the ductus epididymis of P. platurus: columnar principal cells, squamous basal cells, and mitochondria-rich apical cells. This is the first report of apical cells in a snake. In addition, occasional principal cells possess a single cilium, which has not been reported in reptiles previously but is known in some birds. Finally, the ductus epididymis of P. platurus differs from other snakes that have been studied in possession of apical, biphasic secretory vacuoles. All of the proximal ducts are characterized by widening of adjacent plasma membranes into wide intercellular spaces, especially between the principal cells of the ductus epididymis. Our results contribute to a larger, collaborative study of the evolution of the squamate reproductive tract and to the potential for utilizing cellular characters in future phylogenetic inferences.

Paleogene Sea Snakes from the Eastern Part of Tethys

Nessovophis tamdy gen. et sp. nov. (Nigerophiidae, middle Eocene, Bartonian), Nessovophis zhylga sp. nov. (early Eocene, Ypresian), Palaeophis ferganicus sp. nov. (early Eocene, Ypresian), Palaeophis udovichenkoi sp. nov. (middle – ?late Eocene, Bartonian – ?Priabonian), Palaeophis nessovi sp. nov. (late Eocene, Priabonian), Palaeophis sp. (middle Eocene, Bartonian), and Pterosphenus muruntau sp. nov. (middle Eocene, Bartonian) are described and Vialovophis zhylan Nessov, 1984 (?latest Paleocene) is redescribed on the basis of 45 isolated vertebrae from 8 localities in Kazakhstan, Tajikistan, Kirghizia, Uzbekistan, and Ukraine. Phylogenetic analysis of 8 Cretaceous-Paleogene taxa of sea snakes reveals two monophyletic groups: Palaeophiidae (Palaeophis and Pterosphenus) and Nigerophiidae (Nigerophis, Woutersophis, and Nessovophis).

On the Taxonomic Status of a Mangrove Sea Snake Hydrelaps darwiniensis Boulenger, 1896 (Serpentes, Hydrophiidae)

The erection of the subfamily Hydrelapinae nov. for the mangrove sea snake Hydrelaps darwiniensis Boulenger, 1896 is substantiated. Key for identification of subfamilies of family Hydrophiidae is given. Lectotype and paralectotype of H. darwiniensis is given.

Animal‐Related Fatalities—Part II: Characteristic Autopsy Findings and Variable Causes of Death Associated with Envenomation, Poisoning, Anaphylaxis, Asphyxiation, and Sepsis

In addition to blunt and sharp trauma, animal-related fatalities may result from envenomation, poisoning, anaphylaxis, asphyxiation, and sepsis. Although the majority of envenomation deaths are caused by hornets, bees, and wasps, the mechanism of death is most often anaphylaxis. Envenomation resulting from the injection of a poison or toxin into a victim occurs with snakes, spiders, and scorpions on land. Marine animal envenomation may result from stings and bites from jellyfish, octopus, stonefish, cone fish, stingrays, and sea snakes. At autopsy, the findings may be extremely subtle, and so a history of exposure is required. Poisoning may also occur from ingesting certain fish, with three main forms of neurotoxin poisoning involving ciguatera, tetrodotoxin ingestion, and paralytic shellfish poisoning. Asphyxiation may follow upper airway occlusion or neck/chest compression by animals, and sepsis may follow bites. Autopsy analysis of cases requires extensive toxinological, toxicological, and biochemical analyses of body fluids.

Invasives: Sea of Data Still to Come

Recently, there has been a great deal of discussion about terrestrial and coastal bioinvasions [“Invasives: A major conservation threat,” M. Lambertini et al. , Letters, 22 July, p. [404][1]; and ([ 1 ][2]–[ 3 ][3])]. However, our lack of knowledge regarding the natural history of marine groups, especially marine invertebrates and microorganisms, is alarming. This lack constitutes a major impediment to understanding evolutionary histories of these organisms, ultimately making their conservation more difficult. Top predators are important for the natural dispersal of marine invertebrate populations. As they move between different locations, they transfer genetic material between geographically distant populations. Many free-living species, which include sessile taxa (such as sponges, bivalves, and barnacles) and vagile taxa (such as decapods, gastropods, and echinoderms) live as epibiotic communities on vertebrates (such as fishes, sharks, turtles, sea snakes, and whales). Therefore, long-distance migrations of the vertebrates cause dispersal of a whole biota of marine invertebrates, connecting and even merging previously isolated populations. These new structures are often interpreted as human-mediated introduced species and potentially hazardous bioinvaders, when they are in fact natural distributions. Without a better understanding of the natural history of marine invertebrates, it will be impossible to correctly identify and take environmentally appropriate action to address these species. ![Figure][4] Along for the ride. Barnacles travel with a gray whale as it moves to new locations. CREDIT: DAVID BACON/ALAMY 1. [↵][5]1. G. Rilov, 2. J. A. Crooks , Biological Invasions in Marine Ecosystems (Springer-Verlag, Berlin, 2009). 2. 1. G. Vince , Science 331, 1383 (2011). [OpenUrl][6][Abstract/FREE Full Text][7] 3. [↵][8]1. M. A. Davis 2. et al ., Nature 474, 153 (2011). [OpenUrl][9][CrossRef][10][PubMed][11][Web of Science][12] [1]: http://www.sciencemag.org/content/333/6041/404.2.full [2]: #ref-1 [3]: #ref-3 [4]: pending:yes [5]: #xref-ref-1-1 View reference 1 in text [6]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DVince%26rft.auinit1%253DG.%26rft.volume%253D331%26rft.issue%253D6023%26rft.spage%253D1383%26rft.epage%253D1384%26rft.atitle%253DEmbracing%2BInvasives%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.331.6023.1383%26rft_id%253Dinfo%253Apmid%252F21415332%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [7]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEzOiIzMzEvNjAyMy8xMzgzIjtzOjQ6ImF0b20iO3M6MjQ6Ii9zY2kvMzMzLzYwNDUvOTM2LjEuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [8]: #xref-ref-3-1 View reference 3 in text [9]: {openurl}?query=rft.jtitle%253DNature%26rft.stitle%253DNature%26rft.aulast%253DDavis%26rft.auinit1%253DM.%2BA.%26rft.volume%253D474%26rft.issue%253D7350%26rft.spage%253D153%26rft.epage%253D154%26rft.atitle%253DDon%2527t%2Bjudge%2Bspecies%2Bon%2Btheir%2Borigins.%26rft_id%253Dinfo%253Adoi%252F10.1038%252F474153a%26rft_id%253Dinfo%253Apmid%252F21654782%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [10]: /lookup/external-ref?access_num=10.1038/474153a&link_type=DOI [11]: /lookup/external-ref?access_num=21654782&link_type=MED&atom=%2Fsci%2F333%2F6045%2F936.1.atom [12]: /lookup/external-ref?access_num=000291397800026&link_type=ISI

Development of eleven polymorphic microsatellite loci for the sea snake Emydocephalus annulatus (Elapidae: Hydrophiinae) and cross-species amplification for seven species in the sister genus Aipysurus

We developed eleven microsatellite loci for the turtleheaded sea snake, Emydocephalus annulatus, from partial genomic DNA libraries using a repeat enrichment protocol. Nine loci had high numbers of alleles (11–32) per locus, while the other two loci had six alleles each. All eleven loci amplified successfully and were polymorphic in six of seven sea snake species from the sister genus Aipysurus, while ten loci amplified successfully for the seventh species. Based on these highly successful cross-amplifications we expect these loci to be useful markers for evaluating population genetic structure, gene flow, relatedness and effective population sizes for all Aipysurus group sea snakes.

Light- and flotsam-dependent ‘float-and-wait’ foraging by pelagic sea snakes (Pelamis platurus)

Efficient detection of food patches in oceanic areas by pelagic predators is often linked to large-scale physical structures (e.g. fronts, upwellings) that are usually rich and predictable. At smaller scales, however, predictability of resource becomes less clear because of the lability of smaller physical structures such as slicks and drift lines. Here, we explore how light levels and quantity of flotsam affect the occurrence of foraging Yellow-bellied sea snakes (Pelamis platurus) on slicks. Although this pelagic species was formerly hypothesised to surface randomly and drift passively to reach slicks, our results show that foraging snakes are far more abundant on slicks if light levels are high and if slicks display flotsam. The combination of both light and flotsam should enhance the contrast between a potentially favourable slick and the adjacent waters as seen from an underwater viewpoint. Although our results do not unambiguously demonstrate the ability of Pelamis platurus to visually detect surface drift lines, they clearly suggest a role of both light levels and amount of flotsam on surfacing decision. Accordingly, this hypothesis is supported by several complementary traits that are specific to this species. ‘Float-and-wait’ foraging undoubtedly requires efficient detection of, and orientation to, oceanic slicks—processes that are likely less random and passive than formerly believed. Successful pelagic foraging is no doubt important to this species of sea snake that is the world’s most widely distributed snake species.

Variación de color de la serpiente marina Pelamis platura (Serpentes: Elapidae) en el Golfo Dulce, Puntarenas, Costa Rica

La serpiente marina de vientre amarillo (Pelamis platura) tiene el mayor ámbito de distribución entre todas las serpientes marinas, y a lo largo de su rango la especie exhibe gran variación en su patrón y color. El color de la mayoría de los ejemplares es negro con café y/o amarillo, que se muestran dentro un patrón variable, aunque ejemplares sin patrón de color amarillo brillante se han reportado de ciertas localidades de Costa Rica y Panamá. Recientemente en el interior de la cuenca del Golfo Dulce, al sur de la costa Pacífica de Costa Rica, se descubrió una población donde todos los ejemplares muestran cantidades extensivas de color amarillo. La evidencia sugiere que los patrones de circulación de las corrientes superficiales en el interior y exterior de este golfo de tipo fiordo, aparentemente son suficientes para interrumpir el flujo o intercambio genético entre la población oceánica y la del Golfo Dulce. La falta o pérdida de la pigmentación oscura en el dorso de la población del Golfo Dulce puede haber sido el resultado de las temperaturas del agua y otras condiciones particulares en esta cuenca anóxica, única en la costa Pacífica del Hemisferio Occidental.

Sea snakes (Serpentes: subfamilies Hydrophiinae and Laticaudinae) in Vietnam: a comprehensive checklist and an updated identification key

Sea snakes (Elapidae, subfamilies Hydrophiinae and Laticaudinae) reach a very high species richness in Southeast Asia, but most countries in the region still lack comprehensive and up-to-date identification tools for these snakes. We present an updated checklist of sea snakes in Vietnam. We also provide diagnostic characters for all species and a new complete identification key, chiefly based on easy-to-use external characters. The checklist and key cover the 25 species documented from Vietnam, as well as three likely future additions to its sea snake fauna. By surveying incoming fishing vessels between Nha Trang and the mouth of Mekong River in 2000–2001, we were able to document two species new for Vietnamese waters: Hydrophis belcheri and H. pachycercos. Through these surveys we also secured four specimens of the rare endemic species H. parviceps, formerly known only from two specimens. A comprehensive bibliography of the literature treating sea snakes in Vietnamese waters is provided.Identification key: bibliography, biodiversity, diagnostic characters, Vietnamese waters

The study on venom proteins of Lapemis hardwickii by cDNA phage display

In this study, a cDNA T7 phage display library was constructed from sea snake Lapemis hardwickii venom gland mRNA to analyze the components in venom and find new toxins. All the venom gland cDNA-encoding proteins, including housekeeping proteins and venom proteins were expressed on the surface of bacteriophage T7. This library was then panned with rabbit anti-sea snake venom IgG. Phage particles displaying venom-components with interaction with the antibodies were enriched. Thus, phage-carrying venom proteins, such as short chain neurotoxin, long chain neurotoxin, PLA2-like toxin, and c-type lectin-like protein were found, some of them were never reported previously. Four different short chain neurotoxins (SNT-1, 2, 3, 4) were cloned and expressed in Escherichia coli. The LD50 and analgesic activities of their purified forms were determined. Their structure–function relationship were studied with the aid of a toxin–nAChR complex model constructed by ourselves. Among them, SNT-4 was a new neurotoxin identified in this study and showed potential as pain killer. These results prove that cDNA phage display technique has great advantage than traditional cDNA library method because of the linkage between phenotype and genotype of phage, which provided an effective means to study unknown proteins with target functions.

Vertebrae of the sea snake Palaeophis nessovi Averianov (Acrochordoidea, Palaeophiidae) from the Eocene of western Kazakhstan and phylogenetic analysis of the superfamily Acrochordoidea

The vertebrae of sea snakes from five Eocene localities in western Kazakhstan are assigned to the species Palaeophis nessovi Averianov, 1997. The anterior trunk vertebrae have subcentral ridges, large posterior hypapophysis, and large synapophyses; the middle trunk vertebrae are slightly laterally compressed and their synapophyses are positioned highly; the posterior trunk vertebrae are strongly laterally compressed and have a well-developed haemal keel. Cladistic analysis has shown that the genus Palaeophis is not monophyletic; the genus Archaeophis is a more advanced palaeophiid than was previously thought.

Effect of sulfhydryl group modification on the neurotoxic action of a sea snake toxin.

Pelamis toxin alpha is a major neurotoxin isolated from the venom of Pelamis platurus (yellow-bellied sea snake). The effect of sulfhydryl group modification by NN'-1,4-phenylenedimaleimide on the neurotoxic action of Pelamis toxin alpha has been investigated. The cross-linked toxin having a molecular weight of 11 000 was formed without significant structural changes in the toxin. Lethality tests on the modified toxin indicated that it retained considerable toxicity, although its potency was weaker than that of the native toxin. Binding studies with the acetylcholine receptor isolated from the electroplax of Torpedo californica indicated that the modified toxin binds to the receptor but less effectively than the native toxin. These results suggest that the decreases in toxicity and binding to the receptor are due to a decrease in accessibility of cross-linked neurotoxin to the receptor. This leads us to the conclusion that the region of the neurotoxin containing the sulfhydryl group is not essential for its biological activity. Analysis of the structure and function relationships of the modified toxin suggests that the neurotoxin-acetylcholine receptor interaction requires the proper orientation of the neurotoxin molecule.