Sea Snake Research Articles

Notes on the natural history and identity of the pelagic sea snake Hydrophis platurus (Serpentes: Elapidae) from Golfo Dulce, Puntarenas, Costa Rica

Introduction: The pelagic sea snake Hydrophis platurus has the broadest distributional range of all the snakes and is the only sea snake of tropical waters off the west coast of the Americas. Within the variation in the color pattern of this species, completely yellow specimens were considered very rare or occasional. However, a yellow pattern dominates a population established in the interior of the Golfo Dulce in the Southern Pacific of Costa Rica. Objective: We studied the abundance, activity patterns, morphometry, and feeding behavior of the yellow H. platurus within the Golfo Dulce. Methods: Between February 2009 and July 2018, we conducted surveys for sea snakes from a boat within the perimeter of the Golfo Dulce. Results: Adults from the gulf population are smaller than the bicolor oceanic population, with females having larger bodies. Sea snakes within the gulf float and move with surface currents without being linked to drift lines and debris. These snakes are mainly found in clean, calm waters with little turbulence. They feed on a wide diversity of small fish, which they capture using passive stalking predatory behaviors floating on the surface. Prey are quickly captured and swallowed alive. This species has an almost total absence of predation, a pattern that extends to this yellow population. Conclusions: The characteristics of the gulf and the direction and strength of the surface currents at its entrance might restrict the transit of this yellow population to the outside and the entry of the bicolored snakes of the oceanic population. We do not consider making taxonomic changes in this Golfo Dulce population prudent. This yellow population is relatively common within the basin. However, the high tourist traffic and other activities are risk factors for its conservation. Protection policies must be created to preserve and protect this small population of yellow sea snakes unique within this species' distribution range.

Challenges of regulating commercial use of marine elapid snakes in the Indo-Pacific.

Marine elapid snakes are a diverse, predominantly Indo-West Pacific species group. The persistent removal of some species has an unquantified but potentially dire impact on populations. We conducted the first comprehensive review of the trade in marine elapid snakes based on published literature (1974-2022) and trade data from the only species (i.e., Hydrophis [Lapemis] curtus) whose trade is monitored internationally. Some species and populations were subjected to targeted harvest for their meat and skins for at least the last century; fisheries are possibly the most significant threat to populations of marine elapids, with the highest numbers being exploited either accidentally, incidentally, or opportunistically in Southeast Asian fisheries targeting other seafood, including demersal trawl and squid fisheries. Southeast Asia is the core region for exploitation of marine elapids. Annual offtake is >225,000 individuals of at least 8 species in the Gulf of Thailand. Of 72 recognized marine elapids (all non-CITES [Convention on International Trade in Endangered Species of Wild Fauna and Flora] species), Hydrophis curtus and Hydrophis cyanocinctus dominate the skin trade. Skins of H. curtus are traded mainly in East and Southeast Asia and, to some extent, Europe. Despite some baseline information on the trade of these species, the sustainability of their harvests, particularly in the context of the burgeoning and unmanaged nature of fisheries in the region, remains the major challenge. In an era of declining fish stocks, there has been an increasing trend to commercialize the harvest and use marine elapids that were once considered accidental bycatch and discarded. This trend will continue to pose a significant risk to these snakes unless appropriate fisheries and trade regulations are enforced. Applying the precautionary principle to prevent the overexploitation of sea snakes is an indispensable measure in which trade in regional populations should be regulated through CITES. Accordingly, management plans to identify core distribution regions of exploited species would be crucial for assigning national responsibilities to sustain species and populations in the long term.

Sea snakes

Jenna Crowe-Riddell and colleagues introduce sea snakes.

Barnacle infestation of two sea snakes Hydrophis schistosus and Hydrophis curtus in the Bay of Bengal

Barnacle infestation of two sea snakes Hydrophis schistosus and Hydrophis curtus in the Bay of Bengal

Investigating heavy metal concentrations in sea snakes (Elapidae: Hydrophiinae) as an outcome of oil spill exposure

This study reports the concentration of heavy metals in the tissues of stranded sea snakes that died as a result of exposure to an oil spill on the eastern coast of Sharjah, UAE. Given the limited occurrence of stranded sea snakes observed along Sharjah's eastern coast outside this spill incident, we are using strandings collected from the nearby Arabian Gulf coast of Sharjah to compare the levels of heavy metals in sea snakes affected by the oil spill against their non-oiled counterparts. The sample comprised 14 Arabian Gulf Coral Reef Sea Snakes (Hydrophis lapemoides), 6 Yellow-bellied Sea Snakes (Hydrophis platurus), and 4 Yellow Sea Snakes (Hydrophis spiralis). Overall, our results show significantly higher concentrations of Al, Cd, Pb, Cr, Mn, Fe, Ni, Cu and Zn in sea snakes that were mired in oil.

Dynamic Expansions and Retinal Expression of Spectrally Distinct Short-Wavelength Opsin Genes in Sea Snakes.

The photopigment-encoding visual opsin genes that mediate color perception show great variation in copy number and adaptive function across vertebrates. An open question is how this variation has been shaped by the interaction of lineage-specific structural genomic architecture and ecological selection pressures. We contribute to this issue by investigating the expansion dynamics and expression of the duplicated Short-Wavelength-Sensitive-1 opsin (SWS1) in sea snakes (Elapidae). We generated one new genome, 45 resequencing datasets, 10 retinal transcriptomes, and 81 SWS1 exon sequences for sea snakes, and analyzed these alongside 16 existing genomes for sea snakes and their terrestrial relatives. Our analyses revealed multiple independent transitions in SWS1 copy number in the marine Hydrophis clade, with at least three lineages having multiple intact SWS1 genes: the previously studied Hydrophis cyanocinctus and at least two close relatives of this species; Hydrophis atriceps and Hydrophis fasciatus; and an individual Hydrophis curtus. In each lineage, gene copy divergence at a key spectral tuning site resulted in distinct UV and Violet/Blue-sensitive SWS1 subtypes. Both spectral variants were simultaneously expressed in the retinae of H. cyanocinctus and H. atriceps, providing the first evidence that these SWS1 expansions confer novel phenotypes. Finally, chromosome annotation for nine species revealed shared structural features in proximity to SWS1 regardless of copy number. If these features are associated with SWS1 duplication, expanded opsin complements could be more common in snakes than is currently recognized. Alternatively, selection pressures specific to aquatic environments could favor improved chromatic distinction in just some lineages.

VENOMOUS ENCOUNTER: A CASE REPORT ON SNAKE BITE DURING FULL-TERM GESTATION WITH DELAYED MANIFESTATION

Background: Snake bite is uncommon among pregnant women, that too presentation in third trimester with late presentation, with envenomation is rare. Knowledge about the toxic symptoms and management of snake bite poisoning is very low due the rarity of cases. Case report: Presenting a case of 26 year old female, Primigravida with Premature Rupture of Membranes with Snake bite in Acute Kidney Injury with Disseminate Intravascular Coagulopathy. Appropriate care and management led to the survival of both mother and baby. Discussion: In India, 216 snake species exist, 52 are venomous. Elapids like cobras, kraits, vipers, and sea snakes pose threats. Venom potency varies with seasons and snake color. Envenomation symptoms include local pain, systemic effects, and coagulopathy. Pregnancy complicates management antivenom and careful monitoring are vital. Conclusion: Acute kidney injury with disseminated intravascular coagulopathy arising from systemic poisoning due to snake bite in pregnancy is difficult and challenging. Obstetric and medical line of treatment depends on the severity of envenomation, gestational age at presentation, timing, duration and quality of treatment.

Mimic Octopus

Thaumoctopus mimicus is the scientific name of the Mimic octopus. The Mimic octopus is best known for being a mimic. It is a species of octopus from the tropical southwestern Pacific Ocean. Like other octopuses, it utilizes its chromatophores to camouflage itself with its background. Also, it is noteworthy for being able to mimic a wide range of other marine animals. It imitates other sea creatures, from flatfishes to sea snakes to anemones. It can also match its color scheme to those creatures. Mimics are also subterranean experts. They can dig burrows, navigate underground tunnels, and even blindly stick their arms into holes in search of snacks. Unlike the stereotypical octopus, which likes reefs with many crevices and holes to hide in, the Mimic octopus prefers the muddy areas of river mouths and estuaries. Because of its fantastic ability to change color and behavior and quickly burrow into soft sediment, the Mimic octopus doesn’t need to rely on structures to hide in. This makes wide-open, silty ocean floors a perfect habitat for them.

A Hook-Nosed Sea Snake, Hydrophis schistosus (Daudin 1803), dead due to a fish stuck in Its mouth

A Hook-Nosed Sea Snake, Hydrophis schistosus (Daudin 1803), dead due to a fish stuck in Its mouth

Systematic review and meta-analysis on the efficacy of Indian polyvalent antivenom against the Indian snakes of clinical significance.

Snakebite in India is a severe problem as it causes a mortality rate of 58,000 and a disability rate of 140,000 every year which is the highest among any other country. Antivenom is the primary therapy for snakebite, and its manufacturing techniques have essentially stayed unaltered for over a century. Indian polyvalent antivenom, a scientifically validated medicine for treating the toxic effects of snakebites, is available against the venom of the so-called Big Four snakes namely Spectacled cobra (Naja naja), Saw-scaled viper (Echis carinatus), Russell's viper (Daboia russelli) and the Common krait (Bungarus caeruleus), responsible for majority of the deaths in India. India hosts many other species of snakes, including cobras, kraits, saw-scaled vipers, sea snakes, and pit vipers, responsible for clinically severe envenomation. Neutralization strategy has been applied to access the efficacy of antivenoms, crucial for reducing snake bite deaths and disabilities. This review aims to conduct a systematic review and meta-analysis on the neutralization efficiency of the Polyvalent Antivenom (PAV) and focus on the factors that may contribute to the poor recognition of the antivenom towards the venom toxins. Reports focusing on the investigation of antivenom efficacy were searched and collected from several databases. Preclinical studies that reported the neutralization efficacy of the commercial antivenom against the medically important snakes of India were included. The articles were screened based on the inclusion criteria and 8 studies were shortlisted for meta-analysis. Pooled proportion was calculated for the antivenom efficacy reported by the studies and was found to be statistically significant with a 95% confidence interval. The heterogenicity in the venom toxicity and neutralization potency of the antivenom was evident in the overall estimate (proportion) and individual data. We provide comprehensive evidence on antivenom efficacy against medically important snakes from various parts of India which may aid in identifying the gaps in snake envenomation therapy and the need for novel potentially improved treatment of snakebites.

New chromosome-scale genomes provide insights into marine adaptations of sea snakes (Hydrophis: Elapidae)

BackgroundSea snakes underwent a complete transition from land to sea within the last ~ 15 million years, yet they remain a conspicuous gap in molecular studies of marine adaptation in vertebrates.ResultsHere, we generate four new annotated sea snake genomes, three of these at chromosome-scale (Hydrophis major, H. ornatus and H. curtus), and perform detailed comparative genomic analyses of sea snakes and their closest terrestrial relatives. Phylogenomic analyses highlight the possibility of near-simultaneous speciation at the root of Hydrophis, and synteny maps show intra-chromosomal variations that will be important targets for future adaptation and speciation genomic studies of this system. We then used a strict screen for positive selection in sea snakes (against a background of seven terrestrial snake genomes) to identify genes over-represented in hypoxia adaptation, sensory perception, immune response and morphological development.ConclusionsWe provide the best reference genomes currently available for the prolific and medically important elapid snake radiation. Our analyses highlight the phylogenetic complexity and conserved genome structure within Hydrophis. Positively selected marine-associated genes provide promising candidates for future, functional studies linking genetic signatures to the marine phenotypes of sea snakes and other vertebrates.

Polyphyly of the Dinurinae Looss, 1907 (Digenea: Hemiuridae) and resurrection of the Mecoderinae Skrjabin & Guschanskaja, 1954 based on novel collection of Tubulovesicula laticaudi Parukhin, 1969 from marine elapid snakes in Sri Lanka.

With one exception, the only known hemiurid trematodes that do not use teleost fishes as definitive hosts instead occur in marine elapid snakes. These comprise six species across four genera and three subfamilies, and so presumably indicate at least three independent invasions of marine snakes from teleost fishes. Here, one of these taxa, Tubulovesicula laticaudi Parukhin, 1969 (= T. orientalis Chattopadhyaya, 1970 n. syn.) is reported from Sri Lanka, collected from Shaw's sea snake Hydrophis curtus (Shaw) (Elapidae: Hydrophiinae: Hydrophinii), the annulated sea snake H. cyanocinctus Daudin and the yellow sea snake H. spiralis (Shaw) off Nayaru in the Bay of Bengal, and from H. spiralis in Portugal Bay, Gulf of Mannar. Novel molecular data, for COI mtDNA and ITS2 and 28S rDNA, are the first for a species of Tubulovesicula Yamaguti, 1934. Nominally, Tubulovesicula belongs in the Dinurinae Looss, 1907, but in phylogenetic analyses based on 28S rDNA, our sequences for T. laticaudi resolved relatively distant from that for representatives of Dinurus Looss, 1907, the type-genus, rendering the subfamily polyphyletic. Tubulovesicula laticaudi resolved closest to data for the type-species of the Plerurinae Gibson & Bray, 1979, but that subfamily is also polyphyletic. These findings lead us to re-evaluate an alternative classification considered by Gibson & Bray (1979). We propose restricting the Dinurinae for forms with a permanent sinus-organ (Dinurus, Ectenurus Looss, 1907; Erilepturus Woolcock, 1935; Paradinurus Vigueras, 1958; Qadriana Bilqees, 1971) and resurrect the Mecoderinae Skrjabin & Guschanskaja, 1954 for forms with a temporary sinus-organ (Mecoderus Manter, 1940, Allostomachicola Yamaguti, 1958, Stomachicola Yamaguti, 1934 and Tubulovesicula).

The adaptive significance of large size at birth in marine snakes.

Evolutionary shifts from one habitat type to another can clarify selective forces that affect life-history attributes. Four lineages of snakes (acrochordids and three clades within the Elapidae) have invaded marine habitats, and all have larger offspring than do terrestrial snakes. Predation by fishes on small neonates offers a plausible selective mechanism for that shift, because ascending to breathe at the ocean surface exposes a marine snake to midwater predation whereas juvenile snakes in terrestrial habitats can remain hidden. Consistent with this hypothesis, snake-shaped models moving through a coral-reef habitat in New Caledonia attracted high rates of attack by predatory fishes, and small models (the size of neonatal terrestrial snakes) were attacked more frequently than were large models (the size of neonatal sea snakes). Vulnerability to predatory fishes may have imposed strong selection for increased offspring size in marine snakes.

Effect of illustration art combined with Compound sea snake capsule on Alzheimer

BackgroundAlzheimer is a progressive neurodegenerative disease with a variety of symptoms. Illustrative art teaching and Compound sea snake capsule are considered as potential therapeutic methods, but there is a lack of research on the therapeutic effect of the combination of the two.Subjects and Methods50 patients with Alzheimer’s disease were randomly divided into experimental group and control group. The experimental group received illustration art teaching and Compound sea snake capsule treatment, and the control group received conventional treatment. The treatment period was 12 weeks. Cognitive function was assessed by the Alzheimer’s Disease Assessment Scale - Cognitive Subscale (ADAS-Cog) and Mini-Mental State Examination (MMSE), and statistical analysis was carried out with SPSS23.0.ResultsIn the experimental group, ADAS-Cog scores were 34.2±3.6 and 28.5±4.1, and MMSE scores were 19.8±2.1 and 22.4±2.4. In the control group, the ADAS-Cog scores were 34.5±3.9 and 33.8±4.2, and the MMSE scores were 19.5±2.3 and 19.7±2.6. T-test of independent sample showed that the scores of the experimental group after treatment were significantly lower than those before treatment (P<0.05), while the scores of the control group were not significantly different before and after treatment (P>0.05).ConclusionsIllustration art teaching combined with compound Hai snake capsule is significant in the treatment of Alzheimer’s disease. The cognitive and mental functions of the experimental group improved significantly, while the control group did not change. Therefore, the combination therapy can be used as an effective adjunctive therapy to manage Alzheimer’s disease.AcknowledgementNational Social Science Fund Arts Projects (No.20ZD28); Research Topic of Modern Education Technology of Jiangsu Province (Key Subject), Based on the interaction between teachers and students study of modern information technology (No.2019-R-79374); The Ministry of Education Cooperative Education Project (No.202102300015).

Environmental assessment of oyster beds in the northern Arabian Gulf Coast of the United Arab Emirates

The United Arab of Emirates (UAE) hosts valuable coastal and marine biodiversity, and oysters are one of the habitants of its marine ecosystem. Oysters play an essential role in the nearshore coasts where they work as an active filter. They filter nutrients, phytoplankton, sediments, heavy metals, and toxins out of the water, which improves the water quality. This is the first study that characterizes oyster bed habitats in the UAE by analyzing water quality parameters, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs)and heavy metals in water, sediments and oyster samples collected from five locations along the coasts of Sharjah, Ajman, and Umm al Quwain. Oyster bed areas supported a diverse assemblage of benthic life including oysters, scallops, pen shells, hard corals, and macroalgae. Mobile species in these habitats included groupers, emperors, snappers, sea snakes, among others. The phytoplankton assemblages were dominated by diatoms, dinoflagellates, and small cryptophytes. Harmful diatom Pseudonitzschia was found in all locations. No detectable concentrations of PAHs and OCPs were reported in this study, and water quality parameters were within the acceptable levels for the region. On the other hand, water quality index was reported marginal, mostly due to the presence of higher than acceptable concentrations of chromium and mercury in all sites studied. Bioconcentration factors concluded that oysters were able to bioconcentrate metals such as arsenic, cadmium, chromium, and zinc, when compared to water. No detectable concentrations of lead and mercury were reported in oysters, suggesting higher depuration rates for those metals.

Survey on sea snakebite and related morbidity and mortality among Bangladeshi fishermen in the Bay of Bengal: A pilot study

Around two million people are engaged in marine fishing in the Bay of Bengal. Bites by sea snakes were common hazards feared by millions fishing at sea in earlier days. Current morbidity and mortality are also not known. This study was conducted to document and describe sea snake bites among selected communities of sea-going fishermen in Bangladesh. A questionnaire-based cross-sectional survey was conducted from May to October 2019 among three communities of sea-going fishermen living along the coast of the Bay of Bengal in Cox's Bazar district. Fishermen were first asked by trained interviewers to recall any sea snakebites to themselves and among their fellows on board within the last year, then within the last 5 years and at any time before that. For any bite, related information including outcome was noted. Overall, 25.4% of respondents (62 out of 244) had been bitten by sea-snakes. Mean age was 37.6(±14) years; all males. 51.6% received some sort of treatment locally; 71% hot compress and 48% tourniquets. In 80.6% the affected limb was not immobilized. The bitten site was incised in 29%. 22.6% received treatment from traditional healers, 48.4% from local hospitals, 29% from district hospital. Six victims (9.7%) suffered from severe life-threatening consequences of the sea snakebite but none died. 32% of the fishermen had seen the offending snake. Sea snakebites are potentially dangerous; therefore, educating fishermen to avoid contact with sea snakes would dramatically reduce the incidence of sea snakebites. Most bites are treated initially by local measures which are often not scientific. Provision of proper first aid and treatment might reduce mortality and morbidity. A larger survey on sea snake bites among the fishermen in all coastal areas of Bangladesh is needed to determine the nationwide burden of morbidity and mortality related to sea snakebite.

Morphological and molecular characterization of larval Echinocephalus sp. (Spirurida: Gnathostomatidae), a parasite of the greater lizard fish (Saurida undosquamis) and red porgy or common seabream (Pagrus pagrus).

Larvae of an unidentified Echinocephalus species were obtained from two fish species: red porgy or common seabream (Pagrus pagrus) and greater lizard fish (Saurida undosquamis) from the Red Sea. The prevalence of Echinocephalus sp. larvae in P. pagrus was 4.92% and 4.98% in S. undosquamis. The length, width, cephalic bulb, and spine shape and pattern of the larvae resembled Echinocephalus overstreeti. SSU gene sequences of larvae from P. pagrus and S. undosquamis were identical. Comparison of the SSU sequence to those available in GenBank showed that the larvae from P. pagrus and S. undosquamis are diagnosably distinct. Based on sequence similarity and published phylogenetic analysis, these larvae are most similar to an unknown species of Echinocephalus from an Australian sea snake (Hydrophis peronii). Despite morphological similarities of the Red Sea larvae to E. overstreeti, the SSU sequence differences show that they are not the same species.

Long-distance movements of free-ranging sea snakes (Hydrophis, Elapidae)

Long-distance movements of free-ranging sea snakes (Hydrophis, Elapidae)

Functional Duplication of the Short-Wavelength-Sensitive Opsin in Sea Snakes: Evidence for Reexpanded Color Sensitivity Following Ancestral Regression

Abstract Color vision is mediated by ancient and spectrally distinct cone opsins. Yet, while there have been multiple losses of opsin genes during the evolution of tetrapods, evidence for opsin gains via functional duplication is extremely scarce. Previous studies have shown that some secondarily marine elapid snakes have acquired expanded “UV–blue” sensitivity via changes at key spectral tuning amino acid sites of the Short-Wavelength Opsin 1 (SWS1) gene. Here, we use elapid reference genomes to show that the molecular origin of this adaptation involved repeated, proximal duplications of the SWS1 gene in the fully marine Hydrophis cyanocinctus. This species possesses four intact SWS1 genes; two of these genes have the ancestral UV sensitivity, and two have a derived sensitivity to the longer wavelengths that dominate marine habitats. We suggest that this remarkable expansion of the opsin repertoire of sea snakes functionally compensates for the ancestral losses of two middle-wavelength opsins in the earliest (dim-light adapted) snakes. This provides a striking contrast to the evolution of opsins during ecological transitions in mammals. Like snakes, early mammals lost two cone photopigments; however, lineages such as bats and cetaceans underwent further opsin losses during their adaptation to dim-light environments.

Pterosphenus muruntau – valid species of sea snakes (Squamata: Palaeophiidae) from the middle Eocene of Uzbekistan

A palaeophiid sea snake Pterosphenus muruntau Averianov, 1997 was based on two trunk vertebrae and several vertebral fragments from the middle Eocene (Bartonian) coastal marine deposits of Dzheroi 2 locality in the Central Kyzylkum Desert, Uzbekistan. The species was considered a nomen dubium by Rage and coauthors in 2003 based on alleged poor preservation of the type specimens. However, the preservation of the holotype of P. muruntau is sufficient to discern a slightly laterally compressed vertebra and a low pterapophysis, the characters that distinguish this species from the other species of Pterosphenus. These characters are also clear in a new and better preserved vertebra of P. muruntau from the type locality. Pterosphenus muruntau should be considered a valid species of the genus Pterosphenus.