Sexual dimorphism in size and shape of the head in the sea snake Emydocephalus annulatus (Hydrophiinae, Elapidae)

In snakes, divergence in head size between the sexes has been interpreted as an adaptation to intersexual niche divergence. By overcoming gape-limitation, a larger head enables snakes of one sex to ingest larger prey items. Under this hypothesis, we do not expect a species that consumes only tiny prey items to exhibit sex differences in relative head size, or to show empirical links between relative head size and fitness-relevant traits such as growth and fecundity. Our field studies on the sea snake Emydocephalus annulatus falsify these predictions. Although these snakes feed exclusively on fish eggs, the heads of female snakes are longer and wider than those of males at the same body length. Individuals with wider heads grew more rapidly, reproduced more often, and produced larger litters. Thus, head shape can affect fitness and can diverge between the sexes even without gape-limitation. Head size and shape may facilitate other aspects of feeding (such as the ability to scrape eggs off coral) and locomotion (hydrodynamics); and a smaller head may advantage the sex that is more mobile, and that obtains its prey in narrow crevices rather than in more exposed situations (i.e., males).

The yellow-bellied sea snake, Hydrophis platurus (Squamata: Elapidae), off the Southwestern Pacific coast of Nicaragua, Central America

Introduction: The yellow-bellied sea snake (Hydrophis platurus, formerly Pelamis platurus) is known to occur along the Pacific coast of Central America. However, there are no marine records of this species off the coast of Nicaragua. Objective: Report the first in situ marine observations of the yellow-bellied sea snake observed on three occasions in 2020 during cetacean surveys off the southwestern Pacific coast of Nicaragua. Methods: During the sightings, photographs were taken which allowed the identification of the species based on morphology. Sea surface temperature, sea state, and distance to the coast are presented as descriptors of the habitat of the records. Results: Three field observations of yellow-bellied sea snakes were recorded on separate occasions. Sightings occurred within 30 km of each other and 3.3 km from the coast. Average sea surface temperature was 26.6 °C with low swell and sea state. Conclusions: The present information offers new knowledge about the presence of the yellow-bellied sea snake on the Pacific coast of Central America, contributing to the biodiversity record in Nicaragua.

Venom of the Annulated Sea Snake Hydrophis cyanocinctus: A Biochemically Simple but Genetically Complex Weapon

Given that the venom system in sea snakes has a role in enhancing their secondary adaption to the marine environment, it follows that elucidating the diversity and function of venom toxins will help to understand the adaptive radiation of sea snakes. We performed proteomic and de novo NGS analyses to explore the diversity of venom toxins in the annulated sea snake (Hydrophis cyanocinctus) and estimated the adaptive molecular evolution of the toxin-coding unigenes and the toxicity of the major components. We found three-finger toxins (3-FTxs), phospholipase A2 (PLA2) and cysteine-rich secretory protein (CRISP) in the venom proteome and 59 toxin-coding unigenes belonging to 24 protein families in the venom-gland transcriptome; 3-FTx and PLA2 were the most abundant families. Nearly half of the toxin-coding unigenes had undergone positive selection. The short- (i.p. 0.09 μg/g) and long-chain neurotoxin (i.p. 0.14 μg/g) presented fairly high toxicity, whereas both basic and acidic PLA2s expressed low toxicity. The toxicity of H. cyanocinctus venom was largely determined by the 3-FTxs. Our data show the venom is used by H. cyanocinctus as a biochemically simple but genetically complex weapon and venom evolution in H. cyanocinctus is presumably driven by natural selection to deal with fast-moving prey and enemies in the marine environment.

Resource use and the impacts of fisheries on two sympatric sea snake species on the West Coast of India.

Species interactions are central to community assembly and ecosystem functioning. Sea snakes play an important role as mesopredators and as intermediate links in coastal marine food webs. However, they are impacted by anthropogenic pressures such as fisheries throughout their range. We investigated differences in resource use between two sympatric sea snake species from the west coast of India, Hydrophis curtus and H. schistosus, and described the impacts of fishing on the interactions of these species. We compared habitat use, diet, and isotopic niche width between species to determine resource overlap. We then compared trophic overlap of each species with the fisheries in the region and tested the effect of fishing intensity on their isotopic niche width. We found that H. curtus used deeper habitats than H. schistosus, resulting in increased spatial overlap with fisheries. The two species also had distinct trophic niches and H. curtus prey formed a larger proportion of fishery catch on average than H. schistosus. This greater overlap could make H. curtus more vulnerable to the effects of fisheries. Both species exhibited expansion in short-term and long-term isotopic niche width along a gradient of fishing intensity which may indicate behavioural changes associated with the presence of fisheries. Hydrophis curtus is a trophic generalist, competes with syntopic species and is dominant in most assemblages. However, H. schistosus exhibits higher plasticity in resource use and may have an advantage over H. curtus. Thus, fishing could alter the relative abundance of these mesopredators with cascading effects through coastal food webs.

On the occurrence of Persian Gulf Sea Snake, Hydrophis lapemoides (Gray, 1849) (Reptilia, Squamata, Elapidae, Hydrophiinae), along the coast of Bangladesh

We provide the first evidence of the presence of the Persian Gulf Sea Snake, Hydrophis lapemoides (Gray, 1849), along the coast of Bangladesh. This species was assumed to exist in there, but neither specimens nor confirmed observations exist until now. We document here the first confirmed record of H. lapemoides based on a freshly collected and taxonomically verified specimen from coastal Bangladesh. The Bangladeshi specimen had the following diagnostic characters: 55 black bands, a dorsal scale composition of 35:51:43, 342 ventrals, one pre-ocular, two post-oculars, 2+3 temporals, 8 supralabials (II largest and contact prefrontals; III–IV contact orbit) and 8 infralabials (I–IV contact genials).

Pinpointing Drivers of Extirpation in Sea Snakes: A Synthesis of Evidence From Ashmore Reef

Over the past decade, vertebrate populations globally have experienced significant declines in distribution and abundance. Understanding the reasons behind these population declines is the first step in implementing appropriate management responses to improve conservation outcomes. Uncovering drivers of extirpation events after the fact, however, requires a careful forensic approach to prevent similar declines elsewhere. The once abundant and species-rich sea snake fauna of Ashmore Reef Marine Park, in the Timor Sea, collapsed dramatically in the early 2000s. No such decline has occurred on surrounding reefs. We synthesise the evidence for this collapse and the subsequent slow recovery and evaluate the plausibility of potential drivers for the declines, as well as provide evidence against certain explanations that have been proposed in the past. Our systematic review shows that of seven possible hypotheses considered, at least three are credible and require additional information: (1) stochastic environmental events may have increased the snakes’ susceptibility to pathogens, (2) a resurgence in the abundance of top predators may have induced a localised change in trophic structure, and (3) an acute increase in local boat traffic may have had negative physical impacts. One or more of these factors, possibly acting in combination with as yet other unidentified factors, is the most plausible explanation for the precipitous decline in sea snake populations observed. Based on this position, we identify future research directions with a focus on addressing critical gaps in knowledge to inform and prioritise future management actions.

Clinical report of a human bite by the pelagic sea snake Hydrophis Platurus (Serpentes: Elapidae), in the pacific ocean of Costa Rica

Introduction: The pelagic sea snake, “Serpiente Marina,” Hydrophis Platurus, shows a wide-range distribution in the Indo-Pacific Ocean, reaching the Pacific coast of the Americas. Although the snake bite accidents caused by sea snakes are rare, Costa Rica occasionally presents large quantities of sea snakes stranded in the shore, mainly during the dry season. Discussion: A 12-years-old boy was bitten in Playas del Coco, Sardinal, Guanacaste province, Costa Rica, and almost immediately started to develop pain and paresthesia. A coagulation time test was performed, although its importance is not relevant to the treatment of snakebite accidents caused by sea snakes, mainly due to its neurotoxic characteristics. Conclusion: Although there is no antivenom available to treat snakebite accidents from the pelagic seasnake, its treatment is frequently misinterpreted, incurring in clinical tests that are not necessary and putting aside the tests that have more relevance to the potential clinical symptoms of the snake bite.