Population dynamics of the sea snake Emydocephalus annulatus (Elapidae, Hydrophiinae)

For sea snakes as for many types of animals, long-term studies on population biology are rare and hence, we do not understand the degree to which annual variation in population sizes is driven by density-dependent regulation versus by stochastic abiotic factors. We monitored three populations of turtle-headed sea snakes (Emydocephalus annulatus) in New Caledonia over an 18-year period. Annual recruitment (% change in numbers) showed negative density-dependence: that is, recruitment increased when population densities were low, and decreased when densities were high. Windy weather during winter increased survival of neonates, perhaps by shielding them from predation; but those same weather conditions reduced body condition and the reproductive output of adult snakes. The role for density-dependence in annual dynamics of these populations is consistent with the slow, K-selected life-history attributes of the species; and the influence of weather conditions on reproductive output suggests that females adjust their allocation to reproduction based on food availability during vitellogenesis.

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.

Mistaken identity may explain why male sea snakes (Aipysurus laevis, Elapidae, Hydrophiinae) “attack” scuba divers

Scuba-divers on tropical coral-reefs often report unprovoked “attacks” by highly venomous Olive sea snakes (Aipysurus laevis). Snakes swim directly towards divers, sometimes wrapping coils around the diver’s limbs and biting. Based on a focal animal observation study of free-ranging Olive sea snakes in the southern Great Barrier Reef, we suggest that these “attacks” are misdirected courtship responses. Approaches to divers were most common during the breeding season (winter) and were by males rather than by female snakes. Males also made repeated approaches, spent more time with the diver, and exhibited behaviours (such as coiling around a limb) also seen during courtship. Agitated rapid approaches by males, easily interpreted as “attacks”, often occurred after a courting male lost contact with a female he was pursuing, after interactions between rival males, or when a diver tried to flee from a male. These patterns suggest that “attacks” by sea snakes on humans result from mistaken identity during sexual interactions. Rapid approaches by females occurred when they were being chased by males. Divers that flee from snakes may inadvertently mimic the responses of female snakes to courtship, encouraging males to give chase. To prevent escalation of encounters, divers should keep still and avoid retaliation.

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.

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.

Viviparous sea snakes can be used as bioindicators for diverse marine environments

Shallow tropical marine ecosystems are under great anthropogenic pressure due to habitat destruction, overfishing, shrimping, climate change, and tourism. This is an issue of global concern as such environments hold a tremendous biodiversity much of which remains to be described. The present situation urgently calls for time- and resource-efficient methods to identify and delineate the most valuable remaining areas and to set up priorities for their management and conservation. Using indicator species can be a way to accomplish this goal. In this paper we evaluate whether viviparous sea snakes can serve as bioindicators for other rare or cryptic tropical marine fauna. Based on seven generally acknowledged criteria for bioindicators, we argue that using viviparous sea snakes as bioindicators can help monitoring marine habitats to gauge the effects of climate change, habitat change and loss, decline in biodiversity and other anthropogenic changes. However, to maximize their efficacy as bioindicators, deeper knowledge about viviparous sea snakes natural history is urgently needed. Topics for expanded research programs include the taxonomy of some groups, their breeding and feeding biology, habitat selection and their geographical distribution. Despite these gaps in our understanding, we argue that viviparous sea snakes can be utilized as bioindicators of marine ecosystem health. KEYWORDS: anthropogenic changes, conservation, herpetology, marine habitat, monitoring