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Olive Sea Snake - Aipysurus laevis
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Olive Sea Snake - Aipysurus laevis

[Image: 36041947562_f517bfae15_b.jpg]

Scientific classification
Kingdom:  Animalia
Phylum:  Chordata
Class:  Reptilia
Order:  Squamata
Suborder:  Serpentes
Family:  Elapidae
Genus:  Aipysurus
Species:  Aipysurus laevis  Lacépède, 1804

Aipysurus laevis is a species of venomous sea snake found in the Indo-Pacific. Its common names include golden sea snake, olive sea snake, and olive-brown sea snake.
The olive sea snake swims using a paddle-like tail. It has brownish and purple scales along the top of its body whilst its underside is a white color. It can grow up to a meter in length, and in some cases up to two meters. While it can be aggressive towards prey, attacks on divers or larger animals are usually rare, though if provoked it will engage the attacker. The snake's main predators are sharks and Ospreys.

Distribution
It is a common, widespread species that lives on coral reefs, including the Great Barrier Reef. It can also be found in the eastern Indian Ocean and the western Pacific Ocean. The creature hides in small coves or protective coral areas if not hunting or surfacing to breathe. It feeds on crustaceans, fish, and fish eggs. It uses venom to incapacitate its prey. This snake in particular has venom that contains enzymes which break down the prey from within for easier digestion. The venom also affects both the muscles and nerves of the prey. The snake usually hunts in coral reef areas, searching for food via poking their head through crevices. The creature usually stays away from open water as a hunting ground.
Aipysurus laevis has been found to have photoreceptors in the skin of its tail, allowing it to detect light and presumably ensuring it is completely hidden, including its tail, inside coral holes during the day. While other species have not been tested, A. laevis possibly is not unique among sea snakes in this respect. Dermal light sensitivity is found in all the major animal phyla.

[Image: Aipysurus-laevis-thumb.jpg]

Reproduction
Males can reach sexual maturity in their third year, while females do not until their fourth or fifth year. Courtship usually involves a group of males vying for one female, which occurs in open water. Fertilization is internal and lasts for about nine months. Females can give birth up to five young at a time. In rare cases there can be ten or eleven young at once. Life expectancy of the snake is about fifteen years, sometimes a bit longer.

Threats
While there are not many threats to the Aipysurus laevis, man-made dangers do exist for it. Prawn trawls are one of the greatest threats for the creature, up to 50% of olive sea snakes caught in trawls are killed, while the ones that survive usually suffer injuries. Death from prawn trawls often comes either from drowning or being crushed.

Etymology
The specific name, pooleorum (masculine, genitive plural), is in honor of Australian fishermen "W. and W. Poole" who collected the holotype.




'Seeing' tails help sea snakes avoid predators

February 15, 2019, University of Adelaide

[Image: seeingtailsh.jpg]
Olive sea snake (Aipysurus laevis) diving underwater. Sea snakes live their entire lives at sea and must come up to the sea surface to breath air. Credit: Chris Malam

New research has revealed the fascinating adaptation of some Australian sea snakes that helps protect their vulnerable paddle-shaped tails from predators.

An international study led by the University of Adelaide shows that several species of Australian sea snakes can sense light on their tail skin, prompting them to withdraw their tails under shelter. The study has also produced new insights into the evolution and genetics of this rare light sense.

The researchers found that olive sea snakes (Aipysurus laevis) and other Aipysurus species move their tail away from light. They believe this is an adaptation to keep the tail hidden from sharks and other predators.

"Sea snakes live their entire lives at sea, swimming with paddle-shaped tails and resting at times during the day under coral or rocky overhangs," says study lead author Jenna Crowe-Riddell, Ph.D. candidate in the University of Adelaide's School of Biological Sciences. "Because sea snakes have long bodies, the tail-paddle is a large distance from the head, so benefits from having a light-sense ability of its own.

"The olive sea snake was the only reptile, out of more than 10,000 reptile species, that was known to respond to light on the skin in this way."

The researchers tested for light-sensitive tails in eight species of sea snakes, but found that only three species had the light-sense ability. They concluded the unique ability probably evolved in the ancestor of just six closely related Australian species.

"There are more than 60 species of sea snake so that's less than 10% of all sea snakes," says Ms Crowe-Riddell. "We don't know why this rare sense has evolved in just a few Aipysurus species."

The researchers used RNA sequencing to see what genes are active in the skin of sea snakes. They discovered a gene for a light-sensitive protein called melanopsin, and several genes that are involved in converting light into information in the nervous system.

"Melanopsin is used in a range of genetic pathways that are linked to sensing overall light levels around us. It is even used by some animals, including humans, for regulating sleep cycles and in frogs to change their skin colour as a camouflage," says Ms Crowe-Riddell.

Lead scientist Dr. Kate Sanders, ARC Future Fellow at the University of Adelaide, says: "We've confirmed the ability of olive sea snakes to sense light in their tails and found the same ability in two other species. We've identified a shortlist of genes that are likely to be involved in detecting light. But further study will be needed to target these genes before we can really understand the genetic pathways involved in this fascinating behaviour."

Published in the journal Molecular Ecology, the study is a collaboration between the University of Adelaide, the University of Bristol, the University of Western Australia and the Natural History Museum, London.

Read more at: https://phys.org/news/2019-02-tails-sea-...s.html#jCp



Journal Reference:
Crowe‐Riddell JM, Simões BF, Partridge JC, et al. Phototactic tails: Evolution and molecular basis of a novel sensory trait in sea snakesMol Ecol2019;00:1–16. https://doi.org/10.1111/mec.15022

Abstract
Dermal phototaxis has been reported in a few aquatic vertebrate lineages spanning fish, amphibians and reptiles. These taxa respond to light on the skin of their elongate hind‐bodies and tails by withdrawing under cover to avoid detection by predators. Here, we investigated tail phototaxis in sea snakes (Hydrophiinae), the only reptiles reported to exhibit this sensory behaviour. We conducted behavioural tests in 17 wild‐caught sea snakes of eight species by illuminating the dorsal surface of the tail and midbody skin using cold white, violet, blue, green and red light. Our results confirmed phototactic tail withdrawal in the previously studied Aipysurus laevis, revealed this trait for the first time in A. duboisii and A. tenuis, and suggested that tail photoreceptors have peak spectral sensitivities between blue and green light (457–514 nm). Based on these results, and an absence of photoresponses in five Aipysurus and Hydrophis species, we tentatively infer that tail phototaxis evolved in the ancestor of a clade of six Aipysurus species (comprising 10% of all sea snakes). Quantifying tail damage, we found that the probability of sustaining tail injuries was not influenced by tail phototactic ability in snakes. Gene profiling showed that transcriptomes of both tail skin and body skin lacked visual opsins but contained melanopsin (opn4x) in addition to key genes of the retinal regeneration and phototransduction cascades. This work suggests that a nonvisual photoreceptor (e.g., Gq rhabdomeric) signalling pathway underlies tail phototaxis, and provides candidate gene targets for future studies of this unusual sensory innovation in reptiles.

https://onlinelibrary.wiley.com/doi/abs/.../mec.15022
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