Sea snakes : The most venomous species in the world !
Sea, snakes, and sun: this could be the slogan of some holiday-makers in paradisiacal places 🏖 such as the Great Barrier Reef, near Australia, or the lagoons of New Caledonia. In all the tropical seas of the Indo-Pacific zone, the encounter with a sea snake is possible. These animals, which rarely exceed one or two meters in length. The spectacle can also be frightening, knowing that all sea snakes are very venomous. Swimmers should be careful 🏊♂️: these reptiles are generally discreet and remain hidden under coral blocks or in other shelters. They only expose themselves for feeding, reproduction, or to catch their breath at the surface.
Closely related to cobras, the sea snake is morphologically different from its terrestrial cousins because its body is adapted to survive deep-water immersion and other features of marine life.
Sea snakes are strange animals. They have the reputation of being "gentle" creatures that do not attack if they are not disturbed. Creatures that people can interact with when scuba diving. Some people like to swim close to them, but they would never go near their terrestrial cousins. 🐍
Sea snakes are extremely venomous, more than any other type of snake. These magnificent creatures are related to Australian land snakes, and, unlike pure aquatic animals, this species breathes regularly on the surface.
1. Sea Snake Anatomy
The size of marine snakes varies according to species, between 50 cm and 275 cm for the most notable species ever caught, and according to sex. Females are generally larger than males.
Marine snakes, like their terrestrial cousins, belong to the order of reptiles and the species of the vertebrates and therefore have a skeleton with a skull, vertebrae, and ribs.
Sea snakes are the only snakes that can absorb oxygen through the skin surface. They can provide 25% of their oxygen needs through this system.
Another significant development is the way sea snakes handle salt because they are descendants of terrestrial serpents and cannot tolerate high levels of salinity, unlike other marine creatures. Therefore, they have developed special glands under and around their tongues that allow them to remove excess salt from their bodies.
The body is often compressed laterally, and the nostrils are on top of the head to help to breathe, and some species can breathe partially (up to 25% of their needs) top skin.
The final evolution of sea snakes is in their scales. Most terrestrial snakes have overlapping scales. These scales serve to protect their bodies from the constant abrasion of the ground.
However, marine snakes do not need this protection. So their scales are flexible and do not overlap. They are designed to be more hydrodynamic and to act as armor against sharp corals.
2. Marine Snake Habitat
Sea snakes live all over the world in warm and temperate waters ☀️🌊. Like most reptiles, they don't like the cold. So they can be found in all tropical waters from the Caribbean to Australia and the east coast of Africa.
Interestingly, for unknown reasons, this species does not occur in the waters of the Atlantic Ocean or the Mediterranean Sea. It is even though they are warm enough to live there.
This phenomenon is particularly curious because it means that, for some unknown reason, sea snakes are unwilling or unable to cross the Panama Canal or the Suez Canal, unlike many other species that have made this crossing.
Marine snakes all live in the warm tropical and subtropical waters between the latitudes of North Korea and South Tasmania. They are found in Australia, in the Indian Ocean, from East Africa to Asia.
The western Pacific is the area where marine snakes are most abundant.
3. Deadly Venom
A. Dangerous venom for a shy snake
Sea snakes, like their land cousins, are venomous. Even though bites are rare, they do occur occasionally. Unlike terrestrial species, marine snakes do not usually inject large amounts of venom when they bite.
The bite is often painless, and symptoms do not appear right away. However, any snake bite is dangerous because even with the small amount of poison injected, their venom is potent. The victim will die within 8 to 12 hours if no antidote is applied. ☠️
The fangs of sea snakes are shorter than those of land snakes, which is why they rarely pass through divers' wetsuits. Furthermore, it has been found that more than half of sea snake bites, like those of land snakes, are "white" and are not followed by an injection of venom.
From there to think that the snake only uses its venom to kill edible prey...?
B. Toxicological analysis of sea snake venom
Toxicological analysis has shown that venoms are a cocktail of several toxins, each with specific properties. The sea snakes' viruses are potent, some of them twenty times more powerful than those of the terrestrial cobra!
The most dangerous ones are neurotoxins. They act on neuromuscular transmission and cause paralysis. Furthermore, mycotoxins destroy muscle cells, resulting in the release of a protein, myoglobin, which, via the bloodstream, will cause occlusion of the renal tubules and block the kidney function of the victim.
Other enzymes and toxins also found in the poison can affect the blood and cause hemorrhagic or allergic reactions.
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4. Poisonous species
Sea snakes belong to the Elapidae family in which there are two subfamilies:
A. Laticauda or the sea krait
The only representative of this subfamily. He's an amphibian, oviparous snake with large ventral scales that allow it to move quickly on land. Alternating with black stripes, its color is yellow, blue, white, or grey, depending on the species and location. The average size of an adult is 1 m. It feeds mainly on small fish, moray eels, or conger eels.
He's fearful and not at all aggressive so much so that some children in New Caledonia are sometimes used to playing with him. He rarely bites, and only when he feels endangered. Its venom is nevertheless ten times more potent than that of the royal cobra!
B. Coral reef snakes (Hydrophiinae)
14 genera and 47 species of sea snakes represent the subfamily Hydrophiinae. They are all venomous snakes, adapted exclusively to aquatic life, so much so that if they accidentally ashore on a beach during a storm, they die because they are unable to move, their ventral scales are small and therefore not adapted to sliding.
C. Yellow-bellied sea snake (Pelamis platurus)
It is undoubtedly the most widespread and best-known. Its area of life is very vast, and it is the only known pelagic sea snake that can only live in the open sea and crosses the Indian and Pacific Oceans from Asia to America following the currents, forming migratory colonies of several thousand individuals.
Its coloration is typical, black on top, yellow underneath, and its tail is flattened yellow with black spots. The adult size of the male is more significant than that of the female but rarely exceeds one meter. The female ovoviviparous gives birth to 2 to 6 eggs, and it has the particularity of having only one lung distributed throughout its body, occupying up to 10% of its total volume.
D. Olive sea snake (Aipysurus laevis)
It is a giant snake (1.50 m), equipped with photoreceptors in its flattened tail, which allows it to know its exact position at any time. He is inquisitive, attracted by everything that moves or shine, but he is very fearful and not at all aggressive.
E. Enhydrina schistosa
He has the most toxic venom of all sea snakes, and he's also the most dangerous. Its size is about 5 feet tall. The amount of venom delivered by a single bite is potentially enough to kill 50 people! 😨
F. Annulated sea snake (Hydrophis Cyanocinctus)
With blue stripes would be the most significant sea snakes known to date. One of these was measured at 7 feet. Their food consists mainly of eels.
5. Sea Snake Myths
✅/❌The most common myth about sea snakes is that, with their small fangs, they can't get through a wetsuit. And that they can only bite the diver at the earlobe and the area of skin between the thumb and forefinger.
👉It's completely wrong. Most sea snakes are very docile and shy by nature. We even see many fishers untangling them from their nets and putting them back into the sea. However, we should not confuse the snake's unwillingness to bite and poison with a lack of ability to do so.
Marine serpents can bite and penetrate human skin, and, because most are highly poisonous, they can cause death if no antidote is administered in time.
6. Sea serpent feeding
The food of this ophidian species is fish, which it swallows whole. It also eats eels and crustaceans, and some of them eat fish eggs. 🐠
The diet of marine snakes is variable depending on the species and the environment. It can be diversified, with many species of fish on the menu and more rarely invertebrates, crabs, shrimps, cephalopods, or on the contrary, be very specialized. Some snakes feed on only one kind of prey: eels, gobies, crabs, or fish eggs. When the dish of the day is a fish, it is always swallowed head first, so that its spines cannot get caught to stand up and cause injury.
Furthermore, in order not to be intoxicated by the amount of salt ingested, marine snakes have glands located under the tongue at the lower jaw level, capable of concentrating salt and excreting it each time they stick out their tongues.
7. Do sea snakes shed their skin?
All snakes change their skin at regular intervals. Molting is more frequent in marine snakes, every two to six weeks, and occurs only once or twice a year for terrestrial snakes. It starts at the back of the head and continues towards the tail, the snake coming out of its old skin by turning it over.
If you want to know more about snake shedding, we have written an article, especially on this topic.
8. The reproductive system of the marine snake
Marine snakes are an ovoviviparous species, meaning that the eggs develop inside the mother's body until birth or shortly before hatching. Only one species, the sea Krait, is oviparous and lays its eggs on the ground.
The young are born alive in the water, where they complete their entire life cycle. The progeny are quite large in some species. Sometimes the size is half the size of the mother's body. The baby becomes independent at birth. This makes them one of the few animal species that do not require maternal care.
9. What to do in case of accidents of envenomation?
A. Biting risks
The risk of being bitten by sea snakes is exceptional for a swimmer or diver, even in areas where they are abundant, as they are most often shy and flee at the slightest warning. Sometimes other more curious ones come very close, without showing the slightest sign of aggressiveness, as long as you don't panic. However, the number of fatal bite cases is not negligible, and there are more than 150 bite fatalities per year in Southeast Asia and the Philippines.
Marine snake bites are not very painful, sometimes almost painless, and are only accompanied by venom injections in 10 to less than 50% of cases. According to studies, in case of envenomation, within minutes of the bite, tingling and progressive numbness of the bitten limb appears, with a sensation of :
- heavy salivation
C. Emergency first aid gestures
As in any situation that can turn out to be dramatic, it is important not to panic, and the priority must be to calm and reassure the injured person. You must also not waste time on uninteresting, even dangerous gestures such as pumping the area with a syringe, incising the wound, applying a tourniquet, applying a source of heat, or "black stone," or washing the wound with some kind of liquid...