In the early stages of snake evolution, there were huge sea snakes on earth, these large sea snakes only existed for a short time and then became extinct, leaving only a few fossils as a witness to their old life on earth.
Modern sea snakes are not very large, and they have adapted to the marine environment to varying degrees. In the north from the Philippine Islands, south to the northern part of Oceania. West to the Indian coast of the vast sea area there is a kind of history of the oldest sea snake - file snake, which is the sea snake in the rare non-venomous snakes, the body length of about 60 centimeters to 1 meter between the flaccid muscle, the body is yellowish-brown, the surface of the very fine granular scales. The file snake's cardiovascular and respiratory physiology is very well suited to life in the water; its hemoglobin oxygen delivery is particularly efficient, and its heart rate can drop to less than one beat per minute when diving. Its incubation time in water can be as long as 5 hours, and 13% of its respiratory function during this time is through the skin. The file snake's lips have tissue and scales that seal its mouth to the point of dripping, and its jaw has a salt-secreting gland that is used to share the heavy burden of salt excretion from the kidneys. File snakes are now very rare.
There are about 50 species of sea snakes in existence, and they are closely related to cobras. Most of the world's sea snakes congregate in the waters between northern Oceania and the peninsulas of South Asia. These sea snakes survive in large numbers in the sea because they are all good swimmers with flat tails like oars, and because they all have fangs that kill their catch and deter enemies. These sea snakes also have salt-secreting glands similar to those of file snakes and mouths that can close tightly. But in general, their physiology is not as well adapted to the sea as that of file snakes, probably because they have not lived in the sea as long as file snakes.
Sea snakes prefer to inhabit shallow waters around continental shelves and islands, and are rare in open ocean waters deeper than 100 meters. While some of them prefer to stay in mixed water on sandy or muddy bottoms, others prefer the clear water around coral reefs. Sea snakes dive at different depths, some deeper, some shallower. Sea snakes have been seen at depths of 40 to 50 meters. Shallow-water sea snakes usually dive for no more than 30 minutes, and stay at the surface for a very short time, each time just showing their heads, and then quickly take a breath and dive back into the water. Deep-water sea snakes stay at the surface longer, especially in the evening and at night. They can dive for up to two to three hours.
Sea snakes are selective about what they eat, and many have feeding habits related to their size. Some sea snakes have large, thick bodies with long, thin necks and surprisingly small heads, and such snakes feed almost exclusively on burrowing eel fronts. Some sea snakes feed on fish eggs, and these snakes have small teeth and small fangs and venom glands. Some sea snakes like to feed on fish with venomous spines, and in the Northern Sayan Sea of the Philippines, there is a sea snake that feeds exclusively on the eel-tailed catfish. Eel-tailed catfish have venomous spines that are so painful that they can seriously injure a person, but sea snakes don't care about that. In addition to fish, sea snakes also attack larger creatures.
During the reproductive season, sea snakes tend to gather together to form long snake formations that stretch for tens of kilometers, a large-scale gathering phenomenon that occurs when sea snakes are reproducing. Some harbors sometimes boil over as groups of sea snakes float to the surface. Completely aquatic sea snakes reproduce as ovoviviparous, giving birth to three to four 20-30 centimeter long baby sea snakes each time. Sea snakes that can come ashore, on the other hand, remain ovoviviparous, laying their eggs on seaside beaches and allowing them to hatch naturally.
Sea snakes also have natural enemies, sea eagles and other carnivorous seabirds eat sea snakes. They see sea snakes swimming in the sea, they swoop down from the air, pick up a far away, although the sea snake is fierce, but once it left the water there is no offensive ability, and almost completely unable to defend themselves. In addition, some sharks also feed on sea snakes. Not much else is known about the sea snake's natural predators.
The venom of sea snakes is among the most powerful animal poisons. Hook-billed sea snake venom is twice as toxic as cobra venom and 80 times more toxic than sodium cyanide. Sea snake venom is composed of neurotoxins similar to cobra venom, however, strangely enough, its venom damages the human body mainly in the area of random muscles rather than the nervous system. Sea snake bite painless, its toxicity attack and there is a period of incubation, by the sea snake bite 30 minutes or even 3 hours after there are no obvious symptoms of poisoning, however, this is very dangerous, easy to paralyze people. In reality, sea snake venom is absorbed by the body very quickly, the first thing you feel after poisoning is muscle weakness, soreness, drooping eyelids, jaw straightening, a bit like the symptoms of tetanus, while the heart and kidneys will also be seriously damaged. Those bitten may die within a few hours to a few days. Most sea snakes injure people when they are harassed.
There are five species of amphibious sea snakes*** that are quite gentle and can be left to their own devices. Unlike other oviparous sea snakes, amphibious sea snakes are oviparous, and during the spawning season, amphibious sea snakes often travel in groups to fixed islands to lay their eggs, and the Philippine island of Gato is one of the islands frequented by sea snakes. For many years, people have been commercially trapping snakes on these islands, and currently 180,000 snakes are trapped annually on Gato Island, with similar trapping occurring in the Ryukyu Islands.
Like terrestrial snakes, sea snakes have high economic value, with their skins used to make musical instruments and handicrafts; their meat and eggs are edible and delicious; and certain internal organs are used for human medicine.
There are 8 genera and 12 species of **** recorded along the coast of China. This family of animals abdominal scales are mostly degraded, underdeveloped or even disappeared; nostrils are mostly open on the back of the muzzle, only need to expose the nostrils to the surface of the water will be able to breathe the air, in the submerged, nostrils close the flap to prevent seawater from entering. Sea snakes inhabit the estuarine zone of semi-saline water along the continental coast. There is a sea snake in Lake Taal in the Philippines that lives its entire life in fresh water, hence the name freshwater sea snake. Sea snakes feed primarily on fish, often consuming elongated fish. Most are oviparous. In the subfamily of sea snakes, many species are long, with very slender heads, necks, and anterior halves of the body, and give birth to young.
Common in China are the green ringed sea snake, ringed sea snake, flat-chinned sea snake, small-headed sea snake, long-nosed sea snake, sea viper and other species. Flat-tailed snake subfamily is adapted to sea water life is not too long sea snake class, the trunk before and after the thickness of the difference is not big, only the tail side flat; which flat-tailed snake genus nostrils are still open on the side of the muzzle, individual species to the shore to lay eggs. People were bitten by sea snakes, due to snake venom damage to the transverse muscle fibers, there will be myoglobinuria, and lead to respiratory paralysis.