Venomous sea creatures

Olive sea snake
Olive sea snake

Sea snakes are venomous snakes that live in the water for most or all of their lives. Though they evolved from terrestrial ancestors, most are adapted to aquatic life completely and they cannot move on land, except for one genus (Laticauda), which still has some characteristics from its ancestors and can therefor move on land limitedly. 

Sea snakes are found in the warm coastal waters of the Pacific and Indian Ocean. All species a have paddle-like tail and almost all of them have lateral compressed bodies which make them look like eels. They don't have gills though, so they have to come up to the surface once and a while to breathe. Nevertheless, they are among the most completely aquatic of all air-breathing vertebrates. Among this group are species that are listed as the most venomous of all snakes. Some are quite gentile and bite only when they are provoked, while others are much more aggressive. Currently, 17 genera are described as sea snakes, comprising 62 species.

Behaviour

People that have studied sea snakes all say that they're usually mild temperate and only bite when they are provoked, but there is of course a variation among individuals and species. The Aipysurus laevis, Astrotia stokesii, Enhydrina schistosa and Hyprodhis ornatus are reported as more aggressive.

Studies make clear that sea snakes are active both during the day and during the night. In the morning or late afternoon you can sometimes see them at the surface while they're sunbathing. 

Sea snakes have been seen swimming at a depth of around 90 meters deep and they can stay submerged for a few hours. This depends on the temperature and the degree of activity.

Feeding and reproducing

A few species of sea snakes feed on fish, especially eels. A few others feed only on fish eggs, which is quite unusual for a venomous snake. One species prefers mollusks and crustaceans. 

All sea snakes are ovoviviparous which means that the young are born alive in the water where they will live the rest of their lives. The genus Laticauda is oviparous which means that they lay their eggs on the land where they hatch.

Venom

Sea krait (Laticauda)
Sea krait (Laticauda)

The majority of sea snakes is highly venomous. When a bits occurs it's not likely that large amounts of venom will be injected. Nevertheless sea snakes should be handled with great caution.
If a bite with venom injection does occur it's often painless and may not even be noticed. Sometimes teeth are left behind in the wound. The most important symptoms are rhabdoyolysis (rapid breakdown of skeletal muscle tissue) and paralysis.

Early symptoms include headache, a thick-feeling tongue, thirst, sweating, and vomiting. Symptoms that can occur after 30 minutes to several hours post bite include generalized aching, stiffness, and tenderness of muscles all over the body. Passive stretching of the muscles is also painful, and trismus, which is similar to tetanus, is common. This is followed later on by symptoms typical of other elapid envenomations: a progressive flaccid paralysis, starting with ptosis and paralysis of voluntary muscles. Paralysis of muscles involved in swallowing and respiration can be fatal. After 3-8 hours, myoglobin as a result of muscle breakdown may start to show up in the blood plasma, which can cause the urine to turn a dark reddish, brown, or black color, and eventually lead to acute renal failure After 6-12 hours, severe hyperkalemia also the result of muscle breakdown, can lead to cardiac arrest.

source: www.wikipedia.org

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