Sea
snakes have small mouths and can’t bite humans
By
far the most commonly held myth is that, although sea snakes are
venomous they are not dangerous because they have very small mouths
so cannot bite anything larger than a human finger. There are couple
of components to this myth.
Venom
The first is that they are venomous. This is correct for most true
sea snakes (hydrophiids) and sea kraits (latitcaudids). Apart from
a couple of notable exceptions, these two groups of sea snakes are
extremely venomous.
The
exceptions are the turtlehead sea snakes (hydrophiids) that have
evolved to feed primarily on fish eggs. Their mouths of turtlehead
sea snakes have become adapted to this specialised diet. Scales
at the sides of their mouths have fused to form a scraping plate,
which makes them look like turtles, hence their name. These species
have lost the ability to produce venom and the venom apparatus has
atrophied, so they are no longer venomous.
Acrochordid,
homalopsid and natricid sea snakes are either mildly venomous or
not venomous at all.
Mouth
Size
Most sea snakes however, do not have small mouths. They have mouths
large enough to swallow small to medium sized fish whole, and are
able to dislocate their jaws in the same manner as terrestrial snakes.
The main exceptions are the species that have specialised to feed
on eels that live in burrows. These species tend to have small heads
and slender necks, presumably so they can easily poke down burrows
and catch their prey. But in general marine snakes have mouths that
can open widely and can bite humans on their limbs if they want
to.
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