Tet Zoo picture of the day # 15

i-a8b0bd7e35b93f7b1d547da9db87b31c-turtle-headed sea snake.jpg

Among the most surreal snakes are (in my opinion) the turtle-headed sea snakes, or Aipysurus-group hydrophiids...

They are specialist predators of fish eggs: with their reduced compliment of stiffened labial scales, they scrape the eggs off rocks, and also use the spike on the snout tip to dig eggs out of the substrate. Their jaw musculature is unique (probably because they employ suction to get the eggs into the mouth), and they have a strongly reduced dentition. I published two articles on sea snakes on ver 1 here and here, and have yet to get round to publishing the promised third article: this will cover turtle-headed sea snakes and stuff on how sea snakes are related to other elapids. I'm pretty sure the accompanying photo was borrowed from Rick Shine's site, but I don't see it there now. Shine's site is a must-see if you're interested in herpetology.

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Wow, that's really strange. I had no idea that such highly specialized snakes actually exist. If you write more about them, will you also add some information about the ability of (some?)marine snakes to absorb oxygen from the water?

[from Darren: you might want to check the sea snake articles on ver 1, as one of them covers cutaneous respiration]

Enlightening and edifying as always, thank you.

sea snakes with suction? hm, sounds like a good canidate for something that might - given enough time - become a plankton-eater.

By Keenir@hotmail.com (not verified) on 16 Jun 2007 #permalink

Eating plankton might be a tough step, but not inconceivable. Some members of the Aipysurus group have very numerous and closely spaced but very fine, bristle-like teeth, so a baleen-like straining function already seems to be established (other egg-eating spp. are nearly edentulous, so teeth have been sepcialised in two ways for the same prey type, perhaps independently, from the fairly typical elapid dentition of basal Aipysurus). To eat plankton you need to engulf or suck in a lot of water and then spit it out through your teeth (or equivalent), then have some way of getting the gunk off the teeth again and swallowing it. Engulfing or sucking in large volumes may be a tricky step to evolve (though Cundall's study on drinking by snakes found huge variation in the rate at which different snakes suck in water, and a lot of two-way flow as well); but the teeth-cleaning apparatus may be more of a difficulty because snake tongues are reduced and specialised for sensory functions and generally have no role in food-handling.
There are a number of South American colubrids sometimes referred to as 'goo-eating snakes', specialising on snails, slugs, amphibian eggs and such; I don't know much about their morphology but they would help illustrate some of the (presently) unrealised potential of the Aipysurus group. Remember that sea-snakes are a young radiation (probably not much more than 15 Ma, and molecular dates have tended to be even younger) and already very diverse in morphology and ecology, and 60+ species; plus they thrive in really warm water, so they ought to have a bright future.

I think the reason why sea snakes matched to develop such a large variation within a comparably short time is because they managed to handle the evolutionary obstacle of becoming marine. Many families of animals needed a comparably long time to become really marine, afer a long time of amphibic or semi-amphibic time. If a group of animals has finally matched to life for their whole life (or nearly most of the time) in the sea, the get a huge opportunity for further specialization.

I'm fiending Darren........More!!!!!!

...But seriously, I understand you're quite busy as an adviser for _Primeval_.If you make sure those idiots never screw up like calling an anapsid _Scutesaur_ a dinosaur again, we will all be in your debt.

[from Darren: sorry, I am not an advisor for Primeval!]

Ah, My apologises.