29 March 2012

Serrated teeth of the crabeater seal

This seal, Lobodon carcinophagus, is called a crab-eating seal, but its main diet consists of krill, which it filters out of the water through its complexly cusped teeth.
Via Evolution, where the teeth are compared to fossil whale teeth -


- which may offer some insight into the predecessors of modern filter-feeding baleen whales. Not quite.  See BJN's note in the comments.

One puzzler:  According to Wikipedia, crabs are not found in the Antarctic habitat of the crabeater seal.  So why are they called that?

Photo credit: Dr. Alistair Evans, Monash University, Australia.

3 comments:

  1. BJNMarch 29, 2012 at 1:38 PM

    Baleen isn't a modified tooth structure, it's a keratin. In fact the predecessors of baleen whales likely had non-functional teeth. The somewhat similar straining function of crabeater seal teeth is parallel evolution.

    From Wikipedia:

    "Baleen is believed to have evolved around thirty million years ago, possibly from a hard, gummy upper jaw, like the one a Dall's porpoise has. In fact, it resembles baleen closely at the microscopic level.

    Many early baleen whales also had teeth, but these were probably used only peripherally, or perhaps not at all (again like Dall's porpoise, which catches squid and fish by gripping them against its hard upper jaw)."

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  2. AnonymousMarch 29, 2012 at 10:05 PM

    Here's another image where the cusped teeth can be seen quite clearly:

    http://www.cruzine.com/wp-content/uploads/2010/07/313-underwater-animals.jpg

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