Tuesday, December 1, 2009

Sea stars, eating and being eaten

First, watch this mesmerizing time-lapse video from the BBC...
Now, let me tell you some of the remarkable things I have learned about the sea star, a.k.a. the starfish:
  • Sea stars live in all oceans - including the Antarctic, where the video was filmed and where the 24-inchers in the 2nd photo were caught - and at all depths.
  • Most of the 1,800 species have 5 rays (or arms), but some have as many as 50.
  • The small circle near the center of a sea star is porous and functions as a water valve.
  • "Tube feet" emerge from the grooves on the underside of the rays to assist in eating and locomotion.
  • Most sea stars move slowly, but some are capable of rapidly "gliding" across the sea floor.
  • A microscopic eye on the end of each ray allows the sea star to distinguish between light and dark.
  • Sea stars have 2 stomachs, one of which can protrude out of the mouth to engulf food.
  • They have complex nervous systems, but no brain.
  • Sea stars reproduce sexually or asexually, releasing gametes either by pairing one-to-one or "free-spawning" in groups.
  • Some species can reproduce by fragmentation, with an entire sea star growing from a detached arm. Others can regenerate their own lost arms.
Various sea stars eat clams, oysters, mussels, snails, dying fish, worms, decomposed plant and animal material, coral, sponges, and plankton. Sea stars, in turn, are eaten by crabs, other starfish, a particular marine snail known as the Charonia tritonis (4th photo), shore birds, sea otters, seals, etc. They are also eaten by the Chinese, well-known for having a wide palate, who offer them up fried on a stick (5th photo). The other ocean marvel I blogged about recently, flying fish, is also a foodstuff, in Japan and Barbados. I was once telling octopus stories at the table and remarked that I couldn't believe people ate such a smart creature, at which point my vegan friends promptly responded, "Some of us feel that way about cows."

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