The Runaway part II

Windy ride

By  Nicole Webster

Amanda posted a few weeks back about the ‘runaway anemone’.

Lo and behold, while I was in Bamfield, a Stomphia was picked up! I was really excited. There’s something special about seeing it for yourself. So one evening I went over and casually dropped a leather star (Dermasterias imbricata) beside the anemone to get the infamous response.

The Stomphia was in a really shallow tank, hence some of its difficulty swimming. I also think it depends at least partially on the current to help carry it away quickly. What you miss is it instantly contracting upon contact with the seastar.

I didn’t speed up the video. I know its slow, but it gives you a good idea of what is actually going on, how slow this process really is.

(You may want to turn your sound down – that’s the constant running water sound of working in a sea table lab)

The video ends when it encounters the Anthopleura xanthogrammica on the side of the tank. I let it try to escape for about a minute, then took it away. I’m not sure that it wouldn’t have been eaten… Anemones are voracious.

After placing it in a safe location in the tank, it took about 2min for Stomphia to right itself and settle onto a rock.

There are two species of Stomphia supposedly found in the region, S. diademon (probably shown here) and S. coccinea. S. diademon are found usually rather deep, at least 80m deep on soft sediment, are are mostly pulled up via trawling.

A Snail’s Odyssey has a nice summary of some of the Stomphia literature (midway down the page:swimming):

  • Dermasterias imbricata and Hippasteria spinosa are two sea star predators most likely to incite the swimming response, as is Aeolidia papillosa (nudibranch) (Yentsch & Pierce 1955 Science 122). Many others do not cause a reaction.
  • Different sensory pathways excite the same excite escape response for different predators (Robson 1961 J Exper Biol 38: 685).
  • Feeding inhibits the escape response (Doesn’t want to loose its lunch?) (Ross & Sutton 1964 J Exp Biol 41: 751).
  • Nematocyst discharge is deactivated during swimming and takes time to reactivate (20-60min) (Ross & Sutton 1964 J Exp Biol 41: 751).
  • They are highly sensitive: for Dermasterias, as little as 50ng of the compound ibricane is what causes the escape response (Ward 1965 J Exper Zool 158).

Further reading:
E-fauna BC
Dave Cowles
A Snail’s Odyssey


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