Escapee

By Nicole Webster

This was an interesting little incident encountered in a tidal pool. We saw an amphipod get caught by an anemone, then escape!

This was in a reasonably large tidepool on Nudibranch point.

View of the point Credit. N. Webster

View of the point Credit. N. Webster

The amphipod (sand hopper) trapped (probably Traskorchestia traskiana but there are many species of intertidal ampipods that need a microscope for ID) in the tentacles (Anthopleura elegantissima) Credit: N. Webster

We saw this happen several time in just a few minutes, so it must happen constantly. The anemone did react, pulling the amphipod in, but to no avail.

The same amphipod happy on the edge of the anemone. Credit: N. Webster

The same amphipod happy on the edge of the anemone. Credit: N. Webster

I can imagine that the anemones do catch and eat one every now and then, but there was no thrashing or panic evident on the part of the amphipod, it simply, carefully, kinda crawled out. It would not be a very viable strategy to swim seemingly randomly around the tide pool without being able to escape small anemones. I think it would be a different story escaping from the larger Anthopleura xanthogrammica.

A view of the full size of the strangely elongated anemone. This might be from growing above some large mussels that have since died. Credit. N. Webster

A view of the full size of the strangely elongated anemone. This might be from growing above some large mussels that have since died. Credit. N. Webster

Another A. elegantissima stretching around a mussel in the same pool. Credit: N. Webster

Another A. elegantissima stretching around a mussel in the same pool. Credit: N. Webster

These anemones also don’t appear typical, they are missing their green colouration, and are strangely elongate. The white colouration is probably bleaching, a loss of the symbiotic zooxanthellae, just like you hear about for coral. There could be several causes, but I think that this loss is due to chemical or temperature stress. The tide pool was fairly high up, and may have been low salinity (based on the algae?)

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