URCHIN CTENOPHORE Coeloplana
bannwarthii
"I wondered
whether you could help me out regarding some worms that I observed
on Diadema during a night dive last week. These feather-like
creatures (see attached pictures) hang from small, red thickenings
in the urchin's spines that were otherwise black. The number of
these organisms varied between 1-30 per urchin and while the larger
ones induced these red bumps, smaller ones were coming from a small
hole in the urchin's spine. All these featherlike creatures were
flapping around in the current and retracted once they caught some
particle that floated by. I estimate that ~80% of the urchins (Diadema
only) at this site (Kahekili/ Maui) carried these additions around.
I wondered if you might know this organism by name and/ or reputation
and would be willing to guide me on what to think of this."
Best regards
Mark Vermeij
Hi
Mark,
Those are ctenophores - most species drift in the water like jellyfish
(popularly known as comb jellies), but are a few live on the bottom
or attach to other animals. It's probably Coeloplana bannwarthii
Krumbach, 1933, which according to Reef and Shore Fauna of Hawaii
Section 1 [Bishop Museum Special Publication 64(1)], p. 267,
is symbiotic with urchins of the genus Echinothrix and Diadema
in Hawaii.
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