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PYROSOMA I
Pyrosoma atlanticum?
Divemaster
Zoe Greenberg took these rare photos in August 2011 off Lana`i.
Zoe's "animal" was about 2 ft. long. In fact, this is
not a single animal but a colony of hundreds of tiny tunicate animals
that together form a tube, closed at one end and open at the other.
The tube is covered with short, slender, pointed projections (papillae)
and, if you look closely, a tiny reddish organ is visible inside
the translucent body of each of the little tunicates. In Hawai`i,
these pyrosomas are typically about 4-5 inches long; to see one
at all is unusual, and to find one of this size is practically unheard
of. These strange drifting creatures look gelatinous but are actually
rigid and surprisingly hard to the touch. Pyrosomas propel
themselves by expelling water from their open end. Each animal takes
water in along the outer part of the tube, filters it for microscopic
food particles, and empties it into the inside of the tube, where
it exits at the open end. The genus name Pyrosoma means "fire
body" and these animals are brightly luminescent if disturbed.
Probably the luminescence is visible only in the dark. An internet
search turned up something that looks very much like it called Pyrosoma
atlanticum, which is supposed to be the most common Pyrosoma
in temperate and tropical waters worldwide. Sure enough, a visit
to the Bishop
Museum site shows that 2 subspecies of P. atlanticum
have been recorded from Hawaii: Pyrosoma atlanticum hawaiiensis
and Pyrosoma atlanticum paradoxum. It would probably take
an expert to determine which is which. Susan Scott wrote a fun
column on these animals. For more detailed information, check
out the neat Jellieszone
website.
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