PYROSOMA I
Pyrosoma atlanticum?
Divemaster
Zoe Greenberg took these rare photos off Lana`i in August 2011 at
a depth of about 60 ft. 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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