Moridilla c.f. brockii Bergh, 1888
One of the largest and most colorful aeolids in Western and Northern Australia, Moridilla brockii is a beautiful and interesting critter. Closely related to members of the genus Phidiana, this species is a very active animal and displays agnostic behavior bristling its cerata when disturbed or irritated. Another striking example of aposomatic "warning" coloration, it follows up the threat made by its bright red ceratal tips by uncoiling the long rolled, medial cerata, pointing their nematocyst packed tips at the annoyance (see Bill Rudman's Moridilla brockii page on the Sea Slug Forum). This is one creature that really "puts its money where it mouth is."
In the minds of some, there seems to be some question as to this species identity. While Marc's specimens shown here are almost identical to those presented on Rudman's site and in Wells and Bryce (1993) as M. brockii, Bryce identified identical looking specimens shown in Debelius (1998) as Moridilla sp. All have bright red rhinophores and cephalic tentacles, the latter being extremely long, and a red line down the tail. Some variation seems to occur between specimens concerning the presence of white pigmentation on the cephala tentacles.
This species bares two forms of cerata, a series of short, more typical cigar shaped cerata at the outer edge of the ceratal bundles, and very long tapering, coiled ones along the inner margin. It is these inner cerata that display the pugnacious behavior when disturbed. The two forms differ slightly in color as shown here.
Moridilla brockii was originally described from Java, Indonesia, and then
redescribed by Roa (1965) from India. Except for the photo of a South
African specimen in Gosliner (1987; sp. 247) and Bob Bolland's
specimens from Okinawa, all the photographic material I could find
seems to be from Western and Northern Australia. The distribution of M.
brockii is reported to be tropical Indo-West Pacific, but one must wonder if
more than one species is involved here. Our web master, Senor Miller, has
photographed specimens in the Batangas region of the Philippine
Islands. The Philippine, South African and Okinawan specimens are all
similar in color having a white band halfway on the cephala tentacles, and
differing also from the Australian material in ceratal coloration, the
latter having dramatically contrasting red-orange and white. It has been
suggested to me, that a closer look may be indicated here, to determine if
we are dealing with the same or two different species. Hopefully one of my
colleagues will get right on that.
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Taxonomic information courtesy of Dave Behrens
Photographs courtesy of Dr. Marc Chamberlain
David W. Behrens
Pacific Coast Nudibranchs
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