Moridilla c.f. brockii

Photo courtesy of Dr. Marc Chamberlain
Perth, Western Australia

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.

Dave Behrens
Oct. 1999


Debelius, H. 1998. Nudibranchs and sea snails - Indo-Pacific field guide. IKAN. Frankfurt.
Gosliner, T.M. 1987. Nudibranchs of Southern Africa, A guide to Opisthobranch molluscs of southern Africa. Sea Challengers.
Roa, K. P. 1965. Moridilla brockii Bergh, 1888, redescribed with notes on anatomy and early development. J. Mar. Biol. Assoc. India 7: 61-68.
Wells, F. & C. Bryce. 1993. Sea slugs and their relatives of western Australia. Western Australian Museum, Perth.

Marc Chamberlain is by vocation a neurologist and by avocation a wildlife photographer. He enjoys traveling during which he is always toting cameras. His diving holidays have been to the Carribean, up and down the west coast of the Americas and throughout the Indo-Pacific. His photographs have appeared in numerous magazines including: National Geographic; International and National Wildlife; Ocean Realm; Outside; and various Cousteau Society publications. Marc has collaborated on several books and presently is working on a book of Indo-Pacific nudibranchs. Marc was also San Diego Underwater Photographic Society Photographer of the Year six times during the time he lived in the San Diego County area. Marc has participated in thirteen consecutive San Diego Underwater Society Film Festivals which has to be a club record!

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Taxonomic information courtesy of Dave Behrens
Photographs courtesy of Dr. Marc Chamberlain

David W. Behrens

Author: Pacific Coast Nudibranchs
Co-Author Coral Reef Animals of the Indo Pacific
Propriator of Sea Challengers Natural History Books !

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© The Slug Site, Michael D. Miller , 1999. All Rights Reserved.