Ceratosoma brevicaudatum with red "dorsal horn" immediately behind gills
Ceratosoma brevicaudatum Abraham, 1876
Ceratosoma brevicaudatum was easily the most common nudibranch Jim Black and I saw on a recent trip to South Australia. We saw it at four differenent dive locations spanning a distance of some 500 Kilometers from Melbourne to Adelaide. This species is easily identified by the red "horn" like appendage in the tail area as seen in the photo to the left.
The following is a discussion of this odd dorsal "horn" by Bill Rudman on his Sea Slug Forum
"... Ceratosoma trilobatum usually have a long recurved dorsal 'horn' which sticks up from the body behind the gills. This horn has an interesting defensive function because it is where the animal stores distasteful and noxious chemicals its has removed from its sponge food. The horn appears to act as a sacrificial lure, tempting fish to take a bite. When or if they do they get a mouth full of nasty chemicals which teach them to leave Ceratosoma alone. As the 'hom' has no other function, the slug can live quite happily without it. It seems that Ceratosoma brevicaudatum represents an early stage in the evolution of the dorsal horn. In the close-up alongside I have ringed the swollen 'bump' which is found in this species. It is packed full of noxious chemicals and is usually more brightly coloured thyan the rest of the body - again acting as a lure. If you look at some of the other messages on thsi species, which are attached to the Fact Sheet, you will see that in juveniles the horn is even more brightly coloured. The name brevicaudatum means 'short tail' in Latin, which is a reference to this very short dorsal horn..."
One has to say again, isn't nature absolutely amazing!
Jim on location at Anilao, Philippines, May 2013
Jim Black is retired from US Airways after 27 years as a pilot..., flying Captain on an Airbus 330 Internationally.
Diving since 1970...with over 7000 dives logged. Shoots Nikon D-300 in Subal Housing with Ikelite strobes. Macro Mate on 105mm for supermacro.
Jim's photography has been featured in a number of books and publications including Helmut Debelius' Nudibranchs and Sea Snails of Gosliner, Behrens and Williams Coral Reef Animals of the Indo-Pacific. A photo of Jim petting a shark in "Sleeping Shark Caves" off Isla Mujeres Island, Mexico, taken by Amy Foster his significant other, recently appeared in Dave Behrens' Diving Guide to Cozumel, Cancun & The Riviera Maja.
Jim has been a solid supporter of the Slug Site since day one. His countless contributions put him near the top of the list of photographers who have greatly expanded our knowledge of sea slugs. There are a lot of kids in the formative stage of their education who are getting their first introduction to our sea slug friends via the great photographs Jim and other contributors have made to the site. My hat is off to Jim for making this presentation possible!
Send Jim email at firstname.lastname@example.org