The contribution of chemical ecology to an understanding of functional morphology and evolution.

Chemical ecology has greatly contributed to the understanding of evolutionary patterns and processes amongst the so-called "sea slugs" (Mollusca: Gastropoda: Opisthobranchia). Chemical defense has played a primary role in the evolution of the group, and preceded the regression of the external shell and its function in mechanical defense.1-4 With the complete loss of the shell in nudibranchs, the primitive function of the mantle of producing the shell has been lost. In some groups this has led to great elaboration of the mantle with the development of papillae, cerata and tubercles, while in others there has been a tendency towards a reduction in its size and importance. Within the genera of the family Chromodorididae, a gradual mantle skirt reduction in relative size can be observed in a series from Glossodoris and Chromodoris, through Hypselodoris and Risbecia, to Ceratosoma where the mantle skirt is almost completely absent.Chromodorid mantle glands, for which a defensive role has been suggested, are also arranged in a characteristic way and in distinct areas of the mantle in each genus.5-11 In this report we describe recent findings on chromodorids collected along the Chinese coast. A combination of chemical analysis on different mantle sections and feeding deterrence assays allowed us to clarify the functional significance of the diversified mantle morphologies within the Chromodorididae. 1. Faulkner DJ, Ghiselin MT, Mar Ecol Prog Ser, 1983, 13: 295-301. 2. Cimino G, Ghiselin MT, Chemoecol, 1998, 8: 51-60. 3. Cimino G, Ghiselin MT, Chemoecol, 1999, 9: 187-207. 4. Cimino G, Ghiselin MT, in Marine Chemical Ecology, McClintock JB, Baker BJ (eds) (CRC Press), 2001, pp 115- 154. 5. Rudman WB, Zool J Linn Soc, 1973, 52: 175-199 6. Rudman WB, Zool J Linn Soc, 1984, 81: 115-273. 7. Rudman WB, Zool J Linn Soc, 1986, 86: 101-184. 8. Rudman WB, Zool J Linn Soc, 1988, 93: 133-185. 9. Rudman WB, in Mollusca: The Southern Synthesis. Fauna of Australia, Beesley PL, Ross GJB, Wells A (eds) (CSIRO Publishing), 1998, pp 999-1000. 10. Mollo E, Gavagnin M, Carbone M, Guo Y-W, Cimino G, Chemoecol 2005, 15: 31-36. 11. Wägele H, Ballesteros M, Avila C, Oceanogr Mar Biol Ann Rev, 2006, 44: 197-276.