ChemInform Abstract: DEFENSE ALLOMONES OF THE NUDIBRANCH PHYLLIDIA VARICOSA LAMARCK 1801

Abstract

SummaryThe defensive secretion of the nudibranch Phyllidia varicosa consists of two isocyanosesquiterpenes: the previously described 9-isocyanopupukeanane (l), and its 2-isomer (4), for which we report the structure and properties. The mixture originates with a sponge, Hymeniacidon sp., where it is produced in varying proportions. CD. measurements and X-ray diffraction data establish the absolute configuration of the two metabolites.Nudibranchs (sea slugs) are marine mollusks which lack an external shell and which are frequently associated with sessile marine invertebrates, e.g. sponges, bryozoans, or coelenterates, in a grazer-prey or in a symbiotic relationship [I]. We recently [2] elucidated the molecular basis of such a relationship between the nudibranch Phyllidia varicosa and its prey, a sponge, Hymeniacidon S P .~) , and we reported the structure of 9-isocyanopupukeanane (l), the defense allomone of the mollusk, which the mollusk in turn obtains from its preferred diet, a sponge. The mollusk accumulates the allomone, which is the active constituent of its mucous skin secretion that is lethal to fish and crustaceans [3].We recognized early in our investigation that the isonitrile fractions of the mollusk and of the sponge were identical binary mixtures of isonitriles. However, the two compounds proved inseparable by chromatography or complexation. On the other hand, degradation of the mixture to 9-pupukeanone (2) [2], or derivatization of 9-methylaminopupukeanane (3) with phenylisothiocyanate [2] led in each instance to isolation of a single compound, having a sesquiterpene skeleton corresponding to 1. These observations indicated that either isomerization of one of the constituents had occurred, or that one constituent had been eliminated during reaction or work-up. We now report the identity and properties of the second iso- I ) 3,In part from the M.S. Dissertation of M.R.H., University of Hawaii, 1978. Present address:

Chemical defense and evolutionary ecology of dorid nudibranchs and some other opisthobranch gastropods

“…The acetylenes found in Peltodoris atromaculata were from the sponge Petrosia ficiformis (Castiello et al, 1980) while the isonitriles from Phillidia varicosa were also isolated from a Hawaiian sponge Hymeniacidon sp. (Hagadone et al, 1979). The chlorinated acetylenes from Diaulula sandiegensis were present in the crude extract of a sponge (probably Haliclona sp.)…”

“…Among dorids this is known only in Dendrodoris limbata (Cimino et al, 1982), which belongs to the specialized suborder Porostomata. As another porostome, Phyllidia, derives its metabolites from food (Hagadone et al, 1979) synthetic capacity has evolved within the group. De novo synthesis has also evolved within the Sacoglossa, again in more modified representatives of the group (Ireland and Scheuer, 1979).…”

Chemical defense and evolutionary trends in biosynthetic capacity among dorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia)

“…(Ceractinomorpha: Halichondrida: Halichondridae) (Burreson et al 1975;Hagadone et al 1979). Fusetani et al (1990) obtained more examples from P. bourguini.…”

Untitled

“…The arrangement of spicules inside the papillae of the mantle tissue (Fig. 3f) increases the body cavity size of the dorsal mantle that could be used as storage for many chemical defenses 4,19 . At the mantle edge, the loose lattice-like arrangement of spicules and the circumference crossed with the radial lines of the body results in an increased body cavity that may allow for more haemolymph to circulate through this space which would allow more flow to the gills.…”