Investigation of the role of diterpenes produced by marine pulmonatesTrimusculus reticulatus andT. conica.
The intertidal pulmonate limpetTrimusculus reticulatus, which is found in caves or crevices along the California coast, was previously reported to contain two novel diterpenoids, 6β-isovaleroxylabda-8,13-dien-7α,15-diol (1) and 2α,7α-diacetoxy-6β-isovaleroxylabda-8,13-dien-15-ol (2). Dissection of the animals prior to extraction revealed that the diterpenoids were concentrated in the mantle, foot, and mucus, but not in the viscera. The presence ofT. reticulatus or its mucus was toxic to veliger larvae of the sabellariid reef-building tube wormPhragmatopoma californica. The major diterpenoid1 was responsible for the observed larvicidal activity. Protection against overgrowth by settling invertebrate larvae is important for the survival of this sessile filter-feeding pulmonate. A related pulmonate,T. conica, which was found in similar intertidal habitats in New Zealand, contained 6β-acetoxy-7α-isovaleroxylabda-8,13-dien-15-oic acid (3) and 1β,7β,12β,18-tetraacetoxy-cholest-5-en-3β-ol (4). The diterpene3 was also localized in the foot, mantle, and mucus ofT. conica but was not larvicidal toP. californica.
Scripps Institution of Oceanography, University of California at San Diego, 92093-0212, La Jolla, California.
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John Faulkner