Evolutionary Ecology

, Volume 11, Issue 3, pp 301–335

Evolution of the Sacoglossa (Mollusca, Opisthobranchia) and the ecological associations with their food plants

  • KATHE R. Jensen

DOI: 10.1023/A:1018468420368

Cite this article as:
Jensen, K.R. Evolutionary Ecology (1997) 11: 301. doi:10.1023/A:1018468420368


Evolution in the opisthobranch order Sacoglossa has been closely linked to their specialized suctorial herbivorous habits. All shelled Sacoglossa (about 20% of the species) feed on one algal genus, Caulerpa. The non-shelled Sacoglossa have 'radiated' to other diets, mainly siphonalean or septate green algae (Class Ulvophyceae). Comparing the phylogeny of sacoglossan genera with the phylogeny of the Ulvophyceae indicates that co-speciation may have taken place at the basal node of the Sacoglossa, and that host switching has taken place several times in the two non-shelled clades. It is suggested that the most important evolutionary process has been speciation by 'resource-tracking'; the resource tracked is most probably cell wall composition of the algal prey. The fossil record of extant sacoglossan genera dates back to the Eocene and, based on the fossil record of siphonalean green algae, the Sacoglossa most likely appeared in the Cretaceous. It is hypothesized that the ancestral sacoglossan was epifaunal, suctorial and herbivorous, and the 'ancestral' food plant was not Caulerpa, but filamentous, calcified, now extinct, Udoteaceae.

ecological associationsevolutionintegrative biologyOpisthobranchiaresource trackingSacoglossaUlvophyceae

Copyright information

© Chapman and Hall 1997

Authors and Affiliations

  • KATHE R. Jensen
    • 1
  1. 1.Zoological MuseumCopenhagenDenmark