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Comparison of Alimentary Systems in Shelled and Non‐shelled Sacoglossa (Mollusca, Opisthobranchia)
Author(s) -
Jensen Kathe R.
Publication year - 1991
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1991.tb00941.x
Subject(s) - opisthobranchia , biology , appendage , anatomy , dorsum , mollusca , gastropoda , zoology , evolutionary biology
The Sacoglossa (= Ascoglossa) comprise a ‘complete’ evolutionary series from species with a large shell into which the animal can withdraw completely, through species with a reduced shell covering only the visceral mass, to shell‐less (‘nudibranchiate’) forms some of which have lateral wing‐like extensions, parapodia, others bearing leaf‐like or cylindrical dorsal appendages, cerata. The Sacoglossa are all specialized suctorial feeders, and almost all are stenophagous herbivores. Hence many anatomical adaptations to a particular food occur in the alimentary system. However, a number of characters seem to reflect phylogenetic relationships as well. Among these are presence/absence, shape, and position of pharyngeal pouches, basic shape of radular teeth, branching pattern of digestive gland, and position of anus. The classificatory significance of these characters is discussed.