An unusual dendrodorid: redescription of the tropical nudibranch Dendrodoris atromaculata (Alder & Hancock, 1864) (Anthobranchia: Doridoidea: Dendrodorididae)

Abstract

Dendrodoris atromaculata (Alder & Hancock, 1864) is a large, tropical nudibranch mollusc living in the Indo-west Pacific Ocean. A detailed description of the external morphology of the living animal and an investigation of internal anatomy are presented for the first time. In addition the microstructure of certain organs (i.e., notal tissue and the vestibular gland associated with the reproductive system) are compared with other Dendrodoris species. Dendrodoris atromaculata is unique among currently described species of Dendrodoris in three respects, the gill structure is “cross-like”, the notum possesses prominent spicules and the notum is covered in finger-like processes. These findings necessitate a reassessment of previously documented generic features of Dendrodoris and reveal a need for changes to future phylogenetic analyses of both porostome and cryptobranch dorids.