Spawn masses of chromodorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia)

Contents

Abstract

The egg mass characteristics of 20 species of chromodorid nudibranchs are presented, representing the genera Chromodoris, Digidentis, Diversidoris, Glossodoris, Hypselodoris, Noumea and Pectenodoris. The egg mass details for 14 of the included species appear previously unrecorded. These results combined with observations from the literature (comprising a total of 67 species from 15 genera) indicate that most genera in the Chromodorididae show only one type of egg mass. The exception to this is the genus Chromodoris, which includes all three egg mass types outlined in this study. Based on anatomical evidence, a group of flat-spawning Chromodoris species has been suggested to belong to a monophyletic clade, whcih indicates that egg mass structure can reflect phylogenetic signal. genera considered to be more derived among the Chromodorididae are more likely to lay an egg mass that is outward sloping or crenulated. Cadlinella shows spawning traits (flat egg mass containing extra-capsular yolk) that indicate it may be ancestral to the Chromodoris lineage. Developmental data is presented for 11 species of Chromodoris, seven of which utilized extra-capsular yolk in their egg masses. The presence of extra-0capsular yolk appears to correlate with upright egg masses within this genus. However, the occurence of extra-capsular yolk appears to be restricted to Indo-Pacific and Red Sea Chromodoris species, while upright spawns from the Caribbean species lack this feature.