Über die Entwicklung der Eikapselvolumina bei verschiedenen Opisthobranchier-Arten (Mollusca, Gastropoda)

Abstract

An attempt has been made to estimate the volumes of eggs and egg-capsules employing the formula for the rotation-ellipsoid, first after oviposition, second for the capsules during different stages of embryonic development until hatching. The results of the calculations permitted analysis of: (a) the relationship between egg-case volume and egg volume immediately after oviposition; (b) the size of capsules during development until hatching; (c) the relationship of the capsule volume at hatching in comparison to that after oviposition (enlargement-factor). Placida dendritica shows no increase in capsule volume during development. Gonidoris nodosa, Rostanga rufescens, Trinchesia viridis, Acanthadoris pilosa, Archidoris pseudoargus, Tritonia hombergi and Aeolidia papillosa show a distinct increase in capsule volume at the time of velarcilia appearance. The degree of egg-case enlargement and the time of its beginning reveal interspecific differences; within some of the species, both also depend on the number of larvae present in the egg-case. The reasons for such behaviour are not yet known; some possible explanations are discussed. © 1971 Biologischen Anstalt Helgoland.