The eggs and hatching stages of some New Zealand prosobranch molluscs

Abstract

Early stages in the life history of 23 New Zealand prosobranchs from Otago waters are reviewed on a family basis. The egg capsules of 6 species, and the newly-hatched stages of 12 species, are drawn and described for the first time. Identification of veligers from local plankton hauls showed that 6 additional species have a planktonic ve1iger stage. The most significant results are that two of the four Otago calyptraeids have direct development and the muricid Zeatrophon ambiguus (Philippi) has indirect development with a long planktonic phase. The eggs of Trichosirius inornatus (Hutton) hatch as free-swimming echinospira larvae. In Maoricoipus roseus (Quay and Gaimard) the eggs are retained in the mantle cavity of the female, probably until they hatch as crawling fry.