Development and Larval Morphology of the Spiny Scallop, Chlamys hastata

¹ Department of Biology, University of Victoria, Victoria, British Columbia V8W 2Y2

The early life history of Chlamys hastata, the spiny scallop, from spawning through metamorphosis to a benthic juvenile is described using light and electron microscopy. Newly released oocytes were about 70 µm in diameter and occasionally were surrounded by a 65 µm-thick jelly coat. A low envelope that is elevated at fertilization was observed in SEM preparations. Gastrulation results from both epiboly and invagination. Primary trochoblasts can be distinguished as two groups of ciliated cells surrounding the blastopore. The D-stage veliger developed by about 50 hours (12°C) and the planktotrophic larval stage is about 40 days in duration. Veliger larvae reached a maximum valve length of 240 µm. Provinculum length remained constant throughout larval life and a ligament may be present in the larval stage. An interlocking crown and groove feature on the larval denticles is described. There is a group of distinctive compound cilia situated at the mouth region that may function in particle sorting. Development of C. hastata is superficially similar to that of other species of pectinids. However, differences in details of larval morphology suggest there is greater variation in larval form and function than is generally assumed.

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