Larval and juvenile development of the doughboy scallop, Chlamys (Chlamys) asperrimus (Lamarck) (Mollusca : Pectinidae)

Abstract

Planktotrophic larvae of C. asperrimus were reared from zygotes with a mean diameter of 61.5µm. The smallest straight-hinged larval shell was 80µm long, and slightly protruding umbones were formed 6 days after fertilization. The length (L) and height (H) relationship of larval shells was described by the allometric growth curve H = 0.309 L^{1 203}. Provincular structure of 13-day-old larval shells was simple and there were nine taxodontal teeth per valve, four at one end of the hinge line and five at the other end. Eye spots were conspicuous and common in pediveligers 160-220µm long. Metamorphosis occurred 20-22 days after fertilization at 17-18ºC when larvae were 190µm or longer. Larvae settled on monofilament nylon collectors. Newly settled juveniles developed a distinctive byssal notch on the right valve but attachment by byssal threads was never permanent. The small size of eggs and early larvae and allometric growth of prodissoconch II shells are the most significant characteristics distinguishing the larval stages of C. asperrimus from other pectinids in Tasmanian waters.