Development and Growth of Larvae of the Dog Conch, Strombus canarium (Mollusca: Gastropoda), in the Laboratory

摘要

Strombus canarium egg masses used in this study were collected while still underneath spawning females, and embryonic and post-hatching larval development was observed in the laboratory. Strombus canarium larvae were reared at 200 larvae/L in 2-L containers with 0.22 mu m filtered seawater medium at a salinity of 30 ± 1 PSU, and fed a single algal species, Isochrysis galbana, at 1000 cells/ml. Fecundity was estimated at 48,745 ± 877 to 93,643 ± 1685 (n = 10) eggs/egg mass. The incubation time wasbetween 110.4 and 134.4 h (mean 122.43 ± 3.07 h, n = 7) at 29 ± 1°C, with a high hatching rate (mean 93.34% ± 1.68% hatched, n = 3). The larvae have 2 velar lobes and 1.5 shell whorls at the time of hatching, with an average shell length of 216.77 ±5.72 mu m (n = 10). Based on prominent larval characters and visible morphological features, S. canarium larvae can be assigned to 4 different development stages, i.e. stages I, II, III, and IV, which are described in this paper. The larvae reached metamorphic competence at 17-23 d post-hatching, and only metamorphosed when settlement cues (sediments from its natural habitat and 15 mM KCI) were introduced. They showed a short period of metamorphic competence, and no spontaneous metamorphosis was observed. Morphological changes and larval behaviors at the onset and during metamorphosis are also described. http://zoolstud.sinica.edu.tw/Journals/48.1/1 .pdf