Abstract

The maturity of gonads, early development of the fertilized egg, spawning period, and morphogenesis of larvae in Limnoperua fortunei were studied from October, 1981 to November, 1982 as on attempt to identify its life cycle. 1) Active motility of its sperm was observed at late May, and matured egg could be found at late June. 2) It was estimated that the spawning was occured from late August. This species was belong to the short-term breeder because it finished its spawning within 20 days. 3) It has free-living trochophore and D-shaped larva stage. The shell lengths of early, middle, and D-larval stage were <TEX>$140.0{\mu}m$</TEX>, <TEX>$167.6{\mu}m$</TEX> and <TEX>$210.0{\mu}m$</TEX>, respectively. The shell heigths of each stage were <TEX>$97.3{\mu}m$</TEX>, <TEX>$137.6{\mu}m$</TEX> and <TEX>$178.2{\mu}m$</TEX>, respectively.