Seed production and growth of Modiolus capax conrad (Bivalvia : Mytilidae) in laboratory conditions

摘要

The complete ontogeny and postlarval growth of Modiolus capax are described for the first time. Spawning was easily achieved by a gradual increase in water temperature (1 degrees C/h) from 26 degrees C to 31-32 degrees C after exposing the breeders to air for 6 h. The veliger stage (103 +/- 8 mu m) was reached 23-24 h after fertilization and the low umbo stage (165 +/- 9 mu m) on the fifth day of culture; growth thereafter was temperature-dependent. At 28.5 +/- 0.5 degrees C, competent pediveligers (275 mu m) were first observed on the tenth day of culture and on the twelfth day at 26.5 +/- 0.5 degrees C, but survival was twice (42%) that obtained at 28.5 degrees C. Most larvae settled between 290 and 310 mu m; metamorphosis took 3-4 days. For settlement, several suspended artificial substrata were tested; ropes of twisted anchovy fishing nets captured the larger percentage. However, the use of a downwelling system was the most efficient strategy for the settlement of M. capax over artificial substratum. After metamorphosis, the shell hinge slowly moved toward a more posterior position, and at 440 mu m the disconch had adventitious serrated hairs. Seed growth was exponential and temperature-dependent. At 28.0 +/- 0.5 degrees C, growth ranged from 26-127 mu m day(-1), and from 24-63 mu m day(-1) at 24.8 +/- 1.7 degrees C. In both cases, survivorship from pediveliger to seed was approximately 80%.