Ova should be suspended in filtered seawater and a sperm suspension made in a separate beaker to create a pale white stock. Mixture of gamete solutions must be done with care. Avoid use of too much sperm for fertilization (zygotes and subsequent embryonic stages become abnormal under conditions of polyspermy). Eggs should be fertilized to provide 10-100 sperm/ovum. Under the microscope sperm attaching to the vitelline membrane are seen at the equator. Concentrations are ideal if several sperm are observed in the plane of view.

     Following fertilization, ova are allowed to sink. This may take over 15 minutes. At that point superficial water is decanted and the eggs resuspended in newly filtered and UV-treated seawater. This process should be repeated at least twice to ensure excess sperm and other potential contaminants are removed.

     We use a series of polyethylene pails (10-Liter volume), distributing approximately 50,000 zygotes to each. Frequently spawning by one or two females provides well over one million eggs.

     Fertilized eggs are incubated without aeration for 24-48 hours until hatching of trochophore larvae. Hatching rate is temperature-dependent (Leighton, 1979). At hatching, larvae concentrate at and near the surface and may be decanted into freshly filtered, UV-treated seawater. Meshing out to completely separate larvae from the culture medium is done as larvae enter the D shell or straight hinge stage (usually 3-4 days postfertilization).

A 55 µm nylon mesh mounted on a buoyant wooden frame immersed in filtered seawater is used in our hatchery/laboratory. Once transferred to a new culture pail, smaller algae such as Pavlova lutheri, Thalassiossira pseudonana, and Isochrysis galbana (Tahitian strain) may be supplied as food. We also use Nannochloropsis, but this alga is not utilized. It is, nonetheless, consumed and serves as a marker or indicator for active feeding.

     Daily transfers of larvae are required throughout the first two weeks of culture. Thereafter and throughout culture of larvae to the eyed stage (200-220 µm, 4-5 weeks) larvae must be meshed out each 2-3 days. Temperatures for culture of larvae from southern California rock scallops should be held in the range 14-20^oC.

Rock scallop larvae two weeks old. Shell width 135 µm.