Artificial oocyte maturation in Patella depressa and Patella vulgata using NaOH-alkalinized seawater

Abstract

Laboratory investigations of environmental factors controlling early development and larval survival of free-spawning marine invertebrates are often limited by the difficulty of inducing spawning under laboratory conditions. Patellid gastropod species must be dissected in order to obtain the gametes from the gonads, often yielding unfertilizable immature eggs. The artificial maturation of oocytes through NaOH-alkalinization methods was investigated in order to improve laboratory experiments on larval ecology of Patella depressa and Patella vulgata. Maturation was accelerated above pH 9.0. Alkalinizing oocytes at pH 9.5 significantly enhanced in vitro fertilization rates, especially at higher sperm concentrations. pH 10 was harmful to eggs. Sperm dilution experiments using alkalinized oocytes suggest the use of sperm concentrations proximate to 106 spermatozoa ml−1.