Artificial Gynogenesis in the Pacific Oyster, Crassostrea gigas: II. Allozyme Inheritance and Early Growth

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Abstract
Juvenile growth and allozyme inheritance were examined in three families of gynogenetic Pacific oysters (Crassostrea gigas) produced by fertilization with ultraviolet-irradiated sperm followed by inhibition of meiosis II with cytochalasin B. Twelve polymorphic enzyme-encoding loci were examined by starch gel electrophoresis. Successful induction of gynogenesis, as measured by the absence of paternal alleles, was estimated at 62%, 89%, and 99%–100% for three families. The mean recombination rate estimated from seven polymorphic loci was 0.74, corresponding to a fixation index of 0.26 per generation. This high level of residual heterozygosity suggests that meiotic gynogenesis is not an effective method for rapid inbreeding in the Pacific oyster. Gynogenetic diploid zygotes were significantly significantly smaller than controls at 10 months of age in one of three families. Variability in size did not differ between gynogens and controls. Three individuals in one family exhibited aberrant genotypes consistent with partial gynogenesis (residual paternal inheritance). More work is needed to determine whether partial gynogenesis may provide a method for gene transfer between taxa incapable of forming viable hybrids, such as many Crassostrea species.

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