HETEROZYGOTE DEFICIENCY IN A COHORT OF OSTREA CHILENSIS (PHILIPPI 1845)

Abstract

A cohort oí Ostrea chilensis settled on artificial collectors in the Quempillén estuary, Ancud, Chiloé was used to investígate genotype frequencies at the LAP, PGI and CA loci, in random samples of oysters taken at 6, 18 and 30 months of age. Individual testing of each locus, using the x: goodness of fit test was carried out, using "D" as an índex of heterozygote deviation. In 6 months oíd oysters no negative valúes for D were found. Significan! deficiency of heterozygous were found at LAP (D= -0.260) and AC (D=-0.153) loci in oysters 18 months oíd. Inadults (30 months) negative valuesof D werepresent at all analyzed loci presenting significant valúes at LAP (D= -0.243 and AC (D=-0.353). Considering that mortality between 6 and 18 months and between 18 and 30 months was 25% and 17% respectively, we conclude that thereisa selection against heterozygotes in juvenile oysters, which is in agreement with the reports in the literature for other mollusc species.