INHERITANCE OF A NUCLEAR-DNA POLYMORPHISM ASSAYED IN SINGLE BIVALVE LARVAE

We examined the inheritance of the Mytilus edulis CaM-1 Intron 3 locus , a non-coding DNA locus with two potentially neutral length-variants. The polymerase chain reaction (PCR) was used to determine the CaM-1 g enotype for 799 larvae obtained from 11 laboratory crosses. Larvae wer e typed singly only 8 to 24 h after fertilization. We find evidence th at each allele can be inherited from either sex, that there are no bar riers to fertilization between gametes of different genotypes, and tha t most larvae have genotypes compatible with Mendelian inheritance of the locus. Deviations from expected genotype frequencies were found in some crosses; we suggest that a contributing factor is aneuploidy in early larvae, but a major cause is more likely to be selection at a lo cus linked to CaM-1, occurring under the artificial laboratory culture conditions. This study demonstrates the feasibility of applying molec ular genetic techniques to early larval stages of marine bivalves, and presents a new non-destructive biopsy method for DNA analysis from li ving adult mussels.