Genetic sex determination, gender identification and pseudohermaphroditism in the knobbed whelk, Busycon carica (Mollusca: Melongenidae).
We report perhaps the first genic-level molecular documentation of a mammalian-like 'X-linked' mode of sex determination in molluscs. From family inheritance data and observed associations between sex-phenotyped adults and genotypes in Busycon carica, we deduce that a polymorphic microsatellite locus (bc2.2) is diploid and usually heterozygous in females, hemizygous in males, and that its alleles are transmitted from mothers to sons and daughters but from fathers to daughters only. We also employ bc2.2 to estimate near-conception sex ratio in whelk embryos, where gender is indeterminable by visual inspection. Statistical corrections are suggested at both family and population levels to accommodate the presence of homozygous bc2.2 females that could otherwise be genetically mistaken for hemizygous males. Knobbed whelks were thought to be sequential hermaphrodites, but our evidence for genetic dioecy supports an earlier hypothesis that whelks are pseudohermaphroditic (falsely appear to switch functional sex when environmental conditions induce changes in sexual phenotype). These findings highlight the distinction between gender in a genetic versus phenotypic sense.
Avise
John C
JC
Department of Genetics, University of Georgia, Athens, GA 30602, USA. avise@uga.edu
Power
Alan J
AJ
Walker
DeEtte
D
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D012734:Disorders of Sex Development / Q000235:genetics; D005260:Female; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D019849:Sex Determination Processes; D012744:Sex Ratio; D012908:Snails / Q000235:genetics*
D017931:DNA Primers