Comparative kinetics of meiosis in hybrid crosses of Pacific oyster Crassostrea gigas and Suminoe oyster C. rivularis with the American oyster C. virginica

Abstract

AbstractInterspecific hybridization of bivalve molluscs within the genera Crassostrea and Pinctada have yielded progeny of one parental type, leading to speculation of gynogenetic or androgenetic development. Therefore, meiotic and early mitotic events of oocytes from the oysters Crassostrea gigas and C. rivularis fertilized with C. virginica sperm, as well as the reciprocal and control crosses, were critically observed in samples taken up to 90 minutes post‐insemination. Chromosomal material in oocytes was visualized with the DNA‐specific fluorochrome DAPI and epifluorescence microscopy. All crosses produced fertilized oocytes which were observed to proceed through meiosis and early mitosis. Fertilization was ∼20% less successful in hybrid than straight crosses of C. gigas and C. virginica (P = 0.022) but no difference in fertilization was evident in C. rivularis and C. virginica crosses (P = 0.169). The time interval between meiotic and mitotic landmarks was not significantly different among all crosses within each full reciprocal cross. There was no cytological evidence of parthenogenetic, gynogenetic, or androgenetic development. In previous reports, non‐hybrid progeny found in hybrid groups were probably contaminants. © 1992 Wiley‐Liss, Inc.