Guo Ximing, Hedgecock Dennis, Hershberger William K, Cooper Kenneth, Allen Standish K
Haskin Shellfish Research Laboratory, Institute of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, New Jersey, 08349.
Bodega Marine Laboratory, University of California at Davis, Bodega Bay, California, 94923-0247.
Evolution. 1998 Apr;52(2):394-402. doi: 10.1111/j.1558-5646.1998.tb01640.x.
A unique feature of sex in Crassostrea oysters is the coexistence of protandric sex change, dioecy, and hermaphroditism. To determine whether such a system is genetically controlled, we analyzed sex ratios in 86 pair-mated families of the Pacific oyster, Crassostrea gigas Thunberg. The overall female ratios of one-, two-, and three-year-old oysters were 37%, 55%, and 75%, respectively, suggesting that a significant proportion of oysters matured first as males and changed to females in later years. Detailed analysis of sex ratios in factorial and nested crosses revealed significant paternal effects, which corresponded to two types of sires. No major maternal effects on sex were observed. Major genetic control of sex was further indicated by the distribution of family sex ratios in two to four apparently discreet groups. These and other data from the literature are compatible with a single-locus model of primary sex determination with a dominant male allele (M) and a protandric female allele (F), so that MF are true males and FF are protandric females that are capable of sex change. The rate of sex change of FF individuals may be influenced by secondary genes and/or environmental factors. Strong maternal and weak paternal effects on sexual maturation or time of spawning were also suggested.
太平洋牡蛎性别方面的一个独特特征是雄性先熟、雌雄异体和雌雄同体现象并存。为了确定这样一种性别系统是否受基因控制，我们分析了太平洋牡蛎（Crassostrea gigas Thunberg）86个成对交配家系的性别比例。一岁、两岁和三岁牡蛎的总体雌性比例分别为37%、55%和75%，这表明相当一部分牡蛎最初作为雄性成熟，随后在几年后转变为雌性。对析因杂交和嵌套杂交中性别比例的详细分析揭示了显著的父本效应，这与两种类型的父本相对应。未观察到对性别有主要的母本效应。两个到四个明显不同组中的家系性别比例分布进一步表明了性别受主要基因控制。文献中的这些以及其他数据与一个单基因座的初级性别决定模型相符，该模型中有一个显性雄性等位基因（M）和一个雄性先熟的雌性等位基因（F），因此MF是真正的雄性，FF是能够发生性别转变的雄性先熟雌性。FF个体的性别转变速率可能受次要基因和/或环境因素影响。还表明了对性成熟或产卵时间有强烈的母本效应和较弱的父本效应。
