Hori Michio, Ochi Haruki, Kohda Masanori
Laboratory of Animal Ecology, Graduate School of Science, Kyoto University, Kyoto, Japan.
Zoolog Sci. 2007 May;24(5):486-92. doi: 10.2108/zsj.24.486.
Antisymmetry in the direction of the mouth opening, to either the right ("lefty") or left ("righty"), was documented in the scale-eating cichlid Perissodus microlepis. This study revealed the presence of lefty and righty mouth morphs in the herbivorous cichlid Neolamprologus moorii, although the degree of deviation was not large. Both species are biparental brooders and guard their young. We examined the inheritance pattern of the dimorphism (laterality) using parents and broods of P. microlepis and N. moorii collected in the wild. In P. microlepis, lefty-lefty pairs had a 2:1 frequency of lefty:righty young, lefty-righty pairs a similar number of each type of young, and righty-righty pairs only righty young. Similar inheritance patterns were observed in N. moorii. We propose two hypotheses to explain the inheritance pattern: Mendelian genetics with the lefty allele dominant over the righty and the dominant allele homozygous lethal, and cross-incompatibility that is predominant in lefty homozygotes.
在以鳞片为食的丽鱼科鱼类小鳞奇丽鱼中，记录到了开口方向的反对称性，即开口向右（“左口型”）或向左（“右口型”）。这项研究揭示了草食性丽鱼科鱼类穆氏新亮丽鲷中左口型和右口型口部形态的存在，尽管偏差程度不大。这两个物种都是双亲育幼并保护它们的幼鱼。我们利用在野外采集的小鳞奇丽鱼和穆氏新亮丽鲷的亲鱼及幼鱼群体，研究了这种二态性（侧性）的遗传模式。在小鳞奇丽鱼中，左口型与左口型的亲鱼所产幼鱼中，左口型与右口型的比例为2:1，左口型与右口型的亲鱼所产两种类型的幼鱼数量相似，而右口型与右口型的亲鱼只产右口型幼鱼。在穆氏新亮丽鲷中也观察到了类似的遗传模式。我们提出了两个假说来解释这种遗传模式：一是孟德尔遗传学，即左口型等位基因相对于右口型等位基因呈显性，且显性等位基因纯合致死；二是交叉不相容性，在左口型纯合子中占主导地位。
