八种鱼类(鲤属和白鱼属)的染色体组型研究

Studies of the karyotypes of eight species of fishes in Cyprinus and Anabarilius

本篇报导了四种鲤属鱼和四种白鱼属的染色体组型研究结果,并从细胞遗传学角度讨论了这些鱼类的物种形成问题,同时提出了这样一种看法:用所研究过的五种鲤属鱼类进行种间杂交,获得能育后代的可能性较大。

By the methods described in a previous paper, [ 1 ] we have studied the karyotypes of eight species of fishes in Cyprinus and Anabarilius, i. e. C. (Cyp.) longipectoralis C. (Cyp.) megalophthalmus, C. (Cyp.) Pellegrini barbatus, C. (Nesocyp.) micristius fuxianensis, A. andersoni, A. macrolepis, A. grahami, as well as A. alburnops taken from Kunming lake and A, alburnops taken from Qilu lake and discussed the genetic and cytogcnetic causes of speciation in these fishes. All the four species in Cyprinus have the same chromosme number (2n = 100), the same formula of groups and complements of chromosomes (22m + 30sm +48st, t) and the same heteromorphic pair of "tentative sex chromosomes" which were identified as sm. In other features of chromosomal morphology, these fishes also show an identity. Having compared the karyotypes of these fishes with that of C. (Cyp.) carpio and Carassius auratus which was analysed in last paper, we can conclude that all the six species in Cyprinu.;Cyprinus and Carassius studied by us are indistinguishable karyoty pically. All the five(?) species in Anabarilius have 2n = 48 chromosomes, hut their karyotypes, appearing to be something of difference, may be distinguished into three kinds. A. andersoni and A. macrolepis have the first kind of karyotypes;the formula of groups and complements of chromosomes is 12m + 24sm+12st;among the group of st (i.e.group C) there are two pairs of chromosomes showing secondary constriction on the long arm. A. grahami and A. alburnops taken from Qilu lake have the second kind of karyotypes. there also are two pairs of st showing secondary constriction on the long arm, but the formula of groups and complements of chromosomes is 14m + 20sm+14st. A. alburnops taken from Kunming lake has the third kind of karyotyps, in which though the formula of groups and complements of chromosomes is 12m + 24sm+12st, there is only one pair of st showing secondary constriction. It is necessary to point out that, due to the difficulty in classifying chromosomes and the technical difficulty, we can not yet decide whether the karyotypical differences just mentioned are really original. The karyotypical data suggest that, the causes bringing about the evolutionary divergences of all the six species in Cyprinus and Carassius, the evolutionary divergences of A. andersoni and A. macrolepis, in addition A. grahami and A. alburnops taken from Qilu lake, obviously are not gross chromosomel rearrangements. In regard to whether minute chromosomal rearrangements or gene mutation made contribution to the speciation of these fishes, it is necessary to do further studies in order to give affirmative conclusion. For those species appearing slightly differed karyotypically in Anabarilius, it is possible to attribute the evolutionary divergences between them to slight grosser chromosomal rearrangements. But because, as we have formerly pointed out, their karyotypic differences can not yet be decided to be really original, so it is quite difficult to consider that gross chromosomal restructuring may played important or direct causative role in the speciation of these fishes. The karyotvpical data of the five species in Cyprinus also suggest that, interspecific hybridization between them would give fertile hybrids in all probability.