Phylogenetic study of the Antarctic fish family Channichthyidae.

本文主要从生态学特征和骨学特征两方面探讨了水鱼科的系统发育关系。本文分析了包括海峡鱼科在内的南极鱼的颚部结构与胃内容物之间的关系。研究结果表明，南极磷虾的巨大生物量可能使渠道鱼类鱼类保持了一些幼体特征，如无血红蛋白状态。根据这些骨学特征的分支分析，该科11属可重新划分为6个类群，即：(1)Champsocephalus类群，(2)Pagetopsis类群，(3)Dacodraco类群，(4)Channichthys类群，(5)Chaenocephalus类群和(6)Chionodraco类群。在上述6个组中，至少有2个组（Pagetopsis组和Cryodraco组）存在童胚性特征。Pagetopsis类群的特征是具有扇形的大腹鳍和第二眶下骨，具有腹侧扩张。在这三个属中，Pagetopsis在体色、第二眶下骨和第三鳃下骨的形状以及体型上都表现出了前发生的特征状态。冷冻龙属在冷冻龙组中有长身体，低垂直鳍和延伸的杆状腹鳍。它的特征通常出现在槽鱼幼虫中。因此，这些条件被认为是晚期的。白血鱼科，水鱼科，被认为是一个单系的群体。各种渠道鱼的生境环境条件相当相似，有些种类是同地生活的。渠道鱼的生态和行为也彼此相似。基于以上的间接证据，我们认为水鱼科物种形成的一个重要过程是幼体发育。此外，在这个家族的所有成员中发现的单一特征，即缺乏血红蛋白，也可能是异时性的结果。

Phylogenetic relationships of the family Channichthyidae had been discussed mainly by their ecological features and osteological characters. Relationships between the jaw structures and stomach contents of the notothenioid fishes including the Channichthyidae were analyzed. The results showed the possibility that the huge biomass of the Antarctic krill enables channichthyid fishes to maintain some paedomorphic characters such as haemoglobinless condition. Based on the cladistic analyzes of these osteological features, 11 genera of this family can be rearranged into 6 groups as, (1) Champsocephalus group, (2) Pagetopsis group, (3) Dacodraco group, (4) Channichthys group, (5) Chaenocephalus group and (6) Chionodraco group. At least in 2 of the 6 groups mentioned above, the Pagetopsis group and Cryodraco group, paedomorphic features were found. The Pagetopsis group is characterized by having fan-shaped large pelvic fins and the second infraorbital bones with ventral expansion. Among the three genera, Pagetopsis shows progenetic character states in body color, shape of the second infraorbital bones and of the third hypobranchial bones, and also in its body size. The genus Cryodraco in the Cryodraco group has long body with low vertical fins and extended rod-like pelvic fins. Its features are usually found in channichthyid larvae. Therefore, these conditions are thought to be neotenic. The white blooded fish family, the Channichthyidae, are convinced to be a monophyletic group. Environmental conditions of habitat of each channichthyid species are considerably similar and some species lives sympatrically. Ecology and behavior of channichthyid species are also similar to each other. Based on above mentioned circumstantial evidences, one of the important process of speciation of the Channichthyidae is thought to be paedomorphosis. Furthermore, the singular character, the lack of hemoglobin, found in all members of this family may also be a result of heterochrony.