Lovejoy David A, Michalec Ola M, Hogg David W, Wosnick David I
Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
Gen Comp Endocrinol. 2018 Aug 1;264:78-83. doi: 10.1016/j.ygcen.2017.09.013. Epub 2017 Sep 19.
The cartilaginous fishes (Class Chondrichthyes) comprise two morphologically distinct subclasses; Elasmobranchii and Holocephali. Evidence indicates early divergence of these subclasses, suggesting monophyly of their lineage. However, such a phylogenetic understanding is not yet developed within two highly conserved peptide lineages, GnRH and CRF. Various GnRH forms exist across the Chondrichthyes. Although 4-7 immunoreactive forms have been described in Elasmobranchii, only one has been elucidated in Holocephali. In contrast, Chondrichthyan CRF phylogeny follows a pattern more consistent with vertebrate evolution. For example, three forms are expressed within the lamprey, with similar peptides present within the genome of the Callorhinchus milii, a holocephalan. Although these findings are consistent with recent evidence regarding the phylogenetic age of Chondrichthyan lineages, CRF evolution in vertebrates remains elusive. Assuming that the Elasmobranchii and Holocephali are part of a monocladistic clade within the Chondrichthyes, we interpret the findings of GnRH and CRF to be products of their respective lineages.
软骨鱼类（软骨鱼纲）包括两个形态上截然不同的亚纲：板鳃亚纲和全头亚纲。有证据表明这些亚纲在早期就已分化，这表明它们的谱系是单系的。然而，在两个高度保守的肽谱系，即促性腺激素释放激素（GnRH）和促肾上腺皮质激素释放因子（CRF）中，尚未形成这样的系统发育理解。软骨鱼类中存在多种GnRH形式。虽然在板鳃亚纲中已描述了4 - 7种免疫反应性形式，但在全头亚纲中仅阐明了一种。相比之下，软骨鱼类CRF的系统发育遵循一种与脊椎动物进化更一致的模式。例如，七鳃鳗体内表达三种形式，在全头亚纲的澳洲银鲛的基因组中也存在类似的肽。尽管这些发现与关于软骨鱼类谱系系统发育年龄的最新证据一致，但脊椎动物中CRF的进化仍然难以捉摸。假设板鳃亚纲和全头亚纲是软骨鱼类单系分支的一部分，我们将GnRH和CRF的发现解释为它们各自谱系的产物。
