An evolutionary insight into the hatching strategies of pipefish and seahorse embryos
An evolutionary insight into the hatching strategies of pipefish and seahorse embryos
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对海龙和海马胚胎孵化策略的进化洞察
DOI：
10.1002/jez.b.22670
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Kaneko T
中科院分区：
文献类型：
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作者：
Kawaguchi M;Nakano Y;Kawahara-Miki R;Inokuchi M;Yorifuji M;Okubo R;Nagasawa T;Hiroi J;Kono T;Kaneko T
海龙形鱼携带它们的卵在一个育雏结构中发现在男性。不同物种的卵结构不同：海马在封闭的卵袋中携带卵，mesmate海龙在半卵袋中携带卵，短吻鳄海龙在腹部的卵室中携带卵。这些保护卵的策略是在海龙形动物进化过程中建立起来的。比较了三种保护地胚胎的孵化方式。电子显微镜观察发现，鳄鱼海龙和messmate海龙卵信封厚比海马，这表明海马产生较弱的信封。此外，分子遗传学分析显示，这两种海龙具有卵被消化酶，高绒膜溶解酶（HCE）和低绒膜溶解酶（LCE），就像许多真硬骨鱼一样。然而，在海马中，仅检测到HCE基因表达。当通过高通量DNA测序搜索整个海马基因组时，我们没有发现功能性LCE基因，只发现了LCE基因外显子的痕迹，证实海马LCE基因在进化过程中被假基因化。最后，我们估计的大小和数量的孵化腺细胞表达孵化酶基因的整体安装原位杂交。海马细胞是三个物种中最小的，但它们的数量最多。这些结果表明，通过父系生育使卵与外界环境隔离，可能导致卵被膜变薄，从而使孵化酶基因发生假基因化。J. Exp. Zool.（Mol. Dev. Evol.）9999 B：XX-XX，2016年。© 2016 Wiley Periodicals，Inc.
Syngnathiform fishes carry their eggs in a brood structure found in males. The brood structure differs from species to species: seahorses carry eggs within enclosed brood pouch, messmate pipefish carry eggs in the semi‐brood pouch, and alligator pipefish carry eggs in the egg compartment on abdomen. These egg protection strategies were established during syngnathiform evolution. In the present study, we compared the hatching mode of protected embryos of three species. Electron microscopic observations revealed that alligator pipefish and messmate pipefish egg envelopes were thicker than those of seahorses, suggesting that the seahorse produces a weaker envelope. Furthermore, molecular genetic analysis revealed that these two pipefishes possessed the egg envelope‐digesting enzymes, high choriolytic enzyme (HCE), and low choriolytic enzyme (LCE), as do many euteleosts. In seahorses, however, only HCE gene expression was detected. When searching the entire seahorse genome by high‐throughput DNA sequencing, we did not find a functional LCE gene and only a trace of the LCE gene exon was found, confirming that the seahorse LCE gene was pseudogenized during evolution. Finally, we estimated the size and number of hatching gland cells expressing hatching enzyme genes by whole‐mount in situ hybridization. The seahorse cells were the smallest of the three species, while they had the greatest number. These results suggest that the isolation of eggs from the external environment by paternal bearing might bring the egg envelope thin, and then, the hatching enzyme genes became pseudogenized. J. Exp. Zool. (Mol. Dev. Evol.) 9999B:XX–XX, 2016. © 2016 Wiley Periodicals, Inc.