Serial block-face scanning electron microscopy of the tail tip of post-metamorphic amphioxus finds novel myomeres with odd shapes and unusually prominent sclerocoels
Serial block-face scanning electron microscopy of the tail tip of post-metamorphic amphioxus finds novel myomeres with odd shapes and unusually prominent sclerocoels
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DOI：
10.1002/jmor.21667
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发表时间：
2024-01-01
影响因子：
1.5
通讯作者：
Holland，Linda Z.
中科院分区：
文献类型：
--
作者：
Holland，Nicholas D.;Holland，Linda Z.
变态后文昌鱼(Branchiostoma Floridae)尾尖的连续块面扫描电子显微镜显示了一些用其他技术从未见过的末端肌群。这些肌群的形态与其更前部的对应肌群的人字形明显不同。组织学上，这些奇形怪状的肌小体从未分化细胞周围的空泡到由发达的肌节、皮肤节和硬化节组成的腹囊。引人注目的是，这些腹囊中的几个形成了乳头状背侧突起，要么完全由硬化节组成，要么由硬化节和肌节的混合体组成。作为一个整体，从后到前，这些形状奇特的后部肌群表明，它们更坚实的腹侧部分可能代表人字形的腹侧肢体，而微妙的突起代表新生的背侧肢体。这一情景与沿着大部分前后轴形成的人字形肌群形成对比。尽管文昌鱼中典型的人字形结构的研究令人惊讶地很少，但它似乎是通过肌节的背腹延伸伴随着V形的假设而实现的；这类似于(至少表面上)在发育中的鱼类发生的情况。文昌鱼奇怪形状的后肌群的另一个不同寻常的特征是它们特别膨胀的硬核。这样做的一个可能的功能可能是，当动物挖洞进入底物时，保护中枢神经系统的后端免受创伤。
Serial block‐face scanning electron microscopy of the tail tip of post‐metamorphic amphioxus (Branchiostoma floridae) revealed some terminal myomeres never been seen before with other techniques. The morphology of these myomeres differed markedly from the chevron shapes of their more anterior counterparts. Histologically, these odd‐shaped myomeres ranged from empty vesicles bordered by undifferentiated cells to ventral sacs composed of well‐developed myotome, dermatome, and sclerotome. Strikingly, several of these ventral sacs gave rise to a nipple‐like dorsal projection composed either entirely of sclerotome or a mixture of sclerotome and myotome. Considered as a whole, from posterior to anterior, these odd‐shaped posterior myomeres suggested that their more substantial ventral part may represent the ventral limb of a chevron, while the delicate projection represents a nascent dorsal limb. This scenario contrasts with formation of chevron‐shaped myomeres along most of the antero‐posterior axis. Although typical chevron formation in amphioxus is surprisingly poorly studied, it seems to be attained by a dorso‐ventral extension of the myomere accompanied by the assumption of a V‐shape; this is similar to what happens (at least superficially) in developing fishes. Another unusual feature of the odd‐shaped posterior myomeres of amphioxus is their especially distended sclerocoels. One possible function for these might be to protect the posterior end of the central nervous system from trauma when the animals burrow into the substratum.