Morphological And Molecular Analyses of an Anatomical Novelty: The Pelvic Fin Filaments of the South American Lungfish
Morphological And Molecular Analyses of an Anatomical Novelty: The Pelvic Fin Filaments of the South American Lungfish
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解剖学新奇事物的形态和分子分析：南美肺鱼的腹鳍丝
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发表时间：
2017
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通讯作者：
I. Schneider
中科院分区：
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作者：
S. Lima;Carinne M. Costa;C. Amemiya;I. Schneider
南美雄性肺鱼（Lepidosiren paradoxa）的腹鳍上装饰着一系列独特的细丝，这些细丝在繁殖季节生长并变得高度血管化。这些腹鳍丝（PFF）与其他脊椎动物的外鳃之间的相似性表明这种鳃状结构用于生理气体交换。有人提出，雄性L. paradoxa独特的腹鳍用于将血液中的氧气释放到环境中，以便为其筑巢的幼崽提供空气，或者相反，通过将环境中的氧气吸收到其血液中，作为辅助呼吸器官。在这里，我们采用组织学、扫描电子显微镜 (SEM) 和定量 PCR (qPCR) 来评估 PFF 的形态和分子特征是否与气体交换中的作用兼容。首先，我们仔细检查了其外部形态，发现 PFF 在雨季由短乳头发育而来，但仍被厚厚的非血管化上皮覆盖。组织学检查证实，细丝内的毛细血管通过基底膜和由四到五个细胞层组成的复层上皮与外部分开。此外，扫描电镜分析显示鳍丝上皮和典型的鳃上皮之间存在显着差异。最后，我们的 qPCR 结果表明，与在常规胸鳍表皮中的表达相比，在鳃中常见表达的 5 个基因在 PFF 中表达下调。总的来说，我们的结果并不直接支持 PFF（通常称为“肢鳃”）在氧气释放或吸收中的作用。
The pelvic fins of male South American lungfish, Lepidosiren paradoxa, are adorned with a distinctive array of filaments, which grow and become highly vascularized during the breeding season. The resemblance between these pelvic fin filaments (PFFs) and external gills of other vertebrates suggested that this gill-like structure was used for physiological gas exchange. It has been proposed that the unique pelvic fin of male L. paradoxa is used for release of oxygen from its blood into the environment in order to aerate its nesting brood, or, conversely, as an auxiliary respiratory organ by absorbing oxygen from the environment into its bloodstream. Here, we employed histology, scanning electron microscopy (SEM) and quantitative PCR (qPCR) to assess whether the morphology and molecular profile of PFFs are compatible with a role in gas exchange. First, we closely examined its external morphology and showed that PFFs develop from short papillae during the rainy season, but remain covered by a thick nonvascularized epithelium. Histological examination confirmed that capillaries within the filaments are separated from the exterior by a basement membrane and a stratified epithelium composed of four to five cell layers. In addition, SEM analysis revealed significant differences between the fin filament epithelium and typical gill epithelium. Finally, our qPCR results showed that five genes commonly expressed in gills were downregulated in PFFs relative to their expression in regular pectoral fin epidermis. Collectively, our results do not directly support a role for PFFs, commonly referred to as "limb gills", in oxygen release or uptake.