Table_2_A Morphological and Histological Investigation of Imperfect Lungfish Fin Regeneration.xlsx

Regeneration, the replacement of body parts in a living animal, has excited scientists for centuries and our knowledge of vertebrate appendage regeneration has increased significantly over the past decades. While the ability of amniotes to regenerate body parts is very limited, members of other vertebrate clades have been shown to have rather high regenerative capacities. Among tetrapods (four-limbed vertebrates), only salamanders show unparalleled capacities of epimorphic tissue regeneration including replacement of organ and body parts in an apparently perfect fashion. The closest living relatives of Tetrapoda, the lungfish, show regenerative abilities that are comparable to those of salamanders and recent studies suggest that these high regenerative capacities may indeed be ancestral for bony fish (osteichthyans) including tetrapods. While great progress has been made in recent years in understanding the cellular and molecular mechanisms deployed during appendage regeneration, comparatively few studies have investigated gross morphological and histological features of regenerated fins and limbs. Likewise, rather little is known about how fin regeneration compares morphologically to salamander limb regeneration. In this study, we investigated the morphology and histology of regenerated fins in all three modern lungfish families. Data from histological serial sections, 3D reconstructions, and x-ray microtomography scans were analyzed to assess morphological features, quality and pathologies in lungfish fin regenerates. We found several anomalies resulting from imperfect regeneration in regenerated fins in all investigated lungfish species, including fusion of skeletal elements, additional or fewer elements, and distal branching. The similarity of patterns in regeneration abnormalities compared to salamander limb regeneration lends further support to the hypothesis that high regenerative capacities are plesiomorphic for sarcopterygians.

再生（Regeneration），即活体动物躯体部分的替代过程，数个世纪以来一直令科学家心驰神往；近几十年来，我们对脊椎动物附肢再生（vertebrate appendage regeneration）的认知已取得显著进展。尽管羊膜动物（amniotes）的躯体再生能力极为有限，但其他脊椎动物类群的成员却展现出颇高的再生潜能。在四足类（tetrapods，四足脊椎动物）中，唯有蝾螈具备无与伦比的后生组织再生（epimorphic tissue regeneration）能力，可近乎完美地替代器官与躯体部分。四足类现存最近的亲缘类群——肺鱼，其再生能力与蝾螈不相上下；近期研究表明，这种高再生能力或许确实是包括四足类在内的硬骨鱼类（osteichthyans）的祖先性状。尽管近年来在解析附肢再生过程中调动的细胞与分子机制方面已取得长足进步，但针对再生鳍与肢体的大体形态学及组织学特征的研究却相对匮乏。同样，关于鳍再生与蝾螈肢体再生在形态学上的对比研究也少之又少。本研究对现存三个现代肺鱼科物种的再生鳍的形态学与组织学特征展开了探究。我们通过分析组织学连续切片、三维重建（3D reconstructions）以及X射线显微计算机断层扫描（x-ray microtomography）的数据，评估肺鱼再生鳍的形态特征、质量及病理表现。研究发现，所有受试肺鱼物种的再生鳍均存在因再生不完全导致的多种异常，包括骨骼元素融合、元素数目增减以及远端分支异常。再生异常模式与蝾螈肢体再生的相似性，进一步为"高再生能力是肉鳍鱼类（sarcopterygians）的祖征"这一假说提供了支持。