Table_1_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.

活体动物的体部再生（即缺失体部的替换修复）数百年来一直令科学家们着迷，近数十年来，我们对脊椎动物附肢再生（vertebrate appendage regeneration）的认知也得到了显著提升。尽管羊膜动物（Amniotes）的体部再生能力极为有限，但其他脊椎动物类群的成员则展现出相当强的再生能力。在四足类（Tetrapoda，四足脊椎动物）中，仅蝾螈具备无与伦比的变形性组织再生（epimorphic tissue regeneration）能力，可近乎完美地替换受损器官与体部结构。四足类现存最近的亲缘类群——肺鱼（lungfish），展现出与蝾螈相当的再生能力；近期研究表明，这类强再生能力或许是包括四足类在内的硬骨鱼纲（Osteichthyes）的祖征。尽管近年在解析附肢再生过程中的细胞与分子机制方面已取得长足进展，但针对再生鳍与肢体的大体形态及组织学特征的研究仍相对匮乏。同样，学界对鳍再生与蝾螈肢体再生的形态学对比情况的认知也十分有限。本研究针对现生肺鱼的三个科的再生鳍开展形态学与组织学分析：研究人员通过分析组织学连续切片、三维重建数据以及X射线显微断层扫描（X-ray microtomography）结果，对肺鱼再生鳍的形态特征、修复质量与病理状态进行评估。我们在所有受试肺鱼物种的再生鳍中均发现了再生不完全导致的多种异常，包括骨骼元素融合、元素数量异常（过多或过少）以及远端分支。再生异常模式与蝾螈肢体再生的相似性，进一步支持了"强再生能力是肉鳍鱼亚纲（Sarcopterygians）的祖征"这一假说。