Barutia Iulia, Sombke Andy
Department of Evolutionary Biology, Integrative Zoology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
Institute for Zoology and Evolutionary Research, Animal Physiology, Friedrich-Schiller-University Jena, Erbertstrasse 1, 07743, Jena, Germany.
Front Zool. 2024 Sep 19;21(1):23. doi: 10.1186/s12983-024-00544-0.
Regenerating legs is advantageous for arthropods as their appendages exhibit crucial functional specializations. Many arthropods possess a 'preferred breakage point', where the appendage is most likely to break and where regeneration likely to occur, however, different taxa exhibit different levels of regenerative potential. Centipede appendage regeneration is categorized as 'progressive' or 'explosive'. In the later, the appendage is fully regenerated after one molt. This term was used for house centipedes that frequently lose their long legs. We chose Scutigera coleoptrata as a model to comprehensively investigate the process of leg appendotomy and regeneration as well as compare it with leg development in anamorphic instars.
The trochanter exhibits a preferred breakage point. Internally, it houses a three-layered diaphragm that effectively seals the lumen. In case of leg loss, the wound is quickly sealed. The epidermis detaches from the cuticle and muscles of the coxa get compacted, giving sufficient space for the regenerating leg. A blastema forms and the leg then grows in a coiled manner. The regenerating leg is innervated and syncytial muscles form. If the leg is lost in an early intermolt phase, progression of regeneration is slower than when a specimen is closer to the next molt. Instars of house centipedes can simultaneously develop and regenerate legs. The legs develop laterally on the posterior segments under the cuticle. As opposed to regeneration, the progression of leg development always follows the same temporal pattern throughout the entire intermolt phase.
Several factors are of major significance in house centipede leg regeneration. First, the ease with which they lose legs: the diaphragm represents an efficient tool for appendotomy. Moreover, the functional extension of the coxa provides space for a leg to be regenerated in. Lastly, the genetic predisposition allows them to regenerate legs within one molting cycle. This "package" is unique among land arthropods, and to this degree rare in marine taxa. Furthermore, observing leg regeneration and anamorphic leg development in parallel suggest that regeneration is most likely an epiphenomenon of development, and the differences are a requirement for the novel context in which re-development occurs.
对于节肢动物来说，再生腿部是有利的，因为它们的附肢具有关键的功能特化。许多节肢动物都有一个“首选断裂点”，附肢最有可能在此处断裂，且此处也最有可能发生再生，然而，不同的分类群具有不同程度的再生潜力。蜈蚣附肢的再生可分为“渐进式”或“爆发式”。在爆发式再生中，附肢在一次蜕皮后完全再生。这个术语曾用于经常失去长腿的家蜈蚣。我们选择蚰蜒作为模型，全面研究腿部切断和再生的过程，并将其与不完全变态幼虫阶段的腿部发育进行比较。
转节呈现出一个首选断裂点。在其内部，有一个三层隔膜有效地封闭了管腔。在腿部缺失的情况下，伤口会迅速封闭。表皮与角质层分离，基节的肌肉收缩，为再生的腿部提供了足够的空间。一个芽基形成，然后腿部以盘绕的方式生长。再生的腿部接受神经支配，合胞体肌肉形成。如果腿部在蜕皮前期早期缺失，再生进程比标本接近下一次蜕皮时要慢。家蜈蚣的幼虫可以同时发育和再生腿部。腿部在角质层下的后段横向发育。与再生不同，腿部发育的进程在整个蜕皮间期总是遵循相同的时间模式。
几个因素对家蜈蚣腿部再生至关重要。首先，它们容易失去腿部：隔膜是切断附肢的有效工具。此外，基节的功能扩展为再生的腿部提供了空间。最后，遗传倾向使它们能够在一个蜕皮周期内再生腿部。这种“组合”在陆地节肢动物中是独一无二的，在海洋分类群中也很少见。此外，并行观察腿部再生和不完全变态腿部发育表明，再生很可能是发育的一种附带现象，而差异是重新发育发生的新环境所必需的。
