Haupt Christian, Richter Stefan
Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstrasse 1, 07743 Jena, Germany.
Arthropod Struct Dev. 2008 May;37(3):221-33. doi: 10.1016/j.asd.2007.09.005. Epub 2007 Oct 6.
The propodial articulation of thoracopods in Malacostraca is revisited. Two major joints at the base of the limb, a thorax-coxa joint and a coxa-basis joint permit promotion-remotion and abduction-adduction, respectively. In representatives of Decapoda, Anaspidacea and Euphausiacea, the coxa forms proximally a dicondylic articulation with the thorax, permitting promotion-remotion, and distally another dicondylic joint with the basis, permitting abduction-adduction. In Lophogastrida and Mysida, the thorax-coxa hinge line is antero-posteriorly oriented, as is the coxa-basis hinge line. Promotion-remotion in Mysida and Lophogastrida is possible because of the presence of an intrabasal joint which is also present in Euphausiacea and Anaspidacea. In Mysida, Lophogastrida and Euphausiacea, the intrabasal joint is only present anteriorly, just distally of the anterior coxa-basis joint between a small, triangular proximal part of the basis and a larger distal part. In Anaspidacea, the intrabasal joint is also present posteriorly and permits abduction-adduction. Homology with the intrabasal joint of the other taxa seems doubtful. Limb articulation in Anaspidacea shows, nevertheless, correspondences with that in Euphausiacea, Lophogastrida and Mysida: the coxa is posteriorly invaginated and has an open ring-like structure very different from the solid coxa in decapods. Despite the high level of structural correspondence between the intrabasal joint in Euphausiacea and that in Lophogastrida and Mysida, their different functional roles make homology implausible. In Lophogastrida and Mysida the intrabasal joint is thought to replace the promotion-remotion movement of the thorax-coxa articulation, which in these taxa permits abduction-adduction only, probably in connection with the evolution of the marsupium. In Euphausiacea, the intrabasal joint might play a role in feeding mechanisms. Neither the feeding basket nor a marsupium can reasonably be suggested for any common ancestor of Euphausiacea and Mysidacea (or Peracarida).
重新审视了软甲纲中胸足的原节关节。附肢基部的两个主要关节，即胸节 - 基节关节和基节 - 底节关节，分别允许前伸 - 后缩和外展 - 内收。在十足目、阿那斯皮目和磷虾目的代表物种中，基节在近端与胸节形成双髁关节，允许前伸 - 后缩，在远端与底节形成另一个双髁关节，允许外展 - 内收。在涟虫目和糠虾目中，胸节 - 基节铰链线呈前后方向，基节 - 底节铰链线也是如此。糠虾目和涟虫目能够进行前伸 - 后缩是因为存在一个基部内关节，磷虾目和阿那斯皮目中也有这个关节。在糠虾目、涟虫目和磷虾目中，基部内关节仅存在于前部，就在基部前基节 - 底节关节的远端，位于基部一个小的三角形近端部分和一个较大的远端部分之间。在阿那斯皮目中，基部内关节也存在于后部并允许外展 - 内收。与其他类群的基部内关节的同源性似乎存疑。然而，阿那斯皮目的附肢关节与磷虾目、涟虫目和糠虾目的关节有相似之处：基节向后凹陷，具有开放的环状结构，与十足目的实心基节非常不同。尽管磷虾目的基部内关节与涟虫目和糠虾目的基部内关节在结构上有高度的对应性，但它们不同的功能作用使得同源性不太可能。在涟虫目和糠虾目中，基部内关节被认为取代了胸节 - 基节关节的前伸 - 后缩运动，在这些类群中，胸节 - 基节关节仅允许外展 - 内收，这可能与育儿袋的进化有关。在磷虾目中，基部内关节可能在摄食机制中起作用。对于磷虾目和糠虾目（或囊虾总目）的任何共同祖先，都无法合理地推测出摄食篮或育儿袋。
