The Identity of Protopodal Segments and the Ramus of Maxilla 2 of Copepods (Copepoda)

The protopod of the maxilla 2 of copepods is composed of a proximal syncoxa with a praecoxal endite proximally and a coxal endite distally. The basis bears two endites, and the ramus is an endopod bearing up to five segments. This interpretation is based on protopodal patterning from the point where the limb articulates with the body, and the assumption that this patterning should result in a derivable enditic configuration on the protopod of the serially homologous limbs maxilla 1 anteriorly and maxilliped posteriorly. Processes that affect the morphological diversity of maxilla 2 among copepods include: truncation of protopodal segmentation, suppression of enditic extension, truncation of endopodal segmentation, and segment elongation. Hypotheses about transformations of the basis suggest the following synapomorphies: neither endite of the basis is attenuate on maxilla 2 of Poecilostomatoida; the basis of maxilla 2 of Siphonostomatoida is elongate ventrally. Le protopodite de la seconde maxille des copepodes est compose d'un syncoxopodite proximal, avec un endite precoxal proximal et un endite coxal distal. Le basipodite porte deux endites, et la rame est un endopodite portant jusqu'a cinq segments. Cette interpretation est fondee sur le patron protopodal a partir du point ou l'appendice s'articule avec le corps, et la supposition que ce modele aboutirait a une configuration enditique derivable sur le protopodite des appendices homologues: premiere maxille anterieurement et maxillipede posterieurement. Les processus qui affectent la diversite morphologique de la deuxieme maxille chez les copepodes incluent: la reduction de la segmentation protopodale, la suppression de l'extension enditique, la reduction de la segmentation endopodale et l'allongement des segments. Les hypotheses concernant les transformations du basis suggerent les synapomorphies suivantes: aucun endite du basis n'est attenue sur la deuxieme maxille des Poecilostomatoida; le basis de la deuxieme maxille des Siphonostomatoida est allonge ventralement.