The identity of protopodal segments and the ramus of maxilla 2 of copepods (copepoda)

Abstract

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.