Shape patterns of genital papillae in pinworms (Enterobiinae, Oxyurida, Nematoda) parasite of primates: A landmark analysis

The Enterobiinae includes 47 species of pinworms parasite of primates. A previous cladistic analysis of this subfamily supported its monophyly and its subdivision into three genera. Based on morphological characters, this cladistic analysis excluded characters describing the shape of the genital papillae of male pinworms, because the corresponding patterns could not be described using discrete characters. In this study, the shape of the genital papillae of the males of 35 within the 47 species is analyzed using geometric morphometric approaches. The aims of this study are to investigate: (i) the relationships between the phylogeny and the shape patterns of the caudal bursa, (ii) the shape differences between and within monophyletic groups, and (iii) the functional implications of the shape patterns observed within the subfamily. Results demonstrate that different patterns of evolution of the caudal bursa, each one characterized by a particular spatial distribution of the phasmids and genital papillae may be recognized, which are consistent with the classification of the Enterobiinae into three groups. On the whole, these patterns may be related to particular mating behavior of the pinworms. When incongruence is observed between shape patterns distribution and species distribution into monophyletic groups, they are found to correspond to homoplasic events. This suggests that convergent selective pressures are involved in the evolution of the shape of the genital papillae. This analysis also confirms that morphometric shape patterns cannot be interpreted unequivocally without the support of a pre-existing phylogenetic framework.