The Missing Fellow: First Description of the Trypanoxyuris pigrae Male (Nematoda: Oxyuridae), a Parasite of the Black Howler Monkey (Alouatta pigra) in Mexico.

The first morphological description of the male of Trypanoxyuris pigrae Solórzano-García, Nadler, and Pérez-Ponce de León, 2016 , is presented in this study. Morphological data are supported by molecular data. Specimens of T. pigrae were recovered after the necropsy of a roadkill black howler monkey (Alouatta pigra) in southeastern Mexico. Males of T. pigrae are characterized by having 3 notched lips and a long esophagus with a posterior bulb; they also show a single crested lateral alae, a single spicule, and 4 caudal papillae. Morphological features coincide with those of the previously described T. pigrae females, and molecular profiles confirmed species identification. Males of T. pigrae are very similar to those of Trypanoxyuris minutus, another species of pinworm that also parasitizes the black howler monkey, A. pigra; however, the shape of the lips represents a very reliable diagnostic feature. Because of this, detailed en face observations are recommended to discriminate between these pinworm species.