Bilateral, perivulval cuticular pores in trichostrongylid nematodes.

A new hypodermal gland was discovered in female nematodes of the family Trichostrongylidae. Because the new structure appears to be associated with the vulva, it was named the perivulval pore. It is similar, based on light and scanning electron microscopy, to phasmids that are located laterally on the tails of nematodes of the class Secernentea. Like phasmids, perivulval pores are paired and bilateral, with cuticular ducts to the surface in the areas of the lateral chords. They are located slightly posterior to the vulva in Haemonchus contortus, Haemonchus placei, Haemonchus similis, Mecistocirrus digitatus, Mazamastrongylus pursglovei, Ostertagia ostertagi, and Cooperia oncophora, but in Trichostrongylus colubriformis they are slightly anterior to the vulva. Because of the location near the vulva and the similarity in structure to phasmids, which are, at least in part, secretory, the perivulval pores should be considered as a possible source of a female attractant for males.