A scanning electron microscope study of the nematode Spirura dentata (Spiruroidea) with notes on the morphometric variations in a Spanish population of this species.

This work provides a detailed morphological description by optic and scanning electron microscopy of the nematode Spirura dentara (Mŏnnig, 1938), a parasite of Herpestes ichneumon in southern and central Spain, together with an analyses of the morphometric variations within this population. Our findings in adult specimens include some important characters not recorded in previous descriptions, and contradict these in a few details: a) the four denticles arising from the inner wall of the oral opening are double, not simple as reported in the original description, b) four simple denticles are present, each located between the corresponding double denticles and the central protuberance of the pseudolabium, c) lateral crests are present running along the first third of the body in the adult, starting a short distance behind the deirids, and d) the pair of small submedian post-cloacal papillae mentioned in the original description has not been observed. The fourth-stage larva is described for the first time. The relative growth rate (i.e., growth rate with respect to body length) of the reproductive zone was higher in females. In adult males, the growth of the left (longer) spicule was positive, whereas that of the right (shorter) spicule was negative.