Free-living dorylaimid nematodes from nature reserves in Costa Rica. The genus Oriverutus Siddiqi, 1971 - species with simple uterus.

Three Costa Rican species with a simple uterus, two new and one known, belonging to the genus Oriverutus are described. Descriptions, measurements and illustrations are provided. A detailed study of O. asaccatus, including SEM pictures, is presented and its diagnosis emended; O. sturhani is regarded as its junior synonym. Oriverutus costaricensis sp. n. is distinguished by its body 1.07-1.24 mm long, lip region offset by constriction and 14-15 μm broad, odontostyle 23.5-24 μm long, neck 277-353 μm long, pharyngeal-expansion 125-179 μm long or 45-51% of total neck length, cardia asymmetrical, a dorsal cell mass present at level of pharyngo-intestinal junction, female genital system amphidelphic, V = 45-48, tail conical and slightly bent dorsad at the end (42-43 μm long, c = 25-29, c′ = 1.7-1.8), and males unknown. Oriverutus hemihystera sp. n. is characterised by its body 0.92-1.17 mm long, lip region offset by shallow depression or almost continuous and 10-11.5 μm broad, odontostyle 22-24 μm long, neck 280-330 μm long, pharyngeal expansion 115-138 μm long or 41-43% of total neck length, female genital system amphidelphic but anterior genital branch reduced, V = 43-45, tail conical and slightly bent dorsad at the end (62-65 μm long, c = 15-18, c′ = 3.1-3.4), and males unknown. [ABSTRACT FROM AUTHOR]