Nematodes of the order Dorylaimida from Romania. The genus Thonus Thorne, 1974. Part I

Abstract

AbstractTwo known and two new species belonging to the genus Thonus, namely T. angulosus sp. n., T. circulifer, T. cylindricus and T. diversus sp. n., collected from several locations in Romania, are described. Thonus angulosus sp. n. is characterised by body 1.53-1.75 mm long, lip region cap-like (i.e., with its inner perioral area elevated) and 12.5 μm diam., odontostyle 13-16 μm long or slightly longer (ca 1.2 times) than lip region diam., neck 335-385 μm long, pharyngeal expansion ca two-fifths of total neck length, female genital system amphidelphic, uterus 1.1-1.7 body diam. long, pars refringens vaginae with two widely separated triangular pieces, vulva a post-equatorial (V = 54-60) longitudinal slit, glands present near the vagina-vulva junction, female tail rounded to convex conoid (30-35 μm, c= 48-56, c′ = 0.8-1.0), and males unknown. Thonus diversus sp. n. is characterised by body 1.41-1.78 mm long in females and 1.33-1.96 mm in males, lip region offset by depression or weak constriction and 15-17.5 μm diam., odontostyle 15-17 μm long and 5.5-6.8 as long as wide, neck 350-410 μm long, pharyngeal expansion occupying 40-48% of total neck length, a ring-like structure surrounding the pharyngeal base-cardia junction, uterus 1.5-3.6 body diam. long, pars refringens vaginae with two closely arranged pieces, vulva a post-equatorial (V = 54-57) transverse slit, gland cells present near the vagina-vulva junction, tail rounded-conoid to rounded (18-23 μm, c = 68-87, c′ = 0.6-0.8 in females; 18-24 μm, c = 58-89, c′ = 0.6-0.8 in males) with abundant saccate bodies and with inner cuticle layer separated from outer layer, spicules 46.5-54 μm long and 4-7 separated ventromedian supplements. Thonus cylindricus is reported for the first time in Europe and T. circulifer is new record for the Romanian nematode fauna. Descriptions, measurements, illustrations, including SEM pictures of T. diversus sp. n. and distribution data of the species are provided.