Rhinoxenus nyttus Kritsky, Boeger & Thatcher, 1988

Domingues, Marcus V. & Boeger, Walter A., 2005, Neotropical Monogenoidea. 47. Phylogeny and coevolution of species of Rhinoxenus (Platyhelminthes, Monogenoidea, Dactylogyridae) and their Characiformes hosts (Teleostei, Ostariophysi) with description of four new species, Zoosystema 27 (3), pp. 441-467 : 451-452

Rhinoxenus nyttus Kritsky, Boeger & Thatcher, 1988

( Fig. 1 C-E)

Rhinoxenus nyttus Kritsky, Boeger & Thatcher, 1988: 92 , 93, figs 18-24.

TYPE HOST AND LOCALITY. — Nasal cavities of Schizodon fasciatus (Anostomidae) , Ilha Marchantaria, Rio Solimões, near Manaus, Amazonas, Brazil, 25.XI.1983.

MATERIAL EXAMINED. — Brazil. Usina Hidrelétrica de ITAIPU, Foz do Iguassu, Paraná, from Schizodon sp. (Anostomidae) , 15.X.1996, voucher specimens ( CHIOC 36292 a-c; INPA 433; MNHN 167 HG-T 1 208-208 bis; USNPC 95235). — Rio Capucapu, Cachoeira das Garças, near Manaus, Amazonas, from Leporinus agassizii (Anostomidae) , 30.X.1989, voucher specimens ( INPA 434; USNPC 95236).

COMPARATIVE MEASUREMENTS. — See Table 5.

REMARKS

Rhinoxenus nyttus is apparently restricted to members of Anostomidae . The specimens analyzed here are similar to those described by Kritsky et al. (1988), except by the possession of a more extensive sclerotized cap on the root ventral anchor ( Fig. 1E ). The original description does not mention the presence of the brims of the MCO, observed in all studied specimens ( Fig. 1C, D ). Parasites of each host species present little variation in size in almost all the analyzed structures.

Rhinoxenus nyttus is characterized by possessing a ventral bar with lateral projections that serve as articulation to the ventral anchor; long chaliceshape vaginal vestibule; and ventral anchor with wavy point, representing 1/3 of the total length of the anchor.

Figures

FIG. 1. — Sclerotized structures of selected Rhinoxenus species; A, R. piranhus Kritsky, Boeger & Thatcher, 1988, male copulatory organ (MCO); B, R. piranhus, vagina; C, R. nyttus Kritsky, Boeger & Thatcher, 1988, MCO; D, R. nyttus, detail of the base of the MCO (distal portion of MCO not shown); E, R. nyttus, ventral anchor; F, R. arietinus Kritsky, Boeger & Thatcher, 1988, MCO. Arrow indicates the circular tandem sclerotized brims. Scale bars: A-D, F, 20 μm; E, 50 μm.