Urocleidoides tocantinensis sp. nov. Figs 22–30, 35, 36 Type host. Psectrogaster amazonica Eigenmann & Eigenmann (Curimatidae). Type locality. Tocantins River (5 ° 27 ' 50 ' S; 47 ° 33 ' 48 ' W), close to the municipality of Embiral, state of Maranhão. Other hosts and localities. Psectrogaster amazonica: Tocantins River (5 ° 32 ' 08.6 ' S; 47 ° 29 ' 41.1 ' W), close to the urban perimeter of Imperatriz, state of Maranhão. Mylesinus pauscisquamatus (Serrasalmidae): Arraias River (12 ° 37 ' 52.3 ' S; 47 ° 08 ' 11.2 ' W), close to the municipality of Babaçulândia, state of Tocantins; Farinha River (6 ° 50 ' 30.5 ' S; 47 ° 30 ' 05.8 ' W), close to the municipality of municipality of Estreito, state of Maranhão, Brazil. Infestation parameters. Psectrogaster amazonica: total number of hosts: 97; prevalence: 9.3 %; total number of parasites: 11; mean intensity: 1.22 ± 0.44; range of infection: 1–2; Mylesinus paucisquamatus: total number of hosts: 7; number of infected hosts: 2; total number of parasites: 12. Deposited material. Psectrogaster amazonica: Holotype CHIOC 39575: paratypes 39577, 39578; INPA 838; Mylesinus paucisquamatus: CHIOC 39576 a-b, INPA 839. Description. Based on 15 specimens: 2 mounted in Gomori's trichrome and 13 mounted in Hoyers' medium. Body fusiform, robust, 200–317 (278; n = 8) long by 68–103 (89; n = 9). Cephalic lobes poorly developed; two pairs of eyespots, posterior pair larger than anterior; accessory chromatic granules dispersed in the cephalic region. Pharynx spherical; esophagus short; two intestinal caeca, posteriorly confluent to gonads, lacking diverticula. Haptor sub-hexagonal, 62–86 (68; n = 12) wide. Ventral anchor with developed superficial root and inconspicuous deep root, evenly curved shaft and point, 21–44 (33; n = 22) long and base 13–20 (17; n = 22) (Fig. 27). Dorsal anchor, smaller than ventral, with well-defined and long superficial root, shorter deep root, evenly curved shaft and robust point, passing from the level of tip of superficial root, 15–29 (22; n = 18) long and base 10–19 (13; n = 16) (Fig. 28). Ventral bar straight, with extremities directed toward posterior extremity, with a median projection arising from the middle portion of the bar, 23–34 (30; n = 9) long (Fig. 24). Dorsal bar straight, 25–41 (30; n = 6) long (Fig. 26). Marginal hooks present, dissimilar in shape: pairs 1 and 5 with straight shank, erected thumb and curved point; filamentous hook (FH) loop about 1 / 3 of shank length (Fig. 30), pairs 2–4, 6, 7 with dilated shank composed of two subunits, erected thumb and point, FH loop about 1 / 3 shank length (Fig. 29). Pair 1, 9–16 (13; n = 15); pair 2, 15–27 (19; n = 19); pair 3, 14–22 (18; n = 18); pair 4, 15–27 (17; n = 17); pair 5, 10–15 (13; n = 14), pair 6, 15–25 (20; n = 6); pair 7, 13–25 (20; n = 14). Copulatory complex composed of male copulatory organ (MCO), which is a straight tube, 23–40 (33; n = 14) long and by bifurcated accessory piece, serving as guide to MCO; accessory piece 41–70 (53; n = 15) long (Figs 22, 35). Gonads overlapping. Vaginal pore sinistral, vaginal vestibule, with a membranous cap at the aperture, tubular, expanded, 28–41 (35; n = 15), giving rise to vaginal canal (Figs 23, 36). Vaginal sclerite composed of a grooved rod, distal hook and a long subterminal projection, 22–35 (27; n = 11) (Fig. 25). Eggs, Mehlis' glands and ootype not observed. Vitelline follicles distributed throughout the body, except in the region of reproductive organs. Etymology. The specific name refers to the locality, Tocantins River. Remarks. Urocleidoides tocantinensis sp. nov. resembles Urocleidoides falxus Zago, Yamada, Yamada, Franceschini, Bongiovani & Silva, 2020 by the absence of coils on the MCO and Urocleidoides surianoae Rosin & Timi, 2016 in the shape of accessory piece, but differs in the morphology of the MCO (MCO reverse J-shaped, with expanded proximal end in U. surianoae and a straight tube in the new species). The new species differs from all other species of the genus by the morphology of the vagina, which present a vaginal vestibule with a membranous cap.

Published as part of de Freitas, Álvaro J. B., Bezerra, Carine A. M., Meneses, Yuri C., Justo, Marcia Cristina N., Viana, Diego C. & Cohen, Simone C., 2021, Three new species of Urocleidoides (Monogenoidea: Dactylogyridae) parasitizing characiforms (Actinopterygii: Characiformes) in Tocantins River, states of Tocantins and Maranhão, and new record for U. triangulus in Guandu River, state of Rio de Janeiro, Brazil, pp. 1-11 in Zoologia 38 on pages 1-11, DOI: 10.3897/zoologia.38.e65001