Urocleidoides mizellei, Justo & Silva & Ottoni & Mendonça & Nigris & Cohen, 2025

Urocleidoides mizellei sp. nov.

urn:lsid:zoobank.org:act:

( Figure 4 View FIGURE 4 , Figure 6E, F View FIGURE 6 )

Type-host: Steindachnerina notonota (Miranda Ribeiro, 1937) ( Characiformes , Curimatidae )

Type-locality: Estrela Stream , balneary of Anapurus , urban zone of the municipality of Anapurus , Munim River Basin , Maranhão State, northeastern Brazil ( 03°40'15.6"S 043°7'9.7" W) GoogleMaps .

Parasitological indices: Total number of hosts examined: 12; number of infested hosts: 5; total number of specimens: 11.

Etymology: This species was named in tribute to Dr. J. D. Mizelle ( Washington State University, Roche Harbor, Washington), acknowledging his extensive work on monopisthocotylean parasites, especially within the Neotropical region.

Specimens deposited: Holotype CHIOC 40872 View Materials a ; Paratypes CHIOC 40872 View Materials b-c, 40873, 40874

Description: (Based on 11 specimens mounted in Hoyer’s medium). Body fusiform, 220 (125–275, n = 10) long by 125 (90–265, n = 11) wide. Three pairs of cephalic glands. Eyespots absent. Pharynx ovate; oesophagus short; two intestinal caeca, confluent posteriorly to gonads, without diverticula. Gonads overlapping, intercaecal; testis dorsal to germarium; seminal vesicle a distal dilation of vas deferens; single prostatic reservoir present. Germarium elongated. Vaginal pore sinistral ( Fig. 4A View FIGURE 4 ); vagina consisting of a sclerotized tube with cone-shaped opening; seminal receptacle not visualized ( Fig. 4A View FIGURE 4 ). Vaginal sclerite robust and very large, with a longitudinal groove in the middle, depressed thumb, 25 (22–28, n = 7) long ( Fig. 4C View FIGURE 4 ). Vitellaria present, heavily distributed throughout the body, except in reproductive organs. Mehlis’ gland and oötype not observed. Copulatory complex comprising male copulatory organ (MCO) and accessory piece. Male copulatory organ as a coiled sclerotized tube, counterclockwise, with 2½ rings, 56 (42–62, n = 9) in total length; first ring 10 (8–12, n = 9) in diameter, base tubular. Accessory piece rod-shaped, enlarging and dividing into two delicate bulbous structures at distal portion, not articulated at the base of the MCO, 9 (8–10, n = 9) long ( Figs. 4B View FIGURE 4 , 6F View FIGURE 6 ). Peduncle short. Haptor subhexagonal 75 (50–95; n = 10) wide ( Figs. 4A View FIGURE 4 , 6E View FIGURE 6 ). Dorsal and ventral anchor with a rectangular-shaped superficial root and deep root distally round, straight shaft in the ventral anchor, evenly curved shaft in the dorsal anchor and acute point, not exceeding base width. Ventral anchor 20 (18–23, n = 11) long; base 13 (11–15, n = 11) wide ( Figs. 4D View FIGURE 4 , 6E View FIGURE 6 ); dorsal anchor 19 (17–20, n = 11) long, base 12 (11–13, n = 11) wide ( Figs. 4E View FIGURE 4 , 6E View FIGURE 6 ). Ventral bar straight and robust, with expanded ends, 25 (22–30, n = 10) long ( Figs. 4F View FIGURE 4 , 6E View FIGURE 6 ). Dorsal bar Y-shaped, 36 (20–40, n = 11) long, with a long posteromedian projection ( Figs. 4G View FIGURE 4 , 6E View FIGURE 6 ). Hooks dissimilar in shape and size. Pairs 1 and 5 smaller than others, protruded thumb, curved point, shank straight 9 (8–9, n = 20) long ( Figs. 4H View FIGURE 4 , 6E View FIGURE 6 ). Pairs 2, 3, 4, 6, and 7 divided into two subunits, protruded thumb, curved point, shank straight with proximal dilation, comprising ⅔ of shank length, 15 (14–17, n = 20) long; FH loop 0.5 of shank length ( Figs. 4I View FIGURE 4 , 6E View FIGURE 6 ).

Remarks: The new species is assigned to Urocleidoides by the presence of the vaginal sclerite, and hook pairs 1 and 5 of reduced size. Of the 63 valid species of the genus, only 14 present a long posteromedian projection on the dorsal bar ( Table 1), a morphological feature also observed in the new species. However, the new species differs from all these species mainly in the morphology of the copulatory complex, considering the accessory piece dividing into two delicate bulbous structures at distal portion. Considering the morphology of the anchors and the number of rings of the male copulatory organ (MCO), the new species shows similarities with Urocleidoides saghirus Yamada, Osaki-Pereira & Silva, 2024 , differing from the latter by presenting a longer and thinner ventral bar, in contrast to the ventral bar of U. saghirus , which is recurved and robust. Furthermore, the vaginal sclerite in the new species is considerably larger (25, 22–28) than that observed in U. saghirus (10, 9–14).

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