Curvianchoratus hexacleidus Hanek, Molnár & Fernando, 1974

Justo, Marcia Cristina Nascimento, Silva, Marciara Lopes, Ottoni, Felipe Polivanov, Mendonça, Gabriela Cristina De França, Nigris, Giovanna Oliveira De & Cohen, Simone Chinicz, 2025, New species of Diaphorocleidus and Urocleidoides with a redescription of Curvianchoratus hexacleidus (Monopisthocotyla: Dactylogyridae) parasitizing characiform fishes from the Munim River Basin, northeastern Brazil, Zootaxa 5729 (1), pp. 135-150 : 143-146

Curvianchoratus hexacleidus Hanek, Molnár & Fernando, 1974

( Figure 5 , Figure 6G, H, I )

Type-host: Steindachnerina argentea (Gill, 1858) (as Curimata argentea Gill ) ( Characiformes , Curimatidae ). Type-locality: Arouca River, Trinidad. Other hosts: Cyphocharax nagelii ( Vieira et al. 2013) , Steindachnerina notonota (Miranda Ribeiro, 1937)

[ present study]

Other localities: Peixe River , Anhembi , São Paulo State, southeast Brazil ( Vieira et al. 2013), 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) [ present study] .

Parasitological indices: Total number of hosts examined: 12; number of infested hosts: 5; total number of specimens: 22.

Specimens deposited: Voucher CHIOC 40869 a-b, 40870 a-d, 40871 a-c

New data from 22 specimens collected and mounted in Hoyer’s medium. Body short, broad, 206 (150–250, n = 20) long, 159 (85–280, n = 20) wide. Tegument smooth. Cephalic region with 4 pairs of lateral lobes well defined; 5 pairs of head organs; cephalic glands not visualized. Eyes 4, anterior pair smaller than posterior pair. Pharynx rounded, muscular, 20 (n = 4) in diameter; oesophagus short. Peduncle inconspicuous. Haptor, 84 (50–120, n = 21) wide ( Fig. 5A ). Ventral bar thin and irregular, 25 (17–34, n = 8) long ( Figs. 5D , 6G ). Ventral anchor with moderately developed deep root and well-developed superficial root; shaft slightly curved, with straight distal point, 17 (13–20, n = 42) long, base, 11 (10–14, n = 42) ( Figs. 5F , 6G ). Dorsal anchor complex heavily modified, composed of 2 subunits: dorsal-median and dorsal. Dorsal-median subunit elongated, curved, tip ending in a stout hook 27 (21–39, n = 44) long, with deep roots poorly developed 18 (10–28, n = 44) long, superficial root inconspicuous ( Figs. 5G , 6G ). Dorsal subunit elongated, thin anterior region, expanding in the anterior third and ending in two foot-shaped structures, one of them with a hook on the side; superficial and deep roots absent, 26 (30–45, n = 32) long ( Figs. 5H , 6H ). Hooks similar in shape, with small distal bulbous base, elongated slender shank, protruding thumb, and curved shaft; FH loop approximately 20% of the shank length. Pairs 1, 5: 8 (6–9, n = 36) long; pairs 2, 3, 4, 6, and 7: 10 (8–10, n = 38) long ( Figs. 5E , 6G ). Copulatory complex comprising male copulatory organ ( MCO) and articulated accessory piece. Male copulatory organ tubular, sclerotized, with a base robust and tubular, 25 (15–31, n = 17) in total length; accessory piece with two-unit process, jar-shaped with a long, thin neck, apparently connected to base of MCO length, 27 (15–35, n = 10) long ( Figs. 5B , 6I ). Testis oval, dorsal to the germarium; seminal vesicle formed by a distal enlargement of the vas deferens; prostatic reservoir single. Germarium pretesticular ( Fig. 5A ). Vagina sinistral cup-shaped; vaginal canal wall sclerotized ( Fig. 5C ); vaginal aperture between germarium and MCO; oviduct, oötype, uterus, and eggs not observed. Vitellaria dense extends over the entire body, except in the region of the reproductive organs and haptor ( Fig. 5A ).

Remarks: The morphological characteristics of the specimens of the present study demonstrate similarities with C. hexacleidus , considering the morphology of the copulatory complex. A comparison between the specimens examined in the present study and the original description revealed morphological differences, especially in the morphology of the haptoral sclerites. Hanek et al. (1974) described the dorsal-median subunit as having a well-developed superficial root. In contrast, the present analysis indicates that the more developed root is the deep root. Differences were also observed in the morphology of the dorsal subunit, which was originally described as elongated, lacking a deep root, and ending in a sickle-shaped tip. In the specimens of the present study, however, the dorsal subunit is elongated with a narrow anterior region that expands into the anterior third and terminates in two foot-shaped structures, one of which bears a lateral hook. Additional morphological variations were observed in the hook structure. In the present specimens, the hooks exhibit a small bulbous region at the distal end. Moreover, the smallest pairs of hooks in our study were pairs 1 and 5, whereas in the original description, they were reported as pairs 6 and 7. These differences are believed to result from the limiting conditions under which the species was originally discovered.

Figures

FIGURE 5. Curvianchoratus hexacleidus Hanek, Molnár & Fernando, 1974. (A) Total, ventral (composite); (B) Copulatory complex, ventral; (C) Vagina; (D) Ventral bar; (E) Hook pair; (F) Ventral anchor; (G) Dorsal-median subunit; (H) Dorsal subunit. Scale bars: (A). 100 µm. (B, C). 15 µm. (D). 10 µm, (E). 5 µm. (F, G, H). 15 µm.

FIGURE 6. Photomicrographs Diaphorocleidus guajajara sp. nov.: (A) Haptoral structures (dorsal); (B) Copulatory complex (dorsal); Diaphorocleidus kritskyi sp. nov.: (C) Haptoral structures (dorsal); (D) Copulatory complex (dorsal); Urocleidoides mizellei sp. nov.: (E) Haptoral structures (ventral); (F) Copulatory complex (ventral); Curvianchoratus hexacleidus: (G) Haptoral structures (ventral); (H) Dorsal subunit; (I) Copulatory complex (ventral). Scale bars: (A, B, D, G, I). 20 µm. (C). 30 µm. (E). 25 µm, (F). 10 µm. (H) 15 µm.