Urocleidoides paratriangulus, de Freitas & Bezerra & Meneses & Justo & Viana & Cohen, 2021

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, Zoologia 38, pp. 1-11 : 1-11

Urocleidoides paratriangulus sp. nov.

Figs 12–21 , 33 , 34

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 Maranhao. Cyphocharax gouldingi ( Curimatidae ): Tocantins River (6 ° 32 ' 24.53 ' S; 47 ° 27 ' 0.75 ' W), close to the municipalities of Aguiarnópolis and Estreito; at the mouth of the Itaueiras River (6 ° 29 ' 58.73 ' S; 47 ° 25 ' 27.48 ' W), in the municipality of Estreito, state of Maranhão. Caenotropus labyrinthicus ( Chilodontidae ): Arraias River (12 ° 37 ' 52.3 ' S; 47 ° 08 ' 11.2 ' W), close to the municipality of Babaçulândia, state of Tocantins; Tocantins River (6 ° 32 ' 24.53 ' S, 47 ° 27 ' 0.75 ' W), close to the municipalities of Aguiarnópolis and Estreito; at the mouth of the Itaueiras River (6 ° 29 ' 58.73 ' S; 47 ° 25 ' 27.48 ' W), municipality of Estreito, state of Maranhão; João Aires River (7 ° 51 ' 10.6 ' S; 47 ° 55 ' 57.3 ' W), close to the municipality of Palmeirantes, state of Tocantins; Farinha River (6 ° 50 ' 30.5 ' S; 47 ° 30 ' 05.8 ' W), close to the municipality of Estreito, state of Maranhão, Brazil. Mylesinus pauscisquamatus Jégu & Santos ( 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 Estreito, state of Maranhão, Brazil.

Infestation parameters.

Psectrogaster amazonica : total number of hosts: 97; prevalence: 11.3 %; total number of parasites: 37, mean intensity: 3.1 ± 2.5, range of infection: 1–9; Caenotropus labyrinthicus : total number of hosts: 8; number of infected hosts: 3; total number of parasites: 4; Cyphocharax gouldingi : total number of hosts: 8; number of infected hosts: 1; total number of parasites: 2; Mylesinus paucisquamatus : total number of hosts: 7; number of infected hosts: 1; total number of parasites: 10.

Deposited material.

Holotype: Psectrogaster amazonica : CHIOC: 39567 a ; paratypes CHIOC 39567 b , 39571 , 39572 , 39573 , 39574 , INPA 836 , 837 . Cyphocharax gouldingi : CHIOC: 39568 a-b . Caenotropus labyrinthicus : CHIOC: 39570 , Mylesinus paucisquamatus : CHIOC: 39569 a-c , INPA 835 .

Description.

Based on 51 specimens mounted in Hoyers' medium: Body fusiform, robust 195–402 (290; n = 15) long by 65–132 (103; n = 15) wide. Cephalic region with cephalic lobes poorly developed; four bilateral pairs of head organs. Eyespots absent; accessory chromatic granules dispersed in the cephalic region. Mouth subterminal, midventral; pharynx spherical, esophagus short; two intestinal caeca, confluent posteriorly to testes. Haptor sub-hexagonal, 60–105 (83; n = 15) wide (Fig. 34 ). Ventral anchor with superficial root elongated, round deep root knob-like, straight shaft and short point, 60–105 (83; n = 15) long, base 13–31 (22; n = 38) (Fig. 18 ). Dorsal anchor with well-developed elongated superficial root and inconspicuous deep root, short shaft and long point, 26–50 (36; n = 27) in length and base 15–30 (22; n = 28) (Fig. 19 ). Ventral bar straight, with an anteromedian groove and rounded extremities, anteriorly directed, 24–45 (33; n = 15) long (Fig. 17 ). Dorsal bar V-shaped, postero-median projection 19–38 (24; n = 12) long, with two variations: a slender or a more robust projection with lateral allae, 33–47 (40; n = 11) long (Figs 15 , 16 ). Seven pairs of robust marginal hooks, five ventral and two dorsal, similar in shape, pairs 1 and 5 reduced in size, presenting curved point, dilated shank, composed of one subunit, protruded thumb, filamentous hook loop about 1 / 6 shank length (Figs 20 , 21 ), pair 1, 7–20 (13; n = 30) long; pair 2, 18–51 (35; n = 23) long; pair 3, 17–37 (28; n = 20) long; pair 4, 15–27 (21; n = 19) long; pair 5, 9–14 (11; n = 17) long, pair 6, 14–42 (29; n = 22) long; pair 7, 6–43 (21; n = 21) long. Copulatory complex consists of male copulatory organ (MCO) and accessory piece, which serve as guide to MCO. Male copulatory organ about two counterclockwise rings, the proximal ring has a smaller diameter than the distal one, 54–100 (75; n = 18) long. Accessory piece not connected to MCO, situated at distal portion of the organ, consisting of a shaft with medial portion enlarged, with distal groove supporting MCO, 21–38 (28; n = 10) long (Figs 12 , 33 ). Vagina ventral, funnel-shaped, consisting of a sclerotized tube, opening dorsally (Fig. 14 ). Vaginal sclerite composed of a long rod, longitudinally grooved, distal extremity hooked and subterminal short projection, 18–32 (23; n = 13) long (Fig. 13 ). Eggs, Mehlis' glands and ootype not observed. Vitellaria distributed throughout the body, absent in the region of reproductive organs.

Etymology.

The specific name refers to the similarity with Urocleidoides triangulus .

Remarks.

Urocleidoides paratriangulus sp. nov. is similar to U. triangulus considering the shape of the anchors and bars. The new species differs from U. triangulus by the projection of the dorsal bar (prominent postero-median process in U. triangulus and slender or a more robust projection with lateral allae in the new species); the number of rings of MCO (2.5 to 3 in U. triangulus and about two in the new species); and by the reduced size of hooks (pairs 1, 5 and 7 reduced in size in U. triangulus and 1 and 5 only in U. paratriangulus sp. nov.). Only five species of Urocleidoides possess a medial projection on the posterior margin of the dorsal bar: Urocleidoides curimatae Molnar, Henek & Fernando, 1974 ; U. neotropicalis ; U. piriatiu ; Urocleidoide tenuis Zago, Yamada, Yamada, Franceschini, Bongiovani & Silva, 2020 ; and U. boulengerellae sp. nov. The medial projection is slenderer than the bar arms in the five species, whereas in U. triangulus and in some specimens of U. paratriangulus sp. nov., the projection is thicker than the arms. Urocleidoides paratriangulus is similar to U. curimatae and U. tenuis also in terms of the triangular shape of the ventral anchor, but it can be differentiated by the number of coils and the length of the MCO (3 coils in U. paratriangulus sp. nov. vs 1.5 coils in U. curimatae and 7.5 in U. tenuis ), as well as through the morphology of the accessory piece (curved shaft in U. paratriangulus sp. nov., straight in U. curimatae and pincer-shaped in U. tenuis ). During a study carried out in the Guandu River by the laboratory team, specimens of U. triangulus were found parasitizing Cyphocharax gilbert (Quoy & Gaimard, 1824) . The morphometry of the specimens studied herein were used to make comparisons with those of U. paratriangulus sp. nov. This was the first record in this host in Brazil.

Figures

Figures 12–21. Urocleidoides paratriangulus sp. nov. from Psectogaster amazonica from Tocantins River: (12) copulatory complex, ventral view; (13) vaginal sclerite; (14) vagina; (15, 16) dorsal bar; (17) ventral bar; (18) ventral anchor; (19) dorsal anchor, (20) hook pairs 1, 5; (21) hook pairs 2–4, 6, 7. Scale bars: 12 = 10 µm, 13–14 = 10 µm, 15–17 = 20 µm, 18–19 = 20 µm, 20 = 5 µm, 21 = 10 µm.

Figures 31–36. Light photomicrographs of Urocleidoides spp.: (31, 32) Urocleidoides boulengerellae: (31) copulatory complex; (32) vaginal sclerite; (33, 34) Urocleidoides paratriangulus: (33) copulatory complex; (34) haptor; (35, 36) Urocleidoides tocantinensis: (35) copulatory complex; (36) vagina. Scale bars: 31–33, 35–36 = 20 µm, 34 = 40 µm.