Diaphorocleidus forcipiformis Silva, Meneses, Cohen and Justo, 2024

Silva, Marciara Lopes, Cohen, Simone Chinicz, Ottoni, Felipe Polivanov, Viana, Diego Carvalho, Meneses, Yuri Costa De & Justo, Marcia Cristina Nascimento, 2024, Two new species of Diaphorocleidus and new data on D. affinis (Monogenoidea: Dactylogyridae) parasitizing Bryconops cf. affinis (Characiformes: Iguanodectidae) from the Munim River basin, State of Maranhão, northeastern Brazil, Zootaxa 5403 (1), pp. 91-103 : 95-97

Diaphorocleidus forcipiformis Silva, Meneses, Cohen and Justo n. sp. ( Figure 3 )

Type-host: Bryconops cf. affinis (Günther)

Site of infestation: Gills

Type-locality: Rural area of Chapadinha in the “Riacho Feio” (03º51’18.1’’S 043º17’14.0’’W) and urban area of Anapurus in the “Riacho Estrela” (03°40’15.6”S 043°7’9.7”W), tributaries of the Munim River, Munim Basin, Maranhão, Brazil .

Parasitological indexes: Total number of hosts: 64; number of infected hosts: 25; total number of parasites: 151; Range of intensity: 1–23

Specimens deposited: Holotype CHIOC 40276 , Paratypes CHIOC: 40277, 40278, 40279 a–b

Etymology: The specific name is from Latin (forceps = clamp; formis = shape of) and refers to the shape of the accessory piece.

Description (Based on 28 specimens mounted in Hoyer’s medium). Body fusiform, flattened dorsoventrally, 382 (198–622; n = 28) long by 151 (71–324, n = 28) greatest width. Tegument thin and smooth. Cephalic lobes developed; three bilateral pairs of head organs; cephalic glands indistinct. Two pairs of eyes, equidistant, anterior pair smaller than posterior. Pharynx spherical 17 (15–18; n = 7) in diameter. Two intestinal caeca, confluent posteriorly to gonads, without diverticula. Gonads overlapping, intercaecal; testis, dorsoposterior to germarium, 25 (22–27; n = 4) long by 23 (18–28; n = 4) wide. Germarium 59 (43–75; n = 4) long, 32 (26–43; n = 4) wide. Vagina with a sinistral submarginal vaginal opening, consisting of a thin sclerotized tube with an oval seminal receptacle, anterior to the germarium. Vitelline follicles scattered throughout the trunk, absent around other reproductive organs ( Fig. 3A ). Eggs, Mehlis’ gland and ootype not observed ( Fig. 3A ). Copulatory complex comprising male copulatory organ (MCO) and accessory piece. MCO sclerotized, tubular 107 (82–136, n = 16) in total length, coiled with 2 ½ rings counterclockwise, first ring 17 (16–19, n = 7) in diameter; base forming a small tube with two circular flanges. Accessory piece bifurcated, claw-shaped, with parts similar in shape and size, one of them distally bifid, serving as a guide for distal portion of MCO, 33 (28–37, n = 7) long by 19 (13–27; n = 21) wide ( Fig. 3B ). Peduncle short. Haptor subhexagonal 110 (82–146; n = 23) wide, with anchor/bar complex, 7 pairs of hooks ( Fig. 3A ). Anchors dissimilar in size and shape. Ventral anchor with well-developed superficial and deep roots; superficial root elongate, subrectangular shape, slightly straight shaft, short point, 29 (23–33, n = 10) long, base 17 (15–20, n = 10) wide ( Fig. 3D ); dorsal anchor with a bump at the proximal portion of the superficial root, evenly curved shaft and short point, 18 (14–20, n = 10) long, base 14 (11–17, n = 10) wide ( Fig. 3C ). Ventral bar, robust, V-shaped, rounded in lateral ends, 39 (31–48, n = 10) ( Fig. 3E ); dorsal bar thin, long, broadly U-shaped, 37 (30–42, n = 10) long ( Fig. 3F ). Hooks similar in shape, with 2 equal subunits, protruding thumb, shaft and delicate point: Pairs 1 and 5, 16 (13–18, n = 18) reduced in size, pairs 2, 3, 6 and 7, 19 (16–22; n = 36), pair 4 longer than the others, 21 (20–23; n = 9); FH loop approximately 50% of the shank length ( Fig. 3G ).

Remarks: The new species resembles D. petrosusi Mendoza-Franco, Aguirre-Macedo & Vidal-Martínez, 2007 by the shape of the accessory piece, but differs in size (18 [16–20] in D. petrosusi ; 33 [28–37] in the new species) and by the bifid termination in one of the processes of the accessory piece in the new species. The new species differs from D. armillatus , D. microstomus (Mizelle, Kristky & Crane, 1968) and D. magnus Zago, Franceschini, Abdallah, Müller, Azevedo & da Silva, 2021 in the morphology of the accessory piece (variable, plate-like in D. armillatus and D. microstomus , and robust, comprising two subunits, wrench-shaped in D. magnus ). With respect to the number of rings of male copulatory organ, D. forcipiformis n. sp. resembles D. armillatus which presents 2 rings, D. magnus with 2 ½ and D. microstomus with 1 ½ to 2 ½ rings. The new species also resembles D. armillatus , D. microstomus and D. magnus by the size of the hooks, in which pairs 1 and 5 are smaller than the others, but differs from them by the morphology of the anchors (absence of medial root at the base of the dorsal anchor in D. armillatus and D. magnus ).

Figures

FIGURE 3. Diaphorocleidus forcipiformis n. sp. from Bryconops cf. affinis (Characiformes, Iguanodectidae) from São José, municipality of Chapadinha and in Riacho Estrela, municipality of Anapurus, River Munim basin, Maranhão, Brazil: (a) total, ventral view; (b) copulatory complex, ventral view; (c) dorsal anchor; (d) ventral anchor; (e) ventral bar; (f) dorsal bar; (g) hook. Scale bars: (a) 100 μm; (b) 15 μm; (c, d) 20 μm; (e, f, g) 10 μm.