Diaphorocleidus munimensis Silva, Meneses, Cohen and Justo n. sp. (Figure 4)

Type-host: Bryconops cf. affinis (Günther)

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 .

Site of infestation: Gills

Parasitological indexes: Total number of hosts: 64; number of infected hosts: 21; total number of parasites: 141; Range of intensity: 1–28.

Specimens deposited: Holotype CHIOC 40280, Paratypes CHIOC 40281, 40282, 40283 a–b, 40284 a–b

Etymology: The specific name is derived from the river basin where the specimens were collected.

Description (Based on 20 specimens, mounted in Hoyer’s medium). Body fusiform, flattened dorsoventrally, 357 (174–644; n = 19) long by 155 (86–309, n = 20) greatest width. Tegument thin and smooth. Cephalic lobes moderately developed; three bilateral pairs of head organs; cephalic glands indistinct. Two pairs of eyes equidistant, anterior pair smaller than posterior. Pharynx spherical 20 (14–27; n = 3) in diameter. Two intestinal caeca, confluent posteriorly to gonads, without diverticula. Gonads overlapping, intercaecal; testis elongate, fusiform, dorsoposterior to germarium, 30 (24–33; n = 4) long by 26 (25–30; n = 4) wide; elongated seminal vesicle and single prostatic reservoir (Fig. 4A). Copulatory complex comprising male copulatory organ (MCO) and accessory piece. MCO sclerotized, tubular, 122 (109–130, n = 16) in total length, coiled with 2 counterclockwise rings, 22 (20–26, n = 14) diameter of the first ring; base forming a small tube with two circular flanges. Accessory piece composed of two large pieces, united in their proximal part, claw-shaped, distally hooked, with a small lateral structure serving as guide to MCO, 33 (28–40, n = 14) long by 22 (14–27; n = 11) wide (Fig. 4B). Germarium 51 (34–62; n = 4) long, 30 (22–42; n = 4) wide. Vagina with submarginal vaginal opening, consisting of a thin sclerotized tube; seminal receptacle not observed. Vitelline follicles scattered throughout trunk but absent around the reproductive organs (Fig. 4A). Peduncle short. Haptor subhexagonal, 98 (78–118; n = 19) wide, with 7 pairs of hooks (Fig. 4A). Anchors dissimilar in size and shape. Ventral anchor with well-developed roots, superficial root rectangular and round short deep root, straight shaft and curved point, 32 (27–34, n = 15) long, base 20 (17–22, n = 15) wide (Fig. 4E); Dorsal anchor with well-developed roots, superficial root elongated, deep root round and short, and a middle root between superficial and deep roots, straight shaft and short point, 21 (17–23, n = 15) long; base 15 (13–17, n = 15) wide (Fig. 4F). Ventral bar, robust, V-shaped, 37 (33–42, n = 12) long (Fig. 4G); dorsal bar thin, long, slightly curved, 39 (33–46, n = 12) long (Fig. 4H). Hooks similar in shape, with subunits of equal size, protruding thumb; hook pairs 1 and 5 reduced in size, 15 (15–16; n = 14) (Fig. 4D), pairs 3 and 4 longer than other pairs, 22 (20–22; n = 14) (Fig. 4C). Pairs 2, 6 and 7 18 (17–19; n = 21) long. FH loop approximately 30% of shank length.

Remarks: Diaphorocleidus munimensis n. sp. resembles D. armillatus and D. forcipiformis n. sp. by the number of the rings of the MCO (2 counterclockwise). However, the new species differs from these mainly by the morphology of the accessory piece (plate-like in D. armillatus, and bifurcated, claw-shaped in D. forcipiformis n. sp.). Diaphorocleidus munimensis n. sp. also differs from D. armillatus by the body length (357 long by 155 wide in the new species vs 280 long by 78 wide in D. armillatus). By the similarity in the morphology of the accessory piece (pincer-shaped, formed by two support processes), the new species resembles D. petrosusi and D. sclerocolpus Santos Neto, Costa, Soares & Domingues, 2018, but differs by the width of the two support processes, which in the new species is very robust, one being wider than the other.