Diaphorocleidus guajajara sp. nov.

urn:lsid:zoobank.org:act: E3274197-6B1B-4BAF-970D-D015D06ACA5E

(Figure 2, Figure 6A, B)

Type-host: Knodus guajajara Aguiar, Brito, Ottoni & Guimarães, 2022 ( Characiformes, Stevardiidae)

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).

Parasitological indices: Total number of hosts examined: 53; number of infested hosts: 1; total number of specimens: 5.

Etymology: The specific epithet refers to the scientific name of the host, Knodus guajajara . The Guajajara are one of the main indigenous peoples in Brazil, inhabiting the eastern margin of the Amazon.

Specimens deposited: Holotype CHIOC 40867a; Paratypes CHIOC 40867 b-e

Description (Based on 5 specimens mounted in Hoyer’s medium). Body filiform, flattened dorsoventrally, 423 (400–460; n = 4) long by 209 (180–245; n = 4) 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 40 (34–45; n = 3) in diameter; oesophagus short; two intestinal caeca, confluent posteriorly to gonads, without diverticula. Gonads overlapping, intercaecal; testis, dorsoposterior to germarium. Vaginal aperture sinistral (Fig. 2A); vagina consisting of a sclerotized tube with wide bevel-shaped opening; seminal receptacle with irregular edges (Fig. 2C). Vitelline follicles distributed throughout the trunk but absent in the regions surrounding the reproductive organs. Egg 49 long by 44 wide (n = 1). 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 1½ rings, 86 (61–102, n = 5) in total length; first ring 20 (16–25, n = 5) in diameter; base forming a small tube with two circular flanges. Accessory piece consisting of two large, articulated subunits: a concave anterior part and a posterior part formed by three tubular-looking structures at proximal portion; apparently serving as a support for the anterior part, the second tube serves as a guide for the MCO, 28 (23–30, n = 4) long (Figs. 2B, 6B). Peduncle short. Haptor subhexagonal 98 (80–120; n = 5) wide, with anchor/bar complex, and 7 pairs of hooks (Figs. 2A, 6A). Anchors of different size, similar in shape, with intermediate root between superficial and deep roots, more prominent in dorsal anchor; superficial and deep roots well developed; superficial root elongated, subrectangular shape, slightly straight stem, short tip. Ventral anchor, 29 (27–31, n = 8) long, base 15 (13–16, n = 8) wide (Figs. 2D, 6A); dorsal anchor, 22 (20–23, n = 8) long, base 12 (9–13, n = 8) wide (Figs. 2E, 6A). Ventral bar robust, open V-shaped, 30 (29–32, n = 4) long (Figs. 2F, 6A); dorsal bar straight, with the expanded ends slightly turned backwards, 37 (31–45, n = 4) long (Figs. 2G, 6A). Hooks similar in shape, with rounded thumb, delicate shaft and tip; shank composed of two subunits, proximal subunit very short, representing about 15% of the total shaft size: Pairs 1 and 5, 13 (10–14, n = 16) long, pairs 2 and 4, 16 (14-17, n=8) long, pairs 3, 6, and 7, 17 (14–19, n = 17) long. Filamentous hook loop approximately 50% of the shank length (Figs. 2 H-J, 6A).

Remarks: Diaphorocleidus guajajara sp. nov. was assigned to the genus Diaphorocleidus based on the overlapping gonads, submarginal sinistral vaginal pore; a copulatory complex comprising an unarticulated MCO; accessory piece with variable shapes divided into subunits; vaginal aperture sinistral, and ventral anchor larger than the dorsal anchor. By the number of rings of the MCO (1½ counterclockwise), the new species resembles Diaphorocleidus kabatai (Molnar, Hanek, and Fernando, 1974) Jogunoori, Kritsky and Venkatanarasaiah, 2004, Diaphorocleidus petrosusi Mendoza-Franco, Aguirre-Macedo & Vidal-Martínez, 2007, Diaphorocleidus neotropicalis Zago, Franceschini, Abdallah, Müller, Azevedo & da Silva, 2021, but differs from these in the accessory piece, which in the new species consists of two large articulated subunits, one of them being formed by three tubular-like structures at the base. The new species resembles Diaphorocleidus forcipiformis Silva, Meneses, Cohen & Justo, 2024, Diaphorocleidus microstomus (Mizelle, Kritsky & Crane, 1968) Jogunoori, Kritsky & Venkatanarasaiah, 2004, and Diaphorocleidus munimensis Silva, Meneses, Cohen & Justo, 2024 by the presence of a middle root between superficial and deep roots, more prominent in the dorsal anchor, but differs in most other morphological structures. The hook pairs of the new species are unique among the species of Diaphorocleidus, with a shaft that is robust throughout its length, ending with a small, rounded portion at the end, representing about 15% of the total shaft size.