Anacanthorus ataidei sp. n.

(Figs. 4–7)

Type-host: Erythrinus erythrinus (Bloch & Schneider), Erythrinidae .

Site of infection: Gills.

Type-locality: Igarapé Cururutuia—Caeté River, municipality of Bragança, State of Pará, Brazil (1°4’44.55”S 46°44’18.54”W).

Other localities: Erythrinus erythrinus (Prevalence: 20% of five hosts examined; Mean intensity: five parasites per host infected), Pratinha Community—Caeté River, municipality of Bragança, Pará State (1°5’2.49”S 46°49’44.67”W); E. erythrinus (Prevalence: 25% of the four hosts examined; Mean intensity: six parasites per host infected), Igarapé Maratininga—Moju River, municipality of Tailândia, Pará State (02º27’55.7”S 048º53’27.6”W).

Prevalence: 50% of two hosts examined.

Mean intensity: 10, 5 parasites per host infected.

Specimens deposited: Holotype: CHIOC no. 40026 a. 19 paratypes: CHIOC nos. 40026 b–k; INPA no. 801; MPEG nos. 151–155. 8 vouchers: CHIOC nos. 40027 a–c; INPA nos. 802–803; MPEG no. 156.

ZooBank registration: The Life Science Identifier (LSID) urn: lsid:zoobank.org:act: 57058C57-7341-4762- B5E7-E6EEA4033EDB.

Etymology: The specific epithet of the species is named after a local legend from the Northeast Pará, Brazil. Ataíde is a man-like being who inhabits the floodplains and mangroves of Pará State and is known for having a prominent genital organ.

Comparative measurements: Table 1.

Description: (Based on twenty specimens, nine mounted in Gomori trichrome, eight mounted in Grey & Wess, and three mounted in Hoyer’s). Body fusiform 301 (213–424; n=17) long, excluding the haptor, 81 (37–122; n=18) wide at the height of germarium (Fig. 7). Four cephalic lobes poorly developed; three groups of head organs; cephalic glands not observed (Fig. 7). Two pairs of ocelli, similar in size; accessory granules present, oval-shaped, little scattered in the cephalic area (Fig. 7). Pharynx spheric 20 (16–29; n=14) long, 20 (15–26; n=15) wide; oesophagus elongated (Fig. 7). Two intestinal caeca, confluent, posterior to the gonads (Fig. 7). Genital pore not observed. MCO 179 (112–239; n=11) long, sclerotized, tubular, elongated, extending proximally from the esophagus to close the peduncle region, comprising approximately 60% of the body length, with ribbon-like ornaments around the MCO (Fig. 4); accessory piece absent (Fig. 4). Seminal vesicle long, ascendant branch of the vas deferens looping the right intestinal caecum and posteriorly with a descendant branch, forming the seminal vesicle dorsal to germarium (Fig. 4). Gonads not overlapping; germarium pyriform 45 (33–62; n=12) long, 27 (19–35; n=12) wide; testis oval 26 (17–31; n=4) long, 22 (19–25; n=4) wide, posterior to germarium (Fig. 7). Uterus, muscular and with thick walls. Prostatic reservoir elongated, located near to the germarium with descendant duct directed to the of the MCO (Fig. 7). Peduncle short (Fig. 7). Haptor sub-hexagonal 34 (18–47; n=15) long, 34 (18–47; n=14) wide (Fig. 7). Similar 4A hooks 10 (9–11; n=7) long (Fig. 6). Seven pairs of similar hooks 16 (14–17; n=6) long; blade relatively elongated and slightly curved, point short and curved, delicate shank without proximal dilatation, thumb erect and slightly depressed (Fig. 5). Hook filament delicate, extending more than the half of the shank (Fig. 5).

Remarks: Anacanthorus ataidei sp. n. is similar to Anacanthorus franciscanus Monteiro, Kritsky & Brasil- Sato, 2010 parasite of Brycon orthotaenia Günther ( Characiformes: Bryconidae) for having an elongated and tubular MCO. The new species differs from A. franciscanus by an elongated MCO, comprising approximately 60% of the body length with ornaments in the form of twisted slides around the MCO (in A. franciscanus, the MCO has no ornaments). Besides, A. franciscanus is characterized by the presence of the shank of hooks with proximal portion dilated in the form of a bulb with two translucent spots (in Anacanthorus ataidei sp. n., the hook has uniform shank).