Mymarothecioides xinguensis Soares and Domingues, 2019

Soares, Geusivam B., Magalhães, Keila X., Silva, Ana Carolina, Carneiro, Jânio S., Barbosa, Lucineia L., Costa, Nayna G. S. & Domingues, Marcus V., 2019, Monogenoids (Polyonchoinea, Dactylogyridae) from Hydrolycus armatus (Characiformes, Cynodontidae) with the description of a new species of Rhinoxenus and the proposal of a new genus from the Xingu River, Pará, Brazil, Zootaxa 4700 (2), pp. 229-245 : 234-236

Mymarothecioides xinguensis Soares and Domingues n. sp.

( Figs. 10–17; 43)

Type host: Hydrolycus armatus (Jardine & Schomburgk) .

Site: Gills.

Type locality: Volta Grande , Xingu River, municipality of Altamira, Pará State, Brazil (03°21’15,7’’S; 52°11’47,5’’W), collected on June 13, 2015 .

Prevalence: 100% of three hosts examined.

Mean intensity: 10 parasites per infected host.

Specimens deposited: Holotype, MPEG nº 181; 7 paratypes, MPEG n° 182–188.

Etymology: The specific name is derived from the type locality, the Xingu River, Pará State, Brazil.

Zoobank Life Science Identifier: (LSID) for Mymarothecioides xinguensis n. sp. is urn:lsid:zoobank.org:act:EE0E7DDE-5148-44C5-A496-D0DC0D75F398

Comparative measurements: see Table 3.

Description (based on eight specimens, three mounted in Hoyer, five mounted in Gomori’s trichrome): Body fusiform, total length excluding haptor 396 (315–450; n= 4), total width at level of germarium 129 (122–142; n=4) ( Fig. 10). Cephalic margin tapered; moderately developed terminal lobes; three bilateral pairs of head organs, with rod-shaped secretion; cephalic glands unicellular, posterolateral to the pharynx. Accessory chromatic granules present in cephalic area. Pharynx ovate, 29 (24–33; n= 3) long, 22 (19–24; n=3) wide. Testis pyriform, 83 (71–103; n=4) long, 45 (41–47; n=4) wide. Prostatic reservoir saccate, posterior to MCO. MCO, 33 (30–36; n=5) long, with small grooves at edges of distal opening; base of MCO with sclerotized margin ( Figs. 11, 43). Accessory piece comprising straight rod, with hook-shaped distal portion. Germarium fusiform, 75 (71–79; n=3) long, 24 (n=3) wide. Eggs, Mehlis’ glands, ootype not observed. Vaginal aperture marginal (dextral), opening at level of vitelline commissure; vaginal vestibule heavily muscular; vaginal canal sigmoid. Seminal receptacle subspherical. Uterus delicate. Vitelline follicles dense. Peduncle broad; haptor pentagonal, 95 (85–100; n=4) long, 119 (100–137; n=4) wide. Anchors similar. Ventral anchor, outer 43 (39–47; n=5) long, inner 42 (36–47; n=5) long; base 24 (22–25; n=5); superficial root triangular, with delicate sclerotization on distal extremity; deep root poorly developed; slightly curved shaft and point; point extending to level of tip of superficial root ( Fig. 16). Dorsal anchor, outer 32 (27–38; n=5) long, inner 34 (30–39; n=5) long; base 24 (22–25; n=5); superficial root triangular, with delicate sclerotization on distal portion; deep root poorly developed; slightly curved shaft and point, point extending just past level of tip of superficial root ( Fig. 17). Ventral bar, 63 (55–71; n=6) long, 12 (11–14; n=5) wide, slightly curved rod, with anteromedial projection, enlarged ends ( Fig. 14). Dorsal bar, 51 (44–61; n=5) long, 6 (5–8; n=5) wide, broadly V-shaped rod with rounded ends ( Fig. 15). Hooks similar in shape, hook pairs 1–4, 6 –7 26 (20–33; n=19) long, with upright thumb, rounded, short shaft, slightly curved, shank divided into two units; filamentous hook loop not observed ( Fig. 12); hook pair 5, 17 (15–20; n=4) long, shank with proximal dilatation comprising approximately 1/3 of the shank length; filamentous hook loop not observed ( Fig. 13).

Remarks: Features that distinguish the new species from most of its congeners include a hook-shaped accessory piece without the subterminal branch at the distal portion, a dextromarginal vaginal pore, and ventral and dorsal anchors with triangular superficial roots.