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.

Figures

FIGURES 10–17. Mymarothecioides xinguensis n. sp. 10. Holotype whole-mount (ventral) (composite). 11. Copulatory complex. 12. Hook pair 1–4, 6–7. 13. Hook pair 5. 14. Ventral bar. 15. Dorsal bar. 16. Ventral anchor. 17. Dorsal anchor.

FIGURES 42–45. The copulatory complex of species of Mymarothecioides n. gen. 42. Mymarothecioides ararai n. sp. 43. Mymarothecioides xinguensis n. sp. 44. Mymarothecioides altamirensis n. sp. 45. Mymarothecioides germanoi n. sp.