Sciadicleithrum kritskyi, Bellay, Sybelle, Takemoto, Ricardo Massato, Yamada, Fábio Hideki & Pavanelli, Gilberto Cezar, 2009

Bellay, Sybelle, Takemoto, Ricardo Massato, Yamada, Fábio Hideki & Pavanelli, Gilberto Cezar, 2009, Two new species of Sciadicleithrum (Monogenea: Dactylogyridae), gill parasites of Geophagus proximus (Castelnau) (Teleostei: Cichlidae), from the upper Paraná River floodplain, Brazil, Zootaxa 2081, pp. 57-66 : 59-62

Sciadicleithrum kritskyi n. sp.

( Figs. 1–2 )

Type-host: Geophagus proximus (Castelnau) ( Perciformes , Cichlidae ). Site: Gill filaments.

Type locality: Upper Paraná River floodplain (22o50’– 22o70’S, 53o15’– 53o40’W). Specimens deposited: Holotype, CHIOC 37188; 3 paratypes, CHIOC 37189, 37190, 37191. Prevalence: 100% (examined 9, infected 9).

Mean Intensity: 14 parasites per parasitized host.

Specimens studied: 12 specimens in Hoyer’s medium and 1 stained with Gomori’s trichrome.

Etymology: The specific name is for Ph. D. Delane Kritsky from the Idaho State University, in honour of his contributions to the study of monogeneans.

Description: (based on 13 adult specimens). Body fusiform, 320 (274–466; n= 5) long; greatest width 58 (26–98; n= 5) in posterior half. Cephalic lobes moderately developed. Eyes 4, subequal; members of anterior pair usually farther apart than those of posterior pair, eye granules elongate ovate; accessory granules sparse in cephalic area. Pharynx semispherical, 18 (18–19; n= 3) long, 17 (17–19; n= 3) wide; oesophagus short; intestinal ceca 2. Peduncle broad; haptor subhexagonal, 70 (61–80; n= 2) wide, 43 (38–49; n= 3) long. Ventral anchor 23 (19–28; n= 11) long, with short deep root, tapering superficial root, short shaft and point, and both with longitudinal lateral grooves; base 14 (13–15; n= 11) wide. Dorsal anchor 52 (45–59; n= 13) long, with elongate superficial root, short deep root, curved shaft, point with longitudinal lateral grooves; base 26 (22–29; n= 12) wide. Ventral bar 10 (8–14; n= 3) wide, 31 (27–39; n= 4) long, yoke-shaped, with delicate umbelliform membranes; dorsal bar 9 (7–11; n= 12) wide, 34(29–39; n= 11) long, with expanded ends and delicate anteromedial projection, with posterior umbelliform membrane. Hooks similar, each with delicate point, upright thumb; hook pair 5, reduced in size; hook pairs 1, 2, 3, 4, 6 and 7: 13 (12–15; n= 13) long; hook pair 5: 10 (9–11; n= 5) long. Filament hook loop ¾ shank length. Male copulatory organ (MCO) a coil with about one and haft couterclockwise rings, MCO 21(17–29; n= 11) long, ring diameter 9 (8–11; n= 7). Accessory piece 23 (19–29; n= 8) long, articulating to MCO base, composed of a slim basal portion and broad distal portion, serving as MCO guide distally. Gonads overlapping. Testis elongate, fusiform, 70 (64–78, n=3) long, 20 (n= 1) wide; vas deferens conspicuous, looping around left intestinal cecum; seminal vesicle large; prostatic reservoir large spherical. Ovary with irregular margin; vagina sclerotized, dextral, opening into large irregular seminal receptacle. Oviduct, ootype, uterus not observed. Vitelline follicles throughout trunk but absent in regions of gonads and copulatory complex. Egg not observed.

Remarks: The most distinctive feature of S. kritskyi n. sp. that distinguishes it from other members of Sciadicleithrum is the presence of the dorsal bar with a delicate anteromedial projection. The new species is similar to S. frequens by having the MCO composed of less than 2 rings, a yoke-shaped ventral bar with delicate umbelliform membranes on the anterior margin, hook pair 5 reduced in size, dorsal anchors that are more than twice as long as the ventral anchors, and longitudinal lateral grooves on the shafts and points of the ventral and dorsal anchors. Sciadicleithrum kritskyi n. sp. has a sclerotized vaginal aperture on the dextral body margin, and MCO with counterclockwise rings, while S. frequens has a nonsclerotized vaginal aperture on the sinistral body margin and MCO with clockwise rings.

Figures

FIGURE 1. Sciadicleithrum kritskyi n. sp. from Geophagus proximus. Composite drawing of whole-mount (ventral view). Scale-bar: 100 µ m.

FIGURE 2. Sciadicleithrum kritskyi n. sp. from Geophagus proximus. a. dorsal anchor; b. dorsal bar; c. ventral bar; d. aperture vaginal; e. hook 1, 2, 3, 4, 6, 7; f. hook 5; g. ventral anchor; h. Copulatory complex – ventral view; Scale-bars: a – g: 25 µ m; h: 12. 5 µ m.