Sciadicleithrum paranaensis, 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 : 62

Sciadicleithrum paranaensis n. sp.

( Figs. 3–4 )

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 37183; 4 paratypes, CHIOC 37184, 37185, 37186, 37187.

Prevalence: 44.44% (examined 4, infected 9).

Mean Intensity: 14 parasites per parasitized host.

Specimens studied: 11 specimens in Hoyer’s medium and 1 stained with Gomori’s trichrome.

Etymology: This species is named for the Paraná River, the main river of the upper Paraná River floodplain.

Description: (based on 12 adult specimens). Body fusiform, 436 (384–516; n= 9) long; greatest width 98 (63–137; n= 11) in posterior half. Cephalic lobes well developed. Eyes 4, equidistant; members of anterior pair usually farther apart than those of posterior pair, eye granules elongate ovate; accessory granules sparse in cephalic area. Pharynx semispherical, 27 (20–42; n= 11) wide, 24 (17–31; n= 10) long; oesophagus elongate; intestinal ceca 2. Peduncle broad; haptor subhexagonal, 100 (88–116; n= 11) wide, 53 (30–78; n= 11) long. Anchors similar, each with poorly developed roots, enlarged base, delicate evenly curved shaft and point, longitudinal lateral grooves on the shafts and points. Ventral anchor 35 (28–37; n= 8) long, base 25 (24–27; n= 8) wide. Dorsal anchor 39 (38–40; n= 3) long, base 29 (25–32; n= 3) wide. Ventral bar 18 (15–24; n= 11) long, 52 (47–62; n= 11) wide, robust, yoke-shaped, with delicate umbelliform membranes; dorsal bar 18 (12–22; n= 7) long, 54 (43–56; n= 7) wide, with posterior umbelliform membrane, and expanded ends. Hooks similar, each with erect thumb, relatively robust point, shank; hook pair 5, reduced in size; hook pairs 1, 2, 3, 4, 6 and 7: 15 (15–17; n= 12) long; hook pair 5: 12 (11–13; n= 8) long. Filament hook loop ¾ shank length. Male copulatory organ (MCO) a couterclockwise coil about one ring, MCO 41 (30–49; n= 7) long, ring diameter 9 (8–10; n= 9). Accessory piece 23 (19–30; n= 8) long, articulating to MCO base, composed of a variable sheath with a ring in medial portion enclosing distal shaft of MCO. Gonads overlapping. Testis elongate, fusiform, 73 (54–88, n= 3) long, 23 (20–29; n= 4) wide; vas deferens conspicuous, looping around left intestinal cecum; seminal vesicle small; prostatic reservoir delicate. Ovary with irregular margin; vagina nonsclerotized, ventral, 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 oval, 70 (57–83; n= 2) long, 35 (32–37; n= 2) wide, with a robust appendage.

Remarks: Sciadicleithrum paranaensis n. sp. differs from the other congeners by the shape of the accessory piece, composed of a variable sheath with a ring in the medial portion enclosing a distal shaft of the MCO. Sciadicleithrum paranaensis n. sp. is similar to S. geophagi by having the vaginal aperture on the ventral body surface, composed of a delicate tube opening into a large spherical seminal receptacle; anchors with poorly developed roots, enlarged bases, delicate evenly curved shafts and points; the MCO composed of less than 2 rings; and an accessory piece articuling to MCO base. Sciadicleithrum paranaensis n. sp. can be distinguished from S. geophagi by the presence of longitudinal lateral grooves on the shafts and points of the ventral and dorsal anchors, MCO with a counterclockwise ring, and by the comparative sizes of the haptor hooks (hook pair 5 smaller than the other hooks pairs of S. paranaensis n. sp.). Sciadicleithrum paranaensis n. sp. can easily be differentiated from S. kritskyi n. sp. by having the vaginal aperture on the ventral body surface, and similar size anchors.

Figures

FIGURE 3. Sciadicleithrum paranaensis n. sp. from Geophagus proximus. Composite drawing of whole-mount (ventral view). Scale-bar: 100 µ m.

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