Jainus peruensis, Cruces & Santillán & Silvera & Morey & Rubin & Chero, 2024

Cruces, Celso L., Santillán, Luis A., Silvera, Jordan F., Morey, Germán Augusto Murrieta, Rubin, Veronica & Chero, Jhon D., 2024, Two new dactylogyrid species (Dactylogyroidea: Dactylogyridae), gill parasites of freshwater fishes from the Peruvian Amazon, including the proposal of Peruanella n. gen., Zootaxa 5443 (4), pp. 591-600 : 594-597

Jainus peruensis n. sp.

( Fig. 2A–G )

Type-host: Brycon amazonicus (Spix & Agassiz) ( Characiformes : Bryconidae ).

Site on host: Gill filaments.

Type locality: Madre de Dios River (12°35’S, 69°10’W), Puerto Maldonado City , Madre de Dios region, Peru .

Type material: Holotype, MUSM-HEL 5392 ; 9 paratypes, MUSM-HEL 5393 a-i.

Etymology: The specific epithet refers to the country where the species was found.

Description: Based on 10 specimens. Body robust, fusiform ( Fig. 2A ), 311–758 (649; n = 10) long; greatest width 144–292 (226; n = 10) usually near mid-length. One terminal, 2 bilateral cephalic lobes poorly developed. Three bilateral pairs of conspicuous head organs. Eyes present. Pharynx spherical, 20–23 (21; n = 10) in diameter. Group of well-developed secretory gland-cells lying on peduncle. Haptor sub-quadrangular ( Fig. 2A ), poorly differentiated from body proper, 58–85 (67; n = 10) long; 72–137 (91; n = 10) wide.Anchors dissimilar in shape and size ( Fig. 2B, C ). Ventral anchor 20–23 (21; n = 10) long, base 7–9 (8; n = 10) wide, rodlike deep root, superficial root bearing irregular sclerotized ornamentation, blade-like shaft and point. Dorsal anchor 40–43 (42; n = 10) long, base 7–8 (7; n = 8) wide, inconspicuous deep root, well-developed superficial root, straight shaft and recurved point. Ventral bar delicate, rod-shaped, with medial projection and slightly curved ends ( Fig. 2D ), 20–27 (24; n = 7) long. Dorsal bar robust, almost V-shaped, grooved ( Fig. 2E ), 27–37 (33; n = 6) long. Hooks similar in shape and size, 11– 13 (12; n = 8) long, each with upright thumb, slender and straight shank, and short and recurved point; filamentous hook (FH) about ¾ length ( Fig. 2F ). MCO 41–49 (46; n = 10) long, slender tube, with crenulated base, forming counterclockwise loop at proximal end ( Fig. 2G ). Accessory piece unarticulated to MCO base, sinuous proximally, well expanded distally, with scythe-shaped distal end ( Fig. 2G ), 18–29 (27; n = 6) long. Testis subspherical, wide; prostatic reservoir and prostatic glands not observed. Ovary elongate, 112–172 (142; n = 2) long, 36–37 (37; n = 2) wide; oviduct, oötype, uterus, vagina and seminal receptacle not observed. Eggs not observed.

Remarks: The new species is clearly a member of Jainus , characterized by its ventral anchor whit elongate rodlike deep root, and an accessory piece that is non-articulated to MCO ( Mizelle et al. 1968). Jainus peruensis n. sp. can be distinguished from other congeners by the morphology of the MCO. The accessory piece (hook-shaped distally) and ventral bar (rod-shaped with a medial projection) morphology suggests a closer resemblance to Jainus iocensis Cohen, Kohn & Boeger, 2012 . Nonetheless, J. peruensis n. sp. differs from J. iocensis by the morphology of the MCO base (with a crenulated base in the new species vs without crenulated base in J. iocensis ), dorsal bar (V-shaped and grooved in J. peruensis n. sp. vs rod-shaped with slightly enlarged ends in J. iocensis ), and by the superficial root of the dorsal anchor (less expanded in the new species vs well-expanded in J. iocensis ). Furthermore, the species differ in the hook morphology, characterized by a proximal shank enlargement that is subcircular in J. iocensis , whereas absent in the new species. Finally, both species, J. peruensis n. sp. and J. iocensis , differ in the morphology of the accessory piece. In J. peruensis n. sp., it is more robust distally and lacks an oval-shaped projection halfway along its length, whereas in J. iocensis , it is less robust distally and exhibits an oval-shaped projection halfway along its length.

Jainus peruensis n. sp. is the eleventh species described in the genus, but it is the first species of the genus described in Peru ( Kritsky et al. 1980; Karling et al. 2011; Abdallah et al. 2012; Cohen et al. 2012; Yamada et al. 2023). One known species of Jainus has been previously registered in Peru, infecting a bryconid host ( Mathews et al. 2014). Additionally, three undescribed species of Jainus have also been reported ( Rengifo-Chota et al. 2022), suggesting that Peruvian Amazon fishes could harbor an exceptionally diverse array of Jainus species.

Figures

FIGURE 2. Jainus peruensis n. sp. from Brycon amazonicus (Spix & Agassiz) (Characiformes: Bryconidae). A. Whole mount (composite, ventral view). B. Ventral anchor. C. Dorsal anchor. D. Ventral bar. E. Dorsal bar. F. Hook. G. MCO.