Characithecium chelatum, Rossin, María Alejandra & Timi, Juan Tomás, 2014

Rossin, María Alejandra & Timi, Juan Tomás, 2014, Characithecium (Monogenoidea: Dactylogyridae) parasitic on the Neotropical fish Oligosarcus jenynsii (Teleostei: Characidae) from the Pampasic region, Argentina, with the emendation of the gen, Zootaxa 3893 (3), pp. 382-396: 390-394

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Characithecium chelatum

n. sp.

Characithecium chelatum  n. sp.

( Figs. 35–42View FIGURES 35 – 42; 51–52)

Type host. Oligosarcus jenynsii (Günther) 

Type locality. Nahuel Rucá 38 °08´S, 57 ° 32 ´W, Mar Chiquita, Buenos Aires Province, Argentina.

Prevalence. 50 %

Mean abundance (intensity range). 8.5 (2–65).

Type material. Holotype (MLP-He- 6801) and paratypes (MLP-He- 6802) are deposited in the Helminthological Collection of the Museo de La Plata ( HCMLP), La Plata, Argentina.

Etymology. The specific name is derived from Latin chela (=claw) and refers to the pincer shape of the accessory piece of the copulatory complex.

Description. Based on 10 specimens. Body small and delicate, 337 (270–426; n = 10) long; greatest width 99 (61–131) usually at middle of body. Two pair of cephalic lobes well developed 1 anterior and 1 lateral. Four pairs of head organs observed. Cephalic glands present. Two pair of eyespots in cephalic region, frequently dissociated, accessory granules often present in cephalic region. Pharynx spherical, 22 (17–28) in diameter; esophagus short.

Haptor 75 (54–96) wide, 58 (49–70) long. Ventral anchor 44 (41–46) long, base 20 (18–23) wide; with welldeveloped and elongate superficial root, shorter deep root, curved shaft and curved distal point, anchor filaments conspicuous. Dorsal anchor 29 (26–31) long, base 16 (13–17) wide, with developed roots, superficial root elongated, straight shaft with curved distal point. Ventral bar 30 (20–33) long, V-shaped, with medial suture and dilated extremes. Dorsal bar curved 32 (28–36) long, posterior ends slightly expanded. Hooks similar in shape, hooks excluding pairs 1 and 5 and length with protruding thumb, delicate point; hooks pairs 1 and 5 reduced in size 15 (14–18) long, longer hooks 20 (18–21); shank comprised of 2 subunits; proximal subunit expanded, filamentous booklet (FH) loop short. MCO a coiled tube with 1 ½ counterclockwise coils, 93 (85–108) long; base of MCO reel shaped, connected to articulation process of accessory piece. Accessory piece 17 (15–23) long, pincer shaped, comprising 2 subunits articulated at proximal ends, both with bifurcate extremes, the shorter serving as guide for MCO. Gonads overlapping; testis dorsal to germarium; seminal vesicle as a distal dilation of a vas deferens, looping before junction to MCO. Prostatic reservoir present. Vitellaria extended throughout trunk, except in regions of reproductive organs. Oviduct, ootype and uterus not observed. Vaginal aperture heavily sclerotized, coup-shaped plate at midbody, lateral and sinistral. Vagina almost straight connecting with a seminal receptacle. Seminal receptacle medial and anterior to germarium. Eggs not observed.

Remarks. Characithecium chelatum  n. sp. is one of the smallest member of the genus; It resembles C. longianchoratum  n. sp. in the general morphology and relative size of anchors as well as by having ventral anchors protruding from haptor. However, C. chelatum  n. sp. can be distinguished from its congeners by the shape of the accessory piece, with 2 subunits articulated at base and with bifurcate extremes, by having 1 ½ coils in the MCO, by the shape and sclerotization of the vaginal aperture and by the absence of a posterior medial projection in ventral bar.