Tereancistrum arcuatus, Cohen, Simone Chinicz, Kohn, Anna & Boeger, Walter A., 2012

Cohen, Simone Chinicz, Kohn, Anna & Boeger, Walter A., 2012, Neotropical Monogenoidea. 57. Nine new species of Dactylogyridae (Monogenoidea) from the gill of Salminus brasiliensis (Characidae, Characiformes) from the Paraná River, State of Paraná, Brazil, Zootaxa 3149, pp. 57-68 : 66-67

Tereancistrum arcuatus sp. n.

( Figs. 37–42 )

Type locality. Paraná River below and above of the reservoir of Itaipu Hydroelectric Power Station in the localities of Guaira (24º04’48’’S, 54º15’21’’W), State of Paraná, Brazil

Prevalence. 11.5% (3 of 26 fishes examined)

Specimens studied. Holotype, CHIOC 37628; 5 paratypes, CHIOC 37609, 37665, 37674a–b, 37678.

Etymology. The new species refers to the arcuate shape of the male copulatory organ

Description. (Based on 7 specimens). Body 358 (300–425; n=3) long, 100 (n=3) wide near midlength. Cephalic region broad, cephalic lobes moderately developed, with 3 pairs of lateral head organs; cephalic glands indistinct. Eyespots subequal, posterior pair with lenses, closer than the anterior pair. Pharynx 33 (n=1) in diameter. Haptor subtrapezoidal, with 7 pairs of hooks, with ancyrocephaline distribution. Ventral bar 85 (82–92; n=4) long, with subterminal constrictions and expanded ends. Dorsal bar 49 (45–54; n=3) long, straight, rod–shaped, with slightly enlarged ends. Ventral anchor 65 (61–70; n=8) long, with robust base, poorly distinguishable deep and superficial roots, evenly curved shaft and point, base width 28 (26–30; n=6). Accessory anchor sclerite 37 (35–40; n=5) long, with longitudinal groove, articulated to superficial root of ventral anchor. Dorsal anchor 53 (50–56; n=8), with robust base, poorly differentiated roots, long straight shaft, short strongly recurved point; base width 19 (15–22; n=7). Hook pair 1 15 (n=2), pair 5 13–14 (n=2), pairs 2–4, 6 –7 22 (21–23; n=7). Hook with depressed thumb, shaft, recurved point, shank of two portions, proximal portion enlarged. FH loop about 0.5 shank length. MCO 118 (105–138; n=4) a strongly arcuate sclerotized tube with a small base and large distal flap. Accessory piece non-articulated, bifurcated, with pointed distal ends; branches of accessory piece connected near midlength by a flat sclerotized element. Vagina sinistral, marginal. Vitellaria scattered throughout the trunk except in the regions of copulatory complex and gonads. Eggs not observed.

Remarks. Five species of Tereancistrum are presently known, each from fishes of different host families: T. kerri Kritsky, Thatcher & Kayton, 1980 from Brycon melanopterus (Cope) , in Brazil, T. ornatus Kritsky, Thatcher & Kayton, 1980 from Prochilodus reticulatus Steindachner from Colombia, T. parvus Kritsky, Thatcher & Kayton, 1980 from Leporinus fasciatus (Bloch) , T. toksonum Lizama, Takemoto & Pavanelli, 2004 and T. curimba Lizama, Takemoto & Pavanelli, 2004 , both from Prochilodus lineatus (Valenciennes) in Brasil. The new species can be easily distinguished from the others by the MCO, which is an arcuate tube, while the other five species present a coiled copulatory organ.

Figures

FIGURES 37 – 42. Sclerotized parts of Tereancistrum arcuatus sp. n. from the dourado, Salminus brasiliensis, from Paraná River, Brazil. 37. Copulatory complex (ventral view). 38. Hook. 39. Ventral anchor. 40. Dorsal anchor. 41. Ven t ral bar. 42. Dorsal bar. All figures are drawn to the 50 µm scale, except fig. 38 (10 µm scale).