Gyrodactylus decemmaculati n. sp.

(Figures 1–5, 11, Table 1)

urn:lsid:zoobank.org:act: 808A328D-B540-4591-8386-771A0F30400A

Type host: Cnesterodon decemmaculatus (Jenyns, 1842) ( Cyprinodontiformes: Poeciliidae).

Type locality: Arroyón stream, Cinco Saltos, Argentina (38°43’39.2”S 68°02’15.5”W) .

Other localities: Negro River, Cipolletti, Río Negro (38°59’36.6”S 67°59’31.1”W); Neuquen River, Vista Alegre, Neuquen, Argentina (38°59’36.6”S 67°59’31.1”W).

Site of infection: Body surface.

Specimens studied: holotype, MACN-Pa 676; paratypes MACN-Pa 677/1, MACN-Pa 677/2; hologenophore, MACN-Pa 678.

Specimens sequenced: ITS1 (GenBank accession numbers: MK 299423, MK 299424, MK 299425), ITS2 (Gen- Bank accession numbers: MK 312457, MK 312458), COII (GenBank accession numbers: MN 066554, MN 066555, MN 066556).

ZooBank registration: The life Science Identifier (LSID) Gyrodactylus decemmaculati n. sp. is urn:lsid:zoobank.org:act: 808A328D-B540-4591-8386-771A0F30400A.

Etymology: The specific name refers to the host specific epithet.

Description: (Based on 11 specimens) Body elongate, 333 (266–408; n = 10) long, 68 (48–96; n = 10) wide. Cephalic glands, head organs, spike sensilla conspicuous. Cephalic glands anterolateral, lateral, posterolateral to pharynx. Pharynx composed of two tandem bulbs. Distal pharyngeal bulb muscular 21 (20–22; n = 3) wide; digitiform projections of distal pharyngeal bulb present; proximal pharyngeal bulb glandular 24 (21–29; n = 3) wide. Male copulatory organ (MCO) 9 (8–10; n = 3) wide, armed with one spine, one row of five to six large spinelets, each with wide, truncate base. Testis not observed. Germarium ovate, 24 (18–30; n = 3) long, 22 (20–23; n = 3) wide. Uterus with up to 2 generations of embryos. Syncytial follicles overlapping and immediately posterior to distal portions of caeca. Anchor 63 (61–66; n = 12) long; straight, recurved point; deep root poorly developed (knob like); elongate superficial root. Superficial bar 38 (35–42; n = 7) long, 33 (27–38; n = 8) wide, with two robust, round, anterolateral projections, each one with a ventral lobe; subtriangular shield. Deep bar robust, with tapering extremities. Hook 30 (28–31; n = 8) long, with uniform shank provided by inconspicuous proximal bulb; hooklet slender, 6 (6–7; n = 8) long; recurved delicate point reaching toe limit, almost 90º angled; shafts elongate, straight; heel round; toe acute, depressed; shelf slightly convex; FH loop about 1/2 of shank length.

Remarks: Gyrodactylus decemmaculati n. sp. resembles Gyrodactylus unami García-Vásquez, Razo-Mendivil & Rubio-Godo, 2015, Gyrodactylus pictae Cable, Van Oosterhout, Barson & Harris, 2005, and Gyrodactylus turnbulli Harris, 1986 from cyprinodontiform fishes in having certain similarities in the morphology of the hooklet (Figure 11). Gyrodactylus unami differs by having a squarish heel and an almost straight point, forming a right angle with hooklet shaft. Additionally, G. unami differs from G. decemmaculati n. sp. by a shallow “M” notch at the dorsal edge of the superficial bar. Gyrodactylus pictae differs in the shape of the toe, the slightly recurved shaft and the posteriorly-divided shield of the ventral bar (Cable et al., 2005). The hooklets of G. turnbulli are larger than those of G. decemmaculati, and have a recurved shaft, robust base, and non-prominent heel (Harris, 1986). Gyrodactylus pictae and G. turnbulli differ from G. decemmaculati n. sp. by short anterolateral projections of the superficial bar.

Moreover, G. decemmaculati n. sp. resembles other neotropical gyrodactylids such as Gyrodactylus carolinae Boeger, Ferreira, Vianna & Patella, 2014, found in characiform fishes, in the morphology of its superficial bar. However, G. carolinae differs by having hooklets with a triangular base, short shafts and a round, prominent heel (Boeger et al., 2014).