Acrobrycon tarijae Fowler, 1940

Brinoccoli, Yanina F., Bogan, Sergio, Arcila, Dahiana, Rosso, Juan J., Mabragana, Ezequiel, Delpiani, Sergio M., Astarloa, Juan Martin Diaz de & Cardoso, Yamila P., 2022, Molecular and morphological evidence revalidates Acrobrycon tarijae (Characiformes, Characidae) and shows hidden diversity, ZooKeys 1091, pp. 99-117 : 99

Acrobrycon tarijae Fowler, 1940

Figs 2 , 3

Acrobrycon tarijae Fowler, 1940:50 [Type locality: Lipeo River, branch of Bermejo River, Department of Tarija, Bolivia (currently the Lipeo River type locality was relocated to the province of Salta, Argentina)].

Amended diagnosis.

Acrobrycon tarijae is distinguished from A. ipanquianus by the lower number of vertebrae [37 (1), 38 (3+holotype+3 paratypes), 39 (1+2 paratypes) vs. 41 (2 paratypes), 42 (holotype+2 paratypes)], and pleural ribs (12 (1 paratype), 13 (5+holotype+4paratypes) pairs vs. 14 (holotype+2 paratypes) pairs in the type series). Acrobrycon tarijae is distinguished from A. starnesi by the number of perforated scales of the lateral line [51 (1), 52 (1), 54 (4), 55 (2), 56 (1) 57 (7), 58 (5), 59 (7), 60 (2) vs. 61 to 66], and the number of horizontal-scale rows around the caudal peduncle (19 (12), 20 (9), 21 (9) vs. 22 to 26). Acrobrycon tarijae can be distinguished from A. ortii by the number of branched anal-fin rays [23 (3), 24 (9), 25 (10), 26 (7), 27 (1) vs. 19 to 21].

Description.

The description of A. tarijae follows Arcila et al. (2013), including some adjustments to the ranges as indicated below. Acrobrycon tarijae is a characid of moderate size (can exceed 114 mm of standard length, SL), with an elongated body. Greater body depth in the sector behind the origin of the pectoral fins and before the dorsal-fin origin. Dorsal profile convex from the tip of the snout to the origin of the dorsal fin, slightly depressed along the nape, almost straight along the base of the dorsal fin and slightly concave along the caudal peduncle. Ventral profile convex. Dorsal-fin origin anteriorly than the origin of the anal fin. Rounded muzzle in lateral view.

Terminal mouth slightly upwards. Maxilla extending posteriorly beyond the vertical through the anterior margin of the orbit, but not reaching the vertical through the posterior border of the pupil. Posteroventral border of the maxilla convex and posterior margin concave. Premaxillary teeth in two different rows, outside row with 4-5 teeth and internal row with 4 teeth. Larger teeth with five cusps; smaller teeth with three cusps. Maxillary teeth 6-11. Larger anterior maxillary teeth with 1-3 cusps, other smaller teeth with 1-2 cusps. Dentary with 4 large anterior teeth with 5 cusps, followed by 6-10 smaller teeth with 1-3 cusps.

Tip of the pelvic fin does not reach the anal-fin origin, cycloid scales, with 4 to 8 rays along the exposed surface over most of the body and 14 to 17 rays on scales bordering the opening of the caudal pocket. Lateral line with 51-60 perforated scales. Predorsal scales 19-26. Horizontal-scale rows around caudal peduncle 19-21.

Dorsal-fin rays ii+8. Some specimens with posteriormost dorsal ray unbranched and others with a branched condition in this ray, although this is restricted to a very small part of its distal tip. Small adipose fin. Anal fin with v,vi-23-26. Pectoral fin with i, 9-10. Pelvic-fin rays i, 7 (12), 8 (18). Caudal fin with two well differentiated lobes, with i, 9-10.

Sexual dimorphism.

Mature males present a hypertrophied terminal caudal-fin squamation forming a caudal pocket and also have bony hooks on the anal, pelvic, and caudal-fin rays.

Coloration in live specimens.

Gray ochre dorsal coloration from the nostrils to the caudal peduncle. Silvery flanks, paler at ventral section and with purplish-bluish reflection dorsally. A golden to greenish coloration bordering the lateral line. A silver wide band behind the humeral spot progressing distally to the end of the body, continuing with a marked black pigmentation in the medial rays of the caudal fin. Circum-orbital bones generally silver, the fifth and sixth infraorbitals may have purplish reflections. Operculum with conspicuous violet reflections, turning greenish above and ahead this bone. A conspicuous humeral dark spot vertically elongated. Pectoral and ventral fins whitish. The dorsal and adipose fins smoothly yellowish. The anal fin gray or yellowish usually with a whitish lower margin (Suppl. material 1: Fig. S2).

Coloration in alcohol.

Preserved specimens, body brown, with darker dorsum. Humeral spot dark, with a well-defined upper part and a fainter lower expansion. In many specimens the lower expansion of humeral spot absent. The lateral band dark, thin at the level of the humeral spot, and shortly wider until the distal end of the body. This band conspicuous in some specimens and very faint in others. The middle rays of the caudal fin black.

Figures

Figure 2. Pictures of the series types of A. tarijae. A holotype B-E paratypes. Scale represents 1 cm. Images from K. Luckenbill, cortesy Academy of Natural Sciences, Drexel University.

Figure 3. Count of vertebrae in holotypes of A A. tarijae and B T. ipanquianus. Abbreviation W represents the first four vertebrae of the Weber complex. Images from K. Luckenbill, cortesy Academy of Natural Sciences, Drexel University.