Astyanax superbus Myers, 1942

Ruiz-C, Raquel I., Román-Valencia, César, Taphorn, Donald C., Buckup, Paulo A. & Ortega, Hernán, 2018, Revision of the Astyanax orthodus species-group (Teleostei: Characidae) with descriptions of three new species, European Journal of Taxonomy 402, pp. 1-45 : 22-24

Astyanax superbus Myers, 1942

Figs 4 , 10 , Table 2

Astyanax superbus Myers, 1942: 92 , fig. 2. Original description, type locality: small brook tributary to Río Tamanaco at Camoruco, 20 km NE of San Carlos, Cojedes state, Venezuela.

Diagnosis

Astyanax superbus is a member of the orthodus species-group of Astyanax , differing from all other members of the group by the presence of longitudinal, wavy alternating dark and silver stripes on the sides of the body (vs pigment pattern reticulated, outlining scales, or sides of body uniformly pigmented) and the roughly rectangular shape of the caudal-peduncle spot, whose anterior margin diffusely fades out across the midlateral stripe, but does not surpass a vertical line through origin of the anal fin (vs spot on caudal peduncle extending anteriorly as a black stripe across the midlateral stripe reaching the humeral region in A. villwocki, or spot on caudal peduncle restricted to the caudal peduncle in A. orthodus and A. embera sp. nov.; or a conspicuous, rhomboid with short anterior extension that does not extend anteriorly beyond vertical line through origin of anal fin in A. bopiensis nom. nov.; or an inconspicuous spot on caudal peduncle in A. gandhiae sp. nov.). Astyanax superbus also has fewer epineurals than other members of the orthodus group (31–32 vs 33–34). It is distinguished from A. moorii comb. nov.

by having the preanal distance less than 63% SL (vs more than 63% SL), the interorbital distance more 32% SL (vs less than 32% SL) and the length of the upper jaw less than 32 HL (vs more than 46% HL).

Etymology

The meaning of the name superbus was not explained in the original description. It is based on the Latin adjective ‘superbus’ meaning ‘proud’, probably used in a positive way, meaning 'magnificent', as in the English word 'superb'.

Material examined

Holotype

VENEZUELA: 79.4 mm SL, Cojedes State, Orinoco River Basin, small brook tributary to Tamanaco River at Camoruco , 20 km NE of San Carlos ( SU 36489 ).

Other material

VENEZUELA: 1 specimen (sex unknown), 43.3 mm SL , 2 specimens (sex unknown) C&S, 45.7– 49.8 mm SL, Portuguesa State, Guache River , Portuguesa River drainage ( INHS 28666 ); 2 specimens (sex unknown), 64.1–87.8 mm SL , 2 specimens (sex unknown) C&S, 65.7–68.8 mm SL, Barinas State, Musao Uno Creek, Socopo-Barinas highway ( MCNG 6350 ) ; 3 specimens (sex unknown), 67.3– 70.4 mm SL, Portuguesa State, Guanare, Guache River at Garabote ( MCNG 36349 ) .

Description

Body compressed, greatest body depth at or anterior to dorsal-fin origin. Mouth terminal. Dorsal profile straight between snout tip and posterior tip of supraoccipital spine, convex between head and dorsal fin, convex between last dorsal-fin ray and adipose-fin origin. Caudal peduncle arched, with dorsal profile concave, ventral profile convex. Ventral profile convex from snout tip to posterior end of anal-fin base.

Premaxillary teeth in two series; outer series with four tricuspid teeth covering three most medial teeth of internal series; inner row with five pentacuspid teeth. Maxilla long, of same width along entire length, with 2–6 tricuspid teeth set in anterior most part of ventral margin. Dentary with anterior four teeth pentacuspid, followed by 10–12 teeth smaller, progressively inclined posteromedially, varying from trito unicuspid; proportion of tri- vs unicuspid teeth quite variable.

Pored lateral line scales 39(2), 40(3), 41(2), 42(1) (n = 8); transverse scales from lateral line to origin of dorsal fin 7(4), 8(4) (n = 8); scales from lateral line to origin of anal fin 7(4), 8(4) (n = 8); scales from lateral line to insertion of pelvic fin 6(7), 7(1) (n = 8). Predorsal midline series of scales incomplete; midline scales alternating with lateral scales overlapping on anterior two-thirds of predorsal series, continuous only in posterior part of predorsal area. Dorsal-fin rays iii 9 (n = 8), first simple ray small, easily visible only in C&S specimens, detectable in with dissecting needle in non-C&S specimens (n = 4); second simple ray about half length of third simple ray; distal margin of dorsal fin slightly convex. Adipose-fin origin anterior to vertical through insertion of last anal-fin ray. Pectoral-fin rays i 11 (1), i12 (4), i 13 (3) (n = 8). Anal-fin rays iii 27 (3), iii 28 (4), iii 29 (1) (n = 8). First simple rays only visible in C&S material. Anal-fin origin posterior to vertical through insertion of last dorsal-fin ray ( Table 1 ). Caudal fin with 10 principal rays in both dorsal and ventral lobes; 11(4) procurrent rays in dorsal lobe, 9(3) or 10(1) in ventral. Upper 10(4) principal rays associated with four dorsal hypurals, 9(8) associated with three ventral hypurals.

Total vertebra 36(2), 37(2) (n = 4), including those of Weberian apparatus: precaudal centra 16(2), 17(2), the last three without true ribs; caudal centra 19(2), 20(2). Epipleurals 21(2), 22(2). Epineurals 31(2), 32(2); posterior-most epineural occasionally not reaching anterior surface of urostyle. Hypurals 7(4); first dorsal hypural with anterior margin swollen; first, second and third hypural with anterior margin swollen and contacting urostyle.

Pigmentation in alcohol

Sides of body yellowish, with thin silver and dark wavy stripes over the lateral surface of the body. Silver stripe present from humeral region to caudal peduncle base, overlain by series of chevron-shaped marks formed by dark lines along myosepta between myotomes extending from dorsal region of coelomic cavity to caudal peduncle; pigmented muscle septae forming chevrons not coinciding with scale rows. Chevrons without distal extensions both in juvenile and adult specimens.

Dorsal region of head and body chestnut brown. Sides of cranium and ventral surface of body light brown, not silvery. Melanophores of humeral region forming two spots. Anterior spot formed by two layers of pigment: brown melanophores distributed in a thin superficial layer of the epithelium (Layer 1, Fig. 1 ), deeper layer of dark melanophores (Layer 2, Fig. 1 ). Layer 2 typically forms polygon shaped spot, consisting of two groups of melanophores that do not precisely overlap, forming four-sided spot extending from third to sixth or seventh scale of lateral series. Posterior humeral spot situated two or three scales posterior to the anterior humeral spot, arc- or sigmoid-shaped, inconspicuous, covering two to three scales above lateral-line. Caudal-peduncle spot roughly rectangular, with anterior margin diffuse, not extending anteriorly beyond vertical through anal-fin origin. Dorsal, pectoral, pelvic and anal fins hyaline.

Sexual dimorphism

Undetected in examined adults.

Distribution

This species is present in upland tributaries of the Apure River, a left-margin tributary to the Orinoco River in Venezuela ( Fig. 4 ).

Figures

Fig. 4.Distribution of speciesof the Astyanaxorthodus species-group(symbol includestypelocalities).

Fig. 10. Astyanax superbus Myers, 1942, 70.4 mm SL, Guache River, Garabote, Portuguesa state, Venezuela (MCNG 36349). Scale bar = 1 cm.

Fig.1.A.DistributionofpigmentinthehumeralregionofAstyanaxspecies.B.A.bimaculatus(Linnaeus, 1758).C.A.caucanus(Steindachner,1879).D.A.mexicanus(DeFilippi,1853).E.A.courensisBertaco, Carvalho & Jerep, 2010 (modified from Bertaco et al. 2010). The anterior humeral spot consists of two overlapping layers of pigment identified by numbers 1 and 2 (see Román-Valencia et al. 2015: fig. 1): 1. Diffuse vertical bar. 2. Horizontal spot with concentrated pigments.