Astyanax moorii ( Boulenger, 1892 ) Ruiz-C & Román-Valencia & Taphorn & Buckup & Ortega, 2018

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 : 30-32

Astyanax moorii ( Boulenger, 1892) comb. nov.

Figs 4 , 13 , Table 2

Tetragonopterus moorii Boulenger, 1892: 11 , pl. 2 fig. 1. Original description, type locality: Chapala Plateau , Mato Grosso State, Brazil.

Astyanacinus moorii – Eigenmann 1910: 435; Pearson 1924: 41. (Beni River Basin at Tumupasa; Popoi River, Upper Beni; Ixiamas; Huachi; Rurrenabaque).

Diagnosis

Astyanax moorii comb. nov. is a member of the orthodus species-group of Astyanax , differing from other species of the group in having an inconspicuous spot in the caudal peduncle (vs conspicuous peduncle spot) and by the length of the upper jaw more than 47% HL (vs less than 47% HL), and from A. orthodus , A. superbus , A. yariguies and A. gandhiae sp. nov. in the interorbital distance being 27.4– 31.4% HL (vs> 32% HL); it is distinguished from A. bopiensis nom. nov. and A. gandhia e sp. nov., A. orthodus and A. embera sp. nov. by the distance between the dorsal and pectoral fins 37.4–40.3% SL (vs more than 40.4 SL); from A. villwocki by the absence of a dark band on the side surface of the body (vs present) and from A. bopiensis nom. nov. by the maxillary length 34.0–37.9% HL (vs 46.7–58.9% HL).

Etymology

The specific epithet moorii refers to the collector Mr. Spencer le Marchant Moore, who collected the type material of Astyanax moorii comb. nov.

Type material

Lectotype (examined from photograph)

BRAZIL: 1 specimen, 65.2 mm SL; Upper Paraguay Chapala Plateau , Mato Grosso State (BMNH 1892.4.20.51; photo BMNH 1892-4-20-51-2 2 ) .

Paralectotype

BRAZIL: 1 specimen, SL unknown; Upper Paraguay Chapala Plateau , Mato Grosso State (BMNH 1892.4.20.52; photo BMNH 1892-4-20-51-2 1 ) .

Material examined

BRAZIL: State of Mato Grosso: 2 specimens (sex unknown), 50.3–64.7 mm SL, stream ("riacho") near Manso Hydro-Electric Plant, Cuiabá River Basin, in the region of Fazenda Nova ( MNRJ 29284 ) ; 3 specimens (sex unknown), 43.2–59.0 mm SL, Forte Stream ("ribeirão"), tributary of the Coxipó-Açu River, Cuiabá River Basin , Municipality of Cuiabá ( MNRJ 1190 ) .

Description

Body compressed, greatest body depth at or anterior to dorsal-fin origin. Mouth terminal. Anterior half of dorsal profile of head slightly straight; profile between posterior margin of supraoccipital spine and dorsal-fin origin as between last dorsal-fin ray and adipose-fin origin is slightly convex. Dorsal and ventral margins of caudal peduncle straight. Ventral profile convex from tip of snout to pelvic-fin insertion, feature visible in both sexes.

Premaxillary teeth in two series; outer series with three to five tricuspid teeth, so the outer lateral tooth; inner tooth row with five pentacuspid teeth. Maxilla with three to four teeth in anterior-most part of ventral margin. Dentary with four anterior teeth pentacuspid, followed laterally by 6–10 smaller teeth of increasing posterior inclination, reducing from tri- to unicuspid.

Pored scales of lateral line 41(1), 44(2), 45(1), 46(1), 47(1), 50(1), (n = 7), transverse scales from lateral line to origin of dorsal fin 8(5) a 9(2) (n = 7), scales from lateral line to origin of anal fin 6(1), 7(5), 8(1) (n = 7), scales from lateral line to insertion of pelvic fin 6(5), 7(2), (n = 7). Predorsal midline covered with bilobed medial scales for more than ¾ of its length, naked anteriorly. Rays of dorsal fin iii 9 (n = 7); first simple ray small, only visible in cleared and stained specimens; second simple ray about half length of third simple ray. Distal margin of dorsal fin slightly convex. Origin of adipose fin anterior to vertical line through insertion of last ray of anal fin. Rays of pectoral fin i 12 (1), i 13 (5), i 14 (1). Pelvicfin rays i 6 (1), i 7 (6). Rays of anal fin iii(2), iv(v) and 28(1), 29(4), 30(1) and 32(1), first simple rays only visible in cleared and stained material. Origin of anal fin posterior to vertical line through insertion of last dorsal-fin ray.

Caudal-fin rays10–9, dorsal lobe with 11(5), 13(2) procurrent rays, ventral with 10(7) procurrent radios. Upper 10(5) principal rays of caudal fin associated with four dorsal hypurals, next 9(2) associated with three ventral hypurals and last principal ray associated with last hemal spine. Total vertebrae 37(3), including those of the Weberian apparatus: precaudal centra 15(2) y 16(1), last two without true pleural rib. Caudal centra 19(2), 20(1). Epineurals 36(1), 38(2), 40(1), 41(1) posterior-most epineural may not reach anterior surface of urostyle; epipleurals 20(5). Caudal skeleton with seven hypurals. First three hypurals with swollen anterior margins in contact with urostyle.

Pigmentation in alcohol

Sides of body yellowish, without reticulated pattern, with silver midlateral 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 with 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 (anterior and posterior) humeral spots. The anterior spot is formed by two layers of pigment, with brown melanophores distributed in thin superficial layer of the epithelium (Layer 1, Fig. 1 ); deeper layer that with dark melanophores (Layer 2, Fig. 1 ). Layer 2 forming polygon-shaped spot, with two parts, forming vertices on margins, usually forming four-sided spot located from second to fifth or sixth scale of lateral series. Posterior humeral spot situated two scales posterior to anterior humeral spot, rectangle-shaped, inconspicuous and covering two to three scales above lateral-line. Individual scales on sides of body without spots or dots. Caudalpeduncle spot rhomboid with short anterior extension over silver lateral stripe not surpassing anal-fin origin, dark pigment of caudal peduncle stripe continued on to middle caudal-fin rays with dark pigment present on tips of remaining rays. Pectoral, pelvic, dorsal and anal fins hyaline.

Sexual dimorphism

No sexual dimorphism was observed, no hooks found on fins.

Taxonomic comments

This species is transferred from Astyanacinus to Astyanax because it shares the anteriorly directed V-shaped chevrons along myomere junctions with members of the orthodus species-group. The conspicuous polygon-shaped humeral spot is also similar ( Fig. 1 ), consisting of dark melanophores.

Distribution

Known from the Alto Paraguay River in Brazil ( Fig. 4 ).

Figures

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

Fig. 13. Astyanax moorii (Boulenger, 1892), 64.7 mm SL, Creek near the Manso Hydroelectric Plant, Cuiabá River drainage, Fazenda Nova region, Mato Grosso State, Brazil (MNRJ 29284). 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.