Astyanax boliviensis, 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 : 10-13

Astyanax boliviensis sp. nov.

urn:lsid:zoobank.org:act:A4DF0719-0A75-4401-9F8D-D52AA7FFDDF6

Figs 4–5 , Table 1

Diagnosis

Astyanax boliviensis sp. nov. is a member of the orthodus species-group of Astyanax , differing from other species of the group in having lines extending from the tips of the chevrons on both the anterior and posterior extremes (proximal and distal sections of chevron extensions), forming extensions between the chevrons (vs chevrons without lines extending from their tips), except A. moorii comb. nov. which is distinguished by the number of lateral-line scales 39–42 (vs 44–50). It also differs from A. moorii comb. nov. in the upper jaw length> 34% HL (vs <47% HL). It further differs from A. villwocki by the absence of a dark stripe on the sides of the body (vs dark lateral stripe present or anterior prolongation of the caudal peduncle spot extending over the silvery lateral stripe). It further differs from A.orthodus , A. embera sp. nov. and A. yariguies in having a conspicuous rhomboidal caudal-peduncle spot with a short, anterior, prolongation that does not surpass a vertical through the anal-fin origin (vs spot on caudal peduncle a short polygon shape not surpassing the posterior tip of the anal fin in A. orthodus and A. embera sp. nov.; spot on caudal peduncle elongated as a stripe, continuing anteriorly to humeral region in A. villwocki). It differs from A. bopiensis nom. nov., in having fewer than four teeth extending over less than one third of the maxillary (vs more than five teeth extending over more than two thirds of the maxillary).

Etymology

The specific epithet boliviensis refers to Bolivia, the country where the type series was collected.

Material examined

Holotype

BOLIVIA: 87.9 mm SL, La Paz, Iturralde Province, Amazon River Basin, Madeira-Beni-Madidi- Candelaria River drainages, Candelaria River at La Candelaria , 13º35′21.88″ S, 68º41′31.06″ W, 304 m a.s.l. ( CBF 13504 ).

Paratypes

BOLIVIA: Iturralde, La Candelaria, Ami National Park, Madidi River drainage : 5 specimens (sex unknown), 33.1–89.5 mm SL ( CBF 7592 ) ; 8 specimens (sex unknown), 57.0– 72.6 mm SL, 2 specimens (sex unknown) C&S, 49.0– 75.2 mm SL ( CBF 7434 ); 12 specimens (sex unknown), 32.3–76.7 mm SL ( CBF 7594 ); 4 specimens (sex unknown), 43.6–63.3 mm SL, 1 specimen (sex unknown) C&S, 72.2 mm SL, Ixiamas ( CBF 2828 ) . – Isiboro, Mamoré River drainage : 8 specimens (sex unknown), 44.7–58.1 mm SL, de Villa River ( UMSS 4692 ) ; 4 specimens (sex unknown), 49.4–86.0 mm SL, Rancho Cuatro Esquinas ( UMSS 3750 ); 15 specimens (sex unknown), 54.7–79.0 mm SL, Colonia River San Carlos ( UMSS 5282 ) .

PERU: Puno, Sandia province : 2 specimens (sex unknown), 40.9–73.9 mm SL , 2 specimens (sex unknown) C&S, 70.3 mm SL, Tavara River 2 km from the mouth of Quebrada Grande, Zona Reservada, Tambopata-Candamo ( MUSM 3410 ) .

Description

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

Premaxillary teeth in two series; outer series with four tricuspid teeth covering three most medial teeth of inner series; inner tooth row with five pentacuspid teeth. Maxilla long, of same width along entire length, with three teeth in anterior-most part of ventral margin; anterior-most teeth pentacuspid; remaining two teeth tricuspid. Dentary with four anterior teeth pentacuspid, followed laterally by 8–11 smaller teeth of increasing posterior inclination, reducing from tri- to unicuspid.

Pored scales of lateral line 39(2), 40(10), 42(3)(n = 15), transverse scales from lateral line to dorsal-fin origin 7(1), 8(1) 10(13) (n = 15), scales from lateral line to anal-fin origin 7(2) 8(13) (n = 15), scales from lateral line to pelvic-fin insertion 6(3), 7(2), 8(10) (n = 15). Predorsal midline covered with bilobed medial scales for more than ¾ of its length, naked anteriorly.

Dorsal-fin rays iii 9 (n = 15); 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. Adipose-fin origin anterior to vertical through insertion of last anal-fin ray. Pectoral-fin rays i 10 (10), i 11 (1), i 14 (4). Pelvic-fin rays i 6–7 i. Anal-fin rays iii 23–30, first simple rays only visible in cleared and stained material. Anal-fin origin posterior to vertical through insertion of last dorsal-fin ray ( Table 1 ).

Caudal-fin rays 10–10; dorsal lobe with 12(4), 14(1) procurrent rays, ventral with 10(5) procurrent rays. Upper 10(5) principal caudal-fin rays associated with four dorsal hypurals, next 9(5) associated with three ventral hypurals and last principal ray associated with last hemal spine. Total vertebrae 35(5), including those of Weberian apparatus: precaudal centra 16(3) and 17(2), last three without true pleural rib. Caudal centra 18(3), 19(2). 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, arc- or sigmoid-shaped, inconspicuous and covers two to three scales above lateral-line. Individual scales on sides of body with spots or dots. Caudal peduncle 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.

Distribution

Known from the drainages of the Madidi and Mamoré Rivers, tributaries of the Madeira River, Upper Amazon River Basin of Bolivia and Peru ( Fig. 4 ).

Figures

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

Fig.5.Astyanaxboliviensissp.nov.,paratype,79.0 mmSL,ColoniaSanCarlosRiver, Isiboro,Mamoré, Bolivia (UMSS 5282). 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.