Astyanax gandhiae, 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 : 13-15

Astyanax gandhiae sp. nov.

urn:lsid:zoobank.org:act:DB1A95AA-8E70-40F4-B739-043872A32906

Figs 4 , 6 , Table 1

Diagnosis

Astyanax gandhiae sp. nov. is a member of the orthodus species-group of Astyanax differing from others members of the group ( A. orthodus , A.villwocki, A. superbus , A. bopiensis nom. nov., A. boliviensis sp. nov., A. yariguies comb. nov. and A. embera sp. nov.) in lacking a spot on the caudal peduncle. It can be further distinguished from A. villwocki by having a short lateral stripe extending from the caudal spot, that does not extend anteriorly beyond a vertical through the origin of the anal fin (vs lateral stripe extending anteriorly beyond a vertical through anterior origin of the anal fin). It differs from A. bopiensis nom. nov. in having fewer teeth that do not cover more than a third of the length of the maxillary (vs a larger number of teeth covering more than two thirds of the maxillary). It differs from A. moorii comb. nov. for dorsal-fin-hypural distance less than 45% SL(vs more than 50), by dorsalpectoral distance greater than 50% SL (vs less than 50), interorbital distance greater than 32% HL (vs less 32) and by upper jaw length than less 35% HL (vs greater than 40).

Etymology

This species epithet is named in homage to the late Mrs Maria Gandhi Calderon, mother of the first author, and used as a noun in apposition.

Material examined

Holotype

PERU: 89.4 mm SL, Department of Amazonas, Condorcanqui Province, Marañon River Basin, upper Cenepa River drainage , 3°58′15″ S, 78°41′15″ W ( MUSM 46845 ) .

Paratypes

PERU: Department of Amazonas, Amazon River Basin, Condorcanqui, upper Cenepa River drainage : 14 specimens (sex unknown), 62.1–109.6 mm SL, Quebrada Capitán ( MUSM 20891 , MUSM 21278 ) ; 2 specimens (sex unknown), 56.1–68.7 mm SL, Capitán Quebrada ( MUSM 21278 ) ; 2 specimens (sex unknown), 85.9–97.1 mm SL, Quebrada Capitán Ponce , 750 m a.s.l. ( MUSM 21287 ) ; 1 specimen (sex unknown), 85.7 mm SL, collected with holotype ( MUSM 21300 ) ; 1 specimen (sex unknown), 65.4 mm SL, Capitan Ponce Bravo Quebrada , 3°46′41.40″ S, 78°20′4.61″ W ( MUSM 21312 ) ; 1 specimen (sex unknown), 64.0 mm SL, Quebrada Platanal , 3°38′24.94″ S, 72°18′40.81″ W ( MUSM 21372 ) ; 11 specimens (sex unknown), 38.7–49.3 mm SL, Ucayali department, Atalaya province, Sepahua, Lazaro Creek, tributary of Mishahua River, Ucayali River Basin , 11°14′15.87″ S, 72°58′26.65″ W, 248 m a.s.l. ( MUSM 35474 ) ; 1 specimen (sex unknown), 44.5 mm SL, Huacamayo River, km. 155 on road from Pucallpa to Tingo-Maria, Padre Abad province, Ucayali River Basin ( MUSM 2392 ) ; 1 specimen (sex unknown), 93.9 mm SL , 2 specimens (sex unknown) C&S, 59.0– 61.2 mm SL, Víbora Creek, tributary of Pisqui River , Loreto, upper Amazon ( MUSM 46846 ) ; 3 specimens (sex unknown), 50.0– 98.6 mm SL, Tavara River 2 km from mouth of Quebrada Grande, Puno, Sandia, Zona Reservada Tambopata-Candamo ( MUSM 46847 ) .

Description

Body compressed, greatest body depth at or anterior to dorsal-fin origin. Mouth terminal. Dorsal profile of head straight between snout tip and posterior margin of supraoccipital spine, convex between head and dorsal fin, convex between head and at base of dorsal fin, convex between last dorsal-fin ray to adipose-fin origin. Dorsal and ventral caudal-peduncle margins straight. Ventral profile convex between tip of snout and pelvic-fin insertion.

Premaxillary teeth in two series; outer series with four tricuspid teeth covering three medial most teeth of inner series; inner row with five pentacuspid teeth. Maxilla long, of same width along entire length, with 3–6 tricuspid teeth set in anterior-most part of ventral margin. Dentary with anterior four teeth pentacuspid, followed laterally by 8–9 smaller teeth that progressively increase in postero-medial inclination, decreasing from tri- to unicuspid; number of lateral teeth highly variable.

Pored scales of lateral line 40(15), 41(3), 42(1) (n = 18), scales from lateral line to origin of dorsal fin 8(18) (n = 18), scales from lateral line to origin of anal fin 7(10), 8(8) (n = 18), scales from lateral line to insertion of pelvic fin 6(11), 7(7) (n = 18). Rays of dorsal fin iii 9, 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 through insertion of last ray of anal fin. Rays of pectoral fin i 10 ii (11), i 12 ii (7). Rays of pelvic fin i 7 (18). Rays of anal fin iii–iv 25–27; first simple rays only visible in cleared and stained material. Origin of anal fin posterior to vertical through insertion of last ray of dorsal fin ( Table 1 ).

Caudal fin with 10–9 principal rays; dorsal lobe supporting 12(4), procurrent rays; ventral lobe, 10(4) procurrent rays. Upper 10(4) principal caudal-fin rays associated with four dorsal hypurals, next 9(4) associated with three ventral hypurals.

Total vertebrae 37(4), including those of Weberian apparatus: precaudal centra 17(2) and 18(2), last two without true pleural rib. Caudal centra 19(2), 20 (2). Epineurals 34(2); posterior-most epineural occasionally not reaching anterior surface of urostyle; epipleurals 21(2). Caudal skeleton with seven hypurals. First dorsal three hypurals with swollen anterior margin in contact with urostyle.

Pigmentation in alcohol

Sides of body yellowish, without reticulated pattern over dorsal region of coelomic cavity, silvery stripe extending from humeral region to base of caudal peduncle, 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 lacking 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 formed by two layers of pigment, with brown melanophores distributed in thin superficial layer of epithelium (Layer 1, Fig. 1 ) and another deeper layer consisting of dark melanophores (Layer 2, Fig. 1 ). Layer 2 forming polygon-shaped spot made up of two different layers of melanophores that do not precisely overlap, forming vertices on lateral margins, usually resulting in four-sided spot located between third and 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. Individual scales on sides of body lacking spots or dots. Spot on caudal peduncle absent. Lateral stripe formed by dispersed brown pigment present only on posterior portion of body, located above posterior two-thirds of anal-fin base and extending on to caudal peduncle. Pectoral, pelvic, dorsal and anal fins hyaline; pigment present on interradial membranes of middle caudal-fin rays.

Sexual dimorphism

No sexual dimorphism observed, no hooks found on fins.

Distribution

Astyanax gandhiae sp. nov. is known from the Ucayali and Madre de Dios River drainages, Cenepa River, tributary from Marañón River, Upper Amazon Basin, Peru ( Fig. 4 ).

Figures

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

Fig. 6. Astyanax gandhiae sp. nov., holotype, 89.4 mm SL, Condorcanqui, Amazonas, Upper Cenepa River drainage (MUSM 46845). 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.