Astyanax villwocki Zarske & Géry, 1999

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 : 24-27

Astyanax villwocki Zarske & Géry, 1999

Figs 4 , 11 , Table 2

Astyanax villwocki Zarske & Géry, 1999: 200 , figs 1–2. Original description, type locality: Rio Pacal , Rio Pachitea Basin, Departamento Ucayali, Peru.

Diagnosis

Astyanax villwocki is a member of the orthodus species-group of Astyanax differing from the other members of the group by the absence of a distinct caudal-peduncle spot (vs present) and having instead a dark stripe, continuing anteriorly to the humeral region (vs absent).

Etymology

Named after Prof. Wolfgang Villwock, Hamburg, who collected some of the first specimens of the type material, including the holotype, and made them available for study.

Material examined

Holotype

PERU: 98.1 mm SL, Ucayali, Peruvian Amazon Basin, Pachitea River drainage, Pacal River ( MTD F 22400 ).

Other material

PERU: 1 ♀, 118.8 mm SL, Ucayali department, Coronel Portillo province, Instituto Veterinario de Investigaciones Tropicales y de Altura ( IVITA) Ivita Piscigranja, Pucallpa, Ucayali ( MUSM 148 ) ; 1 ♀, 43.6 mm SL, Madre de Dios department, Manu Province, Manu National Park Manu River, Pakitza Lavandería Creek ( MUSM 2285 ) ; 4 ♀♀, 43.4–54.4 mm SL, Madre de Dios, Manu, Manu National Park, Picaflor Creek ( MUSM 2499 ) ; 8 ♀♀, 33.2–42.6 mm SL, Madre de Dios, Manu, PNM, Picaflor Creek ( MUSM 4288 ) ; 2 ♀♀, 50.4–101.6 mm SL, Cusco, La Convención, Echarate, Urubamba River , quebrada Hayanamato ( MUSM 14461 ) ; 16 ♀♀, 55.1–95.5 mm SL, Loreto, Ucayali, Rashaya,Víbora Creek, Pisqui River Basin ( MUSM 15881 ) ; 1 ♀, 69.3 mm SL, Loreto, Corrientes River, Andoas ( MUSM 28664 ) ; 2 ♂♂, 2 ♀♀, 95.0– 110.2 mm SL, Ucayali, department, Coronel Portillo province, Yucamia River, Ucayali River Basin ( MUSM 33560 ) ; 1 ♂, 4 ♀♀, 98.2–112.5 mm SL, Ucayali, Coronel Portillo, Pucallpa Pichaya River ( MUSM 33609 ) ; 1 ♂, 122.3 mm SL, Loreto, Maynas, Pucacuro River , 175 m a.s.l. ( MUSM 34168 ) ; 1 ♀, 75.5 mm SL, Ucayali department, Coronel Portillo ( MUSM 34977 ) ; 2 ♂♂, 114.6–115.8 mm SL, Ucayali, Coronel Portillo , Blanca stream, Ucayali River Basin ( MUSM 34994 ) .

COLOMBIA: 1 ♀, 87.9 mm SL, Caquetá, Yurayaco, Amazon River Basin, Inchiyaco River, on the road from Villa Garzón to San José de Fragua ( IUQ 121 ) ; 1 ♀, 84.3 mm SL, Caquetá, Yurayaco River, on the road from Yurayaco to Villa Garzón ( IUQ 180 ) ; 1 ♀ C&S, 60.4 mm SL, Caquetá, Creek tributary Yurayaco River, road Villa Garzón ( IUQ 1218 ) ; 1 ♂, 96.5 mm SL, Putumayo, Amazon River Basin, Orito Creek, south of the farm La Palma , ca 1 km from the Guamez River, vereda Calimonte, Orito ( IUQ 1871 ) ; 1 ♂, 47.4 mm SL, Caquetá, Amazon River Basin, Yurayaco River, in the village Yurayaco ( IUQ 1893 ) ; 1 ♂, 63.5 mm SL, Pazalosa Creek, village in Usmo , Caquetá River ( IUQ 1888 ) ; 1 ♀, 77.7 mm SL, Caquetá ( IUQ 3593 ) .

ECUADOR: 1 ♂, 2 ♀♀, 71.3–80.4 mm SL, Napo, Sunka flooded area (“estero”) at 20 minutos or 0.5 Km from Sunka Well ( MEPN 2723 ) ; 3 ♀♀, 72.3 mm SL, Napo, Sunka flooded area (“estero”) at 20 minutos or 0.5 Km from Sunka Well ( MEPN 2769 ) ; 1 ♀, 13.4 mm SL, Pastaza, Santi flooded area (“estero”) at 2 Km from Manalí Well at la Trucha No. 3 ( MEPN 6176 ) ; 2 ♀♀, 116.0– 118.9 mm SL, 1 ♀ C&S, 111.5 mm SL, Pastaza, Danta River 500 m from the exploration platform ( MEPN 6180 ) ; 1 ♂, 3 ♀♀, 81.5–91.7 mm SL, 1 ♂ C&S, 72.3 mm SL, Amazon River Basin, Sovelca flooded area (“estero”), tributary Napo River ( MEPN 6186 ) ; 1 ♀, 88.52 mm SL, Sucumbios, 300 m, Bocapore River to 2 km, at 50 m de la valvula del pozo Capiron , 00°31′18″ S, 76°29′28″ W ( MEPN 8422 ) ; 2 ♀♀, 116.3–119.3 mm SL, Yeye River , 200 m from head of Ginta Well, Sucumbios ( MEPN 9560 ) .

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, straight between supraoccipital spine and dorsal-fin origin, convex between head and at base of 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 tip of snout to pelvic-fin insertion.

Premaxillary teeth in two series; outer series with four tricuspid teeth covering three most medial teeth of inner series; inner row with five pentacuspid teeth. Maxilla long, of same width along entire length, with 3–5 tricuspid teeth set in anterior most part of ventral margin. Dentary with anterior four teeth pentacuspid, followed by 7–9 teeth smaller, progressively inclined posteromedially, varying from tri- to unicuspid; proportion of tri- vs unicuspid teeth quite variable.

Pored scales of lateral line 39(4), 40(4), 41(6), 42(3), 44(1) (n = 18); transverse scales between lateral line and origin of dorsal fin 7(18), 8(1) (n = 19); scales between lateral line and origin of anal fin 6(3), 7(15) (n = 18); scales between lateral line and insertion of pelvic fin 6(13), 7(5) (n = 18). Predorsal midline covered with bilobed medial scales for more than ¾ of its length, naked anteriorly. Rays of dorsal fin iii 9 (n = 18); first simple ray small, easily visible only in C&S specimens, detectable with dissecting needle in non-C&S 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 anal-fin ray. Rays of pectoral fin i 12 (8), i 13 (10) (n = 18). Rays of anal fin iii 25 (10), iii 26 (7), iii 27 (2); first simple rays only visible in C&S material. Origin of anal fin posterior to vertical line through insertion of last ray of dorsal fin. Caudal fin with 9(1), 10(2) principal rays in dorsal lobe and 10(1), 11(2) in ventral lobe, dorsal lobe with 10(3) procurrent rays, ventral with 8(2), 9(1). Principal rays of dorsal lobe associated with four dorsal hypurals, those of ventral lobe associated with three ventral hypurals.

Total vertebrae 36(1), 37(2), including those of the Weberian apparatus: precaudal centra 17(1), 18(2); last two vertebrae modified with elongate transverse process not in contact with dorsal tip of its rib; caudal centra 19(3). Epipleurals 21(1), 22(2). Epineurals 30(1), 32(2), posterior-most epineural occasionally reaching anterior surface of urostyle. Hypurals 7(3); first dorsal hypural with anterior margin swollen, without projections that articulate the urostyle; second and third hypural dorsal with anterior margin swollen that contacting urostyle.

Pigmentation in alcohol

Sides of body yellowish, without reticulated pattern over the lateral surface of the body. Dark lateral stripe from humeral region to caudal-peduncle base, overlain by series of chevron-shaped marks formed by dark lines along myosepta between myotomes extending from anterior third of anal fin; only distal tips of chevrons located to midlateral stripe visible, chevron-shaped marks less evident in adults (≥ 3 cm SL). Pigmented muscle septae that form series of chevrons not coinciding with horizontal rows of scales, not aligned with scale edges. Chevrons present in juveniles, immature specimens and adults, without distal extensions.

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 thin superficial layer of the epithelium (Layer 1, Fig. 1 ), deeper layer of dark melanophores (Layer 2, Fig. 1 ). Layer 2 forms a polygon-shaped spot consisting of two groups of melanophores that do not precisely overlap, typically forming four-sided spot. Second humeral spot located one scale posterior to anterior humeral spot, arc- or sigmoid-shaped, inconspicuous, covering two to three scales above lateral line. Spot on caudal peduncle absent. Pectoral fins mostly hyaline; melanophores present on distal tips of pelvic-fin rays and interradial membranes of dorsal, caudal and anal fins.

Sexual dimorphism

Distribution of hooks on fins varying from 12–16 in the pelvic fin, 15–17 in the anal fin; males with longer unbranched rays in dorsal, pectoral and pelvic fins; distal tips of latter two fins extend posteriorly to pelvic-fin origin and anal-fin insertion, respectively.

Distribution

Amazon River drainages of Peru, Ecuador and Colombia ( Fig. 4 ).

Comments on type specimens of Astyanax villwocki

Astyanax villwocki was described by Zarske & Géry (1999) based on specimens from the drainages of the Pachitea River in Peru, the Beni River in Bolivia and the Madeira River. However, examination of the type specimens revealed differences among specimens included in the original description. Specimens from the Madeira River (MTDF 2214- 22115; ZFMK 20781) do not have the diagnostic characters of A. villwocki; they lack the lateral stripe (vs dark lateral stripe present) and have a series of chevrons extending along the entire lateral stripe (vs chevron series not surpassing anterior third of anal fin). We therefore re-identify the specimens from the Madeira River as Astyanax boliviensis sp. nov.

Figures

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

Fig. 11. Astyanax villwocki Zarske & Géry, 1999, 74.7 mm SL, Caquetá River, Colombia (IUQ 3593). 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.