Astyanax bopiensis, 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 : 16-19

Astyanax bopiensis nom. nov.

Figs 4 , 7 , Table 2

Astyanacinus multidens Pearson, 1924: 41 , pl. 9 fig. 4. Original description, type locality: Bolivia, Colorado River, lower Bopi River.

Diagnosis

Astyanax bopiensis nom. nov. is a member of the orthodus species-group, differing from other species of the group in having a reticulated pattern on the sides of the body formed by dark pigment on the medio-distal margins of scales (vs reticulated pattern absent); and in having 7 to 13 teeth on the maxilla covering at least half the length of its ventral margin (vs 0–6 teeth); there are four scales touching the base of the pectoral fin along its ventral margin (vs three scales along ventral margin of pectoral-fin base; Fig. 9 ); number of neural spines from the fourth vertebra to the first pterygiophore of the dorsal fin 7 to 11 (vs 5 to 6). It differs from A. moorii comb. nov. in having the dorsal-fin-hypural distance less than 45% SL (vs more 50% SL), by body depth less 34% SL (vs more 34% SL), by dorsal-fin length less 28% SL (vs more 28% SL), by dorsal pectoral-fin distance more than 50% SL (vs less than 50% SL), by pectoral-fin length less 21.5% SL (vs more than 21.5% SL), by pelvic-fin length less 16% SL (vs more than 16% SL), by maxilla length more than 46.5% HL (vs less than 40% HL) and by upper jaw length less 45% HL (vs more than 45% HL).

Etymology

The specific epithet bopiensis refers to the river where the original type material was collected. It is used as a noun in apposition.

Material examined

Lectotype

BOLIVIA: (sex unknown), 96.9 mm SL, Colorado River, Lower Bopi ( CAS 39955 ).

Paralectotypes

BOLIVIA: (sex unknown) 79.8–122.9 mm SL, Río Colorado, Lower Bopi ( CAS 236977 )

Non type material

PERU: 1 specimen (sex unknown), Puno, Sandia ( MUSM 3410 ) ; Madre de Dios ( MUSM 3418 , MUSM 3758 ) ; 1 specimen (sex unknown), 143.9 mm SL ( CAS 38955 ); 2 specimens (sex unknown), 49.4– 50.5 mm SL , 1 specimen (sex unknown) C&S, Puno, Sandia Tavara River, Zona Reservada Tambopata- Candamo ( MUSM 3410 ) ; 5 specimens (sex unknown), 38.9–57.3 mm SL , 2 specimens (sex unknown) C&S, Culli Creek, Alto Madre de Dios River, Madre de Dios River Basin , Manu , Madre de Dios ( MUSM 3814 ) ; 1 specimen (sex unknown), 143.9 mm SL, Madre de Dios, Manu, Culli stream, Madre de Dios River , Upper Amazon River ( MUSM 3758 ) .

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 from last dorsal-fin ray to adiposefin origin. Dorsal and ventral caudal peduncle margins straight. Ventral profile convex from tip of snout to 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 7–13 teeth on anterior-most part of ventral margin; anterior-most teeth tricuspid then with less well-defined cusps, 4 or 5 posterior teeth conical. Dentary with anterior four pentacuspid teeth, followed laterally by 11–13 smaller teeth of increasing posterior inclination, decreasing from tri- to unicuspid. Pored scales of lateral line 39(4), 40(4) or 41(2), scales from lateral line to dorsal-fin origin 7(4) to 8(6) (n = 10), scales from lateral line to anal-fin origin 7(8) to 8(2) (n = 10), scales from lateral line to pelvicfin insertion 5(3) to 6(7) (n = 10), predorsal midline with complete series of scales along dorsal midline.

Dorsal-fin rays iii 9 (n = 10); 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 11–12 i. Pelvic-fin rays i 7 i. Anal-fin rays iii–v, 22(2), 23(5), 24(1), 25(1) (n = 10), first simple rays only visible in cleared and stained material. Anal-fin origin posterior to vertical through insertion of last dorsal-fin ray.

Total vertebrae 36–38(3), including those of the Weberian apparatus: precaudal centra 18(2), 19(1), last three without true pleural rib. Caudal centra 18(1), 19(2). Epineurals 33(2), 35(1), posterior-most epineural occasionally not reach anterior surface of urostyle; epipleurals 21(1), 22 (2). Caudal fin with seven hypurals; dorsal and ventral lobes approximately equal in length and width; second hypural thickened anteriorly; 11(1), 12(2) dorsal procurrent rays; 10(3) principal rays in dorsal lobe, 10(2), 11(1) ventral procurrent rays, 9(3) principal rays in ventral lobe.

Pigmentation in alcohol

Sides of body yellowish, with reticulated pattern over upper region of coelomic cavity, silver stripe extending 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.

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 and posterior humeral spots). Anterior spot formed by two layers of pigment: brown melanophores (Layer 1, Fig.1 ) distributed in thin superficial layer of epithelium, another deeper layer consisting of dark melanophores (Layer 2, Fig. 1 ). Layer 2 forming polygon-shaped anterior humeral spot, divided in two groups of melanophores that do not precisely overlap, forming four-sided spot extending from the third to fourth or fifth scale of lateral series. Posterior humeral spot situated two or three scales posterior to anterior humeral spot, arc- or sigmoid-shaped, inconspicuous, covering two to three scales above lateral-line. Scales on sides of body with spots or dots.

Caudal peduncle spot rhomboid with short anterior extension (over silver lateral stripe) that does not extend anterior beyond vertical through anal-fin origin; dark pigment of caudal peduncle stripe continued onto 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 observed.

Taxonomic comments

Our assignment of Astyanacinus multidens Pearson, 1924 to the genus Astyanax relegates it to the status of a junior secondary homonym of Astyanax multidens Eigenmann, 1908 . We propose the replacement name, Astyanax bopiensis nom. nov., following rules established in Article 59 of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999).

Distribution

Known from the drainages of the Madidi and Mamoré Rivers, Colorado River, lower Bopi River, tributaries of the Madeira River, upper Amazon Basin of Bolivia and Peru (Puno and Madre de Dios) ( Fig. 4 ).

Figures

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

Fig. 7. Astyanax bopiensis nom. nov., 143.9 mm SL, Quebrada Culli, Madre de Dios River drainage, UpperAmazon, Peru (MUSM3758). Scalebar = 1 cm.

Fig. 9. Squamation of pectoral-fin base, ventral view. A. Astyanax bimaculatus (Linnaeus, 1758). B. Astyanax yariguies (Torres-Mejía, Hernández & Senechal, 2012) comb. nov. In A, the pore of pectoral-fin is inepithelial tissue, covered or circumscribed by threescales indicatedby thecurved line, while in B, the pore of the base of pectoral-fin is part of a scale circumscribed by four scales, indicated by the curved line. Scale bars = 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.