Astyanax panamensis ( Günther 1864 )

Schmitter-Soto, Juan J., 2017, A revision of Astyanax (Characiformes: Characidae) in Central and North America, with the description of nine new species, Journal of Natural History (J. Nat. Hist.) 51 (21 - 24), pp. 1331-1424 : 1400-1402

Astyanax panamensis ( Günther 1864)

( Figures 28 , 42 )

Tetragonopterus panamensis Günther 1864: 324 .

Tetragonopterus fi scheri Steindachner 1879: 151.

Astyanax grandis Meek and Hildebrand 1912: 67 .

Astyanax ruberrimus Eigenmann 1913 .

Astyanax orthodus non Eigenmann: Ornelas-García et al. (2008).

Diagnosis

Diagnosed from other Astyanax species in Panama and north-western Colombia as follows: humeral spot, P-shaped or indistinct (circular or oval in A. atratoensis , A. bimaculatus and A. orthodus ); no caudal spot, or only faintly on peduncle, never on anal fin rays (usually present and reaching anal fin rays in A. atratoensis , A. bimaculatus and A. orthodus ); mean body depth, 39% SL (mean 36% in A. orstedii ); mean pectoral-fin length, 22.3% SL (20.5% in A. orstedii ); predorsal series of scales, complete (incomplete in A. atratoensis , A. bimaculatus and A. orthodus , all three in subgenus Poecilurichthys ); caudal vertebrae, 19 (vs 20 or more).

Redescription

A species of Astyanax , subgenus Astyanax (i.e. with a complete predorsal series of scales).

Head profile ‘somewhat concave’ ( Günther 1864); snout roundish; mouth terminal, lips even. Pectoral fins usually reach pelvic fin origin; anal and dorsal fins may overlap. Lower lobe of caudal fin, slightly longer.

D. 9–11; A. 22–28, modally 24; pect. 11–12. Procurrent unsegmented dorsal rays on caudal fin, variable. Gill rakers on first arch, 19–23, modally 21; on lower limb, 11–15, modally 13. Scales on lateral line, 33–38, modally 34; predorsal scales, 10–13, modally 11; scale rows from lateral line to base of first dorsal-fin ray, 7–8.5, modally 8; to base of pelvic fin, 6–8; to base of pectoral fin, modally 4, up to 5; circumpeduncular scales, 15–17, modally 16. Scaly sheath on anal-fin base, long, with imbricated scales. Nuptial tubercles may be bifid. Total vertebrae 32–33, 19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 100.7 mm SL. Body usually rather deep, 32–44% SL, mean 39%. Head length, 20–29% SL; orbital diameter, 30–38% HL; interorbital distance wide, 7.9–10.5% SL, mean 9.2% SL (further morphometric data appear in Table 4).

Anterior fontanel short, straight-sided, sharp-tipped. Supraoccipital process in dorsal view, short, wide-based, angled to concave in lateral view. Vomer rostrally slightly concave. Arms of premaxilla, variable; teeth, 4–5. Highest tooth on dentary, first or third; posterior teeth, variable size. Maxillary, with a convex anteroinferior edge, 0–3 teeth. Quadrate, dorsal process not expanded. Metapterygoid, rostral arm longer than ventral; only 1 dorsorostral projection. Infraorbital II, triangular with a short convex base; infraorbital IV, square. Urohyal rostral end turned up, blunt; its ventrorostral edge convex, the ventral apex about equidistant between rostral and caudal ends; ceratohyal foramen oval or absent. Upper pharyngeal bones, crescentshaped; lower pharyngeal plates, variable. Dorsal side of hyomandibular, convex. Opercular dorsal side, convex; sides of dorsal half, parallel. Interopercular posterior edge, straight-convex. Preopercular posteroventral edge, curved; 2 divergent canals at angle. Four or 5 predorsal bony elements. Coracoid with 2 interdigitations in suture to cleithrum. Caudad process of postcleithrum, globose. Dorsal tip of scaphium, truncate; dorsoposterior edge, slightly concave. Postanal element, short. Sixth caudal vertebra from tail, with a haemal spine displaced caudad. Largest hypuric plate, with a straight anterior border. Epuric plate on last neural spine, straight-edged.

Humeral spot, P-shaped or indistinct. Pigment on anal fin, sparse, distal and posterior, absent anteriorly. No caudal spot, or only faintly on peduncle, never on anal-fin rays.

Type material and depositor

Lectotype BMNH 1864.1.26.415, ‘the Pacific coast of Panama’, coll. F.D. Godman and O. Salvin, 1861 ( Figure 42 ). Unique, no paralectotypes; the syntypes from Lake Izabal are not A. panamensis , but A. belizianus (see Remarks; shows the Guatemalan syntypes from ZMB 6801, have the profile, meristics, and especially the caudal-fin spot typical of the latter species, q.v.).

Distribution

Panama, both versants, to Istmina in adjacent Colombia ( Figure 28 ).

Proposed common names

Panamanian tetra, sardinita panameña.

Remarks

The syntypic series, with two type localities, is a composite. It seems clearest to reserve the name A. panamensis for the southern Central American form in Panama and leave the name A. belizianus for the northern Central American species of Belize and Izabal to coastal Honduras. Astyanax grandis , from Río Juan Díaz, Pacific Panama, A. fi scheri from Río Mamoni near Chagres, and A. ruberrimus from Istmina, Colombia, are junior synonyms, sharing the distribution and the diagnosis of A panamensis , including the conspicuous absence of the caudal spot from the fin rays. Regan (1908, p. 171) commented: ‘ Steindachner [1879] had formerly given the name T. fi scheri to the specimens which he [later] determined and figured as T. panamensis ’.

Figures

Figure 28. Map of lower Central America, showing distribution localities of Astyanax bransfordii, A. cocibolca, A. nasutus, A. nicaraguensis, A. orstedii and A. panamensis. Astyanax bransfordii and A. cocibolca co-occur in Lake Nicaragua. A larger symbol denotes the type locality (uncertain for A. nicaraguensis and A. panamensis).

Figure 42. Astyanax panamensis, lectotype, BMNH 1864.1.26.415. © The Natural History Museum, London. Reproduced by permission of The Natural History Museum, London. Permission to reuse must be obtained from the rightsholder.