Astyanax argentatus Baird and Girard 1854

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 : 1361-1364

Astyanax argentatus Baird and Girard 1854

( Figures 4 (b), 7(a), 12, 20, 21)

Astyanax mexicanus non de Filippi: Valdez-Moreno 1997, Kavalco and de Almeida-Toledo 2007, Miller et al. 2009, and others.

Astyanax mexicanus ssp., Jelks et al. 2008

Astyanax ‘Texas’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in central-northern Mexico as follows: A. 19–23, mode 20 (21–25, mode 23, in A. mexicanus , and 18–20, mode 18, in A. rioverde sp. nov.); modally 7 scale-rows between lateral line and dorsal-fin origin (modally 8 in A. mexicanus and A. acatlanensis sp. nov.); nuptial spines or tubercles, just on anal-fin rays, all simple (just on pelvic fins in A. rioverde sp. nov., and at least some bifid in A. mexicanus and A. acatlanensis sp. nov.); body slenderer than A mexicanus and A. rioverde sp. nov., mean 34% SL (vs mean 37% SL); anterior fontanel, sharp-tipped (blunt in A. mexicanus ); infraorbital IV, rectangular, with no projections (square, with projections in A. acatlanensis sp. nov., A. mexicanus and A. tehuacanensis sp. nov.); ventral side of ceratohyal, straight (vs undulate). Posterior edge of interopercle, without a spine (with a spine in A. mexicanus and A. tehuacanensis sp. nov.); postcleithrum caudad process concave-sided (straight in A. mexicanus ); largest hypuric plate, rostral border straight (concave in A. mexicanus ).

Redescription

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

Head profile usually convex; snout round. Lips even; mouth terminal. Pectoral fins usually do not reach pelvic fin origin; anal and dorsal fins never overlap. Lobes of caudal fin, subequal.

D. 10; A. 19–23, modally 20; pect. 11–13. Procurrent unsegmented dorsal rays on caudal fin, 9 or fewer. Gill rakers on first arch, 17–20, modally 18; on lower limb, 10–13, modally 11. Scales on lateral line, 32–37, modally 33; predorsal scales, 10–13, modally 11; scale rows from lateral line to base of first dorsal-fin ray, 6 – 8, modally 7; to base of pelvic fin, 5–6; to base of pectoral fin, 3–4; circumpeduncular scales, 14–17, modally 15. A single, short scale row on anal fin base. Nuptial tubercles, always simple. Total vertebrae 32–33, 18–19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 114.3 mm SL. Body slender, 30–37% SL, mean 34%. Head short, 23–26% SL; orbital diameter, 16–34% HL, mean 28%; interorbital distance, 8.1– 10.7% SL, mean 9.2% SL (further morphometric data appear in Table 4).

Anterior fontanel short, convex-sided, sharp-tipped. Supraoccipital process in dorsal view, short, wide-based, caudally slightly concave in lateral view. Vomer rostrally slightly concave. Arms of premaxilla, subequal; 0–4 teeth. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Dorsal edge of longer articular arm, straight. Maxillary, with a convex anteroinferior edge; 1–3 teeth. Quadrate, dorsal process expanded. Metapterygoid, rostral arm longer than ventral; dorsorostral projections, 1 or 2. Infraorbital II, triangular with a long convex base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, rectangular with a projection; contact between infraorbitals II and III, wide. Urohyal rostral end turned up, pointed; its ventrorostral edge convex, its ventral apex closer to caudal end; no ceratohyal foramen; rostral vertices of ceratohyal angled, the ventral side straight. Epibranchial III, insertion of uncinate process round. Upper pharyngeal bones, S-shaped; lower pharyngeal plate single, its caudal side concave. Dorsal side of hyomandibular, convex. Opercle, sides of dorsal half, parallel; posterior edge, dorsally concave, ventrally straight-convex; ventral tip, sharp. Interopercle, posterior edge, straight-convex. Preopercle, anterodorsal edge, straightconcave; ventral rim, straight; posteroventral edge, curved; 2 canals at angle. Five predorsal bony elements; rostral edge of first pterygiophore curved. Coracoid with 3 interdigitations in suture to cleithrum, a concave caudal edge, a single posteroinferior spine. Caudad process of postcleithrum, globose to digitiform. Proximal edge of pelvic bone, convex. Dorsoposterior edge of scaphium, slightly concave. Neural spines under dorsal fin, straight. Postanal element, short. Fifth or sixth caudal vertebra from tail, with a haemal spine displaced caudad. Largest hypuric plate, rostral edge straight; epuric plate on last neural spine, convex-edged.

Humeral spot, rectangular-triangular or indistinct . Almost no pigment on anal fin . Caudal spot, both on peduncle and on fin rays . Live colours were reported for the type population in Texas ( Baird and Girard 1854, p. 27): ‘ Belly reddish . Fins reddish yellow’ . A live specimen from Nuevo León is shown in Figure 20 .

The species (as ‘ A. mexicanus ’ from Nuevo León) has been reported to have 50 chromosomes, with the karyotypic formula 4M+9SM+6ST+6A ( Kavalco and de Almeida-Toledo 2007).

Type material and depositor

Lectotype BMNH 1883.12 .14.107, 114.3 mm SL, ‘upper tributaries to the Río Nueces’ , Texas, USA, coll. J.H. Clark ( Figure 21 ) . Paralectotypes: MCZ 858 (3 specimens), USNM 869 (28 specimens) . Same collection data.

Distribution

A Nearctic representative of a Neotropical clade: northern Mexico and Texas ( Figure 12 ).

Figures

Figure 4. (a) An infraorbital IV square, with a rostroventral projection (Astyanax mexicanus, UMMZ 169835); (b) rectangular, with projection (A. argentatus, UMMZ 170107).

Figure 12. Map of Mexico, showing distribution localities of Astyanax acatlanensis sp. nov., A. argentatus, A. mexicanus, A. rioverde sp. nov., A. salvatoris sp. nov., A. tamiahua sp. nov. and A. tehuacanensis sp. nov. A larger symbol denotes the type locality (ambiguous for A. mexicanus; see text).

Figure 20. Astyanax argentatus live from Aramberri, Nuevo León. © J.M. Artigas Azas. Reproduced by permission of J.M. Artigas Azas. Permission to reuse must be obtained from the rightsholder.

Figure 21. Astyanax argentatus, lectotype, BMNH 1883.12.14.107. © The Natural History Museum, London. Reproduced by permission of The Natural History Museum, London. Permission to reuse must be obtained from the rightsholder.