Astyanax belizianus ( Bocourt 1868 )

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 : 1368-1371

Astyanax belizianus ( Bocourt 1868)

( Figures 24–26 )

Tetragonopterus belizianus Bocourt 1868: 62 .

Astyanax aeneus non Günther, partim. Greenfield and Thomerson 1997.

Astyanax ‘Belize’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in the region as follows: anal-fin rays, on average 25–27 (mean 21–24 in A. brevimanus ); body deeper (‘du T. petenensis elle s’ en distingue par une plus grande élévation du corps’: Bocourt 1868, p. 62); interorbital, on average 8% SL (mean 9–10% SL in A. bacalarensis sp. nov., A.brevimanus , and A. petenensis ); supraoccipital in lateral view, usually caudally angled (concave in A. bacalarensis sp. nov. and A.brevimanus ); infraorbital IV, square (vs rectangular).

Redescription

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

Head profile concave to straight; snout usually round (may be somewhat pointed); lips even, or upper lip slightly protruding; mouth terminal. Pectoral fins usually reach pelvic fin origin; anal and dorsal fins usually overlap. Lobes of caudal fin, subequal.

D. 10, sometimes 9; A. 22–29, mean 26; pect. 11–12. Procurrent unsegmented dorsal rays on caudal fin, 9 or fewer. Gill rakers on first arch, 20–25, modally 21; on lower limb, 11–15, modally 13. Scales on lateral line, 32–39, modally 36; predorsal scales, 9–13, modally 11; scale rows from lateral line to base of first dorsal-fin ray, 6.5–8.5, modally 7; to base of pelvic fin, 5–7; to base of pectoral fin, 4, rarely 3 or 3.5; circumpeduncular scales, 14–17, modally 16. A single, short row of 9–10 scales 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, 109.9 mm SL. Body deep, 35–42% SL. Head length, 23–28% SL; orbital diameter 28–35% HL; interorbital distance, 5.2–9.5% SL, mean 8.2% SL (further morphometric data appear in Table 4).

Anterior fontanel long. Supraoccipital process in dorsal view, short, wide-based, slightly concave to angled in lateral view. Vomer rostrally slightly concave. Arms of premaxilla, variable; teeth, 0–5. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Dorsal edge of longer articular arm, angled. Maxillary, with a convex anteroinferior edge; 1–3 teeth. Metapterygoid, rostral arm longer than ventral; dorsorostral projections, 1 or 2. Infraorbital II, triangular with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, square, with a projection; contact between infraorbitals II and III, wide. Urohyal rostral end turned up, usually pointed; its ventrorostral edge convex, its ventral apex closer to caudal end; ceratohyal foramen oval; rostral vertices of ceratohyal round, the ventral side variable. Epibranchial III, insertion of uncinate process angled, the distal segment of the main body straight. Upper pharyngeal bones, crescent-shaped; lower pharyngeal plate single, its caudal side concave. Dorsal side of hyomandibular, usually convex. Opercle, sides of dorsal half, parallel; posterior edge, dorsally concave, ventrally straight-convex. Interopercular posterior edge, straight-convex. Preopercle, anterodorsal edge, with a median convexity; ventral rim, straight; posteroventral edge, curved; 2 canals at angle. Four or 5 predorsal bony elements, expanded; rostral edge of first pterygiophore usually angled. Coracoid with 2–3 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. Dorsal tip of scaphium, truncate; its dorsoposterior edge, slightly concave. Neural spines under dorsal fin, straight. Fifth to seventh caudal vertebra from tail, with a haemal spine displaced caudad. Hypuric and epuric plates, variable.

Humeral spot, P-shaped or indistinct ( Figure 25 ). Pigment sparsely distributed on anal fin, distally or uniformly. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Lectotype MNHN 2016–320 , 113.0 mm SL, Mullins River , Belize, coll. F. Bocourt ( Figure 26 ) . Paralectotypes: MNHN 5224 and 5225 (12 specimens), same collection data . Apparently, also an uncatalogued paralectotype at BMNH ( Eschmeyer 2014) .

Distribution

River Mullins, central Belize, south to tributaries of Lake Izabal, Guatemala and northern coast of Honduras ( Figure 24 ).

Proposed common names

Belizean tetra, sardinita beliceña.

Remarks

The species is part of clades VI of Ornelas-García et al. (2008) and E of Strecker et al. (2004). The complexity of Petén, with several Astyanax species present, was genetically verified by Ornelas-García et al. (2008).

There are some clines in meristic traits along the distributional range of A. belizianus . For example, Belizean populations have modally 7 scale rows between the lateral line and the pelvic-fin origin and also 7 between the lateral line and the dorsal-fin origin, whereas populations farther south have, respectively, 6 and 8.

Figures

Figure 24. Map of northern Central America, showing distribution localities of Astyanax baileyi, A. belizianus, A. brevimanus, A. cubilhuitz sp. nov., A. dorioni and A. petenensis. A larger symbol denotes the type locality.

Figure 25. Astyanax belizianus, live in Moho River, southern Belize. © J.M. Artigas Azas. Reproduced by permission of J.M. Artigas Azas. Permission to reuse must be obtained from the rightsholder.

Figure 26. Astyanax belizianus, lectotype, MNHN 2016-320. © MNHN - C. Ferrara. Reproduced by permission of MNHN - C. Ferrara. Permission to reuse must be obtained from the rightsholder.