Astyanax brevimanus 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 : 1373-1376

Astyanax brevimanus Günther 1864

( Figures 3 (b), 24, 29, 30)

Tetragonopterus brevimanus Günther 1864: 325 .

Tetragonopterus cobanensis Bocourt 1868: 62 .

Astyanax mexicanus non de Filippi, Lima et al . 2003.

Astyanax sp. 9 . Ornelas-García et al. 2008.

Astyanax ‘Quiché’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in Atlantic Guatemala and Chiapas as follows: body depth, 36% SL or less (36% or more in A. bacalarensis sp. nov.); head length, 28% or less (29% or longer in A. ocotal sp. nov.); pectoral falling quite short of pelvic-fin origin (almost always reaching in A. angustifrons , A. belizianus and A. fi nitimus); anal-base length, 27% or shorter (28% or more in A. belizianus ); anal-fin rays, on average, 21–24 (mean 25–27 in A. baileyi and A. belizianus ); gill rakers on lower arm of first arch, mean 11–12 (vs mean 12 or more); scale rows from lateral line to base of first dorsal-fin ray 6–7 and circumpeduncular scales 13–15 (6.5–8 and 16–17, respectively, in A. belizianus ); supraoccipital in dorsal view, short, broadbased (long, narrow-based in A. baileyi , A. belizianus , A. cubilhuitz sp. nov. and A. fi nitimus); infraorbital IV, rectangular (square in A. baileyi , A. belizianus and A. cubilhuitz sp. nov.).

Redescription

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

Head profile straight to convex; snout usually round; lips even, or upper lip slightly receding; mouth terminal. Pectoral fins usually do not reach pelvic fin origin; anal and dorsal fins usually do not overlap. Lobes of caudal fin, subequal.

D. 9–11; A. 20–24, mean 22; pect. 11–12. Procurrent unsegmented dorsal rays on caudal fin, variable. Gill rakers on first arch, 18–22, modally 20; on lower limb, 10–12. Scales on lateral line, 33–38, modally 35; predorsal scales, 10–14, modally 12; scale rows from lateral line to base of first dorsal-fin ray, 6–7.5, modally 7; to base of pelvic fin, 5–6, rarely 7; to base of pectoral fin, 3–4; circumpeduncular scales, 13–16, modally 14. A single, short row of scales on anal-fin base. Nuptial tubercles simple. Total vertebrae 32–34, 18–20 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 81.7 mm SL. Body depth 29–36% SL. Head length, 24–29% SL; orbital diameter 24–34% HL; interorbital distance, 6.0–9.7% SL, mean 8.3% SL (further morphometric data are given in Table 4).

Anterior fontanel long (short in Chiapas), sides and tip variable. Supraoccipital process in dorsal view, short, wide-based. Vomer rostrally slightly concave. Dentigerous arm of premaxilla, longer and more robust; 0–4 teeth. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Longer articular arm, pointed. Maxillary, with a convex, notched anteroinferior edge; 1–3 teeth. Quadrate variable. Metapterygoid, rostral arm longer than ventral, 2 dorsorostral projections. Infraorbital II, triangular with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, rectangular, with a projection; contact between infraorbitals II and III, wide. Urohyal rostral end turned up; its ventrorostral edge usually angled, its ventral apex closer to caudal end; ceratohyal foramen oval; rostral vertices of ceratohyal angled, the ventral side variable. Epibranchial III, insertion of uncinate process angled or round, the distal segment of the main body straight (curved in Chiapas). Upper pharyngeal bones, oval to S-shaped; lower pharyngeal plate single, its caudal side concave. Dorsal side of hyomandibular, convex. Opercle, dorsal edge convex (undulate in Chiapas); sides of dorsal half, parallel; posterior edge, dorsally concave, ventrally straight-convex. Interopercular posterior edge, straight-convex, with a spine. Preopercular ventral rim, straight; 2 divergent canals at angle. Five to 6 predorsal bony elements, expanded; rostral edge of first pterygiophore angled. Coracoid with 2–3 interdigitations in suture to cleithrum, a concave caudal edge, a single posteroinferior spine. Caudad process of postcleithrum, globose, with a dorsal protuberance followed by a notch. Proximal edge of pelvic bone, straight. Postanal element, usually long. Neural spines under dorsal fin, bent at tips. Sixth to eighth caudal vertebra from tail, with a haemal spine displaced caudad. Rostral edge of largest hypuric plate, straight (concave in Chiapas). Epuric plate on last neural spine, straight (roundish in Chiapas).

Humeral spot, triangular to P-shaped or indistinct. Pigment on anal fin, sparse, concentrated distally. Caudal spot, both on peduncle and on fin rays ( Figure 29 ).

Type material and depositor

Lectotype BMNH 1864.1 .26.388, 86.7 mm SL, Río San Gerónimo (or Jerónimo), Baja Verapaz, Guatemala, coll. F.D. Godman and O. Salvin, 1861 ( Figure 30 ) . Paralectotypes BMNH 1864.1 .24.177 (3 specimens), 2016.9. 13.3–4 (2 specimens), same collection data . The syntypes BMNH 1861.8 . 12.20–21 and MRAC 7057 from Lake Izabal are not A . brevimanus, but A. belizianus (see Remarks ).

Distribution

Highlands of Chiapas (upper tributaries of Río Grijalva), south and east to Quiché and Baja Verapaz, Guatemala ( Figure 24 ) .

Proposed common names

Quiché tetra, sardinita del Quiché.

Remarks

The syntypic series, with two type localities, is a composite. It seems clearest to reserve the name A. brevimanus for the highland form in Baja Verapaz to Chiapas and leave the name A. belizianus for the lowland form of Belize and Izabal to coastal Honduras.

The species is clade III of Ornelas-García et al. (2008), in part (their ‘species 9’), and clade E of Strecker et al. (2004).

One of Bocourt’ s (1868) laconically described species, T. cobanensis , clearly corresponds to A. brevimanus in distribution and characters.

Astyanax brevimanus was regarded by Eigenmann and Ogle (1907), Lima et al. (2003), Miller et al. (2009) and other authors as a Guatemalan form of A. mexicanus , because of its low anal-fin ray count, slender body and usually convex supracephalic profile. In addition to the genetic differences discovered by Ornelas-García et al. (2008), the two species differ in several osteological traits, such as the shape of the pelvic bone, infraorbitals II and IV, epibranchial III, urohyal and epuric plate. Contreras-Balderas and Lozano-Vilano (1998) realised that this species was distinct from A. mexicanus , but did not suggest an applicable name.

The westernmost populations (near Cintalapa, Chiapas) are somewhat divergent, with a deeper body, sometimes longer pectoral fins, lower scale counts (up to 12 predorsal scales, not 14; as few as 32 scales on lateral line, vs 34 or more; modally 5 scales between lateral line and pelvic-fin origin, not 5.5–6). There are also some osteological variants (see above).

The complexity of Petén and environs, with several Astyanax species present, was genetically verified by Ornelas-García et al. (2008).

Figures

Figure 3. (a) A supraoccipital caudal process, long, narrow-based (Astyanax aeneus, UMMZ 178568); (b) shorter, wide-based (A. brevimanus, UMMZ 173731).

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 29. Astyanax brevimanus, live, from a tributary of Río La Venta near Cintalapa, Mexico, Grijalva drainage. © A.E. Gómez González. Reproduced by permission of A.E. Gómez González. Permission to reuse must be obtained from the rightsholder.

Figure 30. Astyanax brevimanus, lectotype, BMNH 1864.1.26.388. © The Natural History Museum, London. Reproduced by permission of The Natural History Museum, London. Permission to reuse must be obtained from the rightsholder.