Aphyocharax brevicaudatus, Brito, Pamella Silva de, Guimaraes, Erick Cristofore, Carvalho-Costa, Luis Fernando & Ottoni, Felipe Polivanov, 2019

Brito, Pamella Silva de, Guimaraes, Erick Cristofore, Carvalho-Costa, Luis Fernando & Ottoni, Felipe Polivanov, 2019, A new species of Aphyocharax Guenther, 1868 (Characiformes, Characidae) from the Maracacume river basin, eastern Amazon, Zoosystematics and Evolution 95 (2), pp. 507-516 : 507

Aphyocharax brevicaudatus sp. nov. Figs 1 , 2

Holotype.

CICCAA 02293, (male) 35.9 mm SL, Brazil, Maranhão state, Maracaçumé municipality, Maracaçumé River, 2°3'14"S, 45°57'16"W; 29 Jun 2018, E.C. Guimarães and P.S. Brito.

Paratypes.

All from Brazil, Maranhão state: CICCAA 02294, 1 (female), 32.4 mm SL, CICCAA 02295, 35 (males), 20.9-31.7 mm SL,CICCAA 02296, 94 (females), 21-32.1 mm SL, CICCAA 02297, 30 (females) C&S, 22.2-30.8 mm SL, CICCAA 02312, 2 (males) C&S, 28.3-32.1 mm SL, UFRJ 11746, 10 (female), 24.2-30.2 mm SL; all collected with holotype.

Diagnosis (PAA).

Aphyocharax brevicaudatus sp. nov. differs from all its congeners by possessing the upper lobe of the caudal fin longer than the lower lobe in mature males (vs upper and lower lobes similar in length, see Figs 1 , 2 ; Tagliacollo et al. 2012: fig.4). Additionally, the new species is distinguished from Aphyocharax avary and A. pusillus by having hyaline middle caudal-fin rays (vs black or dark brown middle caudal-fin rays, Brito et al. 2018: fig. 3); from Aphyocharax colifax , A. yekwanae , and A. rathbuni by having caudal-fin light red colouration never surpassing the vertical line of the adipose-fin (vs red colouration extending to the lateral midline of body, Willink et al. 2003: fig. 1); from A. gracilis by having a larger body depth at dorsal-fin origin (body depth), 24.5-29.2% SL (vs 20.1-20.6% SL); and from A. pusillus by having teeth along 2/3 of the maxillary extension (vs along proximal half of the bone, Brito et al. 2018: fig. 4).

Description.

Morphometric data is presented in Table 2 . Body shape is generally fusiform, slightly elongate, greatest body depth slightly anterior to dorsal-fin base; dorsal body profile straight or slightly convex from snout to vertical through anterior nostrils; straight or slightly convex from posterior nostrils to tip of supraoccipital bone; straight or slightly convex from this point to dorsal-fin origin; slightly convex along dorsal-fin base; postdorsal profile straight from base of last dorsal-fin ray to adipose-fin origin; slightly concave from adipose-fin to end of caudal peduncle; ventral profile convex from snout to pelvic-fin insertion; straight or slightly convex from this point to anal-fin origin; straight along anal-fin base; long snout, with its length larger than orbital diameter; five infraorbital bones; fourth infraorbital absent and sixth infraorbital reduced; posterior border of maxilla rounded, extending vertically through anterior margin of orbit, not reaching third infraorbital.

All teeth unicuspid or tricuspid and lateral cusps, when present, much smaller; premaxillary teeth in one rows with 6(9), 7(23) tricuspid teeth; maxilla with 11(3), 12(12), 13(14), or 14(3) unicuspid teeth; dentary with 6 (2) or 7 (30) larger tricuspid teeth followed by 6(26) or 7(6) smaller tricuspid teeth.

Scales cycloid and same size over entire body generally. Predorsal scales mostly regular, but sometimes irregular just posterior to supraoccipital and/or slightly anterior to dorsal-fin. Scales covering anterior third of caudal-fin, with up to two, three, or four scales beyond posterior margin of hypural plate. Lateral line interrupted; last scale on caudal-fin base, with 9+1(12),10+1(74), 11+1(50), or 12+1(5). Longitudinal scales series including lateral-line scales 35(3), 36(3), 37(56), 38(49), or 39(30). Longitudinal scales rows between dorsal-fin origin and lateral line 5(1), 6(93) or 7(47). Horizontal scale rows between lateral line and pelvic-fin origin 4 (141), Axillary scale present. Scales in median series between tip of supraoccipital spine and dorsal-fin origin 13+1(24),14+1(65), 15+1(26), or 16+1(26). Circumpeduncular scales 13(18), 14(115), or 15(8).

Dorsal-fin rays i+10(99) or ii+10(42). Dorsal-fin origin situated posterior to vertical through pelvic-fin insertion, near middle of body. First dorsal-fin pterygiophore main body located of 8th and 9th vertebrae. Adipose-fin present. Anal-fin i+14(20), iii+15(18), ii+16(61), iii+16(24), ii+17(10), iii+17(5), ii+18 (3). Anteriormost anal-fin pterygiophore inserting at 14th and 15th vertebrae. Anterior anal-fin margin slightly convex, with anteriormost rays more elongate and slightly more thickened than remaining rays, forming a distinct lobe. Remaining rays smaller with straight distal margin. Pectoral-fin rays i+9(8), i+10(113), or i+11(20). Tip of pectoral-fin not reaching pelvic-fin origin, when adpressed. Pelvic-fin rays i+7(120) or ii+7(21). Tip of pelvic-fin not reaching anal-fin origin, when adpressed. Caudal-fin with a sexually dimorphic pattern, described below ( Fig. 1 ). Principal caudal-fin rays 10+9(130) or 10+10(11); dorsal procurrent rays 8(2), 9(3) or 10(27) and ventral procurrent rays 7(2), 8(3) or 9(27).

Branchiostegal rays 4(32). Supraneurals 6(4) 7(27) or 8(1). Total vertebrae 31 (1), 32(30) or 33(1).

Colour in alcohol.

Ground colouration light brown to yellowish brown. Inconspicuous light brown to light gray stripe from humeral spot to caudal-fin base, more conspicuous on posterior half. Humeral region with one conspicuous dark brown to black humeral spot. Smaller dark brown or black chromatophores homogeneously scattered. Smaller dark brown or black chromatophores homogeneously scattered along body, except on chest. Head ground colouration similar to trunk, with dark brown chromatophores present on jaws, tip of snout, opercle, and dorsal portion of head. Dorsal, adipose, anal, caudal, pectoral, and pelvic fins hyaline to light brown.

Sexual dimorphism.

Caudal-fin of mature males with upper lobe longer (about 2/3 longer) than lower one, while both cauldal-fin lobes have similar leght in females ( Fig. 1 ). Gill glands were found in all analyzed mature males of Aphyocharax brevicaudatus sp. nov. and were always absent in females. They were always located on anteriormost portion of lower branch of first gill arch, extending posteriorly through variable number of gill filaments.

Etymology.

The name brevicaudatus is a contraction of the Latin words brevis meaning “short” and cauda meaning “tail”, an allusion to the shorter caudal-fin lower lobe in the mature males of the new species.

Geographic distribution.

Aphyocharax brevicaudatus sp. nov. is currently known only from a single locality, the Maracaçumé river basin, a small and isolated coastal river basin of the eastern Amazon region ( Fig. 3 ).

Figures

Figure 1. Aphyocharax brevicaudatus sp. nov. a. CICCAA 02293, holotype (male), 35.9 mm SL; b. CICCAA 02294, paratype (female), 32.4 mm SL, Brazil: Maranhao state: Maracacume river basin. (Photographed by Erick Guimaraes).

Figure 2. Caudal-fin of Aphyocharax brevicaudatus, holotype, CICCAA 02293, (male).

Figure 3. Type locality of Aphyocharax brevicaudatus sp. nov.