Hasemania piatan, Zanata & Serra, 2010

Zanata, Angela M. & Serra, Jane P., 2010, Hasemania piatan, a new characid species (Characiformes: Characidae) from headwaters of rio de Contas, Bahia, Brazil, Neotropical Ichthyology 8 (1), pp. 21-26 : 22-24

Hasemania piatan , new species

Figs. 1-3

Holotype. MZUSP 104538, 54.0 mm SL, Brazil , Bahia , município de Piatã, riacho Três Morros around bridge on road between Piatã and Núbia, tributary of rio de Contas, 13°04’43”S 41 ° 51 ’ 44 ”W, 1.340 m a.s.l., 13 Sep 2007, A. M. Zanata, P. Camelier & A. G. A. Borges .

Paratypes. UFBA 4299, 57, 21.6-44.7 mm SL (20, 21.6-44.7 mm SL), collected with holotype. UFBA 4298, 126, 3 c&s, 22.4-41.4 mm SL, (20, 22.4-41.4 mm SL); DZSJRP 11933, 20, 3 c&s, 23.1- 33.5 mm SL; MZUSP 104539, 20, 21.2-44.4 mm SL, Brazil , Bahia , município de Piatã, córrego das Piabas, south of Fazenda Piabas, tributary of rio de Contas, 13°08’49”S 41°50’33”W, 1.336 m a.s.l., 13 Sep 2007, A. M. Zanata, P. Camelier & A. G. A. Borges.

Diagnosis. Hasemania piatan can be distinguished from its congeners by having eighteen principal caudal-fin rays (vs. nineteen). It differs further from the majority of its congeners by the absence of scales covering the anal-fin base (vs. presence, except in H. kalunga and H. maxillaris ), presence of only five infraorbitals (vs. six infraorbitals, except in H. crenuchoides ), and presence of a humeral spot (vs. absence, except in H. kalunga and H. nambiquara ). The new species can be further distinguished from H. hanseni , H. maxillaris and H. nambiquara by having 10-13 branched anal-fin rays (vs. 16-19), and from H. crenuchoides , H. kalunga , H. maxillaris , H. melanura , and H. nambiquara by having 10- 12 circumpeduncular scales (vs.14 or 16). Hasemania piatan differs further from H. hanseni by having six branched pelvicfin rays (vs. seven), from H. maxillaris by having six branched pelvic-fin rays (vs. five) and the majority of teeth with three or more cusps (vs. conical teeth), and from H. nambiquara by the absence of a broad black lateral band (vs. presence). The new species differs also from H. nana by having 27-32 scales in the longitudinal series (vs. 20-26) and 10-13 branched analfin rays (vs. 13-16), and from H. melanura by having 27-32 scales in the longitudinal series (vs. 23-26) and one to three maxillary teeth (vs. none). From H. crenuchoides the new species differs further by the absence of black blotch extending to median caudal-fin rays (vs. presence) and ossification in the position primitively occupied by infraorbitals three and four relatively small, not reaching the preopercle sensory canal posteriorly (vs. ossification large, reaching the preopercle sensory canal). Hasemania piatan differs also from H. kalunga by having 27-32 scales on longitudinal series (vs. 33-36) and absence of caudal blotch (vs. presence).

Description. Morphometric data of holotype and paratypes in Table 1. Body relatively elongated and transversely rounded, somewhat flattened posterior to terminus of dorsal fin base. Greatest body depth at dorsal-fin origin. Dorsal profile of head distinctly convex from margin of upper lip to region around vertical through anterior nostril, nearly straight or slightly convex from that point to posterior tip of supraoccipital spine. Dorsal profile of body slightly convex from tip of supraoccipital spine to dorsal-fin origin, posteroventrally-inclined along dorsal-fin base, nearly straight from posterior terminus of dorsal-fin base to origin of dorsalmost procurrent caudal-fin ray. Ventral profile of head and body distinctly convex from anterior tip of dentary to isthmus, gently convex from this point to anal-fin origin, nearly straight and posterodorsally inclined along anal-fin base. Ventral profile of caudal peduncle nearly straight. Head obtusely rounded anteriorly in lateral profile.

Jaws equal, mouth terminal. Posterior terminus of maxilla slightly trespassing vertical through anterior border of orbit on smaller specimens or reaching vertical near or to center of eye on larger ones. Premaxillary teeth in two rows. Outer row with 2(5), 3*(32), or 4(2) uni- or tricuspid teeth. Inner row with 4(8) or 5*(31) teeth bearing three to five cusps. Symphyseal tooth of inner series asymmetrical, with lower number of cusps on anteromedial side; symphyseal tooth with four cusps and posteriormost tooth with three cusps. Maxilla with 1(17), 2*(21), or 3(1) teeth bearing one to three cusps. Dentary with four or five larger teeth anteriorly, with three to five cusps, followed by four or five distinctly smaller conical ones (5); anteriormost teeth usually with three cusps, except in largest specimen with five cusps ( Fig. 3).

Scales cycloid, circuli absent on exposed area of scales, with various divergent radii extending to posterior margin of scales. Lateral line incomplete, pored scales 5(1), 6(3), 7*(13), 8(13), 9(2), 10(4), 11(2) or 14(1). Longitudinal scale series including perforated scales 27(2), 28*(4), 29(11), 30(7), 31(4) or 32(2). Scale rows between dorsal-fin origin and pelvic-fin insertion 9*(25), 10(10) or 11(2). Scales along middorsal line between tip of supraoccipital process and origin of dorsal fin 10(7), 11*(7) or 12(9) when not desorganized. Horizontal scale rows around caudal peduncle 10*(14), 11(20) or 12(3). Caudal fin not scaled.

Dorsal-fin rays ii,7*(36) or 8(4). Distal margin of dorsal fin usually rounded. Dorsal-fin origin slightly posterior to middle of standard length. Base of last dorsal-fin ray slightly anterior to vertical through anal-fin origin. First dorsal-fin pterygiophore inserting behind neural spine of 11 th (2) or 12 th (2) vertebra. Adipose fin absent. Anal-fin rays iii-iv,10(4), 11*(25), 12(9), or 13(1). Distal margin of anal fin straight. First anal-fin pterygiophore inserting behind haemal spine of 18 th (1) or 19 th (1) vertebra. Basal portion of anal-fin rays not covered by sheath of scales. Pectoral-fin rays i,9(3), 10(18), 11*(13) or 12(6). Tip of pectoral fin not reaching vertical through pelvic-fin insertion. Pelvic-fin rays i,6(40). Caudal fin forked, lobes rounded, similar in size. Principal caudal-fin rays 9+9 (40). Eight(1) or 9(3) dorsal procurrent caudal-fin rays, and 7(1) or 8(3) ventral procurrent caudal-fin rays. First gill arch with 5(2) or 6(2) epibranchial, 8(4) ceratobranchial, 1(4) on cartilage between ceratobranchial and epibranchial, and 1(4) hypobranchial gill-rakers. Vertebrae 34(1) or 35(3). Supraneurals 5(1) or 6(2). Branchiostegal rays 4(4).

Color in alcohol. Preserved specimens lack guanine on body and head ( Fig. 1 ). Overall ground color tan. Small dark chromatophores distributed over entire scales, slightly more concentrated on middorsal surface of head and body. Area of third to fifth infraorbitals and opercle with somewhat larger, scattered dark chromatophores. Ventral portion of body from head to origin of anal fin yellowish, usually with scattered, small dark chromatophores. Humeral region with verticallyelongated, relatively narrow blotch, well defined in some specimens but somewhat less conspicuous in others. Dorsal portion of humeral blotch broader, covering two scales. Blotch anteroventrally inclined, with its anteriormost ventral portion overlapped by opercle membrane. Midlateral dark line extending from vertical through base of first dorsal-fin ray to or nearly to end of caudal peduncle. All fins with small dark chromatophores over rays and interadial membranes, more concentrated over rays and along its borders. Pectoral and pelvic fins somewhat less pigmented.

Color in life. Freshly collected specimens had overall coloration tan, with yellowish ventral portion of body ( Fig. 2 ). Silvery hue present over some scales, major portion of iris, posterior infraorbitals, preopercle, and opercle. Dorsal portion of iris darkened. Humeral blotch usually not as conspicuous as in preserved specimens. Dark lateral longitudinal line most evident posterior to vertical through base of first dorsal-fin ray and extending to end of caudal peduncle. Dorsal, anal, and caudal fins with proximate areas of rays and interradial membranes yellowish or reddish-orange. Distal portion of those fins clearer. Pectoral and pelvic fin hyaline to yellowish.

Sexual dimorphism. Bony hooks were observed over first to sixth branched anal-fin rays in various male specimens of 26.0 to 37.2 mm SL. One to six hooks occurs per ray, being two or three hooks the usual condition. Two specimens have one or two hooks also over the longest unbranched ray. The observed hooks are relatively small, similar in size, and distributed on distal portion of rays.

Geographic distribution. Hasemania piatan is known from the streams riacho Três Morros and córrego das Piabas, small tributaries of upper rio de Contas drainage, Piatã, Bahia, northeastern Brazil ( Fig. 4 ).

Ecological notes. The riacho Três Morros is a clear headwater stream, with low to medium water current, sandy bottom, greatest depth of 1.30 m, width of 0.8 to 4.5 m and with a relatively large amount of riparian and submerged vegetation. The córrego das Piabas, a smaller stream nearby, had small amount of water (less than 50 cm deep) probably in consequence of the dry season, and several specimens where trapped in a small sandy pool. On the smallest stream only H. piatan was sampled and on riacho Três Morros only Hoplias sp. occurs syntopically. The analysis of the stomach contents of four specimens revealed presence of larvae and adult fragments of Trichoptera, adult Diptera, fragments of unidentified arthropods, large amount of filamentous algae, and organic debris.

Etymology. Named after Piatã, the county where the species is found. A noun in apposition.

Figures

Fig. 1. Hasemania piatan, holotype, MZUSP 104538, 54.0 mm SL; Brazil, Bahia, Piatã, riacho Três Morros, tributary of rio de Contas drainage.

Fig. 2. Hasemania piatan, freshly preserved paratype showing living color pattern, UFBA 4299, 37.5 mm SL; Brazil, Bahia, Piatã, riacho Três Morros, tributary of rio de Contas drainage.

Fig. 4. Rio de Contas basin, Bahia, northeastern Brazil, showing collection locality of Hasemania piatan (square = two close localities).