Polycentrus jundia, Coutinho & Wosiacki, 2014

Coutinho, Daniel Pires & Wosiacki, Wolmar Benjamin, 2014, A new species of leaffish Polycentrus Müller & Troschel, 1849 (Percomorpha: Polycentridae) from the rio Negro, Brazil, Neotropical Ichthyology 12 (4), pp. 747-753 : 747-753

Polycentrus jundia , new species

Figs. 1 and 2A ; Table 1

Holotype. MZUSP 54586 , 28.3 mm SL, Brazil, Amazonas, município de Iranduba, Paricatuba, rio Negro basin, lake on the right bank of the rio Negro, 11 Nov 1972, Expedição Permanente da Amazônia (EPA).

Paratypes. All from Brazil, Amazonas, município de Santa Isabel do Rio Negro, rio Negro basin, collected by EPA . MZUSP 62191 , 1 , 20.3 mm SL, lake channel in São João , near Tapurucuara [= Santa Isabel do Rio Negro], 0°24’0”S 65°2’0”W, 23 Oct 1972 . MPEG 29926 , 3 (1 c&s), 19.2- 24.9 mm SL; and MZUSP 55113 , 3 (1 c&s), 15.7-19.6 mm SL, igarapé in São João near Santa Isabel do Rio Negro, 0°24’0”S 65°2’0”W, 27 Oct 1972 . MZUSP 59204 , 1 , 19.4 mm SL, igarapé in São João near Santa Isabel do Rio Negro, 0°24’0”S 65°2’0”W, 23 Oct 1972 . MZUSP 62169 , 1 , 10.5 mm SL, floodplain igarapé of the rio Negro , 0°24’0”S 65°2’0”W, 19 Oct 1972 .

Diagnosis. Polycentrus jundia is distinguished from P. schomburgkii by: diagonal upper postorbital band being shorter than orbital diameter ( Fig. 2A ) vs. longer ( Fig. 2B ); presence of the median postorbital horizontal band (vs. absence); subocular band being shorter than orbital diameter ( Fig. 2A ) (vs. length of subocular band equal to or greater than orbital diameter ( Fig. 2B )); snout blunt (vs. protruding); mouth isognathous (vs. prognathous); serrations absent on lower edge of lacrimal or two tiny serrations at the posterior end (vs. 8-14 conspicuous serrations distributed throughout the lower edge); posterior edge of vertical arm of preopercle fully serrated (vs. smooth edge); presence of five pungent opercular spines, the three dorsalmost largest (vs. one or two short spines); subopercle widely serrated along most of the edge (vs. no serrations); cleithrum with serrations on posterior dorsal margin (vs. no serrations); interopercle with widely serrated edge (vs. clusters of three to five serrations along the edge of varying position between individuals); fourth pectoral-fin ray reaching vertical through anal-fin origin (vs. reaching vertical from spine III or IV of anal fin); lower number of scales on dorsal-fin base 19-20 (vs. 26-31); lower number of scales on anal-fin base 12-14 (vs. 16-20); the lower number of predorsal scales 19-21 (vs. 28-30); absence of the median opercular blotch (vs. presence).

Description. Meristic and morphometric data are shown in Table 1. Body ellipsoid in lateral view, slightly elongate; noticeably compressed and ellipsoid in cross section at median of body length. Dorsal profile convex in long curve with upward slope in predorsal region, continuing in downward convex arc along dorsal-fin base to posteriormost ray. Ventral profile almost straight from lower lip to isthmus, posteriorly arched, slightly convex, from that point to anal-fin origin, becoming slightly more pronounced from anal-fin base to last ray. Caudal peduncle compressed, short, deep; straight in both dorsal and ventral profiles.

Head in dorsal view, broad and rounded; obtuse in lateral profile. Males in reproductive state with discrete adipose gibbosity in occipital region. Snout broad, short, obtuse. Mouth wide, protractile, terminal, isognathous, and directed obliquely dorsally; anterior extremity at half of head depth, bordered by thin lips.

Dentigerous plate with villiform teeth on premaxilla from anterior margin up to one quarter of ascending process; villiform teeth on dentary from inner edge of mandibular symphysis to angulo articular. Ascending process of premaxilla half length of neurocranium. Absence of dentigerous plates on parasphenoid, ectopterygoid, basihyal and third hypobranchial.

Posterior tip of maxillary reaching vertical through posterior border of orbit or slightly anteriorly. Ventral margin of lacrimal smooth, single specimen with two tiny serrations posteriorly. Horizontal process of preopercle serrated, edge of ascending process with tiny serrations, straight up to pore p5, convex between p5 and p6-7.

Two conspicuous spiny processes on posterodorsal edge of opercle, dorsal to two or three serrations. Interopercle with smooth ventral edge on anterior third, serrated posteriorly. Subopercle with serrations at median region of length, anterior and posterior regions smooth. Three or four tiny serrations on posttemporal. Cleithrum serrated (10 or 11 tiny serrations) on posterior dorsal margin.

Sensory canal system with tiny pores: angulo-articular aa1 and 2, dentary d2-4, extrascapular ex3 and 4, frontal f2 and 3, lacrimal l1-3, nasal n1 and 2, preopercle p1-5, posttemporal po2, and pterotic pt2 and 3. Coronal and infraorbital pores absent. Series of neuromasts bordering infraorbital region. Lateral line restricted to single scale posterior/ventral to posttemporal.

Scale series: predorsal, 19(1), 20(7) and 21*(1); vertical, 12(3), 14*(3) or 15(1); horizontal, 20(1), 21(2), 23*(3) or 24(1); circumpeduncular, 15(1) or 16*(4). Cycloid scales in predorsal and ventral regions and anterior margin of preopercle. Ctenoid scales on cheek, subopercular, interopercular and opercular regions. Ctenoid scales moderately large on posterior region of body.

Scale sheath on dorsal fin present, free from base of fin, evident from spine IV, half to one scale deep on terminal portion of fin base, ending ventral to base of soft rays. Scale sheath on anal fin present, free from fin base, one scale deep, evident throughout extension.

Dorsal-fin rays XVI.8*(8), XVI.7(1) or XV.9(1), origin at posterior margin of opercular process and on insertion of dorsal opercular bone, spine I shortest, equivalent to one third of spine IV, which longest. First and last soft rays unbranched; remaining soft rays branching once on distal quarter.

Pectoral-fin rays ii,11(1), 12(8) or 14*(1), fourth branched longest; fin reaching vertical through anal-fin origin, edge rounded, rays branching once on distal quarter. Pelvic-fin rays I,5, spine nearly straight, distal tip of fin reaching urogenital opening, second ray longest, reaching beyond urogenital opening, proportionately shorter in females, reaching beyond anal-fin spine IV in male specimens.

Anal-fin rays XII.6*(6), XI.6(2) or XII.5(2) rays, origin at vertical through insertion of dorsal-fin seven; distal tip of soft rays reaching half length of caudal fin. Insertion of soft rays of dorsal and anal fins at 45°. Distal tip of soft portions of dorsal and anal fins slightly tapered. Caudal fin subtruncate or slightly convex when expanded, dorsal and ventral rays slightly shorter than central rays; caudal-fin rays I,7+7,i; not covered with scales.

Vertebrae, 11(2) preanal + 12(2) caudal. Pleural ribs 7(2). Branchiostegal rays 6(2).

Dentary teeth 82-100 in one side, all sharp, short, those near symphyseal region larger, gradually decreasing posteriorly; teeth of symphysis in four irregular series on large part of tooth-plate, teeth close to coronoid process in two or one series. Premaxillary teeth about 150 in one side, in five irregular series, all sharp, short; medialmost teeth larger, gradually decreasing posteriorly.

Pharyngeal lower tooth-plate, paired, dorsoventrally compressed with long posterior process and moderate anterior process; around 60 short teeth similar in size, slightly curved latero-posteriorly, posterior medial slightly larger, irregularly distributed, not in rows ( Fig 3 ).

Sexual dimorphism. Presence of discrete adipose gibbosity between the occipital and coronal region in males, absent in females. Vent of gravid females yellowish in individuals preserved in alcohol.

Color in alcohol. Ground color light brown with dark brown, diffuse chromatophores forming longitudinal series of dark spots, surrounded by pale spots. Scales usually lighter at focus, with darker submarginal pigmentation. Upper postorbital diagonal band black or dark brown, located postero-dorsally, ascending from orbital margin parallel to predorsal profile towards posttemporal, formed by contiguous points variably coalescing, forming a short band. Postorbital median horizontal band black or dark brown, postero-medial, horizontal, originating at orbital margin, formed by two adjacent blotches, gradually becoming lighter onto preopercle, continuing posteriorly as two points forming rounded spot on proximal medial region of opercle. Suborbital diagonal band, inconspicuous, postero-ventral, inclined ventrally towards prepelvic region, formed by scattered chromatophores onto five to seven scales. Preorbital band inconspicuous, brown, located antero-dorsally, extending from lacrimal towards dentary. A single blotch, not sharply defined, dorsally to dorsal extremity of opercle; a little blotch, few sharp, close to posterior extremity of opercle; a little blotch, few sharp, at posterior border of cleithrum, close to pectoral-fin base.

Region between preopercle and posterior margin of orbit paler than background. Humeral blotch brown, circular or irregular. Juveniles (below 20.0 mm SL) with four vertical, inconspicuous bars originating beneath spines I-III, V-VII, IX-XI, XIII-XV; bars absent in adults (larger than 20.1 mm SL).

Base of dorsal-fin spines dark brown, distal margin whitish or hyaline, five or six notorious brown spots onto rays IV and XII, intervening membrane of branched rays hyaline, rays outlined by row of dark chromatophores.

Intervening membranes of anal-fin spiny portion dark brown, distal margin with a narrow whitish or hyaline border, intervening membranes of branched rays hyaline, with distinct dark spot at base of rays 1-4, rays 1-7 outlined by single row of dark chromatophores.

Pelvic fin dark brown, distal margin with narrow, whitish or hyaline border, pale rays opaque distally. Intervening membranes of pectoral-fin rays hyaline; rays ii/12-14 outlined by single row of black chromatophores. Caudal fin mostly hyaline with tiny brown chromatophores outlining all rays, black chromatophores, and sparse scattered pigmentation onto intervening membranes.

Etymology. The epithet “ jundia ” comes from the Tupi word “jundiá ” meaning “head with spine”, and refers to the large amount of serrations present on the head bones of the new species. Treated here as a noun in apposition.

Distribution. Polycentrus jundia is known from floodplain igarapés of the lower and upper rio Negro ( Fig. 4 ).

Figures

Fig. 1. Polycentrus jundia, new species, holotype, MZUSP 54586, 28.3 mm SL, Brazil, Amazonas State. Left lateral view.

Fig. 2. Left lateral view of the head of (A) Polycentrus jundia, holotype, MZUSP 54586, 28.3 mm SL, and (B) Polycentrus schomburgkii MPEG 3294, 1, 40.7 mm SL; (1) upper postorbital diagonal band; (2) postorbital median horizontal band; (3) suborbital diagonal band. Scale bars = 2 mm.

Fig. 3. Lower pharyngeal tooth-plate of Polycentrus jundia, in occlusal view, MZUSP 55113, paratype. Scale bar = 1 mm.

Fig. 4. Map of north of South America. Black circles are collection sites of Polycentrus jundia, new species; 1= type locality. Black triangles are distribution of Polycentrus schomburgkii. Some points may represent more than one locality.