Chrysobrycon yoliae, Vanegas-Ríos & Azpelicueta & Ortega, 2014

Vanegas-Ríos, James Anyelo, Azpelicueta, María de las Mercedes & Ortega, Hernán, 2014, Chrysobrycon yoliae, a new species of stevardiin (Characiformes: Characidae) from the Ucayali basin, Peru, Neotropical Ichthyology 12 (2), pp. 291-300 : 292-297

Chrysobrycon yoliae , new species

Figs. 1-6a

Holotype. MUSM 46140 , 51.6 mm SL, male, Peru, Ucayali, Coronel Portillo, Abujao, río Ucayali basin, río Yucamia subsystem, unnamed Quebrada , 8°39’13.99”S 73°21’16.63”W, approximately 273 m a.s.l., 4 Oct 2008, F. Cari & I. Gamboa.

Paratypes. All from Peru. CI-FML 5882, 3, 44.8-52.3 mm SL (1 c&s, 44.8 mm SL) ; MLP 10517, 1 , 48.4 mm SL ; MUSM 46141 , 8 , 38.2-51.5 mm SL, all collected with holotype .

Diagnosis. Chrysobrycon yoliae is readily distinguished from its congeners by the anterior tip of pelvic bone situated anterior to the fifth rib (vs. situated posterior to the fifth rib), the presence of 20-26 dentary teeth (vs. 12-19 in C. eliasi , 11-19 in C. hesperus , and 12-18 in C. myersi ), and the possession of a terminal lateral-line tube between caudalfin rays 10 and 11 (vs. the absence of this tube, except in C. eliasi ). Chrysobrycon yoliae differs from C. eliasi and C. myersi by the presence of teeth on third pharyngobranchial (vs. the absence of teeth on this bone). Chrysobrycon yoliae is also distinguished from C. eliasi by the dorsal-fin origin situated vertically between anal-fin rays 5 to 7 (vs. situated vertically between anal-fin rays 8 to 10), the posterior extent of the ventral process of quadrate reaching the vertical through posterior margin of symplectic (vs. not reaching the vertical through posterior margin of symplectic), the dorsalfin to adipose-fin length 26.8-28.8% SL (vs. 23.9-26.8% SL), and the body depth at dorsal-fin origin 34.4-42.2% SL (vs. 24.1-34.5% SL). Furthermore, Chrysobrycon yoliae is distinguished from C. hesperus by the absence of minute bony hooks on distal portion of the anal-fin rays in adult males (vs. the presence of a series of such hooks on distal portion of almost all anal-fin rays). Chrysobrycon yoliae also differs from C. myersi by the dorsal-fin to pectoral-fin length 47.3-53.1% SL (vs. 43.0-46.1% SL), the eye to dorsal-fin origin length 49.6-55.0% SL (vs. 45.8-49.2% SL), the upper jaw length 44.9-48.1% HL (vs. 48.9-55.0% HL), the number of circumpeduncular scales 15-16 (vs. 17-19), and the number of branched anal-fin rays 26-28 (vs. 33-39).

Description. Morphometric data in Table 1 . Largest male 52.3 mm SL and largest female 51.5 mm SL. Body laterally compressed, with maximum depth at vertical through onehalf the length of pelvic fin ( Fig. 1 ). Dorsal profile of body straight over head, slightly concave on supraoccipital area and convex from that area to dorsal-fin origin, straight and slanting ventrally from first dorsal-fin ray to caudal peduncle. Dorsal profile of caudal peduncle slightly concave or straight. Ventral profile of body convex from tip of snout to pelvicfin origin, straight between paired fins, straight and slanting dorsally from anal-fin origin to caudal peduncle. Ventral profile of caudal peduncle straight or slightly concave. Head with anterior region acute. Frontal fontanel absent. Epiphyseal branch of supraorbital canal absent. Anterior nostril rounded and separated by one skin fold from posterior one; posterior opening larger. Two pit organs developed in grooves of head; anterior groove rounded, located between nasal and nostril; posterior groove extended along frontal, from region medial to nares to vertical through posterior portion of orbit, covered with lines of neuromasts.

Dorsal-fin rays ii,8* in all specimens. Nine proximal pterygiophores on dorsal fin (1 c&s). Dorsal-fin origin located at vertical between anal-fin rays 5-7. Adipose fin located at vertical between second and third posteriormost anal-fin ray. Anal-fin rays iv(7) or v*(6), 26*(4), 27(3), or 28(6). Twentyeight proximal pterygiophores on anal fin (1 c&s). Anal-fin origin situated in posterior half of body, always anterior to vertical through dorsal-fin origin. Pectoral-fin rays i(13), 8(1), 9*(8), 10(3), or 11(1). Pectoral fin long, its posterior tip reaching one-third to one-half of pelvic-fin length ( Fig. 1 ). Pelvic-fin rays i, 7 in all specimens; last pelvic-fin ray unbranched in nine specimens but counted as branched. Pelvic-fin origin slightly anterior to half of body. Caudal fin forked with 10/9 principal rays in all specimens.

Mouth superior, lower jaw projecting slightly anterior to upper jaw. Premaxilla with two rows of teeth. Outer row with 3(1), 4(6), 5*(5), or 6(1) teeth; usually tricuspidate, conical to tetracuspidate in two specimens. Inner row with 4*(9) or 5(4) teeth, symphyseal tooth tetracuspidate, remaining teeth pentacuspidate, except posteriormost tricuspidate. Maxilla with 9(2), 10(2), 11(2), 12*(2), 14(2), 15(1), or 16(2) teeth. Anteriormost first to fifth teeth of maxilla usually tricuspidate, rarely conical, bicuspidate or tetracuspidate, remaining teeth conical ( Fig. 2a ). Maxilla bearing teeth along more than 60% of its length in adults. Maxilla relatively short, not reaching vertical through anterior border of pupil. Dentary with 20(3), 21(3), 22*(2), 23(2), 25(1), 26(1), or 27(1) teeth, three anteriormost teeth large and pentacuspidate, one median-sized tooth usually tetracuspidate followed by 16(3), 17(3), 18*(2), 19(2), 21(1), 22(1), or 23(1) smaller conical posterior teeth ( Fig. 2b ).

Scales cycloid, with several radii along posterior field. Lateral line complete, pored scales 40(3), 41(3), 42*(4), 43(1), 44(1), or 45(1). Terminal lateral-line tube present on caudal-fin membrane. Predorsal scales 17(1), 19*(3), 20(8), or 22(1). Scale rows between dorsal fin and lateral line 6(5) or 7*(8). Scale rows between lateral line and anal fin 5(6) or 6*(7). Scale rows between lateral line and pelvic fin 5*(9) or 6(4). Circumpeduncular scales 15*(10) or 16(3). One row of 17(2), 18(3), 19(1), 20(2), 21(3), 23*(1), or 24(1) scales forming sheath along anal-fin base, such sheath usually with an additional second row of scales partially covering anal-fin base. Total number of vertebrae 41(1 c&s), 15 precaudal and 26 caudal. Gill rakers on dorsal limb of first branchial arch 5(5) or 6*(8), ventral limb with 11*(5) or 12(8).

Color in alcohol. Ground color pale yellowish in preserved males and females, scarcely darker dorsally. Scattered dark brown and black chromatophores over all body, more concentrated dorsally, sometimes forming reticulate pattern. Black chromatophores forming one narrow line along middorsal. One narrow line of black chromatophores crossing mid-flank just one scale above of pored lateral-line scales. Lateral band iridescent brownish, extended from posterior region of humeral spot to end of caudal peduncle. In some specimens, caudal peduncle region bearing black and dark brown chromatophores forming somewhat triangular blotch. Black chromatophores forming stripes over myomeres, especially on posterior ventral one-third of body. Humeral spot somewhat rounded, slightly enlarged ventrally in few specimens. Dorsal fin hyaline, with disperse black chromatophores completely scattered on membranes, more concentrated on distal portion and on first ray. Adipose fin hyaline, sometimes with black chromatophores on its base. Anal fin hyaline, with chromatophores located on membranes, more concentrated on distal portion of rays, forming dusky distal area. Caudal fin bearing black chromatophores along membranes and few on rays; concentration of chromatophores on upper- and lowermost rays and middle rays of both lobes, especially on ventral one. Pectoral and pelvic fins hyaline with scattered black chromatophores. Head dark brown dorsally and yellowish ventrally, posterior half of head silvery. Opercle and infraorbitals completely covered by large dark brown chromatophores. Maxilla with few scattered chromatophores. Premaxilla covered by small dark brown chromatophores. Lower jaw with many small dark brown chromatophores. Snout heavily covered by black chromatophores.

Sexual dimorphism. Males and females differing by presence of bony hooks on caudal-, pelvic- and anal-fin rays. Caudal fin with 6-24 tiny hooks on each ray; usually paired and anterodorsally oriented on posterior one-half of rays 13-17. All rays of pelvic fin with short, slender hooks, anteroventrally placed along almost entire length of rays; usually two pairs per segment, and more numerous on medial rays.Anal fin bearing 5-11 husky hooks on each ray, usually one pair per segment, anterodorsally placed on posteriormost unbranched ray and branched rays 1-11; number of hooks increasing in middle rays. Lower lobe of caudal fin of males, but not of females, bearing several scales forming a broadly open pouch. Pouch opening mainly formed by single pouch scale with at least two accessories scales ( Fig. 3 ). Pouch scale relatively small, somewhat elongate, curved and weakly horizontally folded with its lateral face forming concave open pouch. Pouch with medial accessory scale somewhat curved, elongate and located under lateral face of pouch scale (partially visible in lateral view). Pouch with lateral accessory scale large, somewhat elongate posterodorsally and forming part of its laterodorsal region. Pouch scale and lateral accessory scale independent but in contact, both scales strongly attached to each other dorsally through well-developed medial mass of connective tissue. Caudal-fin rays 15 to 18 and anterolateral surface of pouch scale of males with small pieces of apparent glandular tissue.

Gill gland of males relatively long and formed by fusion of anterior 12(1), 13*(2), 14(1), or 15(1) gill filaments of ventral limb of first gill arch. Total number of ventral limb gill filaments 25(1), 28(3), or 29*(1). Gill gland length between 4.7 and 6.9% SL (mean = 5.5% SL), 5.1% SL*. Snout to pectoralfin origin, snout to anal-fin origin, pectoral-fin to pelvic-fin length, and pelvic-fin length sexually dimorphic as function of SL and with differences more pronounced in larger specimens ( Fig. 4 ). Males with higher values than females in snout to pectoral-fin origin and pelvic-fin length, while females with higher values in remaining two measurements.

Distribution. Chrysobrycon yoliae is known from its type locality, an unnamed drainage flowing into the río Yucamia system, río Ucayali basin, Peru ( Fig. 5 ).

Ecological notes. The type locality is a white-water drainage with an average width of 3 m and depth between 0.3 and 1.6 m (very narrow shore). The water color is beige, rather clear and showing at least 20 cm of transparency. The velocity of current is moderate. The substrate is mainly sandy (80%) and covered by pebbles (20%). The riverine vegetation is mainly composed of palms named “aguaje” ( Mauritia flexuosa ), palms locally named “pona” ( Socratea exorrhiza ) and others small plants. The fish samples were obtained from shallow areas with vegetation, rifles, or rapids along 250 m.

Etymology. The new species name yoliae is matronym in honor and gratitude to “Yoli” (Yolanda Ríos Nossa), the mother of the senior author and who has patiently encouraged and supported his academic formation in all senses.

Key to Chrysobrycon species

1a. Thirty three to 39 branched anal-fin rays; 17-19 circumpeduncular scales; adult males with a longer and expanded anal fin and with a series of spinelets developed on pelvic-, anal- and caudal-fin rays...................................... ............................................................ Chrysobrycon myersi

1b. Twenty four to 32 branched anal-fin rays; 14-16 circumpeduncular scales; adult males with shorter and not expanded anal fin and without spinelets on the rays of fins ... ........................................................................................... 2

2a. Adult males with a series of minute bony hooks more distally located on almost all anal-fin rays; larger specimens (usually> 50 mm SL) with anteriormost maxillary tooth usually pentacuspidate (rarely tetracuspidate); terminal lateral-line tube on middle caudal-fin rays absent.............................................. Chrysobrycon hesperus

2b. Adult males without a series of minute bony hooks on distal portion of anal-fin rays; larger specimens (usually> 30 mm SL) with anteriormost maxillary tooth usually tricuspidate (rarely conical, bicuspidate or tetracuspidate); terminal lateralline tube on middle caudal-fin rays present...............................3

3a. Dentary teeth 20-26; depth at dorsal-fin origin 34.4-42.2% SL; dorsal-fin to adipose-fin length 26.8-28.8% SL; dorsalfin origin situated at vertical between anal-fin rays 5 to 7; posterior extent of ventral process of quadrate reaching the vertical through posterior margin of symplectic ( Fig. 6a )...... ......................................... Chrysobrycon yoliae new species

3b. Dentary teeth 12-19; depth at dorsal-fin origin 24.1-34.5% SL; dorsal-fin to adipose-fin length 23.9-26.8% SL; dorsalfin origin situated at vertical between anal-fin rays 8 to 10; posterior extent of ventral process of quadrate not reaching the vertical through posterior margin of symplectic ( Fig. 6b ) .............................................................. Chrysobrycon eliasi

Figures

Fig. 1.Chrysobrycon yoliae, (a) MUSM 46140, holotype male, 51.6 mm SL, Peru, Ucayali, Coronel Portillo,Abujao, río Ucayali basin, río Yucamia system, unnamed Quebrada; (b) MUSM 46141, paratype female, 51.5 mm SL, collected with holotype.

Fig.2. Chrysobryconyoliae, CI-FML 5882, paratype male,44.8 mm SL. Lateral view of jaws:(a) Premaxilla (PM) and maxilla (MX), left side. (b) Dentary (DT), anguloarticular (AAR) and retroarticular bones (RAR), left side. Scale bar = 1 mm.

Fig. 3.Chrysobrycon yoliae, paratype male, CI-FML 5882, 44.8 mm SL. Lateral view of the ventral lobe of caudal fin, left side. Note the scales forming the pouch in this lobe. MAS: Medial accessory scale, LAS: Lateral accessory scale. Scale bar = 1 mm.

Fig. 4. Comparative regression plots of females (n = 8) and males (n = 5) of Chrysobrycon yoliae. All variables as function of SL: (a) Snout to pectoral-fin origin (females: r2 = 0.92; males: r2 = 0.99), (b) snout to anal-fin origin (females: r2 = 0.97; males: r2 = 0.99), (c) pectoral-fin to pelvic-fin length (females: r2 = 0.93; males: r2 = 0.98), (d) pelvic-fin length (females: r2 = 0.55; males: r2 = 0.93).

Fig. 5. Geographic distribution of Chrysobrycon yoliae (yellow triangle).

Fig. 6. Detail of suspensorium of (a) Chrysobrycon yoliae, CI-FML 5882, paratype male, 44.8 mm SL, and (b) Chrysobrycon eliasi, paratype male,AI 287, 39.9 mm SL, comparing the posterior extent of ventral process of quadrate (QUA, white arrows) with respect to the vertical through posterior margin of symplectic (SYM, black arrows). Anterior to left. Scale bar = 1 mm.