Chrysobrycon eliasi, Vanegas-Ríos & Azpelicueta & Ortega, 2011

Vanegas-Ríos, James Anyelo, Azpelicueta, María de las Mercedes & Ortega, Hernán, 2011, Chrysobrycon eliasi, new species of stevardiine fish (Characiformes: Characidae) from the río Madre de Dios and upper río Manuripe basins, Peru, Neotropical Ichthyology 9 (4), pp. 731-740 : 732-737

Chrysobrycon eliasi , new species

Figs. 1-4

Holotype. MUSM 39970 , 34.25 mm SL, male, Peru, Madre de Dios, Tambopata, río Madre de Dios basin, Creek Loboyoc , 12°27’7.27”S 69°7’42.53”W, 210 m a.s.l., 7 Jul 2004, M. Hidalgo, S. Martínez & V. Chipollini.

Paratypes. All from Peru. AI 287, 3, 32.95-43.50 mm SL (2 C&S), Madre de Dios, Tambopata, río Manuripe basin, Creek km 50, 12°11’21.24”S 69°6’57.36”W, 248 m a.s.l., 8 Jul 2004, M. Hidalgo, S. Martínez & V. Chipollini. AI 288, 2, 37.27-37.63 mm SL, Madre de Dios, Tambopata, río Manuripe basin, Creek Yarinal, 12°3’6.12”S 69°4’49.77”W, 250 m a.s.l., 9 Jul 2004, M. Hidalgo, S. Martínez & V. Chipollini. MUSM 39971 , 14 , 26.14-40.81 mm SL (11, 30.13-40.81 mm SL), collected with the holotype. MUSM 39972 , 8 , 28.01-43.15 mm SL (6, 28.01-30.70 mm SL), Madre de Dios, Tambopata, río Manuripe basin, Creek km 50, 12°11’21.24”S 69°6’57.36”W, 248 m a.s.l., 8 Jul 2004, M. Hidalgo, S. Martínez & V. Chipollini. MUSM 39973 , 2 , 36.11-37.63 mm SL, Madre de Dios, Tambopata, río Madre de Dios basin, Creek Loboyoc, 12°27’21.17”S 69°7’41.67”W, 225 m a.s.l., 23 Aug 2004, H. Ortega, B. Rengifo & L. Figueroa. MUSM 39974 , 3 , 29.33-41.22 mm SL, Madre de Dios, Tambopata, San Antonio, río Heath basin, Creek San Antonio, 12°41’03.14”S 68°43’8.86”W, 193 m a.s.l., 28 May 1992, H. Ortega .

Non-type specimens. ROM 66378, 4 of 5, 27.58-31.63 mm SL, Peru, Madre de Dios, Tambopata, La Colpa, lodge, río Tambopata , stream at left bank at 2.1 km .

Diagnosis. Chrysobrycon eliasi is distinguished from its congeners by the maxillary teeth, tricuspidates, bicuspidates, and conical ( Fig. 3 ), vs. all maxillary teeth tricuspidate to pentacuspidate in C. myersi and C. hesperus . Chrysobrycon eliasi also has the terminal lateral-line tube developed between caudal-fin rays 10-11 vs. absence of the terminal lateral-line tube in C. myersi and C. hesperus . Furthermore, Chrysobrycon eliasi differs from C. hesperus by the presence of 6-15 (mode = 11; n = 28) maxillary teeth ( Fig. 5b ) occupying more than 70% of the length of the maxilla in adults, vs. maxilla with 2-9 teeth (mode = 3; n = 11) occupying less than 70% of its length in adults, and a lower number of predorsal scales ( Fig. 5d ) 18-22 (mode = 19; n = 28) vs. 22-23 (mode = 22; n = 11), respectively. Chrysobrycon eliasi is also readily differentiated from C. myersi by a smaller dorsal-fin to hypural complex length 36.32-41.17% SL vs. 42.19-47.38% SL; smaller gill-gland length in males, 3.57-5.05% SL vs. 6.52-6.66% SL; shorter maxillary length, 33.76-38.75% HL vs. 39.85-48.28% HL; and a lower number of branched anal-fin rays ( Fig. 5a ), 24-30 vs. 33- 36. Chrysobrycon eliasi has a different pattern of scales near to the pouch scale of males; the additional small scale is set under the pouch scale and its ventral border is not seen in the lateral view.

Description. Morphometric data for holotype ( Fig. 1 ) and 27 paratypes in Table 1. Largest male 39.90 mm SL, largest female 43.50 mmSL.

Body laterally compressed, with maximum depth at vertical through half length of pelvic fin. Dorsal profile of body straight over head and convex from supraoccipital region to dorsalfin origin, slanting ventrally and slightly concave or smooth from last dorsal-fin ray to caudal peduncle. Dorsal profile of caudal peduncle straight. Ventral profile of body convex from tip of snout to pelvic-fin origin, slanting dorsally and straight from this point to caudal peduncle. Ventral profile of caudal peduncle straight. Dorsal-fin origin located at vertical through anal-fin rays 8 and 10. Adipose fin located at vertical through last anal-fin ray. Anal-fin origin situated in posterior half of body, always slightly anterior to dorsal-fin origin. Pelvic-fin origin slightly anterior to half length of body. Pectoral fin relatively long, its posterior tip reaching half length or about three quarters of pelvic-fin length ( Fig. 2 ).

Head with anterior portion acute. Frontal fontanel absent. Epiphyseal branch of supraorbital canal absent. Nostrils somewhat rounded separated by one skin fold, posterior opening larger. Mouth superior, lower jaw projecting slightly anterior to upper jaw. Maxilla relatively short, not reaching posteriorly vertical through anterior border of pupil.

Dorsal fin ii-iii,7-9 (ii,8*), n = 28. Eight or nine proximal pterygiophores in dorsal fin.Anal fin iv-v,24-30 (v,28*), n = 28. Twenty eight to 30 proximal pterygiophores in anal fin. Pectoral fin i,9*-10 (i,10), n = 28. Pelvic fin i,5-7,i (i,6,i*), n = 28; one specimen with i,7. Caudal fin forked with 10/9 principal rays in all specimens, n = 25. One terminal lateral-line tube present between membranes of caudal-fin rays 10-11, n = 2.

Premaxilla with two rows of teeth. Outer row teeth often tricuspidate and rarely bicuspidate, not aligned, with 4-6 (5*), n = 28. Inner row with teeth pentacuspidate and sometimes tetracuspidate, with 4-5* (4), n = 28. Maxilla bearing teeth in more than 70% of its length in adults. Maxillary teeth 6-15 (11), 12*, n = 28. First one to eight teeth of maxilla tricuspidate or bicuspidate, remaining teeth conical. Dentary with three anterior teeth large and pentacuspidate; one median sized usually tetracuspidate; posterior ones conical and smaller 12-19 (16), 18*, n = 23 ( Fig. 3 ).

Scales cycloid, with several radii along posterior field. Lateral line complete, perforated scales 42*-46 (43), n = 28. Predorsal scales 18-22 (19), 20*, n = 28. Scale rows between dorsal fin and lateral line 6-7 (7*), n = 28. Scale rows between lateral line and anal fin 4-6 (5*), n = 28. Scale rows between lateral line and pelvic fin 4-6 (5*), n = 28. Scale rows around caudal peduncle 15-16* (15), n = 28. One row of scales forming sheath along anal-fin base, with 14-26 (18*) scales, n = 26. Sometimes, several scales located in one row between body scales and sheath.

Total number of vertebrae 42, n = 2. Gill-rakers on dorsal limb of first arch 5-6 (6*), n = 9; ventral limb with 11-12 (12*), n = 9. Branchiostegal rays distributed as follows: three on anterior ceratohyal and one on posterior ceratohyal, n = 2.

Color in alcohol. Ground color pale yellowish in preserved males and females, dorsally darker and slightly lighter ventrally. Scattered chromatophores over all body, dark brown and black, more concentrated dorsally, sometimes forming reticulate pattern. Dark black lateral band extended from posterior region of humeral spot to middle caudal peduncle. Black chromatophores forming two very narrow lines, one along mid-dorsal line and other one crossing mid-flank slightly above lateral-line scales, from about vertical through pelvicfin origin to middle caudal peduncle. Black chromatophores forming stripes over myomeres. Humeral spot somewhat rounded, several specimens with scattered black chromatophores forming spot more ventrally elongated. Caudal peduncle region with scattered black and dark brown chromatophores, infrequently forming blotch. Dorsal and anal fins hyaline with scattered black chromatophores more heavily concentrated along membranes of rays. Pectoral and pelvic fins hyaline with scattered black chromatophores, mainly placed on membranes of rays. Anterior membranes of anal-fin rays with black chromatophores heavily concentrated. Caudal fin hyaline with scattered black chromatophores along membranes and also on rays 1 and 19. Adipose fin hyaline sometimes with black chromatophores in its base.

Head dark brown dorsally and more yellowish ventrally. Chromatophores dark brown scattered on opercle and infraorbitals. Infraorbitals pale yellowish and sometimes slightly silver. Iris silvery. Maxilla with few chromatophores. Snout heavily covered by black chromatophores.

Sexual dimorphism. The males of Chrysobrycon eliasi are differentiated from females by the presence of bony hooks on rays of the caudal, pelvic, and anal fins. Caudal fin bears 6- 21 tiny hooks, anterodorsally oriented on the posterior half of rays 13-17. All rays of pelvic fin bear short, slender hooks, anterolaterally placed almost all over the entire length of the rays; usually two pairs per segment, and more numerous on medial rays. Anal fin has 5-11 husky hooks; one pair per segment, anterodorsally placed on the last unbranched ray and branched rays 1-11; the number of hooks increases in middle rays. The males also differ from females by the presence of modified scales forming a pouch on the lower lobe of caudal fin ( Fig. 4 ). The pattern of scales on the caudal fin includes a pouch scale, somewhat elongate, curved and horizontally folded with its lateral face forming a concave open pocket; the dorsal fold of the pouch scale forms the dorsal region of the pouch opening. An additional small and also curved scale is set under the pouch scale; it is shorter than the length of the pouch scale and its ventral border is not seen in the lateral view. The length of the scale is shorter than the length of the pouch scale.

The males have a gill gland, relatively long and anteriorly formed by ventral limb of gill filaments, 10-15 (12), 11*, joined together; the total number of ventral limb gill filaments is 24- 28 (28), 25*, n = 12. Among all males examined (27.58-39.90 mm SL), the gill gland and hooks on fin rays were absent in one specimen of 32.6 mm SL. The length of the gill gland was 3.57-5.05% SL (mean = 4.21% SL) SL, 4.11% SL*, n = 9. Principal component analysis grouped males of Chrysobrycon eliasi separately from females along PC2, except for three males ( Figs. 6 a-b). The second principal component was strongly affected by caudal peduncle depth (-0.51), pelvic-fin to anal-fin length (0.47), pelvic-fin length (-0.39), caudal peduncle length (-0.35), pectoral-fin to pelvicfin length (0.24) and depth at dorsal-fin origin (-0.16). In addition, two of them, pelvic-fin to anal-fin length (t = 0.85, p = 0.40; F = 4.32, p = 0.01), and caudal peduncle depth (t = -2.20, p = 0.04; F = 1.04, p = 0.95) were found to be significantly different to either t -test or F -test. Regression plots were more informative because of minimal overlapping to characterize males and females in the following variables: depth at dorsal-fin origin, pelvic-fin length, caudal peduncle length and depth, all as function of SL ( Figs. 7 a-d). Usually at higher values of SL, females and males are strongly dimorphic.

Multivariate analyses. The principal component analysis among species separate Chrysobrycon eliasi from C. hesperus and C. myersi along the PC2 axis ( Figs. 6 c-d), except for two specimens of C. hesperus . The second principal component was more strongly affected by caudal peduncle depth (-0.46), maxillary length (-0.32), pelvic-fin to anal-fin length (-0.32), dorsal-fin base length (-0.33), eye to dorsal-fin length (0.27), pectoral-fin length (0.24), snout to dorsal-fin origin (0.23), dorsal-fin to adipose-fin length (-0.23), and upper jaw length (-0.22). Some of the previous values were included in the diagnosis of C. eliasi and used to differentiate it from both C. hesperus and C. myersi ; two values are useful to differentiate C. hesperus and C. myersi : pectoral-fin length (23.97-28.43% SL vs. 22.48-24.59% SL) and pelvic-fin to analfin length (14.54-16.92% SL vs. 12.59-14.25% SL); dorsal-fin base length was not useful to differentiate the species.

Distribution. The new species is known from different localities of the río Madre de Dios basin and the upper río Manuripe basin, both flowing into the río Madeira basin, Peru ( Fig. 8 ).

Ecological notes. Chrysobrycon eliasi is usually found in dark water creeks at 210-250 m a.s.l., often slightly acid with pH ranging between 5.8 and 6.2, and characterized by soft substratum, including sand, clay and fallen leaves, surrounded by primary forest.

Etymology. The species is named as patronym in honor and memory to the late Elias Vanegas G., father of the senior author (J.V-R.).

Remarks. Specimens of Chrysobrycon eliasi from río Tambopata (ROM 66378) were listed as non-type specimens. We did not find any clear differences between samples from río Tambopata and the type series, but some variation was found in the gill-gland length of males: 5.33-6.40% SL, n = 2 vs. 3.57-5.05% SL, n = 9, respectively. Statistical tests are not used herein because of the small number of specimens examined of that population; therefore, we considered them as non-type specimens.

Key to Chrysobrycon species :

1a. Thirty three to 36 branched anal-fin rays; 18-19 longitudinal scale rows around caudal peduncle; distance from snout to dorsal-fin origin 56.59-61.91% SL; distance from dorsalfin to hypural complex 42.19-47.38% SL ....................... ................................................................. Chrysobrycon myersi

1b. Twenty four to 32 branched anal-fin rays; 14-15 longitudinal scales rows around caudal peduncle; distance from snout to dorsal-fin origin 61.15-68.47% SL; distance from dorsalfin to hypural complex 34.32-41.17% SL ............................. 2

2a. Maxilla with 3-9 teeth (frequently 6) tricuspidate to pentacuspidate, occupying less than 70% of its length in adults; males with bony hooks restricted more distally on anal-fin rays as one proceed posteriorly along the fin; 22- 25 predorsal scales ........................... Chrysobrycon hesperus

2b. Maxilla with 6-15 teeth (frequently 11) conical, bicuspidate, and tricuspidate, occupying more than 70% of its length in adults; males without bony hooks on the distal portion of the anal-fin rays; 18-22 predorsal scales .................... ................................................................... Chrysobrycon eliasi

Figures

Fig. 1. Chrysobrycon eliasi, holotype, male, MUSM 39970, 34.25 mm SL, Peru, Madre de Dios, Tambopata, río Madre de Dios basin, Creek Loboyoc.

Fig. 2. Chrysobrycon eliasi, female, paratype, MUSM 39973, 37.63 mm SL, Peru, Madre de Dios, río Madre de Dios basin, Creek Loboyoc.

Fig. 3. Chrysobrycon eliasi, AI 287, paratype, female 32.95 mm SL. Lateral view of jaw and dentition:(a) Upper jaw, right side. (b) Lower jaw, right side. Lateral view of maxilla: (c) C. hesperus, maxilla, left side, male, MUSM 28665.(d) C. myersi, maxilla, right side, male, MUSM 38671. Scale bar = 1 mm.

Fig. 4. Chrysobrycon eliasi, male,AI 287, 39.9 mm SL. Lateral view of the caudal fin, left side. Note the squamation associated to pouch scale in the ventral lobe. Scale bar = 1 mm.

Fig. 5. Comparative Tukey box plots showing the variation of (a) number of branched rays of anal fin, (b) number of teeth in maxilla, (c) number of lateral-line scales, and (d) predorsal scales of Chrysobrycon eliasi, C. hesperus, and C. myersi. Number of specimens between parentheses.

Fig. 6. Principal component analyses of morphometric data by sex of Chrysobrycon eliasi (a-b) and comparing Chrysobrycon species (c-d). PC1, PC2 and PC3 correspond to the first, second and third principal components, respectively.

Fig. 7. Comparative regression plots of males and females of Chrysobrycon eliasi. (a) Depth at dorsal-fin origin as function of SL (females: r2= 0.92; males: r2 = 0.94), (b) pelvic-fin length as function of SL (females: r2 = 0.90; males: r2 = 0.72), (c) caudal peduncle length as function of SL (females: r2 = 0.79; males: r2 = 0.76), (d) caudal peduncle depth as function of SL (females: r2 = 0.87; males:r2= 0.93).

Fig. 8. Geographic distribution of Chrysobrycon eliasi. White circle indicates two localities, including type locality. The inset from upper part of figure is delimited by black line and correspond to a zoom of the rectangle indicate below it.