Bryconadenos weitzmani, Menezes & Netto-Ferreira & Ferreira, 2009

Menezes, Naércio A., Netto-Ferreira, André Luiz & Ferreira, Katiane M., 2009, A new species of Bryconadenos (Characiformes: Characidae) from the rio Curuá, rio Xingu drainage, Brazil, Neotropical Ichthyology 7 (2), pp. 147-152 : 148-150

Bryconadenos weitzmani , new species Figs. 1-3

Holotype. MZUSP 98666 , 40.7 mm SL, female, Brazil, Pará State: Altamira, rio Curuá tributary of rio Iriri , rio Xingu basin, 08º43’50”S 54º57’49”W, 20 Oct 2007, J. L. O. Birindelli, L. M. Sousa, A. L. Netto-Ferreira, M. H. Sabaj-Perez & N. Lujan.

Paratypes. MZUSP 96558 , 10 , 32.0- 41.3 mm SL, collected with holotype . MZUSP 96559 , 20 , 18.0- 36.5 mm SL, Brazil: Pará State: Altamira, vila de Castelo dos Sonhos, tributary of rio Iriri, rio Xingu basin, 08º19’07”S 55º05’23”W, 22 Oct 2007, same collectors as holotype .

Diagnosis. Bryconadenos weitzmani can be distinguished from B. tanaothoros , the only known species of the genus by the presence of a conspicuous dark blotch at the humeral region (vs. absent in B. tanaothoros ), by having fewer scale rows between dorsal-fin origin and anal-fin origin (7-8, mean = 7.03 vs. 8-10, mean = 8.8) and the anal-fin gland cup-shaped in mature males, its lower part much more developed than the upper ( Fig. 2 ). The anal-fin gland in B. tanaothoros (Weitzman et. al. 2005, fig. 7, p. 339) is not cup-shaped, the upper and lower parts being almost equallly developed and sometimes separated by a slit in fully mature males.

Description. Morphometrics of holotype and paratypes are presented in Table 1. Body small reaching at least 41.3 mm SL, elongate and laterally compressed; greatest body depth slightly anterior to dorsal-fin origin at vertical crossing pelvic-fin origin. Dorsal body profile convex at snout, gently convex from above nostril to dorsal-fin origin, straight or nearly so and posteroventrally inclined from this point to caudal peduncle. Dorsal profile of caudal peduncle slightly concave. Ventral body profile convex at tip of lower jaw, gently convex from below anterior margin of orbit to anal-fin origin, nearly straight and dorsally inclined along anal-fin base and slightly concave along ventral margin of caudal peduncle. Lower jaw somewhat included in upper jaw when mouth closed.Posterior tip of maxilla extending beyond vertical crossing anterior border of orbit.

Dorsal-fin rays ii, 8 in all specimens. Posterior most ray split to its base. Adipose fin present. Anal-fin rays iv,17-19 (19), 17.5, posterior most ray split to its base. Strongly developed anterior anal-fin lobe including anterior unbranched rays and first 5-6 branched rays in both sexes.Anal fin of sexually mature males with bilateral bony hooks on anterior five branched rays. Hooks distributed on sides of anterior and posterior primary branches. In a cleared and stained male specimen (MZUSP 96558, 38.5 mm SL) hooks are not always present on both sides of anterior and posterior primary branches. 17 hooks on first branched ray, 9 on second, 8 on third, 5 on fourth, and 2 on fifth. Well-developed cup-shaped gland covering bases of five anterior most anal-fin rays. Pectoral-fin rays i,11-12 (i,11), 11.2. Distal tip of longest pectoral-fin ray not reaching pelvic-fin origin even in mature females, but almost reaching origin of that fin in males, but no differences found in relative lengths of pectoral fins in males and females through regression analysis. Pectoral-fin rays without hooks. Pelvic-fin rays i, 7 in all specimens. No hooks on pelvic-fin rays of sexually mature males. Distal tip of longest pelvic-fin rays extending slightly beyond anal-fin origin. Pelvic-fin length of sexually mature specimens sexually dimorphic ( Fig. 3 ). Principal caudal-fin ray count 10/ 9 in all specimens.

Scales cycloid. Lateral line complete, perforated scales 36-39(38), 37.8. Predorsal scales 10-12(11), 11.1. Scale rows between dorsal-fin origin and anal-fin origin 7-8(7), 7.03. Scale rows around caudal peduncle 13-15(14), 13.8.

Shape, size and arrangement of teeth on premaxilla, maxilla and dentary as described for Bryconadenos tanaothoros (compare Fig. 3 , this paper, with fig. 9 in Weitzman et al., 2005, p. 341). Outer row small teeth on premaxilla 2-5(3), 3.3. Inner row premaxillary teeth 4 in all specimens. Maxillary teeth 2 in all specimens. Dentary with 4 large teeth followed more or less abruptly by 3-4(3), 3.3 smaller teeth. Dorsal limb gill rakers 5-7(6), 6.1; ventral limb gill rakers 10-13(11), 11.4 in first gill arch. Branchiostegal rays 4 in one cleared and stained specimen, 3 rays originating on anterior and 1 on posterior ceratohyal. Vertebrae 36-38(37), 37.1.

Color in alcohol. Body color of Bryconadenos weitzmani identical to that of B. tanaothoros as described by Weitzman et al. (2005, p. 341-342) with exception of: dark lateral stripe extending from behind dorsal part of opercle to caudal peduncle where it broadens, its posterior margin covering bases of 1-16 principal caudal-fin rays; medially on caudal fin stripe continues to distal tip of caudal-fin rays 9-12. Stripe widest above pelvicfin origin, covering at his area three longitudinal scale rows. Conspicuous dark blotch slightly deeper than wide present at humeral region. Longitudinal dark stripe on dorsum extending from occiput to dorsal part of caudal peduncle separated by one and a half longitudinal scale rows from horizontal body stripe, ventrally interrupted on each scale immediately below median dorsal scale row by a small pale area.

Sexual dimorphism. The most obvious sexually dimorphic feature in Bryconadenos weitzmani is the presence of a cupshaped anal-fin gland in sexually active males, not present in females. Histological sections revealed the presence of glandular club cells in the glandular tissue which apparently undergo holocrine secretion. Gill glands are present in sexually active males but not in females, and develop from anterior gill filaments of the first gill arches, consisting of five gill filaments and four chambers. The anterior anal-fin profile of males and females are slightly different ( Fig. 1 ).

Estimation of slope differences between males and females indicated that only the relationship between pelvic-fin length and standard length was significant (difference between slopes = 0.115; standard error = 0.021; t = 5.121; p = 0.00002). Figure 4 suggests that significant differences between males and females start to appear at about the standard length of 30 mm.

Etymology. Bryconadenos weitzmani is named in honor of Stanley H. Weitzman for his outstanding contribution to the knowledge of neotropical freshwater fishes.

Distribution. This species is known from the rio Curuá, a tributary of rio Iriri, rio Xingu basin in Altamira, Pará State, Brazil ( Fig. 5 ).

Ecological notes. Specimens of Bryconadenos weitzmani were collected from two stretches of the rio Curuá. Both localities were clear water rocky rapids, with thick sand on the bottom ( Fig. 6 ). They were observed by one of us (ALN- F) forming small schools of about 10-15 individuals actively swimming against fast flowing waters below a one meter high fall. The new species seems to be very rheophylic, living in streams with fast flowing waters. Specimens of Baryancistrus sp. 1 , Baryancistrus sp. 2 , Caiapobrycon sp. , Crenicichla of the group saxatilis , and Teleocichla sp. were collected below the same waterfall where part of the type specimens (MZUSP 96559) were found. Other 91 species were collected in rio Curuá at the collecting sites near the villages of Castelo dos Sonhos and Cachoeira da Serra, below large waterfalls near the latter which seem to represent an effective barrier isolating the headwater fish fauna from the species living below it (Birindelli et al., in press).

Figures

Fig. 1. Type specimens of Bryconadenos weitzmani. A, holotype, MZUSP 98666, 40.7 mm SL, female; B, paratype MZUSP 96559,36.5mmSL,male.

Fig. 2. Lateral view of the anal-fin organ in Bryconadenos weitzmani,paratype MZUSP96559,36.5 mm SL, male,anterior to left.

Fig. 3. Scanning electronic micrograph of upper and lower jaws ofBryconadenos weitzmani,paratype,MZUSP 96558, 38.5 mm SL, male; lateral view, anterior to right.Scale bar 1 mm.

Fig. 4. Pelvic-fin length as a function of standard length by sex for males and females of Bryconadenos weitzmani. For explanation see text under sexual dimorphism.

Fig. 5. Rio Xingu basin and adjoining areas, showing the collecting sites (black dots) and type-locality (open dot) of Bryconadenos weitzmani.

Fig. 6. Type locality of Bryconadenos weitzmani, at the rapids in the rio Curuá, near the village of Castelo dos Sonhos, Altamira, Pará, Brazil. Photo by Mark S. Perez.