Charax pauciradiatus (Günther, 1864)

Menezes, Naércio A. & de Lucena, Carlos Alberto S., 2014, A taxonomic review of the species of Charax Scopoli, 1777 (Teleostei: Characidae: Characinae) with description of a new species from the rio Negro bearing superficial neuromasts on body scales, Amazon basin, Brazil, Neotropical Ichthyology 12 (2), pp. 193-228 : 218-221

Charax pauciradiatus (Günther, 1864) Figs. 22-23

Anacyrtus pauciradiatus Günther, 1864 [original description, type locality: Brazil, State of Pará, rio Capin (= rio Capim)].

Charax pauciradiata, Eigenmann, 1910: 444 (listed in catalog).

Charax pauciradiatus, Lucena, 1987: 48 (diagnosis; description; comparisons; distribution; geographic variation). - Lucena & Menezes, 2003: 104 (maximum length; distribution).

Diagnosis. Charax pauciradiatus differs from C. apurensis and C. macrolepis by having the orbital diameter 30.4-38.7% of HL (vs. 20-21% of HL, Fig. 4 ) and from C. caudimaculatus and C. notulatus that have the orbital diameter 25-28.5% of HL. Charax pauciradiatus can be distinguished from C. michaeli in the number of the scale rows from the dorsal-fin origin to to the lateral line (13-14 vs. 18-20) and from C. leticiae that has 16-18 scale rows from the dorsal-fin origin to the lateral line. Charax pauciradiatus differs from C. niger and C. gibbosus in having the humeral spot distance 38-44% of SL (vs. 34.7-37.8% of SL, Fig. 3 ). Charax pauciradiatus differs from C. hemigrammus , C. condei , and C. stenopterus in having the lateral line complete (vs. lateral line incomplete), from C. rupununi by the number of scales around the caudal peduncle (15-17 vs. 12) and from C. tectifer , C. metae , and C. delimai by having the anal-fin origin always located anterior to the vertical through the dorsal-fin origin (vs. the anal-fin origin on, or slightly posterior, to the dorsal-fin origin) and the ectopterygoid teeth absent (vs. ectopterygoid teeth present).

Description. Morphometrics of examined specimens presented in Table 13. Body elongate, moderately large (36- 100 mm SL), compressed and moderately deep. Greatest body depth slightly in advance of dorsal-fin origin. Dorsal profile of head and body slightly convex on tip of snout, straight from posterior border of posterior nostril to vertical through posterior border of pupil, slightly concave from that point to base of supraoccipital spine, strongly convex from that point to dorsal-fin origin, nearly straight along dorsal-fin base and from end of dorsal-fin base to caudal peduncle and slightly concave along caudal peduncle. Ventral profile of head and body convex from tip of lower jaw to anal-fin origin, nearly straight along anal-fin base and concave from end of anal-fin base to beginning of procurrent rays. Snout pointed. Lower jaw included in upper jaw when mouth closed. Maxilla extending slightly beyond vertical through slightly posterior of middle of orbital diameter.

Dorsal-fin rays ii, 9 in all specimens, posterior most ray unbranched. Adipose fin present. Unbranched anal-fin rays iv or v, usually iv, branched rays 43-51, 46.6. Sexually mature males with hooks on anterior anal-fin rays ( Fig. 23); one male specimen (MZUSP 19538, 86 mm SL) with tiny bilateral hooks on posterior anterior 10 rays, number of hooks varying considerably, but posteriormost rays with fewer hooks: fourth unbranched ray with 13, first branched ray with 18, second with 22, third with 23, fourth with 24, fifth with 24, sixth with 22, seventh with 15, eighth with 12, nineth with 10, and tenth with 8. Pectoral-fin rays i, 13-17, 14.4. Tips of longest pectoralfin rays reaching to, or slightly beyond, middle of pelvic-fin length. Pelvic-fin rays i, 7. Sexually mature males with tiny hooks on branched pelvic-fin rays ( Fig. 23); male specimen (MZUSP 19538) with 38 hooks on first branched ray, 75 on second, 78 on third, 55 on fourth, 54 on fifth and 38 on sixth. Tips of longest pelvic-fin rays reaching to vertical between bases of third to fifth branched anal-fin rays. Principal caudalfin ray count 10/ 9 in all specimens.

Lateral line complete; perforated scales 52-58, 55.7. Horizontal scale rows from dorsal-fin origin to lateral line 13- 14, 13.9. Horizontal scale rows from pelvic-fin origin to lateral line 9-10, 9.4. Horizontal scale rows from anal-fin origin to lateral line 11-14, 12.6. Predorsal scales 30-38, 34.2. Scale rows around caudal peduncle 15-17, 16.7. Scale row along anal-fin base, extending posteriorly for distance between 2 / 3 and 3 / 4 of fin base length.

Premaxillary with one anterior canine-like tooth followed by a set of smaller conical teeth and another canine-like tooth followed by one or two small conical teeth. Total number of premaxillary teeth 9-15, 11.6. Maxillary teeth conical, 42-67, 52.8; larger specimens usually with higher counts. Dentary with one canine-like tooth followed by 3-5, 3.8 conical teeth, another canine-like tooth and posterior row of 20-31, 24.1 conical teeth.

Vertebrae 34 and 35, in two specimens. Gill-rakers on lower limb of first gill-arch 7-9, 8. Branchiostegal rays 4; 3 rays originating from anterior ceratohyal and 1 from posterior ceratohyal.

Color in alcohol. Body pale to light yellow, slightly darker dorsally than on lateral and ventral regions. Ventral region of body lighter, but with scattered dark chromatophores. Irregularly shaped vertically elongate dark humeral blotch extending about three or four scales horizontally and six or seven vertically. Dorsal part of head, snout and tip of lower jaw darker than remainder of head; dark coloration extending to median and ventral portions of lower jaw, along first and second infraorbitals and between second and third infraorbitals as a very conspicuous subocular stripe extending to lower edge of preopercle. Scattered dark chromatophores on fifth and sixth infraorbitals, anterior and posterior borders of third and fourth infraorbitals and opercular bones. V-shaped lines of chromatophores over miosepta along epaxial and hypaxial muscles more visible on posterior portion of body. Approximately triangularshaped dark blotch on caudal base more conspicuous in young specimens; posterior dark chromatophores. Inconspicuous clear stripe extending for length of fin between darker basal anal-fin region and remaining ventral portion of fin, extending for length of fin. All fins hyaline with scattered dark chromatophores, more visible on interradial membranes. Anterior portion of first and second unbranched rays of dorsal and first unbranched rays of pectoral and pelvic-fin rays darker than remaining rays.

Sexual dimorphism. Females lack tiny anal- and pelvic-fin hooks described above for males.

Distribution. Charax pauciradiatus has been collected on ilha do Marajó, tributaries of the rio Capim, Pará; Paricatuba, Amazonas; rio Aripuanã, Mato Grosso; and rio Madeira basin, Rondônia, Brazil ( Fig. 7 ).

Specimens examined. Brazil, Pará: MZUSP 83763 , 4 , 48-83 mm SL, Castanhal, igarapé Apeú, rio Capim drainage, approximately 1°24’S 46°06’W; MZUSP 20562 , 10 , 38-83 mm SL, lago Maria Preta, rio Capim drainage; MZUSP 20552 , 26 , 36-96 mm SL, rio Capim; MZUSP 19538 , 3 , 86-100 mm SL, rio Apeú , Boa Vista , 1°36’S 47°37’W; MZUSP 33418 , 9 , 48-58 mm SL, rio Apeú, Boa Vista , 1°36’S 47°37’W; MCP 22537, 7 , 52-90 mm SL, tributary of rio Capim and lagoa marginal between Paragominas and Tomé-Açu , about 56 km west of Paragominas, 2°29’13"S 47°9’2"W; MCP 22539, 1 , 92 mm SL, Tomé-Açu, igarapé Urucare , on road between Tomé-Açu and Moju , about 49 km west of Tomé-Açu, 2°29’13"S 48°31’31"W; MCP 39032, 1, 112 mm SL, Rondônia, tributary of rio Madeira , on road BR-364 between Ariquemes and Candeias do Jamari , 8°47’23"S 63°37’37"W. Amazonas: MZUSP 62114 , 2 , 55-56 mm SL, Paricatuba , 4°40’31"S 61°55’33"W; Mato Grosso: MZUSP 60391 , 1 , 64 mm SL, Aripuanã, rio Aripuanã , on road between Colima and Panelas.

Figures

Fig. 22. Charax pauciradiatus MZUSP 19538, female, 100 mm SL, Brazil, Pará, rio Apeú, Boa Vista.

Fig. 4. Orbital diameter as a function of head length for species of Charax.

Fig. 3. Humeral spot distance as a function of standard length for species of Charax.

Fig.7. Map of SouthAmerica showing the collecting sites of the Charax species, and the type locality of Charax delimai (purple circle). Charax apurensis - yellow square; C. caudimaculatus - white circle; C. condei - white square; C. gibbosus - purple triangle; C. hemigrammus - red star; C. leticiae - black circle;C. macrolepis-black triangle;C.metae-yellow triangle;C.michaeli - yellow circle;C.niger -blue triangle; C.notulatus - blue circle; C. pauciradiatus - red triangle; C. rupununi - red circle; C. stenopterus - green triangle; C. tectifer - green circle. Some symbols may represent more than one locality.