Brycon coquenani Steindachner, 1917

Lima, Flávio C. T., 2017, A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae), Zootaxa 4222 (1), pp. 1-189 : 33-35

Brycon coquenani Steindachner, 1917

( Fig. 21 )

Brycon coquenani Steindachner, 1917: 37 –38, pl. 1, figs. 1–2 (Type locality, “ Coquenanflusse in Venezuela”).

Diagnosis. Brycon coquenani can be distinguished from all remaining cis-andean Brycon species, except B. stolzmanni , B. coxeyi , B. devillei , B. insignis , B. vermelha , Brycon howesi , B. dulcis , B. ferox , Brycon vonoi , B. opalinus , and B. nattereri , by possessing a color pattern composed by a humeral blotch and a caudal peduncle blotch (vs. body stripes and caudal/anal fin color markings present; see Fig. 5 ). Brycon coquenani can be distinguished from all these species, except B. insignis , B. vermelha , and B. howesi , by possessing a fifth infraorbital bone wider than high (vs. fifth infraorbital bone about as wide as high; see Fig. 6 ). Brycon coquenani can be distinguished from these species by possessing pointed, tri- to tetracuspidate dentary teeth, with lateral cusps poorly developed (vs. pointed tri- to pentacuspidate dentary teeth, with moderately developed lateral cusps in B. insignis , B. vermelha , and B. howesi ), and by mature males displaying hooks in all rayed fins (vs. hooks present generally only in the anal-fin, rarely also in the pelvic-fins in mature males in B. insignis , and B. howesi , and not present in B. vermelha ).

Description. Morphometric data are presented in Table 4 . Relatively small-sized species, largest examined specimen 170.6 mm SL. Body moderately slender. Largest body height slightly ahead of dorsal-fin origin. Dorsal body profile slightly convex from upper lip margin to vertical through anterior naris, slightly concave from latter point to basis of supraoccipital process, and moderately convex from latter point to dorsal-fin origin, straight along dorsal-fin basis, straight to slightly convex from dorsal-fin terminus to adipose-fin origin. Dorsal profile of caudal peduncle slightly concave. Ventral profile slightly convex from lower lip to pelvic-fin insertion, straight to slightly convex from this point to anal-fin origin and approximately straight along anal-fin base. Ventral profile of caudal peduncle slightly concave.

Head profile slightly acute anteriorly, mouth terminal. Maxillary extending posteriorly to vertical slightly anterior to middle of pupil. Adipose eyelid well developed. Premaxillary teeth in three rows; teeth of third row largest. Small specimens (<84.2 mm SL) with gaps (diastemas) between teeth. Eight (1), 9 (5), 10 (2), or 11 (1) unicuspidate teeth in outer series. Three (2), 4 (2), or 5 (1) tri- to pentacuspidate teeth in second, inner premaxillary row, plus 1(1), 2 (3), or 3 (1) tricuspidate teeth between the first and third rows. Two teeth in third premaxillary row, medial teeth largest, pentacuspidate, symphyseal teeth smaller, tricuspidate. Maxillary with distal portion expanded and rounded in profile. Twenty-five to 31 maxillary teeth, unicuspidate, slightly smaller than teeth of first premaxillary row. Dentary with 8 (1), 9 (2), 10 (1), 11 (3), or 12 (2) teeth in main series. Anterior four dentary teeth assymetrical, considerably larger than remaining teeth, tri- to tetracuspidate. Remaining dentary teeth progressivelly smaller, unicuspidate. Inner (lingual) series consisting of a single unicuspid symphyseal tooth, considerably smaller than teeth of main series anterior to it, plus a row of small, unicuspidate teeth. All teeth with well-developed, pointed central cusp, remaining cusps, when present, poorly developed or vestigial.

Scales cycloid. Lateral line complete, from supracleithrum to caudal-fin base. Forty-four (1), 46 (3), 47 (2), or 48 (3) scales in lateral line series; laterosensory tube simple, straight or deflected downwards. Horizontal scale rows between dorsal-fin origin and lateral line 8 (6), or 9 (3). Horizontal scale rows between lateral line and pelvicfin 4. Circumpeduncular scales 17 (2), or 18 (1).

Dorsal-fin rays ii, 8 (2) or 9 (9). Dorsal fin origin slightly ahead from middle of SL. Dorsal fin displaying numerous (c. 15–30 per fin-ray main branch) small hooks on last unbranched and posterior main branch of all branched rays in one specimen (lectotype, NMW 62702, 170.6 mm SL). Anal-fin rays iii (not including first, small unbranched ray only visible in the cs specimen), 18 (1), 19 (2), 21 (3), 22 (4), 23 (2), or 24 (2). Last unbranched and anterior 2–3 branched anal-fin rays longer, remaining rays progressively shorter towards anal-fin end. Anal fin displaying numerous (c. 20–30 per fin-ray main branch) small hooks associated with dense, gelatinous tissue on last unbranched and posterior main branch branched rays to antepenultimate branched ray in one specimen (lectotype, NMW 62702, 170.6 mm SL). Sheath of scales composed of a single series composed by 15 rectangular scales, covering basis of anal-fin rays. Pectoral-fin rays i, 11 (2), 12 (4), or 13 (3). Branched pectoral-fin rays with minute hooks (c. 10 per branch) on distal portion of posterior ray branches in one specimen (lectotype, NMW 62702, 170.6 mm SL). Pelvic-fin rays i,7. Branched pelvic-fin rays with minute hooks (c.10–20 per branch) on distal portion of posterior ray branches in one specimen (lectotype, NMW 62702, 170.6 mm SL). Main caudal-fin rays 10/9. Small hooks (c. 5–10 per ray branch) on distal portion of inner caudal-fin rays in one specimen (lectotype, NMW 62702, 170.6 mm SL). Caudal fin forked, lobes rounded.

Coloration in alcohol. Color description based on the lectotype, NMW 62702; paralectotypes too faded to allow an accurate color description. Top of head, snout, supraorbital, sixth infraorbital bone, and dorsal portion of body dark brown. Dentary, maxillary, first, second, and upper portion of fifth infraorbital bone, gular area, and ventral portion of body cream-colored. Third, fourth, lower portion fifth infraorbital bones, and opercle silvery, with a brownish tinge. Humeral blotch present, relatively inconspicuous, rounded, extending from first through third lateral line scales. Lateral portions of body cream-colored, with a silvery hue. Caudal peduncle blotch present, conspicuous, rounded, extending throughout 6 last lateral line scales into basis of 4 innermost caudal-fin rays. Caudal, anal and dorsal-fins with numerous small dark chromatophores scattered over interradial membranes. Pectoral and pelvic-fins with relatively few dark chromatophores on interradial membranes. Adipose fin light brown.

Common name. “Aruma”. This common name, mentioned by Steindachner (1917: 37), was recorded by the collector of the type material, John Haseman. In an undated manuscript authored by Haseman, entitled “ Zoogeographical expedition to northeastern South America”, he mentioned (p. 44) “aruma” as the “native” name of an undescribed species of Brycon collected in the Río Kukenan . The Amerindians which helped Haseman during his expedition into the tepuis of northern Roraima state in Brazil and southern Bolívar state in Venezuela belonged to the Arekuna (= Taulipang), so it can be assumed that this common name is originated from this language.

Sexual dimorphism. The lectotype (NMW 62702, 170.6 mm SL) possess numerous small hooks over all rayed fins, including the caudal-fin. However, a dissection was not performed to confirm the specimen’s sex.

Distribution. Brycon coquenani is only known from the upper Rio Kukenan (“Coquenanflusse”), a tributary of the upper Río Caroní, Río Orinoco basin, estado Bolívar, Venezuela ( Fig. 20 ). The exact locality of Brycon coquenani is not known but according to the narrative of Haseman’s travel in the region referred above, the type series was collected in the Rio Kukenan at its valley between the mount Roraima and the Cerro Kukenan, below the “Moromelu Falls” (not located).

Remarks. Steindachner (1917: 37–38) described the species based on a syntypical series of “11 ... juveniles and a larger, very well preserved exemplar 210 mm long” (our translation). We have examined the syntypical series of Brycon coquenani at the NMW. The largest specimen, NMW 62702, is herein designated as the lectotype of the species. The remaining, smaller syntypes, NMW 62703 (10 specimens) became, consequently, paralectotypes. The lectotype is in very good condition, except for missing some scales and for having the top of head bruised, apparently by Steindachner himself, presumably for the examination of the fontanel. In spite of relatively recent collecting efforts in the upper Río Caroní basin, including the Río Kukenan, so far no additional specimens of the species were obtained (Lasso, 1990; Lasso et al., 1990).

Material examined. Type material: NMW 62702 (1, 170.6 mm SL): Venezuela, Estado Bolívar, Río Kukenan, upper Río Caroní basin, Gran Sabana , approximately 5°12’N, 60°46’W; J.D. Haseman, April 1913 . Lectotype of Brycon coquenani Steindachner , by present designation. NMW 62703 (10, 64.7–84.2 mm SL): same data as lectotype . Paralectotypes of Brycon coquenani .

Figures

FIGURE 5. Diagrammatic representation of the patterns of dark colour markings found among cis-andean Brycon species, represented by selected species. A. Brycon stolzmanni. B. Brycon coxeyi. C. Brycon insignis. D. Brycon nattereri. E. Brycon hilarii. F. Brycon whitei. G. Brycon amazonicus. H. Brycon gouldingi. I. Brycon melanopterus. J-L. Brycon falcatus.

FIGURE 6. Diagrammatic representation of the head profile, maxillary and infraorbitals showing the distinct morphologies found among cis-andean Brycon species, represented by selected species. A. Brycon amazonicus, MZUSP 3815, 152.3 mm SL. B. Brycon insignis, MCZ 21112, 232.2 mm SL. C. Brycon dulcis, MZUSP 1531, 146.6 mm SL. D. Brycon falcatus, MZUSP 3845, 195.1 mm SL. E. Brycon opalinus, MCZ 21123, 210.5 mm SL. F. Brycon orbignyanus, MZUSP 3900, 108.9 mm HL. G. Brycon ferox, MCZ 60934, 310.3 mm SL. H. Brycon orthotaenia, MZUSP 2007, 188.7 mm SL. I. Brycon polylepis, MZUSP 70413, 203.9 mm SL. J. Brycon stolzmanni, UMMZ 185306, 120.0 mm SL.

FIGURE 20. Map of northern South America showing known localities of Brycon polylepis (red dots) and B. coquenani (black dot).

FIGURE 21. Brycon coquenani, lectotype, NMW 62702, 170.6 mm SL: Venezuela, Bolívar, Río Kukenan.

Tables

TABLE 4. Morphometric data of Brycon coquenani (A: lectotype, NMW 62702).

	A	n	Range	Mean
Standard length (SL)	170.6	9	72.9–170.6	-
Percentages of standard length
Depth at dorsal-fin origin	25.8	9	17.3–25.8	21.9
Snout to dorsal-fin origin	56.9	9	54.3–56.9	55.9
Dorsal-fin base length	11.4	9	11.1–14.8	12.5
Posterior terminus of dorsal fin to adipose fin	21.7	9	17.0–21.7	18.6
Posterior terminus of dorsal fin to hypural joint	33.1	9	31.6–34.3	32.9
Snout to pelvic-fin insertion	50.7	9	50.7–56.2	54.3
Snout to anal-fin origin	65.4	9	65.4–69.5	68.1
Anal-fin base length	23.1	9	21.1–25.5	22.9
Caudal peduncle length	15.2	9	12.2–15.2	14.4
Dorsal-fin height	18.7	1	18.7	-
Pectoral-fin length	15.8	1	15.8	-
Caudal peduncle depth	7.7	9	6.5–7.7	6.8
Head length	30.9	9	30.9–34.3	32.8
Percentages of head length
Head height	60.6	9	59.8–64.9	61.4
Snout length	29.4	9	27.4–31.8	29.3
Upper jaw length	46.8	9	46.8–51.7	49.7
Horizontal eye diameter	23.1	9	23.1–26.6	25.7
Post-orbital length	51.3	9	40.4–51.3	44.3
Least interorbital width	27.1	9	18.0–27.1	20.6