Characidium bimaculatum Fowler, 1941

Melo, Marcelo R. S. & Espíndola, Vinicius C., 2016, Description of a new species of Characidium Reinhardt, 1867 (Characiformes: Crenuchidae) from the Chapada Diamantina, Bahia, and redescription of Characidium bimaculatum Fowler, 1941, Zootaxa 4196 (4), pp. 552-568 : 559-565

Characidium bimaculatum Fowler, 1941

( Figs. 5 A–C, 6A–F; Table 2 )

Characidium bimaculatum: Fowler, 1941 , pp. 179–180, fig. 90 (original description, “Forteleza (sic), Ceará ”); Rosa et al., 2003: 153, 176 (listed; Caatinga biome).

Holotype. ANSP 69523 , 43.0 mm SL, Fortaleza , Ceará State, Brazil, col. R. von Ihering, 1937 (pictures examined) Paratypes . ANSP 69524 (4), 69528 (1, CS), 29.0–40.0 mm SL, collected with holotype (not examined).

Additional material examined. All from Brazil. MZFS 15015, 1 , 23.1 mm SL, riacho Vaca Brava, Brejo Paraibano , Areias , Paraíba, 7°00’12.3”S, 35°44’04”W, 10 Jul 2012, A.C.A Santos et al. ; MZFS 15036, 14 , 22.63 – 28.31 mm SL, rio Araçaji-Mirim, Brejo Paraibano, Pilões , Paraíba, 6°51’58.6”S, 35°37’17.3”W, 0 8 Jul 2012, A.C.A. Santos et al. ; MZFS 15037, 2 , 20.1 – 30.2 mm SL, rio Macaíba, Brejo Paraibano, Areias , Paraíba, 7°01’23.9”S, 35°42’ 41.9”W; 10 Jul 2012, A.C.A. Santos et al. ; MZFS 15038, 2 , 27.6 – 30.2 mm SL, MZFS 15282, 4 , 24.6 – 28.5 mm SL, Rio Pintura, Brejo Paraibano, Pilões , Paraíba, 6°52’07”S, 35°38’57”W, 8 Jul 2012, A.C.A. Santos et al. ; MZFS 15039, 1 , 25.7 mm SL, MZFS 15329, 6 , 24.0 – 34.2 mm SL, rio Fechada, Brejo Paraibano, Areias , Paraíba, 6°54”39”S, 35°38’58”W, 8 Jul 2012, A.C.A. Santos et al. ; MZFS 15066, 1 , 28.1 mm SL, rio Riachão, Brejo Paraibano, Areias , Paraíba, 7°01’39”S, 35°44’22”W, 10 Jul 2012, A.C.A. Santos et al. ; MZFS 15068, 1 , 26.7 mm SL, rio Pintura, Brejo Paraibano, Pilões , Paraíba, 6°52’07.0”S, 35°38’57”W, 8 Jul 2012, A.C.A. Santos et al. ; MZFS 15073, 1 , 34.0 mm SL, rio Macaíba, Brejo Paraibano, Areias , Paraíba, 7°01’24”S, 35°42’42”W, 10 Jul 2012, A.C.A. Santos et al. ; MZFS 15097, 4 , 26.4 – 36.2 mm SL, MZFS 15254, 9 , 24.7 – 30.6 mm SL, rio Ouricuri, Brejo Paraibano, Pilões , Paraíba, 6°53’23”S, 35°34’03”W, 9 Jul 2012, A.C.A. Santos et al. ; MZFS 15103, 13 , 19.4–38.1 mm SL, Balneário Vale Escuro, Brejo Paraibano, Pilões , Paraíba, 6°52’48,5”S, 35°34’19.2”W, 9 Jul 2012, A.C.A. Santos et al. ; MZFS 15240, 2 , 27.9 – 38.4 mm SL, rio Coringa, Brejo Paraibano, Alagoa Nova , Paraíba, 7°04’42”S, 35°45’35.7”W, 10 Jul 2012, A.C.A. Santos et al. ; MZFS 15287, 12 , 27.1–30.2 mm SL, riacho no sítio Guarabiraba, Brejo Paraibano, Pilõezinhos , Paraíba, 9 Jul 2002, A.C.A. Santos et al. ; MZFS 15326, 17.8 –33.4 mm SL, rio Araçaji-mirim, Brejo Paraibano, Pilões , Paraíba, 8 Jul 2002, A.C.A. Santos et al. ; MZFS 15519, 9 , 29.0 – 30.0 mm SL, stream at Patamuté, Curaçá , Bahia, 9°25’07”S, 39°28’18”W, 1 Dec 2010, E. Santos et al. ; MZFS 15529, 11 , 15.7–30.0 mm SL, riacho Olho d’água, Curaçá , Bahia, 9°16’46”S, 39°48’55”W, 17 Apr 2011, E. Santos et al. ; MZFS 15689, 2 , 28.2–30.2 mm SL, Sitio Guarabira, Brejo Paraibano, Areia , Paraíba, 19 May 2013, A.C.A. Santos et al. ; MZFS 15690, 10 , 17.4–30.4 mm SL, MZFS 15954, 6 , 14.7–27.3 mm SL, rio Macaíba, Brejo Paraibano, Areia , Paraíba, 20 May 2013, A.C.A. Santos et al. ; MZFS 15724, 3 , 31.9–34.3 mm SL, MZFS 15727, 3 , 7.5–11.2 mm SL, MZFS 15820, 3 , 14.9–33.4 mm SL, Balneário Vale Escuro, Brejo Paraibano , Pilões Paraíba, 19 May 2013, A.C.A. Santos et al. ; MZFS 15725, 3 , 23.4–34.9 mm SL, MZFS 15915, 1 , 22.4 mm SL, rio Fechada, Brejo Paraibano, Areia , Paraíba, 19 May 2013, A.C.A. Santos et al. ; MZFS 15738, 2 , 27.7–28.6 mm SL, MZFS 15752, 1 , 30.1 mm SL, MZFS 15822, 1 , 26.67 mm SL, rio Araçaji-Mirim, Brejo Paraibano, Pilões , Paraíba, 19 May 2013, A.C.A. Santos et al. ; MZFS 15781, 9 , 24.4–33.4 mm SL, MZFS 15786, 5 , 14.4–27.8 mm SL, MZFS 15808, 1 , 30.8 mm SL, MZFS 15889, 23 , 26.9–36.7 mm SL, rio Pintura, Brejo Paraibano, Pilões , Paraíba, 6°52’07.0”S, 35°38’56.6”W, 19 May 2013, A.C.A. Santos et al. ; MZFS 15896, 1 , 26.6 mm SL, MZFS 15965, 1 , 27.2 mm SL, rio Riachão, Brejo Paraibano, Areia , Paraíba, 20 May 2013, A.C.A. Santos et al. ; MZFS 15964, 1 , 33.4 mm SL, rio Ouricuri, Brejo Paraibano, Pilões , Paraíba, 19 May 2013, A.C.A. Santos et al. ; MZUSP 120553 (former MZFS 17100 ), 1, 10.5 mm SL, rio Coringa, Brejo Paraibano, Alagoa Nova , Paraíba, 12 Jul 2013, A.R. Carneiro ; MZUSP 77917, 1 , 30.1 mm SL, rio Pitimbu, Paranamirim , Rio Grande do Norte, 5°55’S, 35°15’W [coordinates inferred], 25 Aug 2001, R. Alzier ; MZUSP 57040, 4 , 23.6–27.5 mm SL, Umari, Taipu , Rio Grande do Norte, 5°28’S, 35°35’W [coordinates inferred], 21 Apr 1999, H.C.B. Gurgel et al. ; MZUSP 68965, 2 , 26.3–27.0 mm SL, rio Pitimbu, Macaíba , Rio Grande do Norte, 5°51’S, 35°21’W [coordinates inferred], 18 Feb 2000, T. Oliveira ; MZUSP 68962, 1 , 32.1 mm SL, Rio Guajiru, Ceará-Mirim , Rio Grande do Norte, 5°40’S, 35°25’W [coordinates inferred], 15 Oct 2000, H. Gurgel et al. ; MZUSP 114779, 1 , 36.6 mm SL, stream tributary of riacho dos Carás, rio Jaguaribe drainage, Crato , Ceará, 7°15’S, 39°24’W [coordinates inferred], 28 Apr 1985, W. Gomes ; MZUSP 110781, 1 , 27.4 mm SL, Rio Acaraú, Nova Russas , Ceará, 4°41’36”S, 40°30’03”W, 23 Jul 2009, C.F. Rezende et al.

Diagnosis. Characidium bimaculatum can be distinguished from its congeners except C. bahiense , C. clistenesi , C. laterale , C. nana , C. nupelia , and C. xavante by having an enlarged conspicuous peduncular blotch (vs. peduncular blotch absent). It can be distinguished from C. bahiense , C. laterale , C. nana , C. nupelia , and C. xavante by having a complete lateral line with 32 or 33 perforated scales (vs. lateral line short, not reaching level of dorsal-fin origin, with five to eleven perforated scales), and from Characidium clistenesi by lacking secondary bars, total bars 10–11 (vs. secondary and primary bars bars present, total bars 13–16), peduncular blotch horizontally elongated (vs. peduncular blotch rounded), and mature males having the proximal third of dorsal fin dark (vs. mature males with mostly hyaline dorsal fin with a band of melanophores on its proximal third and sparse melanophores between branches of dorsal-fin rays). Characidium bimaculatum further differs from C. bahiense , C. laterale , C. nana , C. nupelia , and C. xavante by having 14 circumpeduncular scales (vs. 12 in C. bahiense , C. laterale , C. nana , C. nupelia , and C. xavante , and 10 in C. xavante ); from C. nana by having bars elongated, reaching lower portion of body (vs. transversal bars absent or short, not reaching the midbody), stripe thinner than a scale (vs. stripe stout and wide, covering from one to one and a half scales), adipose fin present (vs. absent), and presence of hooks on the branched pelvic-fin rays in mature males (vs. hooks absent).

Description. Morphometric data summarized in Table 2 . Small species of Characidium , reaching maximum size of 43.0 mm SL. Body elongated. Dorsal profile moderately convex between tip of snout and dorsal-fin origin, gently arched at dorsal-fin base, almost straight between dorsal and caudal-fin bases. Ventral profile gently convex between anterior tip of dentary and anal-fin origin, slightly convex at anal-fin base; almost straight between anal and caudal-fin bases. Greatest depth of body at dorsal-fin origin.

Snout short, gently rounded, its tip at level of inferior margin of eye. Mouth small, terminal. Snout to maxillary tip distance equal or slightly longer than eye diameter; maxilla reaching level of anterior margin of orbit. Orbit rounded or slightly elongated antero-dorsally; margin of orbit free. Cheek depth about one third of eye diameter. Nares distinctly separated; distance between nares shorter than distance between posterior naris and eye. Dermal flap along entire border of anterior naris, crescent-shaped and restricted to anterior margin of posterior naris. Parietal branch of supraorbital laterosensory canal absent. Fontanel limited anteriorly by frontals, posteriorly by parietals. Dentary in two rows; outer dentary teeth tricuspid, arranged in single row, increasing in size from lateral to medial portion, numbering 7(3), 8(11), 9(15), 10(1); inner dentary teeth conical, minute, numerous, arranged in single row. Premaxillary teeth tricuspid, arranged in single row, increasing in size from lateral to medial, numbering 6(11), 7(17), 8(1), 9(1). Maxillary teeth absent. Ectopterygoid teeth small, arranged in single row, conical, 9(1), 11(1). Mesopterygoid teeth absent. Branchiostegal rays 4(1); two attached to anterior ceratohyal (1). Total gill rakers on first arch 10(2); gill rakers attached to epibranchial 4(1), 5(1); gill rakers attached to ceratobranchial 5(1), 6(1).

Scales cycloid; parallel radii present on posterior field of scale; circuli absent. Lateral line complete, with all scales perforated; lateral-line scales 30(3), 31(2), 32(6), 33(14), 34(4), 36(1). Scales above lateral line 4(30). Scales below lateral line 5(24), 6(6). Circumpeduncular scales 14(30). Pre-dorsal scales regularly distributed, numbering 10(22), 11(1). Scales between anus and anal fin 2(2), 3(14), 4(9). Isthmus scaled to anterior margin of cleithrum.

Pectoral-fin rays iii,5,iii(1), iii,6,ii(4), iii,7,i(1), iii,7,ii(19), iii,8,i(1), iii,8,ii(3), iii,9,i(1). Pelvic-fin rays i,7,i(30). Dorsal-fin rays ii,9(30); supranumerary element on first pterygiophore of dorsal fin 1(1). Anal-fin rays ii,6(30); supranumerary element on first pterygiophore of anal fin 1(1). Principal caudal-fin rays i,8,9,i (30). Adipose fin present (30).

FIGURE. 7. Map of distribution of Characidium bimaculatum . Highlighting in the inset indicates Northeastern Brazil, with a square indicating the expanded area. Black triangle indicates the type locality, and white triangles additional known records. Each symbol may represent more than one lot. Abbreviations of the Brazilian states are as follows: AL, Alagoas; BA, Bahia; CE, Ceará; MA, Maranhão; PB, Paraíba; PE, Pernambuco; and RN, Rio Grande do Norte.

Precaudal vertebrae 18*(3); total vertebrae 33*(3). Lower procurrent rays 6(1), 7(1); upper procurrent rays 8(1), 9(1). Hypurals 6(2). Epurals 1(2), 3(1). Posterior chamber of swim bladder enlarged, occupying most of peritoneal cavity.

Color of preserved specimens. Ground color of head and trunk tan ( Figs. 5 A–C, 6 E–F). Cheek, distal portion of upper jaw, ventral part of head and opercle, and area around nares pale, with widely spaced melanophores on maxilla and ventral lip; melanophores few or absent on cheek. Dorsal portion of snout and head brown. Dorsal portion of body brown; body yellow; belly pale yellow. Single stripe present, stout, extending from tip of snout to posterodorsal angle of opercle on head, continuing along midbody dorsally to lateral line, extending along base of middle caudal-fin rays. Eyes black with ventral silvery margin. Humeral blotch small, almost indistinguishable, positioned over posttemporal and supracleithrum, overlapped by longitudinal stripe. Peduncular blotch brown, oval, horizontally elongated or arrow-shaped. Basicaudal spot rounded, on base of middle caudal-fin rays, connected with peduncular blotch anteriorly.

Melanophores on body more concentrated on posterior edge of scales, forming overall reticulate pattern on body, bars with chain-like appearance; only primary bars present, secondary bars absent; when present, total bars on body nine to eleven, regularly distributed, not fused on dorsal midline. Bars extending ventrally on flank, not connected ventrally on midline at level of abdominal region; connected ventrally on midline at level of anus and caudal peduncle. Last bar of body overlapped by peduncular botch. Bars more evident in juveniles and females, total bars 9 (1), 10 (7), 11 (7), 12 (6), 13 (1), absent in adult males (8).

Pectoral, pelvic and anal fins mostly hyaline, with interradial membrane hyaline, and melanophores at edges of lepidotrichia. Dorsal fin mostly hyaline, with melanophores concentrated at margin of lepidotrichia, a single band of melanophores present, on proximal third of dorsal fin, and on interradial membrane between branches of dorsalfin branched rays. Dorsal-fin rays and interradial membrane of males with proximal third dark. Adipose fin with melanophores widely spaced. Caudal fin with interradial membrane hyaline, with melanophores concentrated on margins of lepidotrichia.

Sexual dimorphism. Mature males with hooks on pelvic-fin rays and, less often, pectoral-fin rays. Hooks on pelvic-fin rays numerous and irregularly distributed on lepidotrichia of branched rays; hooks on pectoral fin present only in few specimens examined (e.g., MZFS 15103, 1 of 6, MZFS 15889, 1 of 5), one to five irregularly distributed on first and second branched rays. Smallest male with hooks on pelvic-fin rays with 26.9 mm SL ( MZFS 15889). Except for female ( MZFS 15103, 37.8 mm SL), females and juveniles lacking hooks on fin rays. Males larger than 26.0 mm SL with bars less evident, and bars absent in larger males (>30.0 mm SL), general color pattern reticulated, with melanophores concentrated on distal part of scales. Dorsal fin with proximal third uniformly dark; melanophores on interradial membrane between branches of fin rays also darker than in females and juveniles ( Fig. 5 A, B).

Distribution. Characidium bimaculatum is widespread in Northeastern Brazil, along the coastal drainages in Ceará, Rio Grande do Norte, and Paraíba States, and in the tributaries of the lower portion of rio São Francisco, northern Bahia State (Fig. 7).

Habitat. Small coastal streams in Northeastern Brazil and perennial creeks of the Caatinga, a semiarid biome.

Figures

FIGURE 5. Characidium bimaculatum, (A) ANSP 69523, 43.0 mm SL, holotype in lateral view, male; (B) MZFS 15889, 36.7 mm SL, male; (C) MZFS 15889, 29.3 mm SL, female. Photo of holotype courtesy of M. Sabaj.

Tables

TABLE 2. Morphometric data for Characidium bimaculatum. Range values are for selected specimens (MZFS 15103, 15786, 15889, MZUSP 57040, 68962, 68965, 114779). N: total number of specimens examined; SD: Standard Deviation.

Characters	N	Range	Mean	SD
Total length (mm)	30	23.7–46.3	35.9
Standard length (mm)	30	19.4–38.1	29.1
Percentage of standard length
Head length	30	23.6–30.8	27.0	1.9
Prepectoral distance	30	21.2–29.0	25.6	2.1
Pectoral-fin height	29	19.1–24.8	21.6	1.7
Predorsal distance	30	43.8–52.7	48.1	2.1
Dorsal-fin height	27	18.9–25.1	21.4	1.7
Dorsal-fin base	30	11.8–21.0	15.7	2.3
Prepelvic distance	30	47.4–60.2	54.0	3.1
Pelvic-fin height	30	12.6–19.7	15.8	1.6
Preanal distance	30	71.1–79.3	74.9	2.2
Anal-apex distance	30	85.7–95.7	91.2	2.7
Anus to anal fin distance	30	5.8–12.1	8.0	1.5
Anal-fin height	30	12.7–18.7	15.9	1.6
Anal-fin base	30	6.9–13.0	10.1	1.9
Adipose-fin height	28	4.5–7.1	5.6	0.6
Peduncle length	30	7.9–15.6	12.3	1.8
Body width	30	11.6–15.2	13.0	1.0
Body depth at dorsal-fin origin	30	21.0–29.1	24.9	1.7
Body depth at anal-fin origin	30	15.3–21.0	17.8	1.3
Body depth at caudal peduncle	30	10.8–13.8	12.3	0.8
Percentage of head length
Snout length	30	17.7–24.2	20.8	1.8
Snout - maxillary tip	30	17.7–25.2	22.2	1.9
Anterior naris - orbit	30	7.5–13.6	10.1.8	1.5
Posterior naris - orbit	30	3.2–6.7	4.6	0.9
Cheek	30	7.5–11.7	9.2	1.2
Orbital diameter	30	21.2–30.6	26.6	2.3
Interorbital distance	30	18.1–23.6	20.7	1.7