Creagrutus menezesi Vari & Harold 2001

Creagrutus menezesi

DIAGNOSIS.—The combination of the possession of premaxillary dentition arranged in the three components generalized for most of the species of Creagrutus and Piabina without a distinctly larger gap between the first and second teeth of the primary series, 3 or 4 teeth on the maxilla, 6, rarely 7, teeth in the primary tooth row of the premaxilla, 5 or 6, rarely 4, dentary teeth, 37 to 41 lateral line scales without a lamellar process over each pore, 8 to 11 predorsal median scales, 4 scale rows between the dorsal-fin origin and the lateral line, 36 to 38 vertebrae, 9 or 10 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 6 gill rakers on the upper and 11 or 12 gill rakers on the lower limb of the first gill arch, the caudal peduncle depth (11.0%–12.9% of SL), the anal-fin length (17.7%–19.9% of SL), the postorbital head length (35.1%—45.1% of HL), the bony orbital diameter (36.8%–41.8% of HL), the interorbital width (27.4%–34.7% of HL), the relatively well-developed third infraorbital approaching, but not contacting, the horizontal limb of the preopercle, the lack of a series of dark midlateral spots on the body, the distinctly vertically elongate, ventrally tapering humeral mark extending ventral of the lateral line, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus menezesi within the clade composed of Creagrutus and Piabina.

DESCRIPTION.—Morphometric and meristic data for Creagrutus menezesi in Table 35. Head and body moderately robust. Greatest body depth at, to slightly anterior of, dorsal-fin origin. Dorsal profile of head convex from margin of upper lip to vertical through anterior margin of orbit, straight from that point to tip of supraoccipital spine in smaller specimens, slightly convex in that region in larger individuals. Interorbital region transversely convex. Predorsal profile of body slightly convex across size range of examined specimens, without change in alignment relative to dorsal profile of head. Dorsal surface of body with median ridge proximate to dorsal-fin origin, ridge more obvious in largest examined specimens. Ventral profile of head with obtuse angle at anteroventral corner of dentary, gently convex from that point to isthmus. Profile of prepelvic region of body slightly convex at all sizes. Prepelvic region of larger specimens obtusely flattened transversely.

Head obtusely pointed in lateral view and more laterally compressed and pointed in dorsal view. Upper jaw longer than, and distinctly overhanging, lower jaw. Snout slightly fleshy anteromedially, with few scattered papillae above margin of upper lip. Upper lip along with plicae and folds extending between outer and medial premaxillary teeth covered with concentrations of papillae. Lower lip fleshy anteriorly, with papillae concentrated on dorsal margin of lip and immediately proximate portions of anterior and lateral margins of lip.

Infraorbital series relatively well developed. Third infraorbital approaching but not contacting horizontal limb of preopercle. Posterior margins of third and fourth infraorbitals falling slightly short of vertical limb of preopercle.

Premaxillary dentition in three series: primary row curved overall, somewhat sigmoid in larger specimens, consisting of 6, rarely 7, teeth, without pronounced gap between first and second tooth of series but with medial tooth well separated from anterior tooth of contralateral series; triangular cluster of 3 larger teeth; and single tooth of form similar to that of primary series occurring lateral to fourth tooth of primary premaxillary row, or occasionally slightly more anterior of that position. Maxilla with 3 teeth in smaller specimens, with largest examined individuals having 3 or 4 teeth. Teeth shifting ontogenetically from unicuspidate in small specimens, to bicuspidate in medium-sized individuals, to tricuspidate in large specimens. Small specimens with 6 dentary teeth. First through third dentary teeth in juveniles distinctly larger, with first and second teeth subequal and approximately 1.5 times height of third tooth. First and second teeth tricuspidate with middle cusp well developed, second tooth bicuspidate with anterior cusp distinctly larger. Fourth through sixth teeth unicuspidate with posteriorly recurved tip. Larger specimens with 5, rarely 4, dentary teeth. Tricuspidate first and second dentary teeth of larger individuals distinctly larger than other teeth in series, with second tooth larger both vertically and especially horizontally than first tooth; tricuspidate third tooth approximately one-half height of fourth tooth; fourth and fifth teeth (when latter present) distinctly smaller than third toothwith fourth tooth unicuspidate or weakly tricuspidate and fifth tooth unicuspidate.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin slightly anterior of vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. Anal-fin rays ii,9–10. Profile of distal margin of anal fin concave, more so in largest examined specimens in which anterior branched rays form moderate lobe. Mature males with hooks present on first and second branched anal-fin rays. Pectoral-fin rays i, 11–14. Tip of pectoral fin extending posteriorly slightly less than two- thirds of distance to pelvic-fin insertion. Pelvic-fin rays typically i,6,i; sometimes i,7 in larger specimens. Tip of pelvic fin extending posteriorly to anus in smaller specimens, falling slightly short of that point in larger individuals. Mature males with hooks present on all branched anal-fin rays.

Gill rakers 6 + 11–12.

COLORATION IN ALCOHOL.—Overall coloration of majority of specimens ranging from quite pale to light tan. Dark pigmentation on specimens very subtle and often not readily apparent unless examined microscopically. Smaller specimens with dorsal surface of head lacking surface pigmentation, or with few scattered chromatophores in region posterior of snout. Dark, surface chromatophores on posterior portion of head more concentrated, but still relatively sparse, in larger individuals. Field of dark, relatively evenly spaced, deep-lying chromatophores located over surface of posterior portion of brain, with two longitudinally elongate contralateral patches of chromatophores positioned over anterior portion of brain; pigmentation quite dense in many larger specimens. Dark chromatophores scattered over snout. Region immediately anterior to nostrils typically with distinct crescent-shaped patch of chromatophores; patch not obvious in largest specimens examined. Region anteroventral of orbit with diffuse, dark chromatophores forming narrow, posteroventrally angled stripe; stripe not continuous anterodorsally with patch of pigmentation anterior to nostrils. Irregular series of chromatophores along posteroventral margin of orbit. Scattered chromatophores over dorsal portions of infraorbitals and opercle.

Scales of dorsal surface of body with scattered chromatophores along margins and diffuse patch of chromatophores over center of exposed portion of scale; pattern most distinct anteriorly on dorsolateral portion of body. Diffuse pattern of scattered chromatophores covering much of lateral surface of body in smaller specimens, these chromatophores slightly more concentrated midlaterally on caudal peduncle, but not forming discrete horizontal stripe. Diffuse lateral chromatophore field terminating anteriorly approximately two scales posterior of humeral mark resulting in intervening hyaline region. Region anterior to humeral mark in smaller specimens typically hyaline as a consequence of lack of dispersed chromatophores, but with some scattered chromatophores in that region in larger individuals. Humeral mark present, but relatively faint compared to condition in many congeners, albeit with pigmentation in mark more concentrated than scattered chromatophores present on lateral surface of body. Concentration of chromatophores more noticeable on dorsal portion of mark in some individuals. Mark vertically elongate, slightly ventrally tapering, and extending ventrally nearly to horizontal through pectoral-fin insertion. Orientation of mark somewhat variable around vertical line (Figures 63, 64). Smaller specimens with mark continuing dorsally to horizontal through dorsal margin of orbit; mark extending somewhat more dorsally in larger individuals. Dorsal portion of mark with slight anterior extension. Midlateral surface of body with very diffuse dusky band in specimens of most sizes; band anteriorly attenuate and less intense, not reaching to rear of humeral mark. Surface portion of band formed of dispersed, dark chromatophores that overlie narrower, deeper, and more intense region of pigmentation forming most of longitudinal band. Deep-lying, dark pigmentation irregularly dispersed in smaller specimens, with localized areas more intensely pigmented, particularly along myosepta.

Dorsal fin with distal portion of second unbranched ray covered with dark chromatophores. Distal portions of membranes of anterior 4 or 5 branched dorsal-fin rays with scattered chromatophores that form diffuse spot. Anal fin with scattered chromatophores along bases of anterior branched rays. Caudal- fin rays variably outlined by dark chromatophores, those along middle caudal-fin rays forming faint stripe in many specimens; chromatophores on middle caudal-fin rays more concentrated basally in some smaller individuals. Basal portions of rays of mid portions of upper and lower lobes of caudal fin variably outlined by dark chromatophores. Pectoral and pelvic fins hyaline.

ETYMOLOGY.—The specific name, menezesi, is in honor of Naércio A. Menezes, Museu de Zoologia, Universidade de São Paulo, Brazil, in recognition of his myriad contributions to our knowledge of South American fishes and all his assistance to the senior author through the years.

ECOLOGY.—Stomach contents of two specimens prepared for clearing and counter staining consisted of chopped up seeds and insect parts.

Creagrutus menezesi has been captured within the upper Rio Tocantins basin sympatrically with C. atrisignum in the Rio Maranhão and with C. saxatilis and C. figueiredoi in residual pools in the channel of the Rio Tocantins formed during filling of the Serra da Mesa Reservoir. In the upper Rio Araguaia at Barra do Garcas, Mato Grosso, Brazil, C. menezesi was collected jointly with C. seductus and C. figueiredoi.

DISTRIBUTION.—Creagrutus menezesi is widespread in the Rio Tocantins basin and is tentatively considered to occur in the Rio Branco basin and the Rio Negro near the mouth of the Rio Branco (Figure 59, diamonds; see “Remarks,” below, with respect to localities outside the Rio Tocantins).

COMPARISONS.—Creagrutus menezesi can be readily distinguished from the other members of the genus known from the Rio Tocantins and Rio Negro basins by a combination of details of dentition and meristic characteristics (see keys to the species in each basin, above).

MATERIAL EXAMINED.—634 specimens (64, 23.1–75.2).

HOLOTYPE.—BRAZIL. Goiás: Rio Tocantins basin, Ribeirão Paranoa do Meio, at road crossing 11 air km NNE of Formosa (approximately 15°25′S, 47°18′W), collected by W.C. Starnes et al., 13 Nov 1984, MZUSP 50544, 1 (58.7).

PARATYPES.—63 specimens (63, 32.0–75.2).

BRAZIL. Goiás: Rio Tocantins basin, Ribeirão Paranoa do Meio, at road crossing 11 air km NNE of Formosa (approximately 15°25′S, 47°18′W), collected with holotype, MZUSP 50545, 8 (36.5–46.5); USNM 292229, 11 (32.0–64.2; 2 specimens cleared and counterstained for cartilage and bone). Minacu, Cavalcante, Rio Tocantins in Serra da Mesa (13°50′S, 48°19′W), collected by G.W. Nunan and D.F. Moraes, Jr., 20 Oct 1985, MNRJ 12614, 8 (36.1–55.9). Minacu/Colinas do Sul, Rio Tocantins, in large pools below Usina Hidroelectrica Serra da Mesa during filling of reservoir, collected by D.F. Moraes et al., 28 Oct to 3 Nov 1996, MNRJ 17338, 11 (48.8–71.2); USNM 350456, 10 (56.0–75.2; formerly MNRJ 16566, in part); MNRJ 17333, 10 (55.3–69.3); USNM 350456, 5 (61.2–73.7; formerly MNRJ 16562, in part).

NONTYPE SPECIMENS.—570 specimens (18, 23.1–74.0).

BRAZIL. Pará: Rio Itacaiunas, Caldeirão (5°45′S, 50°30′W), MZUSP 30576, 25. Maranháo: Rio Tocantins, Estreito (approximately 6°32′S, 47°27′W), MZUSP 4970, 57 (5, 23.1–25.7; 2 specimens cleared and counterstained for cartilage and bone). Rio Tocantins at Carolina (7°20′S, 47°28′W), CAS 69243, 6. Tocantins: Rio Tocantins at Porto Nacional (10°42′S, 48°25′W), CAS 69258, 1. Goiás: small “brook” into Rio Maranhão at Mosondo, CAS 69262, 2. Ribeirão Tacaural, tributary of Rio dal Almas, CAS 69242, 10. Minacu, Cavalcante, Rio Tocantins in Serra da Mesa (13°50′S, 48°19′W), MNRJ 13343, 5. Minacu, Cavalcante, Rio Tocantins, MNRJ 13049, 39. Campinacu, Niquelândia, Rio Maranhão, at Porto Alfredinho (14°04′S, 48°30′W), MNRJ 12558, 7. Campinacu, Rio Boa Nova, left bank tributary of Rio Tocantins (13°52′S, 48°21′W), MNRJ 12576, 1. Niquelândia, Rio Maranhão, at Estreito, near mouth of Rio Bagagem (13°59′S, 48°22′W), MNRJ 12741, 7. Niquelândia, Rio Maranhão, 20 km above confluence with Rio Bagagem, near mouth of Rio Arara (14°00′S, 48°26′W), MCP 15886, 12. Uruacú, Rio Maranhão, along road between Niquelândia and Uruacú (14°31′S, 49°03′W), MCP 15852, 11. Minacu/Colinas do Sul, Rio Tocantins, in large pools below Usina Hidroelectrica Serra da Mesa during filling of reservoir, USNM 350451 (formerly MNRJ 16566, in part), 10; USNM 350454 (formerly MNRJ 16562, in part), 5; MNRJ 16567, 6; USNM 350455 (formerly MNRJ 16567, in part), 20. Minacu/Colinas do Sul, Rio Tocantins, in large pools formed by a riacho on left bank of Rio Tocantins during filling of Usina Hidroelectrica Serra da Mesa reservoir, MNRJ 16563, 9; MNRJ (ex 16564) 3; USNM 350453 (formerly MNRJ 16564, in part) 16. Mato Grosso: Upper Rio Araguaia basin, Municipio de Barra do Garcas, Córrego Fundo (approximately 15°53′S, 52°15′W), USNM 342236, 1 (74.0, formerly ICLMA 190, in part); USNM 342234, 1 (formerly ICLMA uncataloged, in part).

The following specimens from the Rio Negro and Rio Branco basins are tentatively assigned to Creagrutus menezesi:

BRAZIL. Roraima: Rio Branco, beach of Rio Xeriuini (approximately 1°0′S, 61°50′W), MZUSP 29892, 311 (10, 27.2–29.4). Rio Branco system, Rio Surumu (approximately 3°22′N, 60°19′W), MZUSP 16512, 2 (1, 51.2; other specimen twisted and only proportional head measurements and meristic data taken). Rio Branco, Boa Vista, MZUSP 17714, 1. Amazonas: W of Moura, near junction of Rio Negro and Rio Branco (1°30′S, 61°48′W), ANSP 135566, 1 (29.9); ANSP 146130, 1.