Creagrutus figueiredoi Vari & Harold 2001

Creagrutus figueiredoi

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, 2 or 3 teeth on the maxilla, 5 teeth in the primary tooth row of the premaxilla, 5 or 6 dentary teeth, 36 to 38 lateral line scales without a lamellar process over each pore, 8 to 11 predorsal scales, 4 scale rows between the dorsal-fin origin and the lateral line, 35 to 37 vertebrae, 9 or 10 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, the distance from the snout to the pectoral-fin insertion (22.6%–26.6% of SL), the distance from the snout to the anal-fin origin (31.4%–33.6% of SL), the distance from the dorsal-fin origin to the pectoral-fin insertion (30.6%–34.0% of SL), the postorbital head length (41.2%–45.1% of HL), the snout length (28.3%–33.1% of HL), the bony orbital diameter (33.6%–38.1% of HL), the dorsal-fin length (19.4%–22.3% of SL), the anal-fin length (15.6%–18.5% of SL), the caudal peduncle depth (11.2%–12.6% of SL), the 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 discrete, wide, vertically elongate humeral mark shaped like an inverted comma, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus figueiredoi within the clade composed of Creagrutus and Piabina.

DESCRIPTION.—Morphometric and meristic data for Creagrutus figueiredoi in Table 18. Head moderately robust at all sizes. Body becoming increasingly robust anteriorly with increasing size. Greatest body depth at vertical through dorsal-fin origin in smaller specimens, at that point or shifted somewhat anteriorly in larger individuals. Dorsal profile of head gently convex from margin of upper lip to vertical through posterior nostril, straight from that point to tip of supraoccipital spine in smaller specimens, becoming slightly convex in larger individuals Interorbital region distinctly convex. Dorsal profile of body very slightly convex, without evident change in alignment relative to that of head in smaller specimens, convex with distinct change in alignment relative to that of head in larger individuals. Predorsal surface of body somewhat flattened transversely in region of supraoccipital spine; with middorsal ridge proximate to dorsal-fin origin in larger specimens. Ventral profile of head with distinct obtuse angle at anteroventral corner of dentary, straight or gently curved from that point to isthmus. Ventral profile of body very slightly convex in smaller specimens, more so in larger individuals. Prepelvic region of body obtusely flattened transversely.

Head obtusely pointed in lateral and dorsal views. Upper jaw distinctly longer than, and overhanging, lower jaw. Snout not very fleshy, with few scattered papillae anteromedially. Papillae more concentrated along fleshy margins of lips and particularly on fleshy folds and plicae extending between outer and medial premaxillary teeth. Lower lip moderately fleshy anteriorly. with numerous papillae along dorsal margin and with scattered papillae anteromedially.

Infraorbital series well developed. Ventral margin of third infraorbital approaching, but falling slightly short of, horizontal limb of preopercle even in larger specimens. Posterior margins of third through fifth infraorbitals falling short of vertical limb of preopercle.

Premaxillary dentition in three series: primary row curved, consisting of 5 teeth, occasionally with gap between third and fourth teeth but without gap between first and second teeth of series and with medial tooth of primary series separated from anterior tooth of contralateral series by distinct gap; triangular cluster of 3 larger teeth with posterolateral tooth largest; and single tooth of form similar to that of primary series situated lateral to space between third and fourth teeth of primary premaxillary row. Maxilla with 2 or 3 tricuspidate teeth. Dentary with 5 or 6 teeth; first two teeth subequal and distinctly larger than third; third tooth, in turn, much larger than fourth and fifth teeth. Dentary teeth all tricuspidate (when 5 teeth present) or last tooth conical (when 6 teeth present). Central cusp very well developed proportionally in first through third teeth, less so in fourth and fifth teeth.

Dorsal-fin rays ii,8–9. Dorsal-fin origin anterior to 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 distinctly concave, with last unbranched and anterior branched rays forming distinct lobe. Mature males with hooks present on first and second branched anal-fin rays and occasionally on second unbranched anal-fin ray. Pectoral- fin rays i,11–13. Tip of pectoral fin extending posteriorly approximately three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays i,6,i or i,7. Tip of pelvic fin extending posteriorly approximately to anus. Mature males with hooks present on all branched anal-fin rays.

Gill rakers 6–7–11.

COLORATION IN ALCOHOL.—Overall ground coloration tan. Dorsal surface of head with scattered surface chromatophores overlying more concentrated chromatophores located on membranes of brain. Surface chromatophores more concentrated on snout and in region between and anterior to nostrils. Region immediately anterior to nostrils without more concentrated region of chromatophores forming dark crescent-shaped patch as in many congeners, or patch barely apparent in some specimens. Series of dark chromatophores extending posteroven- trally from under nostrils to join curved band of chromatophores along ventral and posterior borders of orbit. Scattered, dark chromatophores on postorbital portion of head located on dorsal one-half to two-thirds of infraorbital series and opercle.

Scales of dorsolateral and dorsal portions of body with dark chromatophores concentrated along distal margin and on basal section of exposed portion of scale, scale pigmentation most intense on dorsal region of body. Diffuse midlateral stripe formed by dark surface chromatophores extending from slightly posterior of humeral mark to posterior portion of caudal peduncle, somewhat more concentrated posteriorly in some individuals. Humeral mark vertically elongate, with densely pigmented portion immediately dorsal of lateral line. Diffuse, ventrally attenuating series of chromatophores extending slightly ventral of densely pigmented portion of mark. Dorsal portion of humeral mark consisting of variably shaped, vertically elongate patch of chromatophores extending one and one-half to two scales dorsal of dark central portion of mark. Dorsal portion of mark ranging from distinctly lighter than central portion of mark to nearly as dark as that region. Anterior margin of mark ranging from straight to distinctly concave.

Dorsal fin with unbranched rays outlined by dark chromatophores, and distal two-thirds of membranes of anterior 4 or 5 rays with numerous larger chromatophores. Anal fin with anterior margins of first 4 to 7 rays variably outlined with chromatophores and with scattered chromatophores on distal portions of membranes of anterior rays. Caudal-fin rays variably outlined with chromatophores, giving fin overall dusky appearance. Pelvic fin mostly hyaline. Pectoral-fin rays variably delimited by small dark chromatophores.

ETYMOLOGY.—The species name, figueiredoi, is in honor of Jose Lima de Figueiredo, Museu de Zoologia of the Universidade de São Paulo, in recognition of his contributions to South American ichthyology and of his assistance to the senior author over the years.

ECOLOGY.—The type locality is an upland river, approximately 30 m wide, with fast to moderate flowing, moderately turbid water, over a rocky and sand bottom. In the upper Rio Araguaia basin Creagrutus figueiredoi has been captured together with C. menezesi and C. seductus. During the filling of the Serra da Mesa reservoir in the upper Rio Tocantins basin, congeners collected with C. figueiredoi along the developing lake margin were C. menezesi and C. saxatilis.

DISTRIBUTION.—Creagrutus figueiredoi occurs in the Rio Tocantins drainage system in both the upper Rio Tocantins and Rio Araguaia basins (Figure 38, squares).

GEOGRAPHIC VARIATION.—The majority of the available specimens of C. figueiredoi come from the type locality in the Rio Maranhão basin of the Rio Tocantins system in the region of the type locality (Figure 38, square indicated by 3). Five specimens were collected approximately 400 river km to the north of the type locality along the margins of the Serra da Mesa reservoir in the upper Rio Tocantins during the filling of the impoundment (MNRJ 17334, 17339). These specimens fit within the range of variation for meristic and morphometric values for species from the holotype locality and are designated as paratypes (Table 18).

Two specimens from the Município de Barra do Garças, in the upper portions of the Rio Araguaia (USNM 342235) are tentatively identified as C. figueiredoi and are the only known specimens of the species from that portion of the greater Rio Tocantins basin. The Rio Araguaia sample differs from the upper Rio Tocantins samples in proportional values reflecting the depth of the body (dorsal-fin origin to pelvic-fin insertion, dorsal-fin origin to pectoral-fin insertion; Table 18, numbers 7 and 8) and to a lesser degree in the length of the dorsal-fin (Table 18, number 12). Furthermore, the two specimens from the Rio Araguaia have 35 vertebrae. Although this count falls within the range for specimens of upper Rio Tocantins basin (35 to 37 vertebrae), 35 vertebrae are relatively rare in available specimens from the upper Rio Tocantins (frequency of vertebrae in C. figueiredoi samples from that region: 35 (3), 36 (21), 37 (3)).

The Rio Araguaia sample is limited to two specimens, and both individuals are apparently ripe females with expanded abdomens. Such increased proportional body depth would account for the greater relative dorsal-fin origin to pelvic-fin insertion distance and would partially contribute to the increased proportional dorsal-fin origin to pectoral fin insertion distance found in this sample in comparison to the samples from the upper Rio Tocantins. Furthermore, more than 2500 river km separate the collection locality of the two specimens from the Rio Araguaia from the nearest known locality for C. figueiredoi in the upper Rio Tocantins basin. Intraspecific geographic variation in meristic and morphometric values is often the case across such great distances and is found at shorter geographic distances in other Creagrutus species. Thus, the differences in proportional distance from the dorsal-fin origin to the pectoral-fin insertion and the relative length of the dorsal-fin between the Rio Araguaia and upper Rio Tocantins samples are possibly a function of a clinal shift in these features across the range of a single species.

Shifts in modal vertebral counts also occur intraspecifically within various Creagrutus species (e.g., C. flavescens) and other characiforms (e.g., Ctenolucius beani and Boulengerella maculata, Vari, 1995:55, 66), which suggests that the modal shift in vertebral counts between population samples from the upper Rio Tocantins and the limited Rio Araguaia sample is a function of their geographic separation. Other recently analyzed species (e.g., Pituna compacta; see Costa, 1998: 147) have similar disjunct known distributions between the upper portions of the Tocantins and Araguaia basins. Given these factors, and the massive gap in the known distribution of the species, we tentatively identify the Rio Araguaia samples as C. figueiredoi. Further samples from the upper Rio Araguaia and throughout intervening localities in the greater Rio Tocantins basin are necessary to resolve whether such variation should be recognized taxonomically.

MATERIAL EXAMINED.—33 specimens (33, 37.6–63.3).

HOLOTYPE.—BRAZIL. Distrito Federal: Rio Maranhão, upper Rio Tocantins basin, approximately 35 air km N of Brasilia (approximately 15°32′S, 47°49′W), collected by W.C. Starnes et al., 14 Nov 1984, MZUSP 50542, 1 (63.3).

PARATYPES.—27 specimens (27, 37.6–55.5).

BRAZIL. Distrito Federal: Rio Maranhão, upper Rio Tocantins basin, approximately 35 air km N of Brasilia (approximately 15°32′S, 47°49′W), collected with holotype, MZUSP 50543, 9 (40.2–53.1); MNRJ 14482, 2 (42.8–49.6); USNM 292221, 11 (40.1–55.5). Goiás: Minaçu/Colinas do Sul, Rio Tocantins, pools formed below the dam of Usina Hidroelectica (UHE) de Serra da Mesa after closure of dam to fill, collected by D.F. Moraes et al., 28 Oct to 3 Nov 1996, MNRJ 17334, 2 (38.8–52.2); MNRJ 17339, 3 (37.6–48.6).

NONTYPE SPECIMENS.—5 specimens (5, 41.7–63.0).

BRAZIL. Distrito Federal: Rio Maranhão, upper Rio Tocantins basin, approximately 35 air km N of Brasilia (approximately 15°32′S, 47°49′W), USNM 292221, 3 (60.7–63.0; specimens cleared and counterstained for cartilage and bone). Mato Grosso: Município de Barra do Garças, Córrego Fundo (approximately 15°53′S, 52°15′W), USNM 342235, 2 (41.7–52.1; see comments under “Geographic Variation,” above, concerning this lot).

Creagrutus figueiredoi, USNM 292221, 3, 60.7–63.0 mm, paratypes; Brazil, Distrito Federal, Rio Maranhão

Creagrutus flavescens, USNM 340973, 2, 58.1–58.7 mm; Ecuador, Sucumbíos, Río San Miguel basin, Río La Bermeja.

Creagrutus gephyrus, USNM 324461, 1, 41.3 mm; Ecuador, Napo, Río Napo, at Coca. USNM 340953, 1, 47.4 mm; Ecuador, Napo, Río Napo, approximately 25 km downstream of Coca.