Creagrutus seductus Vari & Harold 2001

Creagrutus seductus

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, 6, very rarely 7, teeth in the primary tooth row of the premaxilla, 6 dentary teeth, 39 to 41 lateral line scales without a lamellar process over each pore, 9 or 10 predorsal median scales, 4 scale rows between the dorsal-fin origin and the lateral line, 38 or 39 vertebrae, 11 to 13 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 7 or 8 gill rakers on the upper limb of the first gill arch, 11 to 13 gill rakers on the lower limb of the first gill arch, the distance from the snout to the dorsal-fin origin (46.0%–50.4% of SL), the distance from the dorsal-fin origin to the anal-fin origin (25.5%–32.0% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (23.1%–29.1% of SL), the distance from the dorsal-fin origin to the pectoral-fin insertion (29.6%–33.8% of SL), the caudal peduncle depth (10.6%–11.2% of SL), the head length (24.7%–28.0% of SL), the postorbital head length (40.0%–46.8% of HL), the snout length (26.7%–32.0% of HL), the bony orbital diameter (29.9%–35.4% of HL), the interorbital width (28.4%–31.9% of HL), the moderately developed third infraorbital contacting the horizontal limb of the preopercle in larger specimens, the lack of a series of dark midlateral spots on the body, the moderately vertically elongate humeral mark with concave anterior and convex posterior borders, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus seductus within the clade composed of Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 63.6 32.5–70.3

1. Snout to anal-fin origin 63.2 59.7–65.9

2. Snout to pelvic-fin insertion 48.0 45.4–48.5

3. Snout to pectoral-fin insertion 25.1 23.0–26.4

4. Snout to dorsal-fin origin 48.9 46.0–50.4

5. Dorsal-fin origin to hypural joint 54.9 51.6–58.4

6. Dorsal-fin origin to anal-fin origin 29.2 25.5–32.0

7. Dorsal-fin origin to pelvic-fin insertion 25.2 23.1–29.1

8. Dorsal-fin origin to pectoral-fin insertion 32.4 29.6–33.8

9. Caudal peduncle depth 10.8 10.6–11.2

10. Pectoral-fin length 18.1 17.2–20.5

11. Pelvic-fin length 14.5 14.0–15.8

12. Dorsal-fin length 19.8 19.3–23.4

13. Anal-fin length 17.6 16.7–19.1

14. Head length 27.0 24.7–28.0

15. Postorbital head length 44.8 40.0–46.8

16. Snout length 29.7 26.7–32.0

17. Bony orbital diameter 32.6 29.9–35.4

18. Interorbital width 29.1 28.4–31.9

Meristics

Lateral line scales 40 39–41

Scale rows between dorsal-fin origin and lateral line 4 4

Scale rows between anal-fin origin and lateral line 3 3

Predorsal median scales 9 9–10

Branched dorsal-fin rays 8 8

Branched anal-fin rays 13 11–13

Branched pelvic-fin rays 7 6–7

Pectoral-fin rays 12 11–13

Vertebrae 38 38–39

DESCRIPTION.—Morphometric and meristic data for Creagrutus seductus in Table 53. Head and body relatively elongate in smaller specimens, larger individuals with anterior portion of body relatively deeper and more robust. Greatest body depth typically at dorsal-fin origin; shifted somewhat anterior of that point in ripe females. Dorsal profile of head slightly convex from margin of upper lip to vertical through anterior nostril, straight or very slightly convex from that point to tip of supraoccipital spine. Interorbital region convex. Predorsal profile of body very slightly convex across size range of examined specimens, without change in alignment relative to dorsal profile of head. Predorsal surface of body transversely flattened anteriorly in some specimens, with middorsal ridge proximate to dorsal-fin origin. Ventral profile of head with obtuse angle at anteroventral corner of dentary, straight or very slightly convex from that point to isthmus. Profile of prepelvic region of body nearly straight in smaller specimens, slightly convex in most larger individuals, convexity most pronounced in ripe females.

Head obtusely pointed in lateral view, more pointed in dorsal view. Upper jaw slightly longer than, and overhanging, lower jaw. Snout slightly fleshy anteromedially with few scattered papillae above margin of upper lip. Papillae more concentrated along ventral surface of upper lip and on folds and plicae extending between outer and medial premaxillary teeth. Lower jaw fleshy anteriorly, with scattered papillae along anteroventral margin and numerous papillae along dorsal margin.

Infraorbital series moderately developed. Ventral margin of third infraorbital typically convex, with central portion of ventral margin of infraorbital approaching (smaller specimens) or contacting (larger specimens) horizontal limb of preopercle. Posterior margins of third through fifth infraorbitals falling distinctly short of vertical limb of preopercle.

Premaxillary dentition in three series: primary row slightly sigmoid, typically consisting of 6 teeth (7 teeth present on one side of head in one specimen) without pronounced gap between first and second tooth of series but with medial tooth separated from anterior tooth of contralateral series by distinct gap; triangular cluster of 3 larger teeth; and single tooth of form similar to that of primary series lying lateral to fourth tooth of primary premaxillary series. Maxilla with 2 or 3 weakly tricuspidate teeth. Dentary with 5 or 6 teeth; anterior 4 dentary teeth tricuspidate with fifth and sixth teeth tricuspidate or distally truncate. Second tooth about one-fourth higher and wider than first tooth and more than twice as high and wide as third tooth. Fourth, fifth, and, when present, sixth teeth distinctly smaller than third tooth and becoming progressively shorter posteriorly. Symphyseal teeth distinctly separated.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin at, to anterior to, vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin straight, or nearly so, in smaller specimens, slightly convex in larger individuals. Anal-fin rays ii, 11–13. Profile of distal margin of anal fin distinctly concave, with last unbranched ray and first and second branched rays forming discrete anterior lobe. Single examined male with hooks on first and second branched anal-fin rays. Pectoral-fin rays i,10–12. Tip of pectoral fin extending posteriorly at least three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays i,6,i in smaller specimens, i,7 in most of larger individuals. Tip of pelvic fin extending posteriorly to anus. Single examined mature male with hooks on all six branched anal-fin rays.

Gill rakers 7–8 + 11–13.

COLORATION IN ALCOHOL.—Overall ground coloration of relatively freshly collected specimens light tan. Dorsal surface of head in smaller specimens with concentrated stellate chromatophores overlying fontanelles and immediately adjoining regions. Field of dark surface chromatophores in larger specimens more extensive, but still most concentrated medially. Membranes overlying brain covered with field of dense dark chromatophores. Chromatophore field on dorsal surface of anterior portion of head, on snout, and on medial portions of upper lip dense at all examined sizes. Region anterior to nostrils with chromatophore field continuous with, and sometimes slightly more intense than, that on snout; chromatophores forming crescent-shaped patch in individuals with more concentrated pigmentation in that region. Region ventral of nostrils and anteroventral of orbit with broad posteroventrally aligned patch of chromatophores continuous posteriorly with curved band of chromatophores continuing around ventral and posterior margins of orbit. Dorsal portions of infraorbital series and opercle with scattered, dark chromatophores.

Scales of dorsolateral portion of body with crescent-shaped pattern of dark chromatophores along margin of scales and wider basal patch of chromatophores. Two chromatophore fields on scales separated by hyaline region in smaller specimens, merging, particularly on dorsalmost scales, in larger specimens. Humeral mark somewhat elongate vertically, with anterior margin typically concave anteriorly and with posterior margin convex. Dark pigmentation most intense in portion of mark immediately dorsal of lateral line, with intensity of pigmentation progressively decreasing dorsally. Some specimens with scattered, dark chromatophores continuing ventral of lateral line to form ventrally tapering extension of main portion of humeral mark. Region immediately anterior to humeral mark hyaline. Area posterior to humeral mark hyaline for distance of approximately one and one-half scales and followed by midlateral body stripe formed by dark surface chromatophores. Density of chromatophores in midlateral stripe increasing in larger specimens. Midlateral stripe continuing posteriorly to rear of caudal peduncle.

Dorsal fin with anterior margin of unbranched rays and margins of distal portions of branched rays outlined by dark pigmentation. Basal two-thirds or less of anterior branched anal-fin rays outlined by dark pigmentation. Caudal fin with pigmentation along margins of dorsal and ventral rays, and along middle rays; central rays of each lobe hyaline or nearly so. Pigmentation on middle caudal-fin rays more concentrated basally, forming indistinct spot; spot more obvious in larger individuals.

ETYMOLOGY.—The species name, seductus, from the Latin for remote or apart, refers to the isolated location of the type locality relative to other sites from which Creagrutus species are known to occur.

ECOLOGY.—Stomach contents of a single specimen prepared for cleared and staining consisted solely of chopped-up seeds.

DISTRIBUTION.—Creagrutus seductus is known only from the upper portions of the Rio Araguaia basin (Figure 83, triangle). As discussed under “Creagrutus and Piabina in Cis-Andean South America,” above, one Creagrutus specimen (ANSP 164289) purportedly collected at Russas, Ceara, in the Rio Jaguaribe, an isolated basin in northeastern Brazil, may be an individual of C. seductus with erroneous locality information.

COMPARISONS.—The Creagrutus species known from the Rio Araguaia basin, in addition to C. seductus, are C. figueiredoi, C. menezesi, C. molinus, and C. mucipu. Creagrutus seductus is readily separable from those species by details of dentition and meristics (see “Key to the Species of Creagrutus in the Rio Tocantins Basin”).

MATERIAL EXAMINED.—27 specimens (27, 32.5–70.3).

HOLOTYPE.—BRAZIL. Mato Grosso: Upper Rio Araguaia basin, Corrego Fundo, Municipio de Barra do Garcas (approximately 15°53′S, 52° 15′W), 19 Sep 1993, C.E. Melo et al., MZUSP 51026, 1 (63.6; formerly ICLMA 229, in part).

PARATYPES.—26 specimens (26, 32.5–70.3).

BRAZIL. Mato Grosso: Upper Rio Araguaia basin, Corrego Fundo, Municipio de Barra do Garcas (approximately 15°53′S, 52°15′W), collected with holotype, MZUSP 51027, 1 (59.9; formerly ICLMA 229, in part); USNM 342233, 1 (66.8; formerly ICLMA 229, in part). Upper Rio Araguaia basin, Corrego Fundo, Municipio de Barra do Garcas (approximately 15°53′S, 52° 15′W), 15 Nov 1993, C.E. Melo et al., MZUSP 51028, 3 (39.5–66.5; formerly ICLMA 190, in part); USNM 342232, 3 (41.0–62.7; formerly ICLMA 190, in part). Upper Rio Araguaia basin, Corrego Fundo, Municipio de Barra do Garcas (approximately 15°53′S, 52° 15′W), 12 Nov 1993, P.C. Venere et al., MZUSP 51029, 9 (32.5–70.3); USNM 342231, 9 (44.9–66.8; 1 specimen cleared and counterstained for cartilage and bone).

Creagrutus seductus és una espècie de peix de la família dels caràcids i de l'ordre dels caraciformes.

Creagrutus seductus es una especie de peces de la familia Characidae en el orden de los Characiformes.

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Creagrutus seductus Creagrutus generoko animalia da. Arrainen barruko Actinopterygii klasean sailkatzen da, Characidae familian.

潛鈎齒脂鯉，為輻鰭魚綱脂鯉目脂鯉亞目脂鯉科的其中一個種，分布於南美洲阿瓜亞河流域，體長可達7公分，棲息在底中層水域，生活習性不明。