Creagrutus magoi Vari & Harold 2001

Creagrutus magoi

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, 6 teeth in the primary series of each premaxilla, 2 or 3 maxillary teeth, 5 teeth on each dentary, 9 to 11 predorsal median scales, 37 to 41 lateral line scales without a lamellar process over each pore, 4, rarely 5, scale rows between the dorsal-fin origin and the lateral line, 3 scale rows between the anal-fin origin and the lateral line, 11 or 12 branched anal-fin rays, 9 to 11 gill rakers on the upper limb and 13 or 14 gill rakers on the lower limb of the first gill arch, the distance from the dorsal-fin origin to the anal-fin origin (29.2%–33.8% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (24.8%–29.0% of SL), the postorbital head length (39.2%–46.2% of HL), the interorbital width (30.4%–34.3% of HL), the contact, or near contact, between the ventral margin of the third infraorbital and the horizontal limb of the preopercle, the lack of a distinct spot of dark pigmentation at the base of the middle caudal-fin rays, the vertically elongate humeral mark in the form of an inverted comma without a secondary, dorsal patch of pigmentation, the absence of a distinct patch of pigmentation on the dorsal fin, and the lack of a series of dark spots along the midlateral surface of the body distinguishes Creagrutus magoi within the clade formed by Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 62.9 18.7–64.8

1. Snout to anal-fin origin 66.7 62.3–66.6

2. Snout to pelvic-fin insertion 49.7 46.3–49.6

3. Snout to pectoral-fin insertion 26.1 24.2–28.8

4. Snout to dorsal-fin origin 48.5 45.3–48.5

5. Dorsal-fin origin to hypural joint 54.8 53.7–58.4

6. Dorsal-fin origin to anal-fin origin 33.7 29.2–33.8

7. Dorsal-fin origin to pelvic-fin insertion 28.9 24.8–29.0

8. Dorsal-fin origin to pectoral-fin insertion 32.9 30.1–33.3

9. Caudal peduncle depth 11.8 10.1–12.2

10. Pectoral-fin length 18.6 18.6–21.5

11. Pelvic-fin length 15.5 14.8–16.6

12. Dorsal-fin length 19.4 19.3–23.4

13. Anal-fin length 15.6 15.0–18.1

14. Head length 27.0 24.9–28.8

15. Postorbital head length 42.4 39.2–46.2

16. Snout length 31.8 27.0–31.9

17. Bony orbital diameter 31.8 31.0–37.1

18. Interorbital width 34.2 30.4–34.3

Meristics

Lateral line scales 38 37–41

Scale rows between dorsal-fin origin and lateral line 5 4–51

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

Predorsal median scales 10 9–11

Branched dorsal-fin rays 8 7–82

Branched anal-fin rays 12 11–12

Branched pelvic-fin rays 6 6

Pectoral-fin rays 13 12–14

Vertebrae 37 36–38

1Five scales between dorsal-fin origin and lateral line present in only 2 of 49 paratypes.

2Seven branched anal-fin rays present in only 1 of 49 paratypes.

DESCRIPTION.—Morphometric and meristic data for Creagrutus magoi in Table 30. Head and body relatively robust, more so in anterior portion of body in larger specimens. Greatest body depth at, or sometimes slightly anterior of, dorsal-fin origin. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior nostril, slightly convex from that point to above center of orbit and then straight to tip of supraoccipital spine. Interorbital region transversely rounded. Dorsal profile of body slightly convex from tip of supraoccipital spine to dorsal-fin origin, but without any distinct change in alignment relative to dorsal profile of head; convexity more pronounced in larger specimens. Dorsal surface of body with obtuse middorsal ridge; ridge more obvious posteriorly. Ventral profile of head with obtuse angle at anteroventral corner of dentary, angle variably obvious, profile slightly convex from angle to isthmus. Prepelvic profile of body barely convex in smaller individuals, only somewhat more convex in certain larger specimens. Prepelvic region of body obtusely flattened transversely.

Head obtusely pointed in lateral view, more compressed in dorsal view. Upper jaw longer than, and overhanging, lower jaw. Anterior of snout, particularly anteromedial portion, with numerous papillae. Papillae more concentrated on fleshy upper lip, especially along ventral margin of lip and on folds and plicae extending between outer and medial premaxillary teeth. Lower lip with numerous papillae on dorsal surface and scattered papillae anteriorly.

Infraorbital series well developed in all specimens larger than 30 mm SL, with ventral margin of third infraorbital contacting, or nearly contacting, horizontal limb of preopercle. Posterior margins of third through fifth infraorbitals distinctly separated from vertical limb of preopercle in smaller specimens; gap decreasing proportionally, but still distinct, in larger specimens.

Premaxillary dentition in three series: primary series sigmoid, with 6 tricuspidate teeth, without pronounced gap between first and second tooth of series but with medial tooth separated from contralateral series by distinct gap; triangular cluster of 3 teeth, all larger to distinctly larger than those of primary series; and single tooth of form similar to that of primary series occurring lateral to fourth tooth of primary series. Maxilla with 2 or 3 tricuspidate teeth. Dentary with 5 tricuspidate teeth; second tooth more massive and about one-third longer than first tooth; second tooth more than twice as high as much smaller third tooth; third tooth two and one-half times as high as fourth tooth; fourth tooth slightly larger than fifth tooth.

Dorsal-fin rays typically ii,8, rarely ii,7. Dorsal-fin origin approximately at vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. Anal-fin rays iii,11–12. Profile of distal margin of anal fin concave, with moderate lobe anteriorly in larger individuals. Single mature male having anal-fin hooks on first and second branched rays. Pectoral-fin rays i, 11–13. Tip of pectoral fin falling 1 or 2 scales short of pelvic-fin insertion. Pelvic-fin rays i,6,i. Tip of pelvic fin nearly contacting, or more typically falling 1 scale short of, anal-fin origin. Single mature male with pelvic-fin ray hooks limited to medial branch of all branched rays.

Gill rakers 9–11 (9 rare) + 13–14.

COLORATION IN ALCOHOL.—Ground coloration tan. Dorsal surface of head in smallest specimens with dense deep-lying pigmentation overlying brain and with scattered, dark chromatophores on dorsal surface of head and snout. Surface chromatophore field getting increasingly dense with larger size, with largest individuals having entire dorsal surface of head covered with dense field of small, dark chromatophores extending anteriorly to margin of upper lip and to distal margin of maxilla in larger specimens. Region anterior to nostrils with pigmentation more intense, forming distinct crescent-shaped patch present in specimens of all sizes. Smaller individuals with narrow band of dark pigmentation extending from anteroventral to nostrils to under orbit; band subsumed into overall darker pigmentation in that region in larger specimens. Region posterior to orbit and dorsal portion of opercle with scattered, dark chromatophores in smaller specimens, chromatophore field expanding ventrally in larger individuals. Largest specimens with patch of scattered chromatophores on posteroventral corner of cheek near angle of preopercle.

Scales of posterolateral surface of body in smaller specimens with patch of dark chromatophores on basal portion of exposed field. Medium-sized specimens with series of small chromatophores along posterior margin of scales; chromatophore field becoming progressively wider in larger individuals and forming reticulate pattern. Humeral mark obvious and vertically elongate in specimens of all sizes. Mark in form of inverted comma, with main body of mark dorsal to lateral line and with chromatophore field density highest in portion of mark within one and one-half to two scales of dorsal midline. Humeral mark in some individuals extending slightly ventral of lateral line as ventrally tapering patch of chromatophores. Midlateral stripe of deep-lying chromatophores limited to posterior two-thirds of body, more intense posteriorly; merging anteriorly into overall dark pigmentation on lateral surface of the body in larger individuals.

Dorsal fin with second unbranched ray and distal portions of first and second branched rays covered with dark stellate chromatophores. Membranes of all but posterior one or two branched dorsal-fin rays with dispersed dark, irregularly shaped chromatophores. Chromatophore field becoming progressive shorter on distal portions of successive fin membranes. First through third unbranched rays along with first and sometimes second branched anal-fin rays unpigmented; otherwise anal-fin rays outlined by small dark chromatophores, particularly basally, with scattered chromatophores on intervening portions of fin membranes. Rays of upper and lower margins of caudal fin along with middle caudal-fin rays outlined to varying degrees by small dark chromatophores; intervening rays hyaline. Large specimens with pronounced darkening of ventral caudal-fin rays with pigmentation almost appearing as dark stripe. Pectoral and pelvic fins hyaline, or with some scattered, small, dark chromatophores in larger specimens.

ETYMOLOGY.—The specific name, magoi, is in honor of Francisco Mago Leccia, formerly of the Universidad Central de Venezuela, in honor of his major contributions to our understanding of South American freshwater fishes and for all his assistance to the senior author through the years.

ECOLOGY.—A portion of the paratype series (ANSP 159834, USNM 353306) and the nontypes collected with them (ANSP 177716) were collected in a caño of up to 1.5 m depth over a bottom of sand, bedrock, aquatic vegetation, and debris.

DISTRIBUTION.—Creagrutus magoi occurs in the Ríos Chaviripa and Parguaza, right bank tributaries to the Río Orinoco in Bolivar, Venezuela (Figure 51, triangles).

COMPARISONS.—Within the Río Orinoco basin Creagrutus magoi is most similar to C. provenzanoi, a species that occurs in the Río Cataniapo, a right bank tributary to the Río Orinoco upstream of the range of C. provenzanoi. The two species can be readily distinguished by differences in the number of gill rakers on the upper limb of the first gill arch (9 to 11, rarely 9, in C. magoi versus 7 or 8 in C. provenzanoi), and in the number of scales above the lateral line to the dorsal-fin origin (4, rarely 5, in C. magoi versus 5, very rarely 4, in C. provenzanoi). The two species also differ in the width of the interorbital region (30.4%–34.3% of HL in C. magoi versus 27.4%–30.1% of HL in C. provenzanoi).

Creagrutus magoi is rather similar in meristics and morphometrics to C. ephippiatus of the Río Siapa, an endemic to a tributary to the upper Río Negro. The species differ, however, in overall body form, which is best reflected in the relative distance from the dorsal-fin origin to the anal-fin origin (29.2%–33.8% of SL in C. magoi versus 27.8%–29.7% of SL in C. ephippiatus), and in details of pigmentation (form of humeral mark and pigmentation of middle caudal-fin rays). The species also have a pronounced modal shift in the number of total vertebrae (C. magoi: 36(6), 37(38), 38(2) versus C. ephippiatus: 38(34), 39(10), 40(1)).

GEOGRAPHIC VARIATION.—Available specimens of Creagrutus magoi originated in two right bank tributaries of the Río Orinoco, the Río Chaviripa, and the Río Parguaza. The samples from these basins agree in morphometrics and meristics, but the population sample from the Río Parguaza has more intense development of body, head, and caudal-fin pigmentation.

MATERIAL EXAMINED.—203 specimens (50, 18.7–64.8).

HOLOTYPE.—VENEZUELA. Bolivar. Río Chaviripa, where crossed by bridge on road from Caicara to San Fernando de Atabapo (approximately 7°11′N, 66°18′W), collected by D.C. Taphorn et al., 14 Apr 1984, UF 80477, 1 (62.9).

PARATYPES.—49 (49, 18.7–64.8).

VENEZUELA. Bolivar: Río Chaviripa, where crossed by bridge on road from Caicara to San Fernando de Atabapo (approximately 7°11′N, 66°18′W), collected with holotype, UF 11079, 6 (30.2–55.9); USNM 353864, 2 (56.3–58.6; 1 specimen cleared and counterstained for cartilage and bone). Río Chaviripa, where crossed by bridge on road from Caicara to San Fernando de Atabapo (approximately 7°11′N, 66°18′W), collected by D.C. Taphorn et al., 6 Apr 1984, UF 80423, 5 (26.8–57.9); USNM 353863, 1 (42.2). Caño 15.1 km E of ferry crossing on Río Parguaza along road from Caicara to Puerto Ayacucho (approximately 6°26′28″N, 67°09′24″W), collected by B. Chernoff et al., Nov 1985, MBUCV V - 17787, 8 (18.7–64.8); USNM 355118, 2 (30.9–48.2); ANSP 159834, 10 (32.7–56.9); USNM 353305, 2 (38.8–44.6). Caño 8 km N of Ciudad Bolivar to Caicara highway on Las Majadas Road, Río Chimaico crossing (7°32′30″N, 64°47′W), collected by W. Saul et al., ANSP 159835, 10 (27.5–49.7); USNM 353306, 2 (36.0–50.9). Rio Agua Blanca, from 100 to 600 m below bridge at crossing of Caicara-Ciudad Bolivar Highway (7°50′N, 63°51′18″W), collected by B. Chernoff et al., 21 Nov 1985, ANSP 161405, 1 (40.8).

NONTYPE SPECIMENS.—153 specimens.

VENEZUELA. Bolivar: Caño 15.1 km E of ferry crossing on Río Parguaza along road from Caicara to Puerto Ayacucho (approximately 6°26′28″N, 67°09′24″W), ANSP 177714, 118. Caño 8 km N of Ciudad Bolivar to Caicara highway on Las Majadas Road, Río Chimaico crossing (7°32′30″N, 64°47′W), ANSP 177715, 28. Río Agua Blanca, from 100 to 600 m below bridge at crossing of Caicara-Ciudad Bolivar Highway (7°50′N, 63°51′18″W), ANSP 177716, 7.

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

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

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

梅氏鈎齒脂鯉，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Chaviripa與Parguaza河流域，體長可達6.5公分，棲息在底中層水域，生活習性不明。