Creagrutus machadoi Vari & Harold 2001

Creagrutus machadoi

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, occasionally 5, teeth in the rimary series of each premaxilla, 2 to 4 maxillary teeth, 5 teeth on each dentary, 8 or 9 predorsal median scales, 38 or 39 lateral line scales without a lamellar process over each pore, 4 scale rows between the dorsal-fin origin and the lateral line, 3 scale rows between the anal-fin origin and the lateral line, 9 or 10 branched anal-fin rays, 5 to 7 gill rakers on the upper limb and 10 or 11 gill rakers on the lower limb of the first gill arch, the distance from the snout to the dorsal-fin origin (46.4%-49.3% of SL), the distance from the dorsal-fin origin to the hypural joint (51.8%-55.9% of SL), the distance from the dorsal-fin origin to the anal-fin origin (25.9%-30.4% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (20.9%-26.3% of SL), the postorbital head length (38.4%-43.8% of HL), the interorbital width (26.1%-30.1% of HL), the bony orbital diameter (33.5%-43.0% of HL), the gap between the ventral margin of the third infraorbital and the horizontal limb of the preopercle, the absence of a distinct spot of dark pigmentation at the base of the middle caudal-fin rays, the vertical humeral mark 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 machadoi within the clade formed by Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 43.8 26.7–44.5

1. Snout to anal-fin origin 66.6 62.4–67.7

2. Snout to pelvic-fin insertion 49.4 46.9–52.1

3. Snout to pectoral-fin insertion 26.3 25.6–27.6

4. Snout to dorsal-fin origin 48.0 46.4–49.3

5. Dorsal-fin origin to hypural joint 55.2 51.8–55.9

6. Dorsal-fin origin to anal-fin origin 30.4 25.9–28.3

7. Dorsal-fin origin to pelvic-fin insertion 26.3 20.9–24.4

8. Dorsal-fin origin to pectoral-fin insertion 32.1 28.3–31.1

9. Caudal peduncle depth 11.1 9.9–11.2

10. Pectoral-fin length 21.7 18.1–21.7

11. Pelvic-fin length 15.6 14.2–16.4

12. Dorsal-fin length 23.0 20.4–24.0

13. Anal-fin length 19.1 17.5–19.6

14. Head length 28.1 26.2–29.8

15. Postorbital head length 43.8 38.4–43.4

16. Snout length 28.5 25.5–32.0

17. Bony orbital diameter 35.1 33.5–43.0

18. Interorbital width 27.8 26.1–30.1

Meristics

lateral line scales 39 38–39

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 8 8–9

Branched dorsal-fin rays 8 8

Branched anal-fin rays 10 9–10

Branched pelvic-fin rays 5–61 6–72

Pectoral-fin rays 13 11–13

Vertebrae 37 36–38

1Five branched pelvic-fin rays with 1 unbranched medial ray present on left side and 6 branched and 1 unbranched medial ray present on right side of holotype.

2Medial pelvic-fin ray unbranched when 6 branched rays present; 7 branched rays present in only 1 specimen.

DESCRIPTION.—Morphometric and meristic data for Creagrutus machadoi in Table 29. Body fusiform to slightly compressed. Greatest body depth 1 or 2 scale rows anterior of base of anteriormost dorsal-fin ray. Dorsal profile of head distinctly convex from margin of upper lip to vertical through anterior margin of orbit, straight from that point across dorsal surface of head to posterior tip of supraoccipital spine. Predorsal profile of body with distinct, but shallow, convexity from tip of supraoccipital to origin of first dorsal-fin ray. Dorsal profile of body straight to slightly concave from dorsal-fin origin to anterior procurrent caudal-fin ray. Ventral profile of lower jaw broadly rounded. Ventral profile of body slightly convex from isthmus to pelvic-fin insertion; straight to slightly convex from anterior anal-fin ray posteriorly to caudal peduncle.

Anterior profile of head forming broadly rounded angle ranging from as low as approximately 90 degrees to about 120 degrees, with its apex located on horizontal plane through ventral portion of orbit. Angle in profile on central portion of lower jaw not as highly accentuated as in many Creagrutus species. Upper jaw longer than, and overhanging, lower jaw, with up to three anterior premaxillary teeth projecting anterior of lower lip. Anterior portion of snout relatively soft and fleshy, with concentration of soft tissues. Minute papillae concentrated on snout and area between nostrils, upper lip, and continuing into mouth on fleshy flaps and plicae between outer and medial premaxillary teeth. Lower jaw distinctly fleshy anteriorly, with papillae concentrated on lip and extending ventrally in decreasing concentrations along surfaces of jaw. Inner surfaces of lower lip convolute and papillose, with fleshy flaps extending into mouth. Papillae apparently absent on isthmus and cheek.

Elements of infraorbital series moderately well developed, with gap separating posterior and posteroventral margins of infraorbitals from vertical limb of preopercle equally at most approximately one-half of width of third infraorbital bone. Shape of third infraorbital hemispherical, with greater curvature to posterior margin of infraorbital than that of orbit. Fourth infraorbital nearly rectangular.

Premaxillary teeth in three distinct series: primary series in form of arch, with 5 (3 of 14 specimens) or 6 unicuspidate to tricuspidate teeth, anteriormost 2 or 3 teeth series unicuspidate; medial, triangular cluster of three large tricuspidate teeth, posterior two largest and with most highly developed cusps; and single outer unicuspidate tooth located approximately lateral to, or slightly posterior of, fourth tooth in main row. Maxilla with 2 to 4 weakly tricuspidate flattened teeth. Dentary usually with 5 unicuspidate to weakly tricuspidate teeth. Two anterior dentary teeth largest with distinct, but small, lateral cusps; third tooth tricuspidate and slightly smaller than preceding teeth; remaining dentary teeth unicuspidate or tricuspidate with indistinct lateral cusps and distinctly smaller than anterior three teeth.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin located slightly anterior to vertical through pelvic-fin origin. Distal margin of dorsal fin slightly concave, resulting from elongation of posterior unbranched and anterior 2 or 3 branched rays, and 2 posterior branched rays. Anal-fin rays ii,9–10 or iii,9 (latter in only one specimen). Anal fin with hooks, when present (one 26.5 mm SL specimen; MCNG 18917), singly on third and fourth segments of first branched ray. Distal margin of anal fin slightly sigmoidal, with second unbranched and first and second branched rays forming slightly elongate lobe. Posterior two anal-fin rays longer than immediately preceding rays. Pectoral-fin rays i,11 to 13, typically 12 to 13. Pectoral fin moderately long, extending posteriorly nearly to pelvic-fin origin. Pelvic-fin rays i,6,i or i,7 (only in one specimen) (holotype with i,6,i on one side and i,5,i on other). Hooks on pelvic-fin rays, when present, on medial surfaces of segmented and unsegmented portions of main shaft and medial secondary branches of all branched rays. Pelvic fin relatively long, in some specimens reaching posteriorly slightly beyond anterior anal-fin ray. Posterior margin of body scales smoothly rounded. Pelvic axillary process comprising a single, elongate scale.

Gill rakers 5–7 + 10–11.

COLORATION IN ALCOHOL.—Overall pigmentation very poorly developed. Ground coloration very pale straw, with observed dark chromatophores very small and punctate, ranging from dark brown to black in most portions of head and body. Dorsal surface of head with scattered, small, dark brown chromatophores, most concentrated over snout and central portion of upper lip, and extending onto plicate tissues of roof of mouth, dorsal surfaces of frontal and parietal portions of cranium, including frontal fontanel. Dark crescent-shaped batch of dark chromatophores located immediately anterior of anterior nares. Little or no dark pigmentation on lateral portions of upper lip and maxilla and interorbital area. Band of scattered, dark brown chromatophores extending from immediately lateral of nares posteroventrally and continuing around ventral and posterior margins of orbit. Dorsal one-half of gill cover in region posterior to orbit with numerous scattered, small, dark chromatophores; number of chromatophores decreasing from posterodorsal region of head ventrally onto upper portion of cheek and gill cover. Lower lip and fleshy portion of jaw speckled with small, black chromatophores; other ventral areas of head unpigmented.

Dark body pigmentation diffuse, mostly confined to region dorsal of lateral line. Pigmentation concentrated as vertical bands along anteriormost exposed portion of each scale on four dorsalmost, longitudinal rows of scales. Scattered chromatophores present in posterior fields of all scales dorsal of lateral line. Small area of middorsal region in area of two median scales with cluster of large dark chromatophores similar in size and color to those of humeral mark. Humeral mark usually in form of anteriorly concave vertical bar without region of particularly dense pigmentation and tapered ventrally to narrow band below lateral line. Flank unpigmented ventral of lateral line except for dark pigmentation associated with humeral bar and posterior portion of lateral stripe, and for very sparsely scattered, dark chromatophores delineating hypaxial myosepta immediately dorsal of anal-fin base. Midlateral stripe highly diffuse anteriorly, with anterior portion overlying first and second scale rows dorsal of lateral line, becoming more densely pigmented and somewhat wider posteriorly and extending ventral of lateral line on posterior portion of caudal peduncle.

All unbranched and anterior four branched dorsal-fin rays darkly pigmented, especially along distal one-fourth to one-half of their lengths. Smaller dark pigment cells associated with basal one-half of all dorsal-fin rays. Unbranched and anterior branched anal-fin rays hyaline; remainder of anal fin with small dark chromatophores located along anterior margin and adjacent membrane of each ray. Caudal-fin rays delineated mainly by dark brown pigmentation, with more lightly pigmented cells over central portion of fin. Caudal fin with distal one-half of dorsal lobe and distal one-fourth of ventral mostly unpigmented. Pelvic and pectoral fins hyaline except in larger (greater than 40 mm SL) specimens, which have dark line of pigmentation delineating lateral pectoral-fin ray and patch of more lightly pigmented chromatophores near tip of longest three or four branched rays.

ETYMOLOGY.—The specific name, machadoi, is in honor of our coauthor on other papers involving Creagrutus, Antonio Machado-Allison of the Universidad Central de Venezuela, in acknowledgment of his assistance to the authors in the laboratory and the field through the years, and in recognition his many contributions to our knowledge of Neotropical fishes.

ECOLOGY.—A specimen of Creagrutus machadoi prepared for clearing and staining in this study had insects in its stomach.

DISTRIBUTION.—Creagrutus machadoi is known only from Río Caura basin, a right bank tributary of the main Río Orinoco (Figure 51, star).

COMPARISONS.—In addition to Creagrutus machadoi, three other members of the genus occur in the Río Caura basin, C. bolivari, C. phasma, and C. xiphos. Creagrutus machadoi is readily distinguished from these other species by the features cited in “Key to the Creagrutus Species in the Río Orinoco Basin.”

MATERIAL EXAMINED.—14 specimens (14, 26.5–44.5).

HOLOTYPE.—VENEZUELA. Bolivar: Departamento Cedeno, upper Río Caura, Caño Yumucukenã, within 4 km of its mouth, collected by B. Stergios et al., 15 May 1988, MCNG 18852, 1 (43.8).

PARATYPES.—11 specimens (11, 26.7–44.5).

VENEZUELA. Bolivar: Departamento Cedeno, upper Río Caura, Caño Yumucukenã, within 4 km its mouth, collected with holotype, MCNG 41717, 6(28.1–44.5); USNM 359641, 2 (31.0–38.2). Departamento Cedeno, Río Caura, at the base of Raudal Sejiato (=Cietao; 5°34′N, 64°19′W), collected by B. Stergios, 22 May 1988, MCNG 18896, 3 (26.7–30.6).

NONTYPE SPECIMENS.—2 specimens (2, 26.5–27.7).

VENEZUELA. Bolivar: Departamento Cedeno, Río Caura, Isla Guanaguanadi, MCNG 18917, 2 (26.5–27.7).