Creagrutus runa Vari & Harold 2001

Creagrutus runa

Creagrutus cf. caucanus.—Goulding et al., 1988:156, 160 [Brazil, Amazonas, Rio Negro; diet].

DIAGNOSIS.—The possession of premaxillary dentition with the three components generalized for the species of Creagrutus and Piabina, but with a distinct gap between the first and second teeth of primary tooth row and a forward position of the triangular cluster of three posteromedial teeth distinguishes C. runa from all members of the clade formed by Creagrutus and Piabina with the exception of Creagrutus maracaiboensis, C. melanzonus, C. muelleri, C. nigrostigmatus, C. ouranonastes, C. peruanus, and Piabina argentea. Creagrutus runa can be distinguished from these seven species by the combination of the possession of 4 teeth in primary series on the premaxilla, 4 to 6 maxillary teeth, 6 to 8 dentary teeth, 8 or 9 predorsal median scales, 39 or 40 lateral line scales without a lamellar process over each pore, 4 scale rows between the dorsal-fin origin and the lateral line, 9 or 10 branched anal-fin rays, 37 to 39 vertebrae, 5 to 7 gill rakers on the upper limb of the first gill arch, 9 to 12 gill rakers on the lower limb of the first gill arch, the distance from the snout to the anal-fin origin (63.6%–68.8% of SL), the distance from the snout to the pectoral-fin insertion (24.3%–27.2% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (18.7%–24.5% of SL), the caudal peduncle depth (8.8%–10.5% of SL), the postorbital head length (36.4%–45.3% of HL), the bony orbital diameter (31.8%–41.8% of HL), the near approach of the ventral margin of the third infraorbital to 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 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.

DESCRIPTION.—Morphometric and meristic data for Creagrutus runa in Table 51. Head and body elongate. Body fusiform to slightly compressed. Greatest body depth slightly anterior of base of anteriormost dorsal-fin ray. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior margin of posterior nares, straight from that point to tip of supraoccipital spine in specimens up to about 45 mm SL. Larger individuals with dorsal profile of head straight as far as posterior tip of supraocciptal spine and slightly convex from that point to tip of supraoccipital spine. Predorsal profile of body straight in specimens up to approximately 45 mm SL, slightly convex in larger individuals. Dorsal profile of body straight from dorsal-fin origin to anterior procurrent caudal-fin ray, with slight dorsal inflection at adipose-fin base. Ventral profile of head with broadly rounded angle approximately midway between margin of lower lip and posterior extremity of dentary, profile slightly convex from angle to isthmus. Ventral profile of body slightly convex to pelvic-fin insertion, straight along anal-fin base, and with slight concavity between base of posteriormost anal-fin ray and anterior ventral procurrent caudal-fin ray.

Characters A B

Morphometrics

Standard length 40.9 31.8–46.2

1. Snout to anal-fin origin 63.6 64.4–68.8

2. Snout to pelvic-fin insertion 46.1 45.3–50.0

3. Snout to pectoral-fin insertion 24.3 26.8–27.2

4. Snout to dorsal-fin origin 46.3 44.7–50.0

5. Dorsal-fin origin to hypural joint 56.3 53.5–58.2

6. Dorsal-fin origin to anal-fin origin 27.5 27.0–31.0

7. Dorsal-fin origin to pelvic-fin insertion 18.7 20.0–24.5

8. Dorsal-fin origin to pectoral-fin insertion 27.9 28.7–32.9

9. Caudal peduncle depth 8.8 9.1–10.5

10. Pectoral-fin length 17.5 16.1–19.1

11. Pelvic-fin length 14.8 12.9–15.4

12. Dorsal-fin length 19.6 18.1–21.6

13. Anal-fin length 15.9 14.1–16.2

14. Head length 24.4 24.2–27.5

15. Postorbital head length 39.8 36.4–45.3

16. Snout length 26.0 27.1–32.1

17. Bony orbital diameter 39.2 31.8–41.8

18. Interorbital width 30.1 25.7–30.2

Meristics

Lateral line scales 41 39–40

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

Scale rows between anal-fin origin and lateral line 3 2–31

Predorsal median scales 8 8–9

Branched dorsal-fin rays 8 8

Branched anal-fin rays 9 9–10

Branched pelvic-fin rays 7 7

Pectoral-fin rays 11 11–132

Vertebrae 37 37–39

1Three scale rows between anal-fin origin and lateral line present in 3 of 17 paratypes from which count could be taken.

2One nontype specimen with 10 pectoral-fin rays present on one side of body and 11 rays on other side.

Anterior profile of head forming broadly rounded obtuse angle of about 120 degrees, with apex of angle located on horizontal plane through ventral portion of orbit; angle of lower jaw not highly accentuated. Upper jaw slightly longer than, and overhanging, lower jaw. Anterior portion of snout relatively soft and fleshy, with concentration of soft tissues; minute papillae concentrated on snout and upper lip, continuing into mouth on fleshy flaps between outer and medial premaxillary teeth. Lower jaw distinctly fleshy anteriorly, with concentrated papillae. Inner surfaces of lower lip convoluted and papillose, with fleshy flaps extending into mouth.

Elements of infraorbital series moderately well developed, with ventral margin of third infraorbital separated from ventral limb of preopercle by narrow gap. Posterior margins of third through fifth infraorbitals separated from vertical limb of preopercle by narrow gap; width of gap equal to, at most, about one-fourth of width of fourth infraorbital, gap practically absent in some specimens. Posterior and ventral margins of third infraorbital usually forming broadly rounded obtuse angle; fourth infraorbital nearly rectangular.

Premaxillary teeth in three distinct groups: primary series consisting of 4 unicuspidate to tricuspidate teeth, 2 anteriormost teeth unicuspidate and separated by distinct gap approximately width of one tooth; medial, triangular cluster of 3 large tricuspidate teeth with anterior tooth partially positioned in pronounced gap between first and second teeth of primary series, posterior 2 teeth largest and with most highly developed cusps; and single outer unicuspidate tooth positioned approximately lateral to second tooth in primary series. Maxilla with 4 to 6 tricuspidate teeth. Dentary with 6 to 8 typically tricuspidate teeth; second tooth slightly higher, but distinctly wider than first tooth and much larger than third tooth, remaining teeth in series distinctly smaller than anterior three teeth; third through sixth teeth slightly recurved.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin located anterior to vertical through pelvic-fin origin; base of second or third ray usually located at vertical through pelvic-fin insertion. Distal margin of dorsal fin slightly concave as consequence of relative elongation of second unbranched, anterior 2 or 3 branched rays, and posterior 2 branched rays. Anal-fin rays ii–iii,9–10. Mature males with 1 or 2 hooks, when present, on segments of first branched anal-fin ray. Distal margin of anal fin slightly sigmoidal, with second unbranched and first through third branched rays forming slightly elongate lobe, outline of posterior 5 or 6 rays concave. Pectoral-fin rays i, 10–12. Pectoral fin short; tip reaching to within 2 to 4 scale rows of pelvic-fin origin. Pelvic-fin rays i,7,i or i,7. Mature males with pelvic-fin hooks, when present, on medial surfaces of segmented and unsegmented portions of main shaft and medial secondary branches of all rays medial of lateral unbranched element. Tip of pelvic fin falling 2 or 3 scales short of anal-fin origin. Posterior margin of body scales smoothly rounded to slightly undulate. Pelvic axillary process well developed.

Gill rakers 5–7 + 9–12.

COLORATION IN ALCOHOL.—Overall pigmentation very poorly developed; ground color very pale straw to light brown, with dark chromatophores ranging from light to dark brown or sepia on most portions of head and body. Dorsal surface of head with scattered, small, light brown chromatophores; chromatophores most concentrated over snout but mostly absent from upper lip. Dorsal surfaces of frontal and parietal portions of cranium pigmented with small, concentrated, stellate, dark chromatophores over frontal fontanel. Largest, darkest chromatophores associated with supraorbital canal and frontal commissure. Poorly developed crescent-shaped patch of dark chromatophores immediately anterior of anterior nares. Band of scattered, light brown chromatophores extending from immediately lateral of nares posteroventrally and continuing along ventral margin of orbit no further than under middle of eye. Region posterior to orbit and dorsal portion of opercle with scattered, small to large chromatophores; chromatophores numerous in some specimens. Lower lip and ventrolateral surface of head unpigmented.

Body pigmentation diffuse, most concentrated dorsal of lateral line. Two dorsalmost rows of scales with vertical bands of very small chromatophores on anteriormost exposed portion of each scale and series of more scattered chromatophores on posterior field of each scale. Middorsal region without any notable concentration of dark chromatophores. Humeral mark usually in form of anteriorly concave, slightly crescent-shaped vertical bar. Pigmentation in bar most concentrated on first scale row immediately dorsal of lateral line. Bar gradually fading dorsally and terminating within about 1 scale row of midline. Lateral surface of body mostly unpigmented ventral to lateral line, other than for chromatophores associated with humeral bar. Some specimens with scattered chromatophores immediately dorsal of anal-fin base and along midventral region between pelvic and anal fins. Larger specimens, more than 50 mm SL, with diffuse midlateral stripe consisting of dispersed, small, dark chromatophores along first and second scale rows dorsal of lateral line. Stripe becoming denser and somewhat wider posteriorly, extending well ventral of lateral line on caudal peduncle.

Dorsal-fin membranes with small number of moderately dark chromatophores associated with distal one-fourth of second unbranched and first 2 or 3 branched rays; basal portions of shafts of all, or nearly all, rays with scattered, dark chromatophores. Anal fin mostly unpigmented other than for dark chromatophores located at base of all rays immediately adjacent to point of insertion. Caudal fin with outer 2 or 3 branched and first unbranched fin rays delineated by brown pigment, with darkest pigmentation confined to basal portions of central 4 branched rays; pigmentation appearing as faint spot under magnification, especially in specimens smaller than approximately 45 mm SL. Pelvic and pectoral fins hyaline.

ECOLOGY.—Goulding et al. (1988:156, 160) reported that Creagrutus runa (identified therein as Creagrutus cf. caucanus) fed on terrestrial insects and terrestrial seeds. Nontype specimens from the upper reaches of the Río Negro in Venezuela (USNM 270228) were collected in black water along the margin of the main river channel along a sand bar over a sandy and rocky bottom.

COMPARISONS.—Creagrutus runa is most similar to C. veruina, an endemic of Río Cataniapo, a tributary of the Río Orinoco, which shares similar dentition and overall body form. The two species can be distinguished by differences in the number of branched anal-fin rays (9 or 10 in C. runa versus 11 in C. veruina), differences in the form of the humeral mark (compare Figures 85 and 91), and relative distance from the snout to the anal-fin origin and the snout to the pectoral-fin insertion (see Tables 51 and 56).

ETYMOLOGY.—The species name, runa, from the Latin for javelin or spear, refers to the elongate body form of the species.

DISTRIBUTION.—Creagrutus runa is limited to the upper portions of the Río Negro basin in northern Brazil and southern Venezuela (Figure 83, diamonds).

MATERIAL EXAMINED.—57 specimens (26, 31.8–62.7).

HOLOTYPE.—BRAZIL. Amazonas: Rio Negro, Paraná do Jacaré (approximately 0°30′S, 66°30′W), collected by M. Goulding, 7 Oct 1979, MZUSP 29888, 1 (40.9).

PARATYPES.—37 specimens (21, 31.8–46.2).

BRAZIL. Amazonas: Rio Negro, Paraná do Jacaré, collected with holotype, MZUSP 55473, 30 (14, 31.8–39.1); USNM 359622, 5 (32.3–45.2). Rio Negro basin, Rio Daraá, Cachoeira do Aracu (approximately 0°30′S, 64°40′W), USNM 270228, 2 (40.4–46.2).

NONTYPE SPECIMENS.—19 specimens (4, 52.5–62.7).

VENEZUELA. Amazonas: Departamento Río Negro, Río Negro, approximately one-half hour upriver of San Carlos de Río Negro (01°58′N, 67°04′W), USNM 270228, 2. Río Guainia, at beach in Maroa (2°43′N, 67°33′W), MCNG 23311, 4 (52.5–62.7; 1 specimen cleared and counterstained for cartilage and bone).

BRAZIL. Amazonas: Rio Negro, Cachoeira de São Gabriel (4°19′N, 72°04′W), MZUSP 29890, 13.