Creagrutus cochui Géry 1964

Creagrutus cochui, MZUSP 28055, 2, 64.2–66.4 mm; Brazil, Amazonas, Rio Içá

Creagrutus cracentis, USNM 353862, 1, 26.1 mm, paratype; Brazil, Para, Rio Tapajós, 5 km S of Itaituba.

Creagrutus crenatus. MHNLS 12900, 1, 57.0 mm, paratype; Venezuela, Lara, Quebrada Sanare, in Yay. INHS 28851, 1, 43.6 mm, paratype; Venezuela, Lara, Río Curarigua, Puente Torres.

Creagrutus cochui Géry, 1964

Creagrutus cochui Géry, 1964:56, fig. 12 [type locality: Peru (Loreto), “Upper Amazon region surrounding lquitos”]; 1977:393, 407 [species included in key, life photo],—Ortega and Vari, 1986:8 [Peru; common name].—Géry and Renno, 1989:5 [comparison with C. planquettei].—Vari and Howe, 1991:15 [holotype depository].—Román-Valencia and Cala, 1996:148 [Colombia, Río Loreto-Yacú, Río Amazonas basin].

DIAGNOSIS.—The presence of a horizontally elongate, but distinct, main body of the humeral mark is unique to Creagrutus cochui within the genus, being approximated only by larger specimens of C. atrisignum, an endemic of the Río Tocantins basin. The latter species, however, has a secondary humeral mark situated dorsal to the horizontally elongate primary mark; this additional patch of dark pigmentation is absent in C. cochui. Other features, which in combination separate C. cochui from the other members of the clade composed of Creagrutus and Piabina, are 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, typically 6 teeth in the primary premaxillary tooth row, 2 or 3 teeth on the maxilla, 5 teeth on each dentary, 38 to 41 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 predorsal scales, 2 post-anal scales anterior to the anal-fin origin, 11 to 13 branched anal-fin rays, the head length (24.1%–26.5% of SL), the interorbital width (27.8%–32.5% of HL), the relatively shallow and transversely rotund body, the well-developed third infraorbital contacting the horizontal limb of the preopercle, the lack of a series of midlateral dark marks on the body, the horizontally elongate humeral mark, and the absence of a discrete patch of dark pigmentation on the middle portions of the anterior dorsal-fin rays.

DESCRIPTION.—Morphometric and meristic data for Creagrutus cochui in Table 14. Greatest body depth at, or slightly anterior of, vertical through pelvic-fin insertion. Dorsal profile of head gently convex from tip of snout to vertical through posterior nostril, nearly straight from that point to tip of supraoccipital spine. Predorsal profile of body gently convex in all examined specimens. Postdorsal profile of body straight to slightly convex. Ventral profile of head with obtuse angle at anteroventral corner of dentary, straight from that point to isthmus. Ventral profile of body convex, more so in larger individuals.

Head obtusely pointed in both dorsal and lateral views. Upper jaw longer than, and overhanging, lower jaw. Snout somewhat fleshy. Papillae concentrated on anterior portion of snout and upper lip, particularly along ventral margin of lip and on folds and plicae extending between outer and medial premaxillary teeth. Lower lip fleshy anteriorly, with papillae concentrated on dorsal surface.

Characters A B

Morphometrics

Standard length 68.3 44.2–79.3

1. Snout to anal-fin origin 64.1 61.3–65.9

2. Snout to pelvic-fin insertion 46.0 44.5–48.3

3. Snout to pectoral-fin insertion 24.0 22.6–25.2

4. Snout to dorsal-fin origin 43.3 42.9–46.1

5. Dorsal-fin origin to hypural joint 59.0 57.8–60.5

6. Dorsal-fin origin to anal-fin origin 32.4 29.9–33.7

7. Dorsal-fin origin to pelvic-fin insertion 24.4 24.0–27.1

8. Dorsal-fin origin to pectoral-fin insertion 29.1 28.9–31.7

9. Caudal peduncle depth 11.4 10.3–11.8

10. Pectoral-fin length – 18.7–21.0

11. Pelvic-fin length 15.6 15.6–18.0

12. Dorsal-fin length – 20.0–24.7

13. Anal-fin length – 17.5–20.3

14. Head length 24.2 24.1–26.5

15. Postorbital head length 42.4 39.0–44.3

16. Snout length 27.3 26.8–30.4

17. Bony orbital diameter 36.3 33.3–39.0

18. Interorbital width 32.1 27.8–32.5

Meristics

Lateral line scales 39 38–41

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 7

Pectoral-fin rays 13 12–14

Vertebrae 37 37–39

Infraorbital series well developed. Anterior one-half of ventral margin of third infraorbital contacting horizontal limb of preopercle. Posterior margins of third to fifth infraorbitals not contacting vertical limb of preopercle, gap between posterior margins of infraorbitals and preopercle progressively decreasing dorsally.

Premaxillary dentition in three series: primary row slightly curved, typically with 6 teeth, 5 teeth present on one premaxilla in one specimen, without pronounced gap between first and second tooth of series but with anterior teeth of contralateral series distinctly separated; triangular cluster of three tricuspidate 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 tricuspidate teeth. Dentary with 5 teeth, first three teeth distinctly larger, with first and second teeth particularly large. Fourth tooth slightly smaller than third tooth. All teeth tricuspidate, with central cusp proportionally much larger on first three teeth and all cusps nearly equal on fifth tooth.

Dorsal-fin rays ii,8. Dorsal-fin origin slightly anterior to vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin concave, more so in larger individuals. Anal-fin rays ii,11–13, rarely iii,12–13. Profile of distal margin of anal fin distinctly concave, with last branched and first 2 or 3 branched rays forming anterior lobe. Mature males with paired hooks present on posterior margins of main shaft of ray and on posterior branches of first through third branched rays; 1 or 2 hooks sometimes present on fourth ray. Pectoral-fin rays i,11–13. Pectoral fin extending posteriorly approximately three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays i,7. Mature males with hooks present on posterior margin of unsegmented and posterior main branch of segmented portions of all branched rays. Hooks also present on all branches except lateralmost branched pelvic-fin ray. Tip of pelvic fin extending posteriorly to anal-fin origin.

Gill rakers 7–8 + 11–14.

COLORATION IN LIFE.—(based on life photo of a paratype of the species in an aquarium, Géry, 1964, fig. 12a; 1977:393). Overall coloration of body brown with guanine highlights on scales, opercle, and infraorbitals. Horizontally elongate, dark humeral mark very obvious. Lighter patch of dark pigmentation extending dorsally from main portion of humeral mark. Distal portion of anterior rays of dorsal fin apparently dark. Dark pigmentation present on basal portions of middle caudal-fin rays. Anterior margin of anal fin white. Light highlights present along rays of dorsal fin.

COLORATION IN ALCOHOL.—Overall ground coloration tan. Smaller specimens with dorsal surface of brain covered by relatively large, dark chromatophores, this pigmentation obscured by thicker bones and surface pigmentation in larger individuals. Dorsal surface of head with scattered, small, dark chromatophores; chromatophore field more concentrated over snout, particularly anterior to nares where pigmentation forms discrete crescent. Posteroventrally inclined band of chromatophores under anterior margin of adipose eyelid. Narrow band of dark chromatophores bordering ventral and posterior margins of orbit in many Creagrutus species absent. Surface of fourth and fifth infraorbitals with scattered, small, dark chromatophores. Distinct patch of large dark chromatophores on dorsal portion of opercle, sometimes also extending anteriorly onto posterior portion of infraorbital series; when well developed chromatophore field forming horizontal dark band posterior of orbit.

Dorsal and dorsolateral surfaces of body with scattered, small, dark chromatophores; chromatophore fields more concentrated over center of scales. Midlateral dark stripe extending from supracleithrum to caudal-fin base. Humeral mark lying within midlateral stripe; main portion of mark consisting of horizontally elongate patch of dark pigmentation. Main portion of humeral mark flanked dorsally by very faint to moderately pigmented anterodorsally angled patch. Some specimens with limited area of scattered, dark chromatophores ventral of main body of humeral mark.

Dorsal fin with interradial membranes between distal portions of last unbranched and anterior 4 to 6 branched rays with vertically elongate patches of dark pigmentation. Interradial pigmentation most intense between last unbranched and first branched and between first and second branched rays. Remainder of dorsal fin with small dark chromatophores outlining rays. Anal fin ranging from hyaline to having distal portions of middle rays somewhat dusky. Caudal fin with variably apparent basal spot formed by chromatophores as large as, and continuous with, those of midlateral stripe. Middle caudal-fin rays and associated membranes with scattered, dark chromatophores, giving region dusky appearance. Pectoral and pelvic fins hyaline to slightly dusky.

ECOLOGY.—Examination of the stomach contents of two specimens prepared for clearing and staining in this study revealed parts of seeds, larval and adult insects, and in one case a portion of the head of a small fish.

In the southern portions of its range Creagrutus cochui was captured sympatrically with C. pila within the Río Neshuya, a tributary of the Río Aguaytia (MUSM 8887 and 5240; MUSM 8885 and 8876, respectively).

COMMON NAME.—Peru: “Majorita” (Ortega and Vari, 1986:8).

DISTRIBUTION.—Creagrutus cochui occurs in the western portions of Amazon basin in Peru, Brazil, and perhaps Colombia (see below, under “Remarks,” concerning latter locality; Figure 33, triangles).

GEOGRAPHIC VARIATION.—The pigmentation in the region of the humeral mark in the samples (MUSM 8885, 8886, 8887) from the southern portion of the species' range in the Río Aguaytia basin of the Department of Ucayali, Peru, differs sightly from that in samples from further to the north. The dark pigmentation situated dorsal of the main body of the humeral mark, which is faint in more northerly population samples, is more obvious in the Río Aguaytia sample. The portion of the midlateral stripe contiguous with the humeral mark in the Río Aguaytia sample also is more heavily pigmented than the remainder of the stripe and the humeral mark. This contrasts with the situation in populations further to the north in which the humeral mark and stripe are equally dark. Additional samples from intervening regions are necessary to determine whether this variation is significant.

MATERIAL EXAMINED.—149 specimens (19, 44.2–79.3).

BRAZIL. Amazonas: Rio Içá, Igarapé Boa Vista, MZUSP 28035, 53 (15, 44.2–73.9; 2 specimens cleared and counterstained for cartilage and bone). Caiauá, Igarapé da Cachoeira, along margin of Rio Içá, MZUSP 17536, 3 (1, 79.3). Igarapé Açu, 7 km below Santo Antonio do Iça (3°05′S, 40°49′W), MZUSP 17574, 63. Igarapé tributary to Rio Iça, 17.4 km downstream of Santo Antonio do Iça, USNM 342927, 10.

COLOMBIA. Meta: Roadside pond and stream 48 km NNE of Vistahermosa (Río Guaviare basin), UF 36678, 1 (see under “Remarks,” above, concerning this specimen).

PERU. Loreto: Upper Amazon [Rio Amazonas], near Iquitos, USNM 200426, 1 (68.3, holotype of Creagrutus cochui); MHNG 2183.36, 1 (54.8, paratype of Creagrutus cochui). Quebrada Carahuayte at km 20 on road between Jenaro Herrera and Colonia Angamos, NRM 26306, 1; NRM 26307, 3 (1, 61.5). Rio Ampiyacu, near Pebas (3°20′S, 71°49′W), CAS 160723 (formerly SU 60723), 6. Ramón Castilla, Beirut, MUSM 194, 1. Ucayali: Provincia Padre Abad, Rio Tahuayo, km 72 on road from Pucallpa to Tingo Mario, MUSM 8887, 1. Provincia Coronel Portillo, Río Aguaytia basin, Río Neshuya (mouth of river at 8°17′S, 75°03′W), MUSM 8885, 3; MUSM 8886, 2.