Creagrutus ortegai Vari & Harold 2001

Creagrutus ortegai

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, 3 or 4 teeth on the maxilla, 6, less commonly 5, teeth in the primary tooth row of the premaxilla, 6 dentary teeth, 37 to 39 lateral line scales without a lamellar process over each pore, 11 or 12 predorsal median scales, 4 or 5 scale rows between the dorsal-fin origin and the lateral line, 36 to 38 vertebrae, 9 to 12 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 9 to 11 gill rakers on the lower limb of the first gill arch, the postorbital head length (44.4%–48.8% of HL), the snout length (24.2%–29.1% of HL), the bony orbital diameter (28.8%–33.3% of HL), the interorbital width (28.3%–31.6% of HL), the moderately developed third infraorbital with its ventral margin approaching or contacting the horizontal limb of the preopercle, the lack of a series of dark midlateral spots on the body, the presence of a rhomboidal humeral mark centered above the lateral line without an associated, slightly more dorsally located, secondary pigment mark, the lack of a distinct spot of pigmentation on the basal portions of the middle caudal-fin rays, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus ortegai within the clade composed of Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 66.5 28.0–71.1

1. Snout to anal-fin origin 63.2 61.0–65.1

2. Snout to pelvic-fin insertion 47.6 44.4–48.5

3. Snout to pectoral-fin insertion 24.5 22.0–25.1

4. Snout to dorsal-fin origin 48.1 46.4–49.7

5. Dorsal-fin origin to hypural joint 55.6 54.7–59.4

6. Dorsal-fin origin to anal-fin origin 32.0 29.4–34.7

7. Dorsal-fin origin to pelvic-fin insertion 28.4 25.1–28.0

8. Dorsal-fin origin to pectoral-fin insertion 33.9 31.7–33.8

9. Caudal peduncle depth 13.2 11.5–13.7

10. Pectoral-fin length 20.5 19.1–20.7

11. Pelvic-fin length 15.8 14.9–17.9

12. Dorsal-fin length 22.0 21.7–24.8

13. Anal-fin length 19.0 17.9–19.1

14. Head length 26.0 24.1–27.3

15. Postorbital head length 47.9 44.4–48.8

16. Snout length 28.9 24.2–29.1

17. Bony orbital diameter 30.6 28.8–33.3

18. Interorbital width 30.6 28.3–31.6

Meristics

Lateral line scales 38 37–39

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

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

Predorsal median scales 11 11–12

Branched dorsal-fin rays 8 7–81

Branched anal-fin rays 10 9–12

Branched pelvic-fin rays 6 5–62

Pectoral-fin rays 13 12–14

Vertebrae 38 36–38

1 Seven branched dorsal-fin rays present in only 1 of 39 paratypes.

2 Five branched pelvic-fin rays present in only 1 of 39 paratypes.

DESCRIPTION.—Morphometric and meristic data for Creagrutus ortegai in Table 41. Head and body relatively robust, more so in specimens larger than 30 mm SL. Greatest body depth at dorsal-fin origin in specimens of approximately 30 mm SL, located at that point or shifted variably anteriorly in larger individuals, and lying approximately midway between dorsal-fin origin and tip of supraoccipital spine in some of largest examined specimens. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior nostril in all specimens larger than 30 mm SL, straight from that point to rear of supraoccipital spine in smaller individuals, slightly convex in that region in larger specimens. Dorsal profile of body convex from rear of supraoccipital spine to dorsal-fin origin, convexity more pronounced in larger specimens; profile angled at dorsal-fin base. Ventral profile of head and body typically smoothly rounded from tip of lower jaw to pelvic-fin insertion. Obtuse angle at anteroventral corner of dentary found in many Creagrutus species either absent, or barely evident. Prepelvic region of body broadly rounded transversely.

Head obtusely rounded in lateral view and more compressed in dorsal view. Upper jaw distinctly longer than, and overhanging, lower jaw. Anterior portion of snout fleshy, with scattered papillae; papillae more concentrated on fleshy upper lip, albeit with papillae less well developed than in many congeners. Lower lip fleshy anteriorly, with numerous papillae on dorsal margin and anterior surface.

Infraorbital series moderately developed, ventral margin of third infraorbital approaching horizontal limb of preopercle in smaller specimens, ventrally in contact with preopercle in larger individuals. Posterior margins of third through fifth infraorbitals distinctly separated from vertical limb of preopercle.

Premaxillary dentition in three series: primary row slightly curved, typically consisting of 6 teeth, although only 5 teeth present in about 5% of examined specimens, without pronounced gap between first and second tooth of series; triangular cluster of 3 larger teeth; and single tooth of form similar to that of primary series located lateral to fourth tooth of primary premaxillary series, or sometimes lateral to area of contact of third and fourth teeth of primary series. Maxilla with 3, or rarely 4, tricuspidate teeth. Dentary with 6 tricuspidate teeth; first and second teeth distinctly larger than other teeth, subequal, approximately 1.7 times height of third tooth; fourth through sixth teeth much smaller and compressed.

Dorsal-fin rays typically ii,8, iii,8 in one specimen, ii,7 in one specimen. Dorsal-fin origin located approximately at vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave in all specimens larger than 30 mm SL. Anal-fin rays ii,9–12, both 9 and 12 branched rays rare. Hooks typically present on anal-fin rays in mature males of many Creagrutus species not present in examined specimens. Profile of distal margin of anal fin with slight anterior lobe and distinctly concave distal margin. Pectoral-fin rays i, 11–13. Tip of pectoral fin extending posteriorly approximately three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays typically i,6,i, i,5,i in one specimen. Tip of pelvic fin extending posteriorly to anal-fin origin. Hooks typically present on pelvic-fin rays in mature males of many Creagrutus species not present in examined specimens.

Gill rakers 6–7 + 9–11.

COLORATION IN ALCOHOL.—More recently collected specimens retaining guanine on scales and head with silvery head and body. Guanine on body somewhat masking dark midlateral body stripe and humeral mark. Ground coloration yellow in relatively recently collected specimens not retaining guanine on body. Specimens preserved in alcohol for longer periods light brown. Dorsal surface of head with dense field of dark chromatophores; chromatophore field not as pronounced on dorsal surface of snout, particularly in smaller individuals, and fading out along anterior margin of upper lip. Denser crescent-shaped patch of dark pigmentation present immediately anterior to nares. Curved band of dark pigmentation extending from posteroventral portion of pigmented region anterior to nares to around ventral and posterior margins of orbit, band widest anteroventral to orbit. Region of head posterior to orbit with scattered, dark chromatophores on infraorbitals and opercle; pigmentation somewhat more concentrated on opercle in many specimens.

Scales of dorsal portion of body with dark chromatophores concentrated over center of exposed portion and along posterior margin of scales; these more highly pigmented regions on each scale separated by hyaline arch. Pigmentation on scales less prominent on dorsolateral portion of body. Dark humeral mark apparent in all examined specimens. Mark with densely pigmented middle region centered above lateral line at all available body sizes. Less heavily pigmented, variably shaped extensions continue dorsally and ventrally from main body of mark. Midlateral body stripe consisting of deep-lying and dark surface pigmentation. Stripe relatively darkest posteriorly and becoming more diffuse anteriorly. Stripe not obvious anterior to vertical through dorsal-fin origin in specimens less than 40 mm SL, denser and more elongate horizontally in larger individuals with stripe extending anteriorly to posterior margin of humeral mark.

Dorsal fin with membranes and fin-ray margins covered with small dark chromatophores, particularly on distal two-thirds of rays; intensity of pigmentation increasing ontogenetically, with number of rays bearing such pigmentation also increasing with body size, albeit not forming black spot even in largest specimens. Central portions of anal-fin rays overlain with dark chromatophores, forming faint longitudinal stripe along fin. Caudal fin with midlateral stripe along body extending very slightly onto extreme basal portion of middle caudal-fin rays. Caudal-fin rays and membranes overlain by dark chromatophores. Pectoral and pelvic fins hyaline.

ETYMOLOGY.—The specific name, ortegai, in honor of our colleague and co-author in other papers, Hernán Ortega of the Museu de Historia Natural, Lima Peru, who collected nearly all known specimens of the species and in recognition of his many contributions to our knowledge of Peruvian freshwater fishes.

ECOLOGY.—At the end of the dry season, the type locality of Creagrutus ortegai is a clear water, moderately swiftly flowing stream about 3 m wide and 40–60 cm deep, with a substrate of stones, pebbles, sand, and debris, with dense vegetation along its banks, and a water temperature of approximately 20–22°C (H. Ortega, pers. comm., 1996). During the rainy season the water volume and flow increase significantly with increased sediment load, making it a white-water stream. The Quebrada Ahuashiyacu, from which some paratypes originated, is slightly larger than, but otherwise similar to, the holotype locality. The Río Cumbaza, another site of origin for some of the paratype series, is significantly larger than the other type localities, being approximately 25 to 30 m wide during the dry season, but with conditions otherwise comparable to the holotype locality.

Stomach contents of two specimens of Creagrutus ortegai prepared for clearing and staining in this study consisted mostly of insect parts and occasional small intact and chopped-up seeds.

DISTRIBUTION.—Creagrutus ortegai is known primarily from the rivers near Tarapoto, Department of San Martin, Peru (Figure 67, filled stars), but the species also occurs further upstream in the Río Huallaga basin and in the headwaters of the Río Aguaytia (see comments under “Remarks,” below).

MATERIAL EXAMINED.—107 specimens (44, 28.0–71.1).

HOLOTYPE.—PERU. San Martin: Provincia San Martin, Banda de Shilcayo, upper portions of Quebrada Choclin, tributary to Río Huallaga, near town of Shapaja (latter locality at 6°36′S, 76°16′W), collected by H. Ortega, 15 Nov 1991, MUSM 7498, 1 (66.5).

PARATYPES.—39 specimens (39, 28.0–71.1).

PERU. San Martin: Provincia San Martin, Banda de Shilcayo, upper portions of Quebrada Choclin, tributary to Río Huallaga, near town of Shapaja (latter locality at 6°36′S, 76°16′W), collected with holotype, MUSM 7499, 2 (42.0–49.8); USNM 340969, 2 (44.3–49.3). Provincia San Martin, Tarapoto, Quebrada Ahuashiyacu (approximately 6°30′S, 76°25′W), collected by H. Ortega, 13 Nov 1991, MUSM 7538, 2 (28.9–52.8). Provincia San Martin, Tarapoto, Morales, Río Cumbaza (6°28′S, 76°28′W), collected by H. Ortega, 14 Nov 1991, MUSM 7539, 3 (35.4–55.3); MUSM 2948, 1 (45.5). Provincia San Martin, Tarapoto, Río Shilcayo (approximately 6°30′S, 76°25′W), collected by H. Ortega, 15 Nov 1991, USNM 340970, 3 (42.5–54.0). Provincia San Martin, Tarapoto, stream tributary to Río Shilcayo (approximately 6°30′S, 76°25′W), collected by H. Ortega, 15 Nov 1991, MUSM 5678, 4 (37.9–64.0); USNM 340971, 4 (35.4–67.0). Provincia San Martin, km 6 along road to Juanjui, Quebrada Pucayacu, collected by H. Ortega and C. Cañas, 18 Dec 1994, MUSM 6571, 2 (39.2–47.5). Provincia San Martin, km 30 along road to Yurimaguas, Rio Cainarachi, collected by H. Ortega and C. Cañas, MUSM 6552, 8 (28.0–71.1); USNM 340972, 8 (29.0–55.0; 2 specimens cleared and counterstained for cartilage and bone).

NONTYPE SPECIMENS.—67 specimens (4, 42.5–49.8).

PERU. San Martin: Provincia San Martin, Río Ahuashiyacu (6°30′S, 76°25′W), MUSM 1626, 4; MUSM 5676, 4 (2, 49.0–49.8); USNM 340968, 2 (42.5–49.7). Provincia San Martin, Tarapoto, Río Shilcayo, MUSM 5677, 4. Provincia Lamas, stream tributary to Río Cainarachi, km 33 on road from Tarapoto to Yurimaguas, MUSM 7540, 3. Provincia Moyobamba, Puerto Juan Antonio, upper Río Mayo, MUSM 1631, 6. Huanuco: Provincia Leoncio Prado, vicinity of Tingo Maria, Cueva de Pavos near Puente Perez, approximately 0.15 km above Río Huallaga (town at 9°19′S, 75°56′W), ANSP 136832, 1; ANSP 136912, 16. Vicinity of Tingo Maria, Río Monzón basin, Río Rondos (=Río Patay Rondos; mouth approximately 9°15′S, 76°05′W), ANSP 136914, 1. Pucallpa: Provincia Padre Abad, Río Aguaytia, Boguerón del Padre Abad, Velo de Novia, MUSM 6572, 3. Provincia Padre Abad, Aguaytia, Río Huacamayo, MUSM 2949, 3. Río Chio, 80 km from Pucallpa on road to Tingo Maria, MUSM 5675, 20.