Creagrutus holmi Vari & Harold 2001

Creagrutus holmi

Creagrutus beni [not of Eigenmann, 1911].—Pearson, 1937a:92 [misidentification] [Peru (Departmento Cajamarca): Balsas, Tingo de Pauca on Río Marañon, Paipay on Río Crisnejas].

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 to 5 teeth on the maxilla, 6, very rarely 5, teeth in the primary tooth row of the premaxilla, 5 dentary teeth, 37 to 40 lateral line scales without a lamellar process over each pore, 9 to 11 predorsal median scales, 4 scale rows between the dorsal-fin origin and the lateral line, 36 to 38 vertebrae, 9 to 11 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 6 to 8 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 dorsal-fin origin to the anal-fin origin (32.2%–38.5% of SL), the postorbital head length (43.9%–50.0% of HL), the interorbital width (28.6%–34.5% of HL), the well-developed third infraorbital closely approaching or contacting the horizontal limb of the preopercle in larger individuals, the lack of a series of dark midlateral spots on the body, the possession of a diffuse, vertically elongate rotund humeral spot, the lack of a distinct dark spot at the base 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 holmi within the clade composed of Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 81.9 45.1–92.0

1. Snout to anal-fin origin 66.4 62.6–69.4

2. Snout to pelvic-fin insertion 48.0 45.0–52.1

3. Snout to pectoral-fin insertion 23.7 22.2–26.5

4. Snout to dorsal-fin origin 47.9 45.5–504

5. Dorsal-fin origin to hypural joint 56.5 54.1–60.1

6. Dorsal-fin origin to anal-fin origin 34.7 32.2–38.5

7. Dorsal-fin origin to pelvic-fin insertion 35.3 28.1–35.4

8. Dorsal-fin origin to pectoral-fin insertion 34.8 32.5–36.4

9. Caudal peduncle depth 11.7 11.5–13.71

10. Pectoral-fin length 20.0 18.5–23.4

11. Pelvic-fin length 15.1 14.9–20.0

12. Dorsal-fin length 20.7 20.6–24.5

13. Anal-fin length 17.2 17.0–20.7

14 Head length 25.3 24.0–28.3

15. Postorbital head length 46.9 43.9–50.0

16. Snout length 28.5 24.6–30.5

17. Bony orbital diameter 29.3 29.2–34.1

18. Interorbital width 30.9 28.6–34.5

Meristics

Lateral line scales 39 37–40

Scale rows between dorsal-fin origin and lateral line 4 41

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

Predorsal median scales 10 9–11

Branched dorsal-fin rays 8 8

Branched anal-fin rays 10 9–11

Branched pelvic-fin rays 6 62

Pectoral-fin rays 13 12–14

Vertebrae 37 36–38

1 Five scales between dorsal-fin origin and lateral line present in only 1 nontype specimen.

2 Five branched rays present in 1 nontype specimen and 7 branched rays present in 3 nontype specimens.

DESCRIPTION.—Morphometric and meristic data for Creagrutus holmi in Table 23. Head and body robust, body proportionally more robust in larger individuals of some populations and in females with well-developed ovaries. Greatest body depth at dorsal-fin origin in most specimens, shifted slightly anterior of that point in ripe females. Dorsal profile of head convex from tip of snout to vertical through posterior nostril, straight or slightly convex anteriorly from that point to tip of supraoccipital spine. Interorbital region distinctly convex. Dorsal profile of body gently curved, with anterior portion continuing alignment of profile of rear portion of head in specimens up to approximately 45 mm SL, more convex with distinct change in alignment relative to that of head in many larger individuals. Dorsal surface of body with obtuse median ridge between tip of supraoccipital spine and dorsal-fin origin. Ventral profile of head with obtuse, but distinct, angle at anteroventral corner of dentary, profile ranging from nearly straight to gently convex from that point to isthmus. Ventral profile of body ranging from slightly to distinctly convex, latter condition typical of ripe females. Prepelvic region of body obtusely flattened transversely.

Head obtusely rounded in both lateral and dorsal views. Upper jaw longer than, and overhanging, lower jaw. Snout slightly fleshy anteroventrally with scattered papillae anteriorly. Upper lip fleshy, with papillae along anterior and ventral margins; papillae continue onto plicae extending between outer and medial premaxillary teeth. Lower lip moderately fleshy with papillae moderately concentrated along dorsal surface and with scattered papillae anteroventrally.

Infraorbital series moderately developed overall. Third infraorbital well developed; ventral margin falling distinctly short of horizontal limb of preopercle in specimens of up to approximately 50 mm SL, but approaching, or in contact with, that bone in larger individuals. Posterior margins of third through fifth infraorbitals falling short of vertical limb of preopercle.

Premaxillary dentition in three series: primary series with 6, very rarely 5, teeth arranged in curved or very slightly sigmoid arch without pronounced gap between first and second tooth of series but with median tooth distinctly separated from its contralateral tooth; triangular cluster of 3 somewhat larger teeth; and single tooth of form similar to that of primary series lying lateral to fourth tooth, or to space between third and fourth teeth, of primary premaxillary series. Maxilla with 3 to 5 tricuspidate teeth. Dentary with 5 tricuspidate teeth; first and second teeth distinctly larger than others and subequal, somewhat less than twice height of third tooth; fourth and fifth teeth distinctly smaller than anterior teeth and compressed.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin approximately at vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin ranging from straight to very slightly concave. Anal-fin rays ii,9–11, rarely iii,10. Profile of distal margin of anal fin straight to very slightly concave with anterior rays forming barely obvious lobe. Anal-fin hooks present in relatively few of examined specimens, perhaps reflecting pronounced seasonality in their presence in mature males; hooks, when present, limited to anterior 2 or 3 branched anal-fin rays. Pectoral-fin rays i, 11–13. Tip of pectoral fin extending posteriorly slightly beyond three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays most commonly i,6,i, but one specimen with i,5,i and another with i,7. Tip of pelvic fin extending posteriorly approximately 1 scale short of anus. Pelvic- fin hooks present in relatively few of the examined specimens, perhaps reflecting pronounced seasonality in their presence in mature males; hooks, when present, located on all branched pelvic-fin rays.

Gill rakers 6–8 + 9–12.

COLORATION IN LIFE.—(Descriptions based on slides of recently captured specimens provided by E. Holm, ROM). Ground coloration ranging from tan to purplish gray. Guanine covering scales more obvious over midlateral body stripe in smaller specimens. Midlateral body stripe obvious, but more pronounced in specimens with darker overall pigmentation. Humeral mark variably obvious, most distinct in some specimens with lighter overall head and body coloration. Caudal fin with reddish tint on rays in some specimens. Anterior rays of anal fin sometimes white.

COLORATION IN ALCOHOL.—Ground coloration of specimens light tan. Dorsal surface of head with dense field of small, dark chromatophores extending anteriorly onto snout, upper lip, and region anterior to orbit. No indication of deep-lying dark chromatophores overlying brain. Variably denser concentration of dark chromatophores anterior to nostrils forming crescent-shaped patch. Posterior margin of maxilla and adjoining region of snout with somewhat increased concentration of dark chromatophores. Chromatophore concentration somewhat greater anteroventral of orbit, but without discrete pattern of chromatophores surrounding ventral and posterior margins of orbit as occurs in some congeners. Scattered, dark, surface chromatophores located ventral and posterior of orbit. Variably present denser concentration of dark chromatophores on middle of opercle, with scattered chromatophores on dorsal portion of opercle.

Scales of dorsolateral portion of body with field of dark chromatophores on basal portion of exposed scales and along distal margins, with chromatophore fields on each scale separated by hyaline region. Midlateral body stripe formed of deep-lying chromatophores extending from slightly posterior of humeral mark to posterior portion of caudal peduncle. Humeral mark vertically elongate, but variable in both intensity and form. Mark ranges from barely obvious, vertically elongate patch of chromatophores merging into surrounding pigmentation to obvious but diffuse dark patch. Some specimens with central region of humeral mark distinctly darker. Darker central region of mark in such specimens with less pronounced fields of chromatophores extending from dorsal and ventral margins. Dorsal portion of humeral mark arched somewhat anteriorly, with anterodorsal section forming distinct anterior process. Ventral portion of mark typically ventrally tapering.

Dorsal fin with rays outlined by small dark chromatophores and with fields of chromatophores over distal one-half of fin membranes. Anal fin with basal one-half to three-fourths of fin rays outlined by dark chromatophores. Caudal fin somewhat dusky. Pectoral and pelvic fins hyaline or with few scattered chromatophores.

ETYMOLOGY.—The species name, holmi, is in honor of Erling Holm of the Royal Ontario Museum, Toronto, who collected many of the specimens that served as the basis for the species description along with numerous other series of Creagrutus specimens valuable to this study and who has been of great assistance to the authors in this and other studies.

ECOLOGY.—The collection locality for the majority of the paratypes of Creagrutus holmi (MUSM 8866, ROM 55331, USNM 341369) was at an elevation of 850 m in a rapidly flowing (1 m/sec), 5 m wide, clear water stream over a substrate composed predominantly of boulders (30%), rubble (30%), and gravel (30%), with the remainder sand (10%). The habitat was approximately 90% riffles and the remainder was pools. The canopy over the water was 80% partially open and the rest was totally open. One other sample (ROM 52247) came from generally comparable habitats, although one lot (ROM 52248) came from an area with silt bottoms and only 10% riffles. Creagrutus holmi appears to be limited to upland regions with the reported elevations ranging between 800 and 1158 m.

Stomach content analysis of four specimens prepared for clearing and staining in this study showed that the species had been feeding on seeds, larval insects, and in one case on a small characid.

DISTRIBUTION.—Creagrutus holmi is limited to the Río Marañon basin above Pongo de Manseriche, in northeastern Peru (Figure 43).

COMPARISONS.—This is the only Creagrutus species known from the Río Marañon basin, and it achieves some of the highest elevations of any member of the genus.

GEOGRAPHIC VARIATION.—Although this species has a relatively limited distributional range, there is a notable, but continuous, degree of variation between different population samples. Some specimens collected in the Río Utcubamba basin are somewhat deeper bodied than those from some other localities, with, however, a notable degree of overlap with the range of values for this feature in other population samples. The humeral mark also shows notable variation in intensity among examined specimens, ranging from being effectively absent to very distinct. To a degree, this variation is a function of the size of the specimens, but the features demonstrate a considerable range within and between population samples. Despite this variation, we did not discover any discrete differences that would justify the recognition of more than one species within the material that is herein identified as Creagrutus holmi.

MATERIAL EXAMINED.—315 specimens (97, 39.8–92.0).

HOLOTYPE.—PERU. Amazonas: Provincia Utcubamba, Bagua Grande, San Antonio, Quebrada Jaimito (approximately 5°47′S, 78°23′W), collected by P. Baltazar, 14 Apr 1988, MUSM 5670, 1 (81.9).

PARATYPES.—38 specimens (38, 45.1–92.0).

PERU. Amazonas: Provincia Utcubamba, Bagua Grande, San Antonio, Quebrada Jaimito (approximately 5°47′S, 78°23′W), collected with holotype, MUSM 8865, 7 (45.1–59.5); USNM 341368, 6 (47.2–76.5; 1 specimen cleared and counterstained for cartilage and bone). Cajamarca: Tributary to Río Huancabamba, approximately 74 km W of road going N to Jaen, between Pucara and Guabel (approximately 5°56′S, 79°15′W), collected by E. Holm and J. Patalas, 8 Jul 1986, MUSM 8866, 5 (51.3–80.7); USNM 341369, 5 (53.5–92.0); ROM 55331, 5 (45.3–91.7); ROM 72379, 10 (61.5–85.8).

NONTYPE SPECIMENS.—276 specimens (58, 39.8–91.7).

PERU. Amazonas: Quebrada Pusac, Huancabamba, approximately 16 km by road upstream from Balsas (approximately 6°53′S, 78°01′W), ROM 52247, 10 (39.8–85.2). Balsas (6°50′S, 78°01′W), at 3500 ft (= 1067 m), USNM 167816, 7 (41.5–64.5; formerly IU 17600, in part; 3 specimens cleared and stained for bone). Tingo de Pauca, at mouth of Río Crisnejas into Río Marañon (7°21′S, 77°50′W), at approximately 3800 ft (= 1158 m), CAS 69292, 12 (formerly IU 17601). Tributary of Río Marañon, at Tsutshunha, near Tutumbertos, downstream from Aramango, at Aguarani Indian Village, ROM 55328, 17 (10, 46.4–66.3). Río Santiago basin, 1 km from Caterpiza (latter locality at approximately 3°55′S, 77°42′W), LACM 41991-7, 6 (63.6–88.7). Río Santiago basin, 3 km from Caterpiza (latter locality approximately 3°55′S, 77°42′W), LACM 41993-13, 5 (44.5–76.8). Quebrada Pastazillio (not located), LACM 39337-9, 7 (40.9–67.0). Río Cenepa, vicinity of Huampani (4°28′S, 78°10′W), LACM 36357-53, 2 (1, 74.0). Río Cenepa basin, Río Huampani, at Huampani (approximately 4°28′S, 78°10′W), LACM 39645-5, 5 (64.9–65.8). Río Cenepa basin, Chigkan entse (=Quebrada Chigkan; approximately 4°28′S, 78°11′W), LACM 39681-2, 1 (80.7). Río Marañon, few km upstream from Puerto Balsas (6°51′S, 78°02′W), ROM 55326, 3 (1, 59.0). Río Marañon, 14 km upstream from Balsas (6°57′S, 78°01′W), ROM 52248, 17. Cajamarca: Tributary to Río Huancabamba, approximately 74 km W of road going N to Jaen, between Pucara and Guabel (approximately 5°56′S, 79°15′W), ROM 55331, 5 (45.3–91.7), ROM 52252, 179.

Creagrutus hysginus Harold, Vari, Machado-Allison, and Provenzano, 1994

Creagrutus holmi

Creagrutus hysginus Harold, Vari, Machado-Allison, and Provenzano, 1994