Creagrutus meridionalis Vari & Harold 2001

Creagrutus meridionalis

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, 2 or 3 teeth on the maxilla, 6, much less commonly 5, teeth in the primary tooth row of the premaxilla, 4 or 5 dentary teeth, 38 to 41 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, 37 to 39 vertebrae, 11 to 13 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 6 to 8 gill rakers on the upper limb and 9 or 10 gill rakers on the lower limb of the first gill arch, the distance from the snout to the dorsal-fin origin (45.5%–49.8% of SL), the distance from the snout to the anal- fin origin (62.1%–66.4% of SL), the distance from the dorsal- fin origin to the pectoral-fin insertion (31.0%–34.8% of SL), the caudal-peduncle depth (10.5%–12.2% of SL), the dorsal-fin length (20.2%–24.0% of SL), the bony orbital diameter (32.0%–36.0% of HL), the postorbital head length (39.3%—44.5% of HL), the snout length (28.0%–31.1% of SL), the interorbital width (30.6%—34.4% of HL), the moderately developed third infraorbital with its ventral margin falling distinctly short of the horizontal limb of preopercle, the lack of a series of dark midlateral spots on the body, the vertically elongate, ventrally attenuating humeral mark, the absence of a spot of dark pigmentation on the basal portion 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 meridionalis within the clade composed of Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 59.9 19.9–62.0

1. Snout to anal-fin origin 64.1 62.1–66.4

2. Snout to pelvic-fin insertion 47.7 46.4–50.5

3. Snout to pectoral-fin insertion 23.7 23.1–25.0

4. Snout to dorsal-fin origin 48.4 45.5–49.8

5. Dorsal-fin origin to hypural joint 56.4 55.8–59.8

6. Dorsal-fin origin to anal-fin origin 34.1 29.3–34.8

7. Dorsal-fin origin to pelvic-fin insertion 30.0 25.1–29.8

8. Dorsal-fin origin to pectoral-fin insertion 34.2 31.0–34.8

9. Caudal peduncle depth 12.0 10.5–12.2

10. Pectoral-fin length 20.0 18.0–20.7

11. Pelvic-fin length 15.4 14.5–17.4

12. Dorsal-fin length 21.7 20.2–24.0

13. Anal-fin length 17.4 16.6–18.9

14. Head length 25.7 24.7–26.8

15. Postorbital head length 44.2 39.3–44.5

16. Snout length 30.5 28.0–31.1

17. Bony orbital diameter 33.1 32.0–36.0

18. Interorbital width 33.1 30.6–34.4

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 10 9–11

Branched dorsal-fin rays 8 8

Branched anal-fin rays 12 11–13

Branched pelvic-fin rays 6 6

Pectoral-fin rays 14 12–14

Vertebrae 38 37–39

DESCRIPTION.—Morphometric and meristic data for Creagrutus meridionalis in Table 36. Examined juveniles (approximately 20–30 mm SL) relatively elongate; specimens larger than 40 mm SL becoming increasingly deep-bodied, with relative body depth greatest in larger specimens. Greatest body depth at vertical through dorsal-fin origin in smaller individuals; located at, or somewhat anterior of, that point in larger specimens. Dorsal profile of head distinctly convex from margin of upper lip to region of vertical through posterior margin of orbit, straight from that point to rear of supraoccipital spine. Dorsal surface of head medially flattened transversely, more so posterior to vertical through center of orbit. Predorsal profile of body smoothly continuous with that of head and very slightly convex in smaller specimens, with notable change in alignment relative to profile of head and convexity distinctly more pronounced in larger specimens. Dorsal profile of body posteroventrally angled along dorsal-fin base; straight from that point to caudal peduncle in smaller specimens, somewhat convex in larger specimens. Ventral profile of head with rounded obtuse angle delimiting anteroventral angle of dentary, angle typically more obvious in larger specimens. Profile of head and body gently convex from anteroventral corner of dentary to anal-fin origin in smaller specimens; convexity more pronounced in larger individuals. Prepelvic region of body somewhat flattened transversely in larger specimens.

Head obtusely pointed in lateral view, more pointed in dorsal view. Upper jaw longer than, and overhanging, lower jaw. Anterior portion of snout fleshy, more so in larger individuals, with numerous papillae scattered over anterior surface, across upper lip, and on plicae and folds extending between outer and medial premaxillary teeth. Lower lip fleshy anteriorly, with numerous papillae over lip.

Infraorbital series moderately developed. Ventral margin of third infraorbital distinctly curved, with ventralmost portion falling somewhat short of horizontal limb of preopercle even in larger examined specimens. Posterior margins of third through fifth infraorbitals falling distinctly short of vertical limb of preopercle, gap gradually diminishing dorsally.

Premaxillary dentition in three series: primary row slightly curved, typically with 6 teeth, but with 5 teeth present on one or both premaxillae in a few specimens, without pronounced gap between first and second tooth of series but with medial teeth of contralateral series distinctly separated; triangular cluster of 3 larger teeth with posterolateral tooth of cluster largest; and single tooth of form similar to that of primary series lying lateral to region of contact of fourth or fifth teeth of primary premaxillary series. Maxilla with 2 or 3 triscupidate teeth. Dentary with 4 or 5 teeth. First and second teeth subequal or second slightly larger; both teeth tricuspidate with middle cusp largest. Third tooth approximately one-half size of preceding teeth, bicuspidate with first cusp distinctly larger. Fourth and fifth teeth (when latter present) compressed and tricuspidate.

Dorsal-fin rays ii,8. Dorsal-fin origin at, or slightly anterior of, vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. Anal-fin rays ii, 11–13. Profile of distal margin of anal fin distinctly concave, with last unbranched and anterior two branched rays forming distinct lobe. Hooks typically present on anal-fin rays in mature males of many Creagrutus species not found in examined specimens. Pectoral-fin rays i, 11–13. Tip of pectoral fin extending posteriorly two-thirds to three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays i,6,i. Hooks typically present on pelvic-fin rays in mature males of many Creagrutus species not found in examined specimens. Tip of pelvic fin extending posteriorly to point somewhat short of anus.

Gill rakers 6–8 + 9–10.

COLORATION IN ALCOHOL.—Dorsal surface of head in smaller specimens with large, stellate, dark chromatophores on membranes overlying brain, and with scattered, dark, smaller surface chromatophores; deep-lying chromatophores in adults obscured by denser field of surface chromatophores, connective-tissue layers, and thick bones. Field of small, dark chromatophores on dorsal surface of head continuing anteriorly across snout to anterior of nares. Pigmentation anterior to nares more concentrated and forming dark crescent-shaped mark. Chromatophore field continuing in medium-sized individuals around ventral and posterior margins of orbit. Pigmentation at posterior margin of orbit continuous with broader pigmentation field on infraorbitals posterior to orbit and on dorsal one-half of opercle in larger specimens.

Scales of dorsal surface of body covered with scattered, dark, small chromatophores, these more concentrated along posterior portions of scales, forming faint reticulate pattern. Obscure midlateral band formed by deep-lying chromatophores; band overlain by guanine in available specimens. Humeral mark vertically elongate in specimens of all sizes, relatively more developed in larger specimens. Mark becoming attenuate ventrally, barely extending ventrally as far as lateral line in smaller specimens, extending approximately 1 scale ventral of lateral line in largest available individuals. Posterior margin of humeral mark typically nearly straight; anterior margin often with distinct concavity in its dorsal portion.

Dorsal fin with scattered, dark chromatophores, more so on distal portions of anterior fin membranes. Basal portions of anterior anal-fin rays outlined by dark chromatophores, with increased concentration of chromatophores on membranes of distal one-half of anterior lobe of fin. Caudal fin with scattered chromatophores on rays and membranes, but without distinct pigmentation pattern. Pectoral and pelvic fins ranging from unpigmented to pale with scattered, dark chromatophores on membranes.

ETYMOLOGY.—The specific name, meridionalis, from the Latin for southern, refers to the distribution of the species in the southern portions of the range of Creagrutus.

ECOLOGY.—The type locality of Creagrutus meridionalis is a small, clear stream. A single specimen prepared for clearing and staining in this study had stomach contents consisting of adult and larval insects.

DISTRIBUTION.—Creagrutus meridionalis is known from the upper portion of the Rio Paraguai basin, Mato Grosso, Brazil, and eastern tributaries to Río Paraguay in Paraguay (Figure 59, triangles).

COMPARISONS.—In addition to Creagrutus meridionalis, only one other Creagrutus species, C. paraguayensis, is known from the Río Paraguay basin. The two species differ in the number of branched anal-fin rays (11 to 13 in C. meridionalis versus 13 to 15 in C. paraguayensis) and in the number of scale rows between the lateral line and the dorsal-fin origin (4 versus 5, respectively).

MATERIAL EXAMINED.—143 specimens (73, 21.5–62.0).

HOLOTYPE.—BRAZIL. Mato Grosso: Ribeirão Chiqueirão (tributary of Rio Jangada that, in turn, drains into the Rio Cuiabá), approximately 21 km W of Jangada (latter locality at 15°14′S, 56°29′W) on road to Barra do Bugres, Município de Jangada; collected by R.E. Reis et al., 10 Aug 1991, MZUSP 50546, 1 (59.9).

PARATYPES.—71 specimens (63, 19.9–62.0).

BRAZIL. Mato Grosso: Ribeirão Chiqueirão (tributary of Rio Jangada, which, in turn, drains into the Rio Cuiabá), approximately 21 km W of Jangada (latter locality at 15°14′S, 56°29′W) on road to Barra do Bugres, Município de Jangada, collected with holotype, MZUSP 50547, 12 (23.1–62.0; 1 specimen cleared and counterstained for cartilage and bone); MCP 18738, 13 (21.5–61.9); USNM 341363, 12 (24.7–61.7; 2 specimens cleared and counterstained for cartilage and bone); FML 2527, 1 (52.0).

PARAGUAY. Amambay. Río Apa, 400 m below bridge to Bella Vista, Río Paraguay basin (22°07′15″S, 56°31′15″W), collected by A. Silfvergrip et al., 14 Jun 1994, NRM 22619, 20 (28.3–45.6); MNHNP 2999, 13 (5, 19.9–44.7).

NONTYPE SPECIMENS.—71 specimens (9, 43.2–54.5).

PARAGUAY. Amambay: Río Aquidaban in Parque Nacional Cerro Cora, approximately 32 km WSW of Pedro Juan Caballero, Río Paraguay drainage (22°38′12″S, 56°03′W), UMMZ 206757, 33. Arroyo Aquidaban-Niqui at monument site and slightly upstream in Parque Nacional Cerro Corá (22°38′S, 56°11′W), NRM 15966, 13 (2, 43.2–45.0). Concepcion: Arroyo Guaireno, at bridge on dirt highway, 33 km S of junction with highway 5, at Yby-Yau, tributary to Río Ypane of Río Paraguay drainage (23°15′18″S, 56°30′00″W), UMMZ 208001, 25 (7, 51.0–54.5).