Comprehensive Description
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англиски
)
добавил Smithsonian Contributions to Zoology
Creagrutus xiphos
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, 6 teeth in the primary series of each premaxilla, 3 maxillary teeth, 5 teeth on each dentary, 9 predorsal median scales, 36 or 37 lateral line scales without a lamellar process over each pore, 4 scale rows between the dorsal-fin origin and the lateral line, 3 scale rows between the anal-fin origin and the lateral line, 9 or 10 branched anal-fin rays, 6 gill rakers on the upper limb of the first gill arch, 10 or 11 gill rakers on the lower limb of the first gill arch, the distance from the dorsal-fin origin to the anal-fin origin (28.6%–29.5% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (25.6%–28.0% of SL), the distance from the dorsal-fin origin to the pectoral-fin insertion (30.9%–32.1% of SL), the caudal peduncle depth (10.8%–11.7% of SL), the anal-fin length (15.0%–17.9% of SL), the postorbital head length (37.9%–39.8% of HL), the bony orbital diameter (37.7%–38.9% of HL), the proximity but lack of contact between the ventral margin of the third infraorbital and the horizontal limb of the preopercle, the absence 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 distinguishes Creagrutus xiphos within the clade formed by Creagrutus and Piabina.
Characters A B
Morphometrics
Standard length 27.7 18.9–26.5
1. Snout to anal-fin origin 64.0 63.9–65.5
2. Snout to pelvic-fin insertion 48.1 48.0–50.9
3. Snout to pectoral-fin insertion 26.9 26.2–27.8
4. Snout to dorsal-fin origin 48.7 48.0–50.3
5. Dorsal-fin origin to hypural joint 53.1 53.0–54.3
6. Dorsal-fin origin to anal-fin origin 28.7 28.6–29.5
7. Dorsal-fin origin to pelvic-fin insertion 27.6 25.6–28.0
8. Dorsal-fin origin to pectoral-fin insertion 31.0 30.9–32.1
9. Caudal peduncle depth 11.2 10.8–11.7
10. Pectoral-fin length 18.7 18.5–19.3
11. Pelvic-fin length 15.2 15.0–16.5
12. Dorsal-fin length 22.8 21.8–23.1
13. Anal-fin length 14.5 15.0–17.9
14. Head length 27.6 27.1–28.0
15. Postorbital head length 39.8 37.9–39.7
16. Snout length 28.3 28.6–29.0
17. Bony orbital diameter 38.1 37.7–38.9
18. Interorbital width 29.5 30.1–32.0
Meristics
Lateral line scales 37 36–37
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
Branched dorsal-fin rays 8 8
Branched anal-fin rays 9 9–10
Branched pelvic-fin rays 6 5–6
Pectoral-fin rays 12 12–13
Vertebrae 37 36–37
DESCRIPTION.—Morphometric and meristic data for Creagrutus xiphos in Table 58. Head and body moderately elongate, more so in smaller specimens. Greatest body depth at dorsal-fin origin in paratypes, located anterior of that point in holotype with expanded abdomen. Dorsal profile of head distinctly convex from margin of upper lip to vertical through anterior nostril, slightly convex from that point to rear of supraoccipital. Interorbital region slightly convex. Dorsal profile of body very slightly convex from supraoccipital to dorsal-fin origin, without pronounced change in alignment relative to dorsal profile of head. Predorsal surface of body with obtuse median keel in larger examined specimens. Ventral profile of head with distinct obtuse angle at anteroventral corner of dentary, straight to very slightly convex from that point to isthmus. Prepelvic profile slightly convex in paratypes, distinctly convex in holotype, which has expanded abdominal region. Prepelvic region flattened to distinctly convex transversely depending on degree of distension of abdomen.
Head obtusely pointed in lateral view, somewhat more compressed transversely in dorsal view. Upper jaw longer than, and overhanging, lower jaw. Snout papillae broadly distributed over anterior portion of snout, increasingly so medially. Numerous papillae present on ventral margin of upper lip and on fleshy folds and plicae extending between outer and medial premaxillary teeth. Anteromedial portion of lower jaw with scattered papillae, and dorsal margin of lower lip with more concentrated papillae.
Infraorbital series moderately developed. Third infraorbital horizontally elongate with ventral and posterior margins approximately matching curvature of corresponding margin of orbital rim. Ventral and posterior margins of third infraorbital approaching, but not contacting, horizontal and vertical limbs of preopercle, respectively; gap between margin of infraorbital and preopercle somewhat greater posteriorly. Posterior margins of fourth and fifth infraorbitals separated from vertical limb of preopercle. No notable variation in degree of development of infraorbital series apparent across size range of available specimens.
Premaxillary dentition in three series: primary series curved and without pronounced gap between first and second teeth of series, with 6 tricuspidate teeth and medial tooth separated from contralateral series by distinct gap; triangular cluster of 3 teeth, larger than those of primary series; and single tooth of form similar to that of primary series occurring lateral to fourth tooth of primary premaxillary row. Maxilla with 3 tricuspidate teeth. Dentary apparently with five tricuspidate teeth (exact count of dentary teeth and determination of form of posterior dentary teeth hampered by lack of specimens for clearing and staining). First tooth about three-fourths height of second tooth, second tooth approximately twice as high, and much more massive than, third tooth.
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 straight or very slightly concave. Anal-fin rays ii,9–10. Profile of distal margin of anal fin slightly concave. Single mature male paratype with hooks on first branched anal-fin ray. Pectoral-fin rays i, 11–12. Tip of pectoral fin reaching posteriorly to point about 2 scales anterior of pelvic-fin insertion. Pelvic-fin rays i,5,i or i,6,i. Tip of pelvic fin reaching posteriorly to, or falling slightly short of, anal-fin origin. Single mature male with hooks on all branched pelvic-fin rays.
Gill rakers 6 + 10–11.
COLORATION IN ALCOHOL.—Ground coloration light tan. Dorsal surface of head in smallest specimens with patches of relatively large dark chromatophores on membranes overlying brain. Chromatophore field becoming more intense over posterior portion of brain in larger individuals. Snout and upper lip with scattered, dark chromatophores in small specimens; chromatophore field somewhat more concentrated in larger specimens and forming moderately developed crescent-shaped, dark mark along base of anterior nostril. Irregular stripe of dark chromatophores extending from under nostrils to anteroventral margin of orbit in larger specimens. Remainder of head either lacking dark chromatophores, or with few scattered chromatophores in region posterior of orbit.
Scale margins along dorsal portions of body in larger specimens outlined with small, dark scales, but not forming well-developed reticulate pattern present in many congeners. Dark pigmentation most developed proximate to middorsal region anterior to dorsal fin and particularly along dorsal-fin base. Scale margins on lateral surface of body with scattered, dark chromatophores in smaller available specimens, with increased numbers of chromatophores present on posterior two-thirds of lateral surface of body in larger specimens. Humeral mark in form of a vertically elongate ovoid in smallest examined paratype, in form of vertically elongate bar in other paratypes and holotype. Bar vertically aligned with nearly straight anterior and posterior margins. Region between humeral mark and posterior margin of pectoral girdle hyaline. Lateral surface of body between rear of mark and vertical approximately three scales posterior of rear margin of humeral mark also lacking dark chromatophores. Chromatophore field slightly more concentrated along posterior two-thirds of midlateral surface of body, but not forming distinct, dark, midlateral stripe within size range of available specimens.
Dorsal fin with scattered, dark chromatophores along last unbranched and first branched rays and on distal portions of second through fourth rays. Anal fin with basal portions of anal-fin rays outlined with dark chromatophores. Caudal fin with faint dark chromatophores outlining rays of lower lobe of fin; extent of pigmentation difficult to determine as a consequence of damage to fins in all available specimens. Pectoral and pelvic fins hyaline in all specimens.
ECOLOGY.—The type locality was along a sand bar over a substrate of sand and logs in water ranging from 10 to 45 cm deep. One congener, Creagrutus phasma (ANSP 139598), was collected with the type series of C. xiphos.
ETYMOLOGY.—The species name, xiphos, from the Greek for sword or saber, refers to the elongate head and body of the species.
DISTRIBUTION.—Creagrutus xiphos is known only from the type locality in the Río Mato in the Río Caura system, a southern tributary of the main Río Orinoco (Figure 90, triangle).
COMPARISONS.—Creagrutus xiphos is most similar to C. zephyrus of the Rio Negro basin in Venezuela and Brazil. The species differ in the number of vertebrae (36 or 37 in C. xiphos versus 38 or 39 in C. zephyrus), the distance from the dorsal-fin origin to the anal-fin origin (28.6%–29.5% of SL in C. xiphos versus 26.1%–27.9% of SL in C. zephyrus), the distance from the dorsal-fin origin to the pelvic-fin insertion (25.6%–28.0% of SL in C. xiphos versus 21.4%–25.4% of SL in C. zephyrus), and the caudal peduncle depth (10.8%–11.7% of SL in C. xiphos versus 9.7%–10.9% of SL in C. zephyrus).
Only two species of Creagrutus are known from the Río Mato basin, C. xiphos and C. phasma, which were collected together at the type locality of the former species. Two other species, C. machadoi and C. bolivari are found in other portions of the Río Caura system. Creagrutus xiphos can be distinguished from all of those species by the features cited in “Key to the Creagrutus Species of the Río Orinoco Basin.”
MATERIAL EXAMINED.—4 specimens (4, 18.9–27.7).
HOLOTYPE.—VENEZUELA. Bolivar: Sand bank along Río Mato (7°02′N, 65°13′W), collected by J.E. Böhlke et al., 1 Feb 1977, ANSP 165815, 1 (27.7).
PARATYPES.—3 specimens (3, 18.9–27.7).
VENEZUELA. Bolivar: Sand bank along Río Mato (7°02′N, 65°13′W), collected with holotype, ANSP 177717, 3 (18.9–26.5).
- библиографски навод
- Vari, Richard P. 2001. "Phylogenetic study of the neotropical fish genera Creagrutus Günther and Piabina Reinhardt (Teleostei:Ostariophysi:Characiformes), with a revision of the cis-Andean species." Smithsonian Contributions to Zoology. 1-239. https://doi.org/10.5479/si.00810282.613
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