Creagrutus melanzonus Eigenmann 1909

Captured in a creek, over sand, gravel and rocks. Rare and appears to frequent the upstream areas of rivers (Ref. 12225).

Creagrutus melanzonus

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 to 5 maxillary teeth, 5 teeth on each dentary, 8 or 9 predorsal median scales, 40 or 41 lateral line scales without a lamellar process over each pore, 4 scale rows between the dorsal-fin origin and the lateral line, 2 or 3 scale rows between the anal-fin origin and the lateral line, 10 to 12 branched anal-fin rays, 5 to 9 gill rakers on the upper limb of the first gill arch, 11 to 13 gill rakers on the lower limb of the first gill arch, the distance from the snout to the pectoral-fin insertion (24.6%–26.4% of SL), the distance from the dorsal-fin origin to the anal-fin origin (26.1%–27.9% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (21.4%–25.4% of SL), the caudal peduncle depth (9.7%–10.9% of SL), the postorbital head length (35.1%–41.0% of HL), the snout length (22.9%–28.6% of HL), the bony orbital diameter (36.9%–40.3% of HL), the proximity of, but lack of contact between, the ventral margin of the third infraorbital and the horizontal limb of the preopercle, the presence of a distinct spot of dark pigmentation at the base of the middle caudal-fin rays, the vertically oriented, elongate bar-like like 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 zephyrus within the clade formed by Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 38.5 25.4–39.8

1. Snout to anal-fin origin 61.8 62.1–63.6

2. Snout to pelvic-fin insertion 47.2 46.2–48.9

3. Snout to pectoral-fin insertion 25.3 24.6–26.4

4. Snout to dorsal-fin origin 45.7 45.4–48.9

5. Dorsal-fin origin to hypural joint 56.8 54.1–56.7

6. Dorsal-fin origin to anal-fin origin 27.9 26.1–27.2

7. Dorsal-fin origin to pelvic-fin insertion 24.0 21.4–25.4

8. Dorsal-fin origin to pectoral-fin insertion 29.8 28.6–31.9

9. Caudal peduncle depth 10.9 9.7–10.9

10. Pectoral-fin length 18.3 15.7–18.8

11. Pelvic-fin length 15.0 14.3–15.8

12. Dorsal-fin length 22.6 20.6–22.4

13. Anal-fin length 16.7 16.7–22.4

14. Head length 25.7 25.8–27.9

15. Postorbital head length 40.6 35.1–41.0

16. Snout length 26.9 22.9–28.6

17. Bony orbital diameter 37.7 36.9–40.3

18. Interorbital width 28.7 27.4–31.4

Meristics

Lateral line scales 40 40–411

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

Scale rows between anal-fin origin and lateral line 3 2–3

Predorsal median scales 8 8–9

Branched dorsal-fin rays 8 8

Branched anal-fin rays 12 10–11

Branched pelvic-fin rays 7 6–7

Pectoral-fin rays 12 13–15

Vertebrae 39 38–39

1 Scales mostly missing in many paratypes so count estimated from scale pockets.

DESCRIPTION.—Morphometric and meristic data for Creagrutus zephyrus in Table 59. Body moderately deep, more so in larger specimens, and somewhat compressed laterally in all available specimens. Greatest body depth at, or slightly anterior of, dorsal-fin origin. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior margin of posterior nares, slightly convex from that point to tip of supraoccipital spine. Predorsal profile slightly convex to anterior of dorsal-fin base, straight to slightly concave from rear of dorsal-fin base to anterior of adipose-fin base, straight to slightly concave from rear of adipose fin to vertical through anterior procurrent caudal-fin rays. Ventral profile of head with distinct obtuse angle of about 120 degrees approximately midway between margin of lower lip and posterior of dentary, slightly convex from that point to isthmus. Ventral profile of body slightly convex from isthmus approximately to anal-fin origin; slightly concave from that point to caudal peduncle.

Snout in the form of broadly rounded obtuse angle with its apex located at dorsalmost point on premaxilla. Upper jaw slightly longer than, and overhanging, lower jaw, with anterior premaxillary teeth anterior to lower lip. Most external surfaces of head covered with minute papillae; papillae most concentrated on lips. Anterior portion of snout relatively firm and without concentration of soft tissues, with minute papillae present on snout and upper lip, papillae continuing into mouth on fleshy flaps between outer and medial premaxillary teeth. Lower jaw distinctly fleshy anteriorly, inner surfaces of lower lip convolute, with papillose flaps as present on upper lip.

Infraorbital series moderately well developed, with ventral margin of third infraorbital separated from ventral limb of preopercle by distinct but narrow gap. Posterior margin of third infraorbital distinctly separated from vertical limb of preopercle by space equal to about one-fourth of the width of fourth and fifth infraorbital bones; posterior and ventral margins of third infraorbital broadly rounded, describing arc of curvature greater than that of orbit. Fourth and fifth infraorbitals narrowly separated from vertical limb of preopercle.

Premaxillary teeth in three distinct groups: primary series consisting of 6, rarely 5, tricuspidate teeth in continuous row without pronounced gap between first and second tooth of series; triangular cluster of 3 large tricuspidate teeth; and single outer tooth positioned lateral to fourth tooth of primary series. Maxilla with 3 to 5 tricuspidate teeth. Dentary with 5 or 6 teeth. Dentary teeth either all tricuspidate (when 5 teeth present) or last tooth unicuspidate (when 6 teeth present). First and second dentary teeth largest and subequal, third tooth about one-half height of second tooth, and remaining teeth in series distinctly smaller than three anterior teeth.

Dorsal-fin rays ii,8 in all examined specimens. Dorsal-fin origin located slightly anterior to vertical through pelvic-fin origin. Distal margin of dorsal fin nearly straight, with very slight concavity as result of elongation of first 3 or 4 rays. Anal-fin rays ii,10–12 or iii, 10–12. Anal-fin ray hooks present in mature males of many congeners not observed in examined specimens. Distal margin of anal fin slightly sigmoid, with posterior unbranched and anterior 3 or 4 branched rays forming relatively elongate lobe, fin margin along posterior 5 or 6 rays approximately straight. Pectoral-fin rays i, 11–14. Pectoral fin short, tip reaching to within 2 or 3 scale rows of pelvic-fin origin. Pelvic-fin rays i,6,i or i,7. Juveniles with tip of pelvic fin falling short of anal-fin origin by 1 or 2 scales; tip of pelvic fin approaching, or reaching, anal-fin origin in larger specimens. Pelvic-fin hooks present in mature males of many congeners not observed in examined specimens.

Gill rakers 5–9 + 11–13.

COLORATION IN ALCOHOL.—Overall ground color straw, with dark pigment cells ranging from light brown to dark sepia. Dorsal surface of head with diffuse pattern of small, light brown chromatophores on upper lip and over snout. Distinct, small, crescent-shaped patch of dark chromatophores present immediately in front of anterior nares. Dorsal surfaces of much of frontal and parietal portions of cranium uniformly and densely invested with medium to large, dark brown, deep-lying chromatophores. Frontal portion of dorsal surface of head nearly unpigmented in area directly above anterior one-half of eye. Band of scattered, dark chromatophores extending posteroventrally from immediately lateral of nares and continuing along ventral margin of orbit. Infraorbitals posterior to orbit and dorsal portion of opercle with scattered, large, dark chromatophores. Lower lip and ventrolateral surface of head unpigmented; reflective guanine not observed in association with head or any other body components.

Dark body pigmentation most concentrated dorsally, delineating or forming central, hemispherical patch on scales of 2 dorsalmost scale rows and middorsal scale row; dark pigmentation also present in form of series of crescent-shaped marks on scales flanking dorsal-fin base. Humeral mark usually in form of anteriorly slightly concave, narrow crescent. Pigmentation of mark most concentrated immediately dorsal of lateral line; extending as less intensely pigmented field about 2 scale rows dorsal from central portion of mark, and continuing ventrally as field of increasingly dispersed dark chromatophores to near pectoral-fin base. Region above anal fin with myosepta outlined by widely spaced dark chromatophores. Largest specimens examined (ANSP 161236) exhibit some very fine lines of dark pigmentation along posterior margins of flank scales ventral of lateral line and along either side of lateral line tube. Dark midlateral stripe on body very diffuse anteriorly, becoming denser and somewhat wider posteriorly, but still not very obvious, on caudal peduncle.

Dorsal-fin membranes with dark chromatophores most concentrated on distal one-fourth to one-third of 4 anterior branched rays; unbranched rays darkly pigmented. Unbranched anal-fin rays unpigmented except for small number of dark chromatophores at base of rays and with proximal one-half of branched rays delineated by dark pigmentation along their anterior surfaces. Caudal fin with all fin rays delineated by dark pigmentation, pigmentation darkest on central and ventral rays. Dorsalmost caudal-fin rays with very small, lighter chromatophores, central rays of fin generally darkest, with pigmentation usually forming rotund basal spot. Dark, deep-lying pigmentation forming variably visible, vertical line delineating posterior extremities of hypural plates. Pelvic fin hyaline. Pectoral fin hyaline except for several isolated dark chromatophores on membrane of medial rays.

ETYMOLOGY.—The specific name zephyrus, from the Latin for west wind, refers to the distribution of the species in the western portion of the range of three very similar species (C. melanzonus, and C. xiphos. and C. zephyrus), two of which (C. melanzonus and C. zephyrus) have been considered conspecific by some previous authors.

ECOLOGY.—Specimens of Creagrutus zephyrus from several localities in the Rio Casiquiare were collected in slightly turbid, sometimes green, waters with slow to moderate current over substrates of sand, mud, leaves, and sticks. Filamentous algae was present at one locality.

Two specimens prepared for clearing and staining in this study (ANSP 161236) had aquatic insect larvae in their stomachs.

DISTRIBUTION.—Creagrutus zephyrus is known from portions of the central and upper portions of the upper Rio Negro in Brazil and Venezuela (Figure 90, dots).

COMPARISONS.—Creagrutus zephyrus is most similar to C. xiphos of the Rio Caura in the Rio Orinoco basin. The two species differ in the number of vertebrae (38 or 39 in C.zephyrus versus 36 or 37 in C. xiphos), the distance from the dorsal-fin origin to the anal-fin insertion (26.1%–27.9% of SL in C. zephyrus versus 28.6%–29.7% of SL in C. xiphos), the distance from the dorsal-fin origin to the pelvic-fin insertion (21.4%–25.4% of SL in C. zephyrus versus 25.6%–28.0% of SL in C. xiphos), and the caudal-peduncle depth (9.7%–10.9% of SL in C. zephyrus versus 10.8%–11.7% of SL in C. xiphos).

MATERIAL EXAMINED.—19 specimens (17, 25. 7–39.8).

HOLOTYPE.—VENEZUELA. Amazonas: Río Casiquiare, playa and backwater about 2 km downstream from mouth of Río Pamoni (2°48′N, 65°57′W), collected by B. Chernoff et al., 21 Mar 1987, ANSP 161238, 1 (38.5).

PARATYPES.—18 specimens (16, 25.4–39.8).

VENEZUELA. Amazonas: Río Casiquiare from mouth of Río Pamoni to 4 km below mouth (02°48′N, 65°57′W), collected by B. Chernoff et al., 17 Mar 1987, ANSP 161236, 10 (25.4–39.8). Río Orinoco at sand playa just upstream from Quiratare (02°59′N, 66°04′W), collected by B. Chernoff et al., 10 Mar 1987, ANSP 161237, 6 (25.7–32.5). Río Casiquiare main channel, near Río Orinoco confluence, ANSP 177829, 2.

Piabina Reinhardt, 1867:49 [type species Piabina argentea Reinhardt, 1867:50, by monotypy. Gender feminine; volume dated 1866 but actual date of publication was 1867 according to Nielsen, 1974:45, 112].—Eigenmann and Eigenmann, 1891:56 [Piabina placed as a synonym of Creagrutus Günther].—Eigenmann, 1910:435 [Piabina resurrected from synonymy of Creagrutus].—Mahnert and Géry, 1988:7 [Piabina returned to the synonymy of Creagrutus].

DIAGNOSIS.—Piabina is phylogenetically diagnosed by the possession of the synapomorphies listed under “Monophyly of Piabina,” above. Piabina is externally distinguished within the clade formed by Piabina and Creagrutus by the posteriorly attenuating, triangular fourth infraorbital, which is excluded in larger specimens of the genus from the posterior margin of the infraorbital series as a consequence of the contact of the proximate posterior portions of the third and fifth infraorbitals.

Creagrutus melanzonus Eigenmann, 1909

Creagrutus melanzonus Eigenmann, 1909:30 [British Guiana (=Guyana), Crab Falls, Warraputa, Tumatumari]; 1910:435 [literature compilation]; 1912:347, pl. 45: fig. 1 [redescription based on type series]; 1927:418, pl. 34: fig. 2 [redescription based on type series].—Henn, 1928:63 [holotype in Carnegie Museum].—Myers and Roberts, 1967:248–249 [in part; citation of species from British Guiana (=Guyana); not cited presence of species in “upper Rio Negro-upper Orinoco” system; not cited specimens of C. melanzonus].—Böhlke and Saul, 1975:27, fig. 4b [form of upper jaw; not citation of species from upper Río Orinoco and upper Rio Negro],—Ibarra and Stewart, 1987:28 [holotype in FMNH].—Planquette et al., 1996:324, fig. [French Guiana, Crique Anne, Fleuve Sinnamary system and Gaa Kaba, Fleuve Maroni basin].—Machado-Allison et al., 2000:16 [Venezuela, Río Cuyuni basin].—Not Böhlke and Saul, 1975:28.—Not Mago-Leccia, 1970:70.