Creagrutus maracaiboensis (Schultz 1944)

Creagrutus maracaiboensis (Schultz)

Creagrutops maracaiboensis Schultz, 1944b:327, figs. 45, 46 [type locality: Venezuela: Lago Maracaibo basin, Río Negro below mouth of Río Yasa].—Mago-Leccia, 1970:23, 70 [Venezuela: Lago Maracaibo].—Vari and Howe, 1991:15 [location of type specimens].—Géry and Renno, 1989:4 [possible phylogenetic relationships].

DIAGNOSIS.—Creagrutus maracaiboensis is unique among Creagrutus and its close allies in having pores only on the anterior 8 to 10 scales of the lateral-line series, an evidently autapomorphic reductive feature. A second autapomorphy for C. maracaiboensis is the reduced laterosensory canal system on the head. Creagrutus maracaiboensis shares with C. nigrostigmatus a reduced number of vertebrae (32 to 33 versus 34 or more in other trans-Andean species) and a low number of lateral-line scales (29 to 31 in C. maracaiboensis and 30 to 32 in C. nigrostigmatus versus a range of 33 to 41 in other trans-Andean species). These low counts may represent synapomorphies for the species pair. The distinct stripe dark pigmentation on the basal portions of the caudal fin also serves to distinguish C. maracaiboensis from all trans-Andean Creagrutus species other than C. hildebrandi, which has a basal caudal spot and C. affinis and C. nigrostigmatus, which have dark pigmentation on the central caudal fin rays forming a horizontal stripe.

DESCRIPTION.—Head and body relatively stout for a trans-Andean species of Creagrutus, somewhat compressed, less so in smaller individuals. Greatest body depth in region from slightly anterior to pelvic fin to midway between pelvic and pectoral-fin origin, variation in position of greatest depth a function of degree of distension of abdomen. Dorsal profile of head distinctly convex from margin of upper jaw to approximately vertical through middle of eye, nearly straight from that point to supraoccipital. Dorsal profile of body nearly straight to slightly convex from supraoccipital to dorsal-fin origin; straight to slightly convex from insertion of dorsal fin to adipose fin. Ventral profile of head with obtuse angle approximately one-third of distance between margin of upper lip and posterior of dentary, straight to convex from that point to pelvic-fin origin, convex to slightly concave along base of anal fin.

Head with orbit relatively large compared to snout. Upper jaw length and degree of overhang variable; variation a function of fleshiness of lower jaw. Anterior of snout fleshy, but not greatly produced anteriorly, with papillae sparsely distributed on snout, more concentrated on upper lip and margin of upper jaw, continuing into mouth on fleshy flaps between premaxillary teeth. Lower jaw fleshy, with small numbers of papillae on lip, most concentrated on anterior surface of lower jaw, with decreasing numbers posteriorly on ventral surface. Elements of infraorbital series reduced in width relative to other trans-Andean Creagrutus species, with ventral and posterior margins of series distinctly separated from preopercle, posteroventral margin of series rounded, concentric with posteroventral margin of orbit.

Teeth arranged as in Creagrutus brevipinnis except that premaxillary teeth apparently in process of regeneration in holotype at time of fixation, perhaps accounting for Géry's comment (1977:410) that the teeth in the species are “atypically set.”

Dorsal fin with ii,8 rays. Dorsal-fin origin slightly posterior of vertical through pelvic-fin origin. Posterior unbranched and anterior two branched rays of dorsal fin longest, forming distinct anterior lobe. Anal fin with ii, 11–12 rays. Anal fin in males with hooks on posterior surface of segmented portions of posterior branch and main shaft of first to sixth rays, number of involved rays and degree of development of hooks varies between specimens and individual fin rays. Distal margin of anal fin slightly concave with distinct anterior lobe. Pectoral fin reaching slightly posterior of pelvic-fin origin. Pelvic fin falling slightly short of anal-fin origin in many species, sometimes reaching fin; with i, 7 rays. Pelvic fin in males with poorly developed hooks on segmented and unsegmented portions of all branched rays.

COLOR IN LIFE.—Schultz (1944b:329) noted that in life Creagrutus maracaiboensis “had a reddish coloration on the upper third of the eye. Peritoneum silvery, with a few scattered black pigment cells at sides dorsally.”

COLOR IN ACOHOL.—Type material with body largely unpigmented perhaps because of poor preservation. Following description based on non-type specimens (UF 23808) from Santa Cruz de Zulia (Figure 7, locality 2). Dorsal surface of head with chromatophores concentrated on central and posterior regions. Entire surface of snout with concentration of smaller chromatophores. Line of diffuse chromatophores extending from snout posteroventrally to margin of orbit, and continuing around ventral and posterior margins of orbit. Body pigmentation very diffuse, heaviest concentration middorsally, particularly at base of dorsal fin and in scale pockets, giving overall reticulate appearance. Humeral spot present, but small and highly diffuse, with chromatophores noticeably darker than in surrounded areas. Pigmentation along flank most concentrated posteriorly and in association with myosepta.

A B

MORPHOMETRICS

Standard Length 21.0 15.9–22.0

1. Snout to anal-fin origin 63.8 62.0–65.5

2. Snout to pelvic-fin origin 48.6 45.1–51.5

3. Snout to pectoral-fin origin 27.6 26.8–27.8

4. Snout to dorsal-fin origin 53.3 50.3–54.8

5. Dorsal-fin origin to hypural joint 52.3 47.8–51.9

6. Dorsal-fin origin to anal-fin origin 32.9 31.2–33.1

7. Dorsal-fin origin to pelvic-fin origin 31.9 28.6–32.6

8. Dorsal-fin origin to pectoral-fin origin 35.2 32.6–37.0

9. Caudal peduncle depth 11.9 11.4–12.6

10. Pectoral-fin length 18.9 19.0–21.6

11. Pelvic-fin length 16.2 15.3–17.7

12. Dorsal-fin length 23.3 23.6–25.5

13. Anal-fin length 19.5 19.2–21.7

14. Head length 26.5 26.5–27.8

15. Postorbital head length 45.0 40.0–45.0

16. Snout length 18.0 18.0–23.0

17. Bony orbital diameter 37.0 35.0–40.0

18. Interorbital width 35.0 31.0–36.0

MERISTICS

Lateral-line scales 30 29–31

Pored lateral-line scales 8 8–10

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 – 10–11

Branched dorsal-fin rays 8 8

Branched anal-fin rays 11 11–12

Branched pelvic-fin rays 7 7

Pectoral-fin rays 13 11–14

Vertebrae 33 32–33

Caudal fin with approximately eight central rays with heavy concentration of chromatophores along basal one-half to two-thirds of rays, chromatophores overlying both rays and membranes. Distal portions of second unbranched and anterior two branched dorsal-fin rays sometimes with diffuse dark pigment. Anterior margin of branched anal-fin rays outlined by lines of small chromatophores. Paired fins apparently unpigmented.

ECOLOGY.—The type-locality was described by Schultz (1944a: 177) as being a “river, 35 to 50 feet wide, with deep muddy holes and gravelly riffles.”

DISTRIBUTION.—Known from only two localities in the rivers of western and southwestern portions of Lago Maracaibo basin (Figure 7). Creagrutus maracaiboensis is sympatric, at least at its type locality, with C. hildebrandi.

MATERIAL EXAMINED.—48 specimens.

VENEZUELA. Zulia: Río Negro, below mouth of Río Yasa, USNM 121531, 1 (21.0, holotype of Creagrutops maracaiboensis); USNM 121532,42 (15,17.9–22.0, paratypes of Creagrutops maracaiboensis). Municipio Santa Cruz de Zulia, 4 km from El Moralito, Hacienda Chiquiquira, UF 23808, 5 (2, 15.9–17.5).