Geophagus dicrozoster , López-Fernández, Hernán & Taphorn, Donald C., 2004
treatment provided by
Geophagus dicrozoster n. sp.
( Figs. 2 View Figure a, 6–9)
Holotype. MCNGAbout MCNG 40996, 193.0 mm SL; Venezuela: Apure: Río Cinaruco: Laguna Larga (6.5339 N 67.4150 W); D.A. Arrington and J. Arrington, 13 April 1999.
Paratypes. MCNGAbout MCNG 30020, 7, 44.8–138.0 mm SL; Venezuela: Bolívar: Río Caroní: Campamento Guri; J.D.Williams and K.M. Ryan, 14 April 1994. — AMNHAbout AMNH 233636 (ex MCNGAbout MCNG 40853), 1, 154.0 mm SL; Venezuela: Apure: Río Cinaruco: Laguna Oheros; D.A. Arrington and J. Arrington, 12 April 1999. — MCNGAbout MCNG 40311, 22, 12.2–84.6 mm SL (2 measured); Venezuela: Apure: Rio Cinaruco: Laguna Guayaba (6.5897°N 67.2400°W); D.A. Arrington and J. Arrington, 16 March 1999. — AMNHAbout AMNH 233635 (exMCNG 47603), 5, 109.6–178.0 mm SL; Venezuela: Apure: Río Cinaruco: Laguna Larga (6.5339 N 67.4150 W); K. Winemiller, H. LópezFernández, A. Arrington, L. KelsoWinemiller, H. LópezChirico and J. Arrington, 1–3 Jan 1999. — MCNGAbout MCNG 47604, 4, 177.0–202.0 mm SL; Venezuela: Apure: Río Cinaruco.
Diagnosis. A preopercular mark distinguishes Geophagus dicrozoster n. sp. from G. grammepareius , G. taeniopareius , G. argyrostictus and G. harreri , which have a complete infraorbital stripe ( Fig. 1 View Figure ), and from G. abalios n. sp., G. brokopondo , G. surinamensis , G. megasema , G. camopiensis , and G. altifrons , which lack head markings. Preserved specimens of G. dicrozoster can be distinguished from other species with preopercular mark by the possession of seven vertical, parallel lateral bars, as opposite to G. winemilleri n. sp. (4 bars) and G. brachybranchus and G. proximus (no bars) ( Fig. 2 View Figure ).
Description. Based on holotype (193.0 mm SL) and the 19 paratypes 63.4–202.0 mm SL with notes on variation among smaller specimens. Measurements and counts are summarized in Table 1. Sexes appear to be isomorphic.
Shape. Moderately elongate; dorsal outline more convex than ventral outline; head broader ventrally than dorsally; specimens 63.4 mm SL and smaller more elongate; interorbital area moderately concave. Dorsal head profile moderately convex, ascending to dorsalfin origin, except in front of orbit where slightly concave, in specimens smaller than 65.0 mm SL, straight from orbit to dorsalfin origin; dorsalfin base descending, arched to last ray, then forming a horizontal, moderately concave line to caudalfin insertion. Ventral head profile straight, slightly descending to chest; slightly convex to pelvicfin insertion; straight, horizontal from pelvicfin insertion to origin of anal fin; analfin base slightly convex, ascending; ventral caudal peduncle moderately concave, slightly ascending or horizontal in specimens 64.0 mm SL and smaller. Lips moderately wide, lower with slightly caudally expanded fold (see Kullander et al., 1992, Fig. 3 View Figure ). Maxilla reaching 1 / 3 – 2 / 3 of the distance between nostril and orbit; ascending premaxillary process reaching slightly above midline of orbit. Opercule, preopercule, cleithrum, postcleithrum, and posttemporal lacking serration.
Scales. E 1 34 (3), 35 (7), 36 (8), 38 (2); scales between upper lateral line and dorsal fin 6.5–8.5 anteriorly, 2.5–3.5 posteriorly. Scales between lateral lines 2. Scales on upper lateral line 19 (1), 20 (7), 21 (8), 22 (4) and lower lateral line 14 (1), 15 (4), 16 (3), 17 (9), 18 (3). Anterior half of cheek naked, remainder with ctenoid scales; cheek scale rows 9–10. Opercule covered with ctenoid scales. Caudoventral area of subopercule naked, remain der with ctenoid scales. Interopercule with cycloid scales caudally. Single postorbital column of ctenoid scales, particularly in largest specimens. Occipital and flank scales ctenoid. Circumpeduncular scale rows 7–9 above upper, 9–11 below lower lateral line, ctenoid.
Fin scales. Anal, pectoral and pelvic fins naked. Dorsal fin scaled on spinous and soft portions, scales ctenoid, and arranged in double or triple columns along interradial membranes up to one third to one half of fin height. Scaly pad at base of dorsal formed by irregularly arranged small, ctenoid scales extending from first spine to third to seventh soft ray. Anal scaleless, scaly pad on base of anal absent, at most a few small scales on base of anterior portion of fin, moderately ctenoid. Caudal fin scaled along its entire surface, except the tip of rays, and part of membranes between D 3 and V 3, scales ctenoid. Accessory caudal fin extension of lateral line between V 4 –V 5, absent on dorsal lobe.
Fins. Dorsal XVI 12 (2), XVI 13 (1), XVII 11 (2), XVII 12 (9), XVII 13 (1), XVIII 11 (2), XVIII 12 (2); anal III 7 (1), III 8 (18), III 9 (1). Dorsalfin spines increasing in length from first to sixth, equal length to ninth, then slightly shorter; lappets pointed, short; soft portion round, reaching just beyond caudalfin insertion; moderately pointed in a 202.0 mm SL, and reaching about a third of caudalfin length; rays 4–6 longest but not produced into filaments; in specimens 63.0 mm SL and smaller dorsal fin not reaching caudalfin insertion. Anal fin round, moderately pointed in largest specimens, with rays 2–5 longest, not reaching caudal fin or barely beyond its base in largest specimens. Caudal fin emarginate with lobes of approximately the same length and without filaments; one specimen 120.2 mm SL with slightly produced ray D 8. Pectoral fin elongate, more or less triangular,
longest at 4 th ray, reaching 1 st or 2 nd analfin spines, then progressively shorter ventrally. Pelvic fin triangular, first ray produced into a filament reaching 3 rd analfin soft ray; in a specimen 202.0 mm SL almost reaching caudalfin insertion; specimens 45.5 mm SL or less with slightly or not produced rays, reaching at most 1 st analfin spine.
Teeth. Outer row of upper jaw with 17–26 approximately cylindrical, frequently blunt, slightly recurved, unicuspid teeth; larger than in inner rows, extending along most of premaxillary length; 6–7 inner rows, separated by a clear gap from outer row; teeth on inner row thin, slightly recurved unicuspids, forming a pad. Outer row of lower jaw with 16–22 blunt, slightly recurved unicuspid teeth; median 3 teeth more labially positioned than rest of row; inner rows 6 (4 in small specimens), forming a pad, separated from outer row by distinct gap; teeth thin, slightly recurved unicuspids.
Gills. External rakers on first gill arch; 10 (11), 11 (1) on epibranchial lobe, 1 in angle and 12 (3), 13 (7), 14 (2) on ceratobranchial, none on hypobranchial. Microbranchiospines on the outer face of second to fourth arches. Gill filaments with narrow basal skin cover.
Tooth plates. Lower pharyngeal tooth plate elongate ( Fig. 8 View Figure ); width of bone 80–82 % of length; dentigerous area 80 % of width; 28 teeth in posterior row, 11 in median row. Anteriormost teeth subconical, laterally compressed and erect; cusps posterior, slightly curved rostrad, small rostral edge ridge; lateral marginal teeth with same cusp pattern, teeth thinner and more laterally compressed towards caudal edge of plate; posteromedial teeth much larger, almost cylindrical, cusps posterior, almost blunt. Ceratobranchial 4 with 5 toothplates with 4–6, 5 – 7, 5–13, 6 – 11 and 3–7 teeth; one of two specimens with 7 toothplates with 6, 4, 5, 5, 4, 3 and 3 teeth on left side.
Vertebrae. 14 + 18 = 32 (1), 14 + 19 = 33 (10), 15 + 18 = 33 (3), 15 + 19 = 34 (1); 11–12 epihemal ribs.
Color pattern in alcohol ( Fig. 6 View Figure ). Background color grayish yellow; nape, snout, upper lip and naked portion of cheek darker gray, scaled portion of cheek lighter; lower lip yellowish white. Vertical, blackish mark in the corner of the preopercule, continued into the interopercule as a faint spot; indistinguishable or faded in specimens smaller than 65.0 mm SL. Opercule with a dark, brown spot on dorsal edge, reaching first scale of upper lateral line, otherwise uniformly dusky yellow or silvery white in some specimens probably depending on preservation. Ventrally, gill cover dusky yellow or yellowish white in some specimens; branchiostegal membrane also yellowish, grayish brown in one specimen 202.0 mm SL. Chest yellow laterally and ventrally, white in many specimens, juveniles with distinctive silverywhite chest region; in best preserved specimens dusky yellow or white extends ventrally to base of caudal fin and to H 3 on caudal peduncle flanks. Flanks with 7, dorsoventrally directed, darkgray bars fading or disappearing ventrally ( Fig. 2 View Figure a). Bar 1 expands from the 7 th– 8 th predorsal scale to the base of the dorsal fin between spines 4–5 forming an inverted triangle; its anterior edge roughly delimited by the extrascapular and its posterior edge descending ventrally to the pectoralfin insertion. Bar 2 extends between the base of dorsalfin spines 6–7 and 9, and runs vertically to H 6–7. Bar 3 extends between the base of dorsalfin spines 10–11 and 12–13, descends ventrally and slightly caudally oriented, fading progressively to H 6–7. A welldemarked, black medial spot is located on bar 3, extending rostrocaudally between scales 11 and 14–15 of E 3 and dorsoventrally between the lower half of E 4 and E 1, such that the upper lateral line traverses the dorsal 1 / 4 – 1 / 3 of the spot. Bar 4 extends between the bases of dorsalfin spines 14–15 to 17, and descends ventrocaudally to the upper lateral line, where it merges with bar 5 such that the two bars form a “ Y ” shaped figure ( Fig. 2 View Figure a); in specimens 50.0 mm SL or less, bar 4 may appear as a spot on the base of the dorsal, not quite reaching bar 5. Bar 5 extends between the base of dorsalfin spine 18 and ray 1 or rays 1–2 and rays 4– 5, it descends vertically fading at H 1–2. Bar 6 extends from the base of the 7–8 dorsal fin rays to the second postdorsal scale in the caudal peduncle, descends vertically and fades at H 1–2. Bar 7 covers the area between the last 4–5 lower lateral line scales and the base of the caudal fin, disappearing ventrally at H 2.
Dorsal fin dusky, lappets dark gray or blackish, forming a faint dark edge along fin; dorsal fin immaculate except a few indistinct whitish spots in the membranes of caudal half of soft portion; in specimens 63.0 mm SL or smaller, three dusky longitudinal, parallel stripes alternate with light stripes along soft portion of dorsal fin. Anal fin hyaline to slightly dusky; 4 longitudinal, parallel gray bands along soft portion; largest specimen with dark gray lappets. Caudal fin graybrown, with whitish longitudinal bands of variable length and elongate spots, forming no evident pattern; specimens up to 85.0 mm SL with 4 dark, vertical bands that gradually turn into the above described pattern with increasing size. Pectoral fin immaculate. Pelvic fin dusky, darker distally; spine and first ray whitish gray to dusky.
Live colors ( Fig. 7 View Figure ). Dark markings as in alcohol specimens. Background color yellowish olive green; head silvery with yellow on gill cover, snout gray, upper lip iridescent blue extending behind lips to preopercular mark. Dorsal fin reddish with faint iridescent blue spots, especially on the soft portion; some specimens with proximal third of spiny portion yellow, probably due to breeding condition; anal fin red or reddish with distinctive iridescent blue horizontal banding; caudal fin reddish with a variable pattern of iridescent blue stripes and spots. Five to seven faint, yellow horizontal stripes alternating with olive green along body, but not always distinct.
Distribution and habitat ( Fig. 9 View Figure ). Geophagus dicrozoster is common in the black waters of the Caura and Caroní drainages of the Guyana Shield; it is also present in all major tributaries of the middle and upper Orinoco, including the drainages of the Cataniapo, Ventuari, Atabapo, Ocamo, and Mavaca, as well as the Casiquiare and the headwaters of the Río Negro. In the llanos, G. dicrozoster is restricted to the moderately blackwatered Río Cinaruco, although further collections will likely show its presence in the nearby Río Capanaparo and its tributaries. No specimens have been captured from white water, or from llanos clear water drainages as the AguaroGuariquito.
Etymology. From the Greek dikros, forked, and zoster, belt. Given in reference to the “ Y ” formed by lateral bars 4 and 5. To be regarded as an adjective in masculine form.
|Geophagus abalios||Geophagus dicrozoster||Geophagus winemilleri|
|n||Mean Min Max Stdev||n||Mean Min Max Stdev||n Mean Min Max Stdev|
|SL 17||107.9 45.5 192.0 42.5||20||129.7 44.8 202.0 51.0||15 86.6 37.0 195.0 54.7|
|Head length 17||31.3 31.0 34.0 0.7||20||31.1 29.5 32.5 0.8||15 31.9 30.3 33.8 1.2|
|Body depth 17||40.7 36.0 46.2 2.9||20||38.8 32.6 42.4 2.4||15 38.9 34.3 44.6 3.7|
|Caudal peduncle depth 17||12.8 11.9 13.7 0.5||20||12.0 10.6 13.0 0.6||15 12.0 11.1 13.1 0.5|
|Caudal peduncle 17 length||19.2 16.7 21.8 1.5||20||20.9 16.7 24.4 1.5||15 19.3 17.5 21.2 0.9|
|Pectoral fin length 17||35.2 31.9 40.5 2.9||20||33.9 28.6 39.0 2.8||15 33.6 27.5 39.8 4.0|
|Pelvic fin length 17||45.3 27.2 79.4 13.1||20||42.8 24.1 64.9 13.8||15 39.6 27.3 69.4 15.0|
|Last D spine length 17||17.4 14.1 19.6 1.4||19||17.0 11.6 20.2 2.8||15 15.8 12.2 20.2 2.5|
|Snout length 17||46.5 38.2 59.7 5.4||20||46.7 36.4 54.9 4.9||15 43.4 34.1 54.8 5.8|
|Orbital diameter 17||31.1 26.8 41.6 3.9||20||31.3 25.8 38.6 3.6||15 33.8 28.3 39.6 3.3|
|Head depth 17||100.0 91.9 113.0 6.6||20||100.7 84.3 112.3 8.8||15 98.6 80.8 120.3 12.6|
|Head width 17||41.6 39.5 45.7 1.7||20||42.2 40.1 44.4 1.1||15 43.0 40.5 46.2 1.8|
|Interorbital width 17||25.3 20.8 28.3 2.3||20||25.7 19.3 29.9 3.0||15 23.1 17.7 33.0 4.3|
|Preorbital depth 17||35.6 25.0 43.8 5.9||20||35.3 22.9 43.0 6.2||15 29.0 19.2 42.1 7.7|
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