Gymnogeophagus constellatus, Malabarba & Malabarba & Reis, 2015

Malabarba, Luiz R., Malabarba, Maria Claudia & Reis, Roberto E., 2015, Descriptions of five new species of the Neotropical cichlid genus Gymnogeophagus Miranda Ribeiro, 1918 (Teleostei: Cichliformes) from the rio Uruguay drainage, Neotropical Ichthyology (Neotrop. Ichthyol.) 13 (4), pp. 637-662 : 648-651

Gymnogeophagus constellatus , new species u r n:l sid:z o ob a n k.or g:a c t: D4824 0 61-DAC B - 49C2-9A0 4 - 35DBC7E28153

Figs. 6c , 9

Holotype. MCP 10499 , male, 117.3 mm SL, Brazil, Rio Grande do Sul, Ijuí, rio Conceição, 28°27’48”S 53°57’17”W, 2 Dec 1985, C. Porto da Silva & M. F. Korndorfer.

Paratypes. Brazil: Rio Grande do Sul: MCP 10478 (8, 41.0- 74.0 mm SL), and MCP 10949 (4, 50.7-77.2 mm SL), small lagoon near rio Conceição, Ijuí , approx. 28°28’S 53°58’W, 4 Dec 1985, C. Porto da Silva & M. F. Korndorfer . MCP 10827 (16 alc., 3 c&s, 54.0- 124.5 mm SL), rio Conceição, Augusto Pestana , approx. 28°32’S 53°58’W, 10 Sep 1986, C. Porto da Silva & M. F. Korndorfer . MCP 10867 (2, 86.6-101.3 mm SL), same locality as MCP 10827, 18 Sep 1986 . MCP 11863 (1, 136.8 mm SL), rio Potiribu, Ijuí , aprox. 28°24’S 53°48’W, 16 Dec 1987, M. F. Korndorfer & Winckler . MCP 34922 (3, 81.2-110.5 mm SL), arroio Pobre, tributary of rio Ijuí on road to Cerro Largo , Salvador das Missões, 28°07’17”S 54°50’58”W, 29 Fev 2004, A. R. Cardoso & V. A. Bertaco . UFRGS 10420 (2, 85.74-101.2 mm SL), rio Ijuizinho , 28°25’28”S 54°17’56”W, 11 Nov 2008, J. Ferrer & G. Frainer . UFRGS 7094 (19, 25.9-136.1 mm SL), creek on road to Pirapó, São Nicolau , 28°10’30”S 55°04’01”W, 5 Mar 2005, M. Azevedo, J. Ferrer, L. R. Malabarba & C. Oliveira . MCP 37021 (2, 49.9-54.6) , ZVCP 12956 (2, 86.3- 104.6), arroio Encantado on road to BR392, tributary of rio Ijuí, Cerro Largo , 28°08’32”S 54°42’27”W, 31 Oct 2004, A. R. Cardoso & V. A. Bertaco .

Additional non-type specimens. Brazil: Rio Grande do Sul: MCP 10831 (5 alc), rio Conceição , Augusto Pestanas, approx. 28°32’S 53°58’W, 9 Sep 1986 . MCP 34866 (4 alc.), arroio Forte, tributary of rio Ijuí , Rolador, 28°15’24”S 54°52’55”W, 01 Mar 2004 . MCP 37263 (9 alc.), same locality as MCP 34866, 12 Jan 2005 . MCP 34884 (3 alc.), Lageado Araçá, tributary of rio Ijuí , 16 de Novembro, 28°12’23”S 54°56’58”W, 01 Mar 2004 . MCP 34915 (5 alc.), arroio Brum, tributary of rio Ijuí , Cerro Largo, 28°11’10”S 54°49’36”W, 1 Mar 2004 . MCP 35345 (2 alc.), same locality as MCP 24915, 12 Jun 2004 . MCP 34940 (1 alc.), Lageado Cerro Azul, tributary of rio Ijuí , 28°14’04”S 054°47’07”W, 01 Mar 2004 . MCP 35304 (3 alc.), same locality as MCP 34940, 12 Jun 2004 . MCP 37249 (7 alc.), same locality as MCP 34940, 12 Jan 2005 . MCP 34951 (1 alc.), arroio Alexandrino, tributary of rio Ijuí , Salvador das Missões, 28°10’25”S 54°48’05”W, 29 Feb 2004 . MCP 34992 (3 alc.), arroio Encantado on road to BR392, tributary of rio Ijuí , Cerro Largo, 28°08’32”S 54°42’27”W, 29 Feb 2004 . MCP 35340 (7 alc.), arroio Albino, tributary of rio Ijuí, São Pedro do Butiá , 28°08’10”S 54°55’28”W, 12 Jun 2004 . MCP 35396 (4 alc.), arroio Pobre, tributary of rio Ijuí , Salvador das Missões, 28°07’15”S 54°50’57”W, 12 Jun 2004 . MCP 37007 (8 alc.), same locality as MCP 35396, 31 Oct 2004 . MCP 37287 (10 alc.), same locality as MCP 35396, 12 Jan 2005 . MCP 37006 (19 alc.), arroio Pedras, tributary of rio Ijuí , 16 de Novembro, 28°12’07”S 054°04’30”W, 30 Oct 2004 . MCP 37192 (5 alc.), same locality as MCP 37006, 11 Jan 2005 .

Diagnosis. Gymnogeophagus constellatus is diagnosed from other Gymnogeophagus species by the possession of a very large midlateral spot, where each scale forming the spot usually bears one large white dot ( Fig. 9 ). In adult males, the midlateral spot almost reaches the dorsal-fin base being about 4-5 scales wide and 4 scales tall, compared with two or three scale rows distance from the dorsal fin base in other species. The midlateral spot of females and juveniles is also large, but usually not extending above the upper lateral line. Upper lateral line with 18-21 scales, usually 18-20 (vs. 13-19 in all other species).

Description. Morphometric data summarized in Table 3. Body comparatively deep, laterally compressed. Dorsal profile of head convex between mouth and interorbital area in young, slightly convex or straight in adults; convex from interorbital region to dorsal-fin origin. Predorsal body profile modified in adult males that may show adipose hump ( Fig. 9a, b ). Dorsal-fin base slightly convex. Caudal peduncle longer than deep, with dorsal and ventral profile straight or slightly concave.

Snout pointed, somewhat blunt and rounded dorsally in young; mostly straight dorsally and ventrally in adults; narrow and anteriorly rounded in dorsal aspect. Eye small, close to dorsal profile of head in juveniles and progressively farther from it in larger specimens (at least one half eye diameter in specimens larger than 70 mm SL); eye slightly posterior or near middle of head length. Interorbital area convex, more strongly so in larger specimens; interorbital width smaller than eye diameter in young (up to 60 mm SL) and progressively larger than eye diameter in larger specimens. Posterior tip of maxilla not reaching vertical line across anterior margin of eye. Upper jaw slightly longer than lower jaw.

Body scales large and ctenoid, smaller around pectoral fins; scales ctenoid even in preventral area. Caudal fin with single series of small ctenoid and elongated scales between contiguous rays reaching proximal third to middle of fin length in both upper and lower lobes. Cheek scales cycloid in 5 or 6 rows; cheek naked anteroventrally. Opercle mostly scaled. Subopercular scales ctenoid in two irregular rows. Upper lateral line 18*(12), 19(3), 20(2), 21(1) [18 in the holotype, but 17th scale not perforated]. Lower lateral line 8(2), 9(1), 10(5), 11*(8), 12(2), with none to 2 small perforated scales continuing onto caudal-fin base. Scales between upper lateral line and dorsal fin 4*(8), 5(10). Scales between upper lateral line and anal fin 8*(11), 9(9). E1 scales 26(3), 27*(9), 28(2), 29(1).

Dorsal-fin spines 13*(4), 14(14), 15(2); dorsal-fin soft rays 8(1), 9(2), 10(12), 11*(5). First dorsal-fin spine inserted at or slightly behind vertical line across posterior bony margin of opercle. Soft dorsal fin in adult females rounded, slightly pointed in young, reaching to or almost reaching caudal-fin base. Soft dorsal fin in mature males pointed, with 4th or 5th ray longest, reaching to proximal third of caudal fin. Anal fin with three spines and 8(16) or 9*(2) soft rays. Anal-fin origin under or slightly behind last dorsal-fin spine; soft portion nearly rounded in young and females and clearly pointed in males. Pectoral fin with rounded tip in young and pointed tip in adults; 3rd and 4th rays longest, reaching vertical crossing anal-fin origin. Pelvic fin pointed, more conspicuously so in adult males; 2nd soft ray longest reaching area between anal opening and anal-fin origin in both males and females. Caudal-fin margin concave.

Jaw teeth small, conical, with slightly recurved tips. Upper jaw with outer regular row of 14-25 teeth in each premaxilla (number increasing with specimen size) distinct from irregular tooth band of slightly smaller teeth. Lower jaw with narrow tooth band arranged in 3-4 irregular rows; all teeth with approximately same size. Outer hemiseries with 18-22 teeth. Lower limb of first gill arch with 7 gill rakers; upper limb lobed with 5 gill rakers on its margin.

Lower pharyngeal tooth plate wide; length of bone 78% of width; dentigerous area covering whole occlusion surface; 20-21 teeth in posterior row, 10 on median row. Anterior teeth cylindrical, erect, not recurved, unicuspid; lateral marginal teeth like anteriormost, smaller on caudal half of plate; posteromedial teeth much larger, cylindrical with medial, blunt cusps of molariform aspect ( Fig. 6c ).

Vertebrae 13 + 16 in three cleared and stained specimens.

Color in alcohol. Mature males ( Fig. 9a ): ground coloration light brown, darker dorsolaterally above upper lateral line, and lighter ventrally. Below pectoral-fin insertion and in preventral area whitish gray. Body covered laterally with 8 to 13 brown, double vertical bars clearly discernible along midventral lateral surface of body, distributed between pectoral-fin base and caudal peduncle; area inside double bars more pigmented than area between double bars. Number of vertical bars increases with body size among examined specimens, usually regularly arranged between pectoral and anal-fin bases and irregular in caudal peduncle. Very large midlateral spot, almost reaching dorsal-fin base on adult males; each scale in midlateral spot usually bearing one large white dot. Midlateral spot of mature males covering scales 8-9 to 11-12 of scale row just above upper lateral line, scales 8-12 of upper lateral line, scales 8-12 of scale row just below upper lateral line and scales 8-11 of E1 scale row. Dark band in front of dorsal-fin origin small, not extending ventrally and posteriorly. Head dark brown, with small series of black markings ventral to eye and very few black spots along opercle and preopercle borders. Distinct dark band covering cheek absent. Isthmus and branchiostegal membrane ligth brown. Pectoral fin hyaline. Pelvic fin somewhat dusky. Spinous dorsal fin with white stripes, and soft dorsal fin covered with very large white dots, sometimes elongated at distal tip and forming large white areas. Proximal half-length of anal-fin rays covered with conspicuous white spots; anal-fin distal border whitish gray. Caudal-fin base covered with large white dots, large and elongated on distal portion of fin.

Color in alcohol of preserved females and juveniles similar to general pattern described for males. Midlateral spot in females smaller than in males, usually not extending above upper lateral line as described for males. Midlateral spot of females and juveniles with fewer white dots centered and not on each scale as described for males. Dark band in front of dorsal-fin origin clearly extending ventrally and posteriorly.

Color in life. Ground coloration of males ( Fig. 9b ) olivaceous dorsolaterally with longitudinal series of bright spots. Head largely yellowish green, with adipose hump and snout light brown. A few red marks on opercle, preopercle and cleithrum. Numerous small roundish to elongate light blue spots ventral to eye and on opercle. Lateroventral portion of body yellow, becoming pale yellow near to anal-fin base and caudal peduncle. Ground color of dorsal fin red, covered with conspicuous light spots which increase distally until forming large white stripes. Pectoral-fin hyaline and pelvic-fin yellowish gray. Anal fin red proximally with numerous white spots; pale yellow with no spots distally. Caudal fin brown on proximal third and pale red distally; numerous white spots covering its base, which become stripes toward caudal margin.

Color in life of females ( Fig. 9c ) similar to that described for males, but much paler. Longitudinal series of bright spots less evident. Most clear differences refer to light brown coloration lateroventrally instead of yellow as in males. Dark band from dorsal-fin origin extending ventrally to scales below upper lateral line. Midlateral spot smaller than in males.

Distribution. Gymnogeophagus constellatus is known from the rio Ijuí and its tributaries in the middle rio Uruguay basin, in the eastern portion of Rio Grande do Sul, Brazil ( Fig. 1 ).

Etymology. From the Latin constellatus meaning studded with stars, in reference to arrangement of white bright spots in the dorsolateral region of the body. An adjective in masculine form.

Conservation status. Gymnogeophagus constellatus is relatively frequent and abundant in the rio Ijuí basin.

Despite the Extent of Occurrence (EOO) is approximately 2,300 square kilometers and hydroelectric dams exist in that basin, no specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria ( IUCN, 2014).

Figures

Fig. 6. Lower pharyngeal tooth plates in occlusal view: a, G. pseudolabiatus, MCP 11228, 71.6 mm SL; b, G. mekinos, MCP 11251, 84.2 mm SL; c, G. constellatus, MCP 10827, 91.4 mm SL; d, G. missioneiro, MCP 12725, 59.3 mm SL; e, G. lipokarenos, MCP 12991, 89 mm SL. Scale bars = 1 mm.

Fig. 9. Gymnogeophagus constellatus: top, holotype, male, MCP 10499, 117.3 mm SL, rio Conceição, Ijuí, Rio Grande do Sul, Brazil; middle, paratype, male, UFRGS 7094, 136.1 mm SL; bottom, paratype, female, UFRGS 7094, 92 mm SL, creek on the road to Pirapó, São Nicolau, Rio Grande do Sul, Brazil.

Fig. 1. Rio Uruguay and adjacent drainages showing the distribution of the examined specimens of Gymnogeophagus lipokarenos (dark blue), G. missioneiro (light blue), G. constellatus (red), G. pseudolabiatus (orange), and G. mekinos (yellow). Stars represent the type localities.