Descriptions of five new species of the Neotropical cichlid genus Gymnogeophagus Miranda Ribeiro , 1918 ( Teleostei : Cichliformes ) from the rio Uruguay drainage

Gymnogeophagus is a Neotropical cichlid genus distributed in the río Paraguay, rio Paraná and rio Uruguay drainages and also in the coastal rivers of Uruguay and southern Brazil. Its monophyly is supported by two derived features: the absence of supraneurals and the presence of a forward spine in the first dorsal-fin pterygiophore. Herein, five new species of Gymnogeophagus are described from middle to upper tributaries of the rio Uruguay drainage and from the rio Negro. All these new species belong to a clade, which includes G. gymnogenys, easily recognized by sharing two synapomorphies: the absence of an oblique bar between the dorsal border of the eye and the nape, and the possession of a black bar originating in the dorsal contour near the dorsal-fin origin and directed downward and backward on the dorsum. A key to all species of Gymnogeophagus is provided.


Introduction
Cichlids are teleost fishes found chiefly in freshwaters.They constitute one of the major vertebrate families with more than 1,677 species (Eschmeyer & Fong, 2015), of which nearly 600 inhabit the Neotropics with many species still undescribed (López-Fernández et al., 2010).Within the Cichlinae (Neotropical cichlids), the tribe Geophagini is a monophyletic clade (López-Fernández et al., 2005a, 2005b, 2010) represented in South America and southern Panama by approximately 18 genera.
In a revisionary paper, Reis & Malabarba (1988) described two additional species, G. lacustris Reis &Malabarba, 1988 andG. meridionalis Reis &Malabarba, 1988, and proposed a hypothesis of phylogenetic relationships among the seven species known at that time.In the hypothesis of Reis & Malabarba (1988) the species of Gymnogeophagus were grouped in two clades with Five new mouthbrooder species of Gymnogeophagus 638 distinguishing morphological and behavioral features: a short bodied, substrate brooder clade and a long bodied, mouth brooder clade, in addition to G. balzanii at the base of the tree.Ten years later, Wimberger et al. (1998) published the first molecular assessment of Gymnogeophagus relationships, including five undescribed species related to G. gymnogenys and shifting the position of G. balzanii to inside the mouthbrooding clade.
In their paper, Reis & Malabarba (1988) asserted that G. gymnogenys, as defined therein, could prove to be a group of species sharing two synapomorphies: the absence of an oblique bar between the dorsal border of the eye and the nape, and the possession of a black bar originating in the dorsal contour near the dorsal-fin origin and directed downward and backward on the dorsum.Reis & Malabarba (1988) have tentatively included in G. gymnogenys some populations from the rio Negro, rio Santa Maria and rio Piratini, which shared these synapomorphies but presented a few differences in body shape when compared to specimens of G. gymnogenys from the laguna dos Patos drainage.These differences, however, showed to be overlapping when all populations were analyzed together.Thus all of them were considered to be G. gymnogenys.Pereyra & Garcia (2008) tested the hypothesis that G. gymnogenys constitute a species complex through a Cytochrome b (Cyt b) analysis and found at least four lineages included in G. gymnogenys distributed along the lagoa Mirim, rio Negro and rio Uruguay tributaries, in Uruguay.One of these lineages corresponds to G. tiraparae recently described by González-Bergonzoni et al. (2009).
New specimens coming from Rio Grande do Sul, Brazil, and Uruguay in the last two decades, including colorful males, allowed the recognition of five new species and prompted the restriction of the distribution area of G. gymnogenys.Based on all this new material, we herein describe five new species distributed from the rio Quaraí, a tributary of the middle rio Uruguay, to tributaries of the upper rio Uruguay (Fig. 1), and restrict the distribution of G. gymnogenys (Fig. 2) to the laguna dos Patos and rio Tramandaí drainages in Rio Grande do Sul, Brazil and Uruguay.

Material and Methods
Counts and measurements were taken according to Reis & Malabarba (1988) and Reis et al. (1992).Meristic data are presented listing all counts followed by the number of individuals in parentheses; counts of the holotype are marked with an asterisk.Vertebral counts are presented as abdominal + caudal, including the last half centrum.Measurements were taken with a caliper on the left side of the specimens (Fig. 3).Measurements are expressed as percents of the standard length (SL) except for subunits of the head which are recorded as percents of the head length (HL).Scale row nomenclature follows Kullander (1996).Cleared and stained specimens (C&S) were prepared following Taylor & Van Dyke (1985).
Institutional abbreviations are as follows: Museu Anchieta, MAPA, Porto Alegre; Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, MCP, Porto Alegre; Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, UFRGS, Porto Alegre; University of Michigan, Museum of Zoology, UMMZ, Ann Arbor; Facultad de Ciencias de la Universidad de la Republica, ZVCP, Montevideo.Non-type specimens are listed to document distributional records and mapped in Fig. 1, but were not used in species descriptions.
Holotype.MCP 35027, male, 92.Snout pointed, straight dorsally and ventrally in lateral aspect; narrow and anteriorly rounded in dorsal aspect.Upper and lower lips thick, large; extremely developed in adult males.Eye small, close to dorsal profile of head in juveniles and far from it 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 in large specimens; interorbital width smaller than eye diameter in young (30-65 mm SL) and progressively larger than eye diameter in larger specimens.Posterior tip of maxilla not reaching vertical line crossing anterior margin of eye.Upper jaw longer than lower jaw.
Dorsal-fin spines 12(1), 13(8), 14*(9), 15(1); dorsal-fin soft rays 9*(3), 10(15), 11(1).First dorsal-fin spine inserted at vertical line across posterior bony margin of opercle or slightly anterior to it in larger specimens.Soft dorsal fin in young and females rounded, reaching to or almost reaching caudal-fin base.Soft dorsal fin in mature males pointed, with 4th ray produced and reaching proximal third to almost end of caudal fin.Anal-fin with three spines and 7*(6), 8(12), 9(1) soft rays.Anal-fin origin under or slightly posterior to last dorsal-fin spine; soft portion nearly rounded in young and females and clearly pointed in males.Pectoral fin pointed, more strongly in adults; 3rd and 4th rays longest, reaching vertical crossing anal-fin origin in young and females and passing that point in males.Pelvic fin pointed, more conspicuously in adult males; 2nd soft ray longest reaching region between anal opening and anal-fin origin in young and females and passing anal-fin origin in adult males.Caudal-fin posterior margin concave.
Jaw teeth small, conical, strongly recurved.Upper jaw with outer regular row of nearly 20 teeth in each premaxilla (number increasing with specimen size) and 3 or 4 indistinct irregular inner tooth bands.Lower jaw with tooth band arranged in 3-4 irregular rows; teeth larger near symphysis.Lower limb of first gill arch with 7-8 gill rakers; upper limb lobed (as in other geophagines) with 5-6 gill rakers in its margin.
Lower pharyngeal tooth plate wide; length of bone 85.7% of width; teeth covering whole occlusion surface; 21 teeth in posterior row, 17 on median row.Teeth on posterior and medial rows larger than remaining ones.Posterolateral teeth small and laterally compressed, with slightly recurved tips; posteromedial teeth much larger, cylindrical with medial, blunt cusps of molariform aspect (Fig. 6a).
Color in alcohol.Mature males (Fig. 4a): base color of body dark brown above longitudinal series of scales bearing lower lateral line, becoming yellowish tan below pectoral-fin insertion and in prepelvic area.Six to 9 vertical bars clearly discernible along midventral surface of body, variable in shape, distributed between pectoral-fin base and caudal peduncle.Midlateral spot not well defined, on scales 8-10 of scale row just below upper lateral line and on scales 7-9 of E1 scale row.Dark band in front of dorsal-fin origin, extending ventrally and slightly posteriorly, almost reaching first scales of upper lateral line.Head light brown, with series of conspicuous black markings surrounding eye ventrally and posteriorly, partially covering opercle.Faint vertical dark band covering cheek.Isthmus and branchiostegal membrane brownish gray.Pectoral fin hyaline.Pelvic fin dark brown.Distal border of entire dorsal fin dark brown.Spinous dorsal fin faint brown with small, narrow and inconspicuous white stripes.Soft dorsal fin faint brown covered with large number of well-defined white spots.About half distal length of anal-fin rays and spines dark brown, without additional distinct marks.Proximal half of anal-fin rays covered with small and conspicuous white dots.Caudal fin covered with white dots along almost its entire length.
Preserved coloration of females and juveniles not clearly distinct from that described for males (Fig. 4b), except for isthmus and branchiostegal membrane light yellow, instead of brown as observed in males.Presence of conspicuous vertical dark band covering cheek, below eye.Color in life.Base color of dorsal region of body in males (Fig. 5a) olivaceous with longitudinal series of bright blue spots.Head largely yellowish green, with lips and lower jaw region pale gray.Adipose hump light brown.Red marks concentrated on opercular region and scattered over nape and anterodorsal scales.Numerous small roundish to elongate light blue spots posterior and ventral to eye and on opercle.Lateroventral portion of body yellowish brown, more intense around pectoral-fin base; yellow pale to white along isthmus and midventral regions.Anterior part of dorsal fin yellow, with hyaline thin stripes; posterior part red with numerous relatively large hyaline spots.Dorsalfin distal margin dark black dorsally and reddish orange posteriorly.Pectoral-fin hyaline and pelvic-fin dark gray.Anal fin reddish orange proximally with numerous hyaline spots, slightly smaller than those from dorsal fin.Anal fin pale red distally with dark gray distal margin.Caudal fin orange proximally and faint red distally with numerous light spots extending along its middle region.Tips of dorsal and ventral lobes dark gray.
Color in life of females (Fig. 5b) similar to that described for males, but paler.Most clear differences refer to light brown and silvery color of opercle and below pectoral fin regions, instead of yellow as observed in males.Conspicuous vertical dark band from posterior eye margin to cheek.
Distribution.Gymnogeophagus pseudolabiatus is known from the rio Quaraí and its tributaries, along the frontier of Brazil and Uruguay in the middle rio Uruguay drainage (Fig. 1).
Ecology.This species is found exclusively in stone bottom habitats covered with stones and rocks of all sizes, found along the rio Quaraí and its tributaries (Fig. 7).Etymology.From the Greek pseudos, meaning false, and labiatus, in reference to a congener species that also presents well developed lips.A noun in apposition.
Conservation status.Gymnogeophagus pseudolabiatus is relatively frequent and abundant in the rio Quaraí basin.Despite its Extent of Occurrence (EOO) is approximately 4,500 square kilometers, no specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria (IUCN, 2014).
Dorsal-fin spines 13(6), 14*(13), 15(2); dorsal-fin soft rays 9(2), 10*( 14), 11(5).First dorsal-fin spine inserted at vertical line across or slightly posterior to posterior bony margin of opercle.Soft dorsal fin in young and females rounded, reaching to or almost reaching caudal-fin base.Soft dorsal fin pointed in mature males, with 3rd and 4th or 4th and 5th ray produced and reaching proximal third to almost end of caudal fin.Anal-fin with three spines and 8(12), 9*(5) or 10(1) soft rays.Anal-fin origin slightly posterior to last dorsal-fin spine; soft portion nearly rounded in young and females and clearly pointed in males.Pectoral fin pointed, more strongly so in adults; 3rd and 4th rays longest, passing vertical across anal-fin origin.Pelvic fin pointed, more conspicuously in adult males; 2nd soft ray longest, reaching anal opening or region between anal opening and anal-fin origin in young and females, and passing anal-fin origin in adult males.Caudal-fin margin concave, upper lobe longest.
Jaw teeth small, conical, with slightly recurved tips.Upper jaw with outer regular row of nearly 20 teeth in each premaxilla (number increasing with specimen size) and an irregular inner tooth band of slightly smaller teeth.Lower jaw with tooth band arranged in 3-4 irregular rows.Lower limb of first gill arch with 6-7 gill rakers; upper limb lobed, with 4-5 gill rakers on its margin.
Vertebrae 13+15(1), 13+16(2) in three cleared and stained specimens.with very small and conspicuous white dots.Caudal fin faint brown with circular white dots along its half proximal length.Ground color in females and young light yellow.Midlateral spot as described for males.Dark band in front of dorsal-fin origin, extending ventrally and slightly posteriorly, reaching first scales of upper lateral line, but not extending anteriorly through dorsal head profile as described for males.Head yellowish brown, sometimes with black markings below eye.Conspicuous vertical dark band covering cheek.Vertical bars conspicuous in small specimens, distributed from pectoral-fin insertion to caudal peduncle.Vertical bars variable in shape.Isthmus and branchiostegal membrane light yellow.
Pectoral and pelvic fins hyaline.Dorsal fin faint brown; soft portion with small white spots.Proximal half of anal and caudal fins covered with small, circular, white spots.
Color in life.Ground color of laterodorsal region of body in males (Fig. 8b) mainly olivaceous with vertical black indistinct bars from pectoral-fin insertion to caudal fin base.Body ventrally bright yellow; pale yellow to white along prepelvic region.Head largely yellowish gray, lower lip and jaw white.Adipose hump also brown, but darker than head.Head with small light dots posteriorly to eye, and on opercle.Dark band on dorsal fin origin extending posteroventrally to upper lateral line scales.Spiny portion of dorsal fin dark yellow with short white stripes; soft portion faint red covered with light roundish spots.Caudal fin olivaceous at base and faint red at distal portion; all covered with light roundish spots.Anal fin faint red with light roundish spots on proximal third; distal portion of rays dusky.Pectoral fins hyaline, and pelvic fins darkly pigmented.
Color in life of females (Fig. 8c) similar to that described for males, but paler.Body coloration pale brown instead of olivaceous and yellow as in males.Most conspicuous difference refers to darker color of head with more numerous light dots distributed over cheek, opercle and surrounding eye.Some body scale series with bright blue spots.
Distribution.Gymnogeophagus mekinos inhabits the río Negro, connected to the lower río Uruguay (Fig. 1).Pereyra & García (2008) have identified specimens belonging to their Clade 1 (recognized herein as G. mekinos) from the río Tacuarí and río Yaguarón (rio Jaguarão in Brazil) basins, both tributaries of the lagoa Mirim, laguna dos Patos drainage.The presence of freshwater fish species from the río Negro drainage in the río Tacuarí and río Yaguarón drainages has been previously reported by Loureiro et al. (2011), which also describe a characteristic elbow of capture involving the río Tacuarí and the río Negro.Although we have not examined those specimens sequenced by Pereyra & García (2008), the presence of G. mekinos in the río Tacuarí / lagoa Mirim drainage is probable based on their DNA analysis.
Etymology.From the Greek mekinos meaning prolonged, in reference to the comparatively elongated body of this species.A noun in apposition.
Conservation status.Gymnogeophagus mekinos is relatively frequent and abundant in the rio Negro basin.The Extent of Occurrence (EOO) is approximately 23,300 square kilometers and no specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria (IUCN, 2014).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).

Gymnogeophagus constellatus, new 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.
Vertebrae 13 + 16 in three cleared and stained specimens.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 pelvicfin 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).
Holotype Description.Morphometric data summarized in Table 4. Body elongate, 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 by small adipose hump (Fig. 10a, b).Dorsalfin base slightly convex.Caudal peduncle longer than deep, with dorsal and ventral profile slightly concave.Snout pointed, slightly 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 in larger specimens (about 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 50 mm SL) and progressively larger than eye diameter in larger specimens.Posterior tip of maxilla not reaching to vertical line across anterior margin of eye.Upper jaw slightly longer than lower jaw.
Jaw teeth small, conical, recurved.Upper jaw with irregular outer row of 18-24 teeth in each premaxilla (number increasing with specimen size).Anterior tip of lower jaw wide, tooth band arranged in 5 or 6 irregular rows; middle and posterior tooth band slender, arranged in 3 or 4 irregular rows.Teeth at anterior tip of dentary thicker than other dentary and premaxillary teeth.Nearly 18 teeth in outer hemiseries.Lower limb of first gill arch with 7-8 gill rakers; upper limb lobed with 4-7 gill rakers on its margin.Fig. 10.Gymnogeophagus missioneiro: top, holotype, male, MCP 23495, 109.3 mm SL, arroio Ximbocuzinho, on the road from São Luiz Gonzaga to Bossoroca, 4 km from São Luiz Gonzaga, Rio Grande do Sul, Brazil; middle, paratype, female, MCP 12725, 72.8 mm SL, arroio Passo do Rosário or Passo da Cancela, on the road from São Nicolau to Garruchos, Santo Antônio das Missões, Rio Grande do Sul, Brazil; bottom, holotype, photo taken just after capture.
Lower pharyngeal tooth plate slightly wider than long; length of bone 96% of width; dentigerous area covering whole occlusion surface; 19 teeth in posterior row, 17 on median row.Lateral marginal teeth smaller on caudal half of plate; posteromedial teeth much larger, cylindrical with medial, blunt cusps of molariform aspect (Fig. 6d).
Vertebrae 13+16 in two cleared and stained specimens.Color in alcohol.Mature males (Fig. 10a): ground color of body pale brown above longitudinal series of scales bearing lower lateral line, becoming yellowish below pectoralfin insertion and in preventral area.Vertical bars clearly discernible along midventral surface of body, between pectoral-fin base and caudal peduncle, not discernible in caudal peduncle.Midlateral spot on scales 8-11 of upper lateral line and on two scale rows below upper lateral line.Dark band in front of dorsal-fin origin small, extending ventrally and slightly posteriorly.Head light brown, with series of dark gray markings ventral and posterior to eye and on opercle; dusky on snout and hump.Dark band covering cheek absent.Isthmus and branchiostegal membrane pale brown.Pectoral fin hyaline; pelvic fin light brown.Spinous dorsal fin and anterior portion of soft dorsal fin faint brown with narrow white stripes.Posterior portion of soft dorsal fin faint brown covered with relatively large circular white spots.Proximal two thirds of anal-fin rays with white dots.Distal third of anal fin rays and spines dark brown, without additional distinct marks.Caudal fin faint brown with circular white dots along its entire length.Color in alcohol of preserved females (Fig. 10b) and juveniles similar to that of males, but vertical bars hardly discernible.Isthmus and branchiostegal membrane light yellow, and pelvic fins hyaline.
Color in life.Ground color of dorsal region of body in males (Fig. 10c) olivaceous with longitudinal series of bright spots.
Head largely brownish green with irregular red markings on opercle and immediate posterior area.Adipose hump brown, but darker than head.Vertical bars hardly discernible.Head with series of light blue dots under and posteriorly to eye, on opercle and preopercle.Lateroventral portion of body dark yellow, more intense around pectoral-fin base; yellow pale to gray along isthmus and prepelvic region.Dorsal fin red covered with light roundish spots proximally and light stripes distally.Caudal fin red entirely covered with light roundish spots aligned between rays.Anal fin orange on base, red in middle and dusky in distal portion.Pectoral fins hyaline; pelvic fins darkly pigmented.

Etymology
Dorsal-fin spines 13*(2), 14 (11); dorsal-fin soft rays 9(5), 10(5), 11*(3).First dorsal-fin spine inserted slightly anterior to vertical line across posterior bony margin of opercle.Soft dorsal fin in young rounded, slightly pointed in adult females, reaching to or almost reaching caudalfin base.Soft dorsal fin in mature males pointed, with 3rd or 4th ray longest, reaching proximal third to distal half of caudal fin.Anal-fin with 3 spines (one specimen with 4) and 7(1), 11(8), 9*(1) soft rays.Anal-fin origin under last dorsal-fin spine or first soft ray; soft portion nearly rounded in young and females and clearly pointed in males.Pectoral fin with rounded tip in young and slightly pointed in adults; 3rd ray longest, reaching to or slightly passing vertical crossing anal-fin origin.Pelvic fin pointed, more conspicuously so in adult males; 2nd soft ray longest reaching area of anal opening in females and passing anal-fin origin in mature males.Caudal-fin margin concave.Pelvic fin dark brown.Dorsal fin faint brown with small, narrow white stripes on spiny portion and circular white spots on soft portion.Anal and caudal fins faint brown covered with circular white dots.Color in alcohol of preserved females (Fig. 12b) and juveniles not clearly distinct from that described for males.Most differences related to isthmus and branchiostegal membrane light brown, instead of dark brown as observed in males, and presence of conspicuous vertical dark band covering cheek, below eye.
Color in life.Vertical bars not visible in freshly collected mature males (Fig. 11b).Ground color of dorsal region of body in males bluish green with longitudinal series of bright spots along scale rows.Middorsal region including adipose hump dark blue.Head largely greenish blue with few red markings on cleithrum.Light blue spots below and posterior to eye, opercle and on body surface above pectoral fin.Lateroventral color bluish white with parts of vertical bars barely discernible.Dorsal fin red with white stripes in spinous portion, and along dorsal border; soft portion yellow covered with round white spots.Caudal fin yellow covered with white spots; dorsal and ventral borders red with white stripes.Most of anal fin yellow covered with white spots; distal region with white stripes.Pectoral fin hyaline; pelvic fin dark.
Distribution.Gymnogeophagus lipokarenos is found in the upper portion of the rio Uruguay drainage and its main tributaries (Fig. 1).
Etymology.From the Greek lipos, meaning fat, and from the Greek kara, meaning head, in allusion to the extremely large adipose hump of adult males (Fig. 11).A noun in apposition.
Conservation status.Gymnogeophagus lipokarenos is frequent and abundant in the upper rio Uruguay.Despite its Extent of Occurrence (EOO) is approximately 7,600 square kilometers, no specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria (IUCN, 2014).

Discussion
The rio Uruguay harbors an extraordinary richness and endemism of several fish groups such as Australoheros, Crenicichla, Cyanocharax, Hisonotus, Hypostomus, Loricariichthys and Rineloricaria (Ričan & Kullander, 2008;Lucena & Kullander, 1992;Malabarba & Weitzman, 2003;Aquino et al., 2001;Reis et al., 1990;Reis & Pereira, 2000;Ghazzi, 2008, respectively).This high richness and degree of endemism is also seen in Gymnogeophagus, with 10 of the 16 extant species of the genus occurring in the Uruguay river basin.One of them, G. lipokarenos, is endemic to the upper portion of the rio Uruguay, corresponding to the Upper Uruguay Ecoregion (Fig. 1; unit 333 - Abell et al., 2008), while G. constellatus, G. mekinos, G. meridionalis, G. missioneiro, G. pseudolabiatus, and G. tiraparae are endemic to the Lower Uruguay Ecoregion, that includes the rio Negro (Fig. 1; unit 332 - Abell et al., 2008).Three of these species (G.constellatus, G. missioneiro, and G. pseudolabiatus) have more limited distributions, being each endemic to a single tributary of the rio Uruguay and absent in the rio Negro.Limited geographic distribution is uncommon among Neotropical cichlids (Nogueira et al., 2010) and it may be related to ecological or historical constrains.It is remarkable that among the seven species of the G. gymnogenys clade occurring in the rio Uruguay (G. australis, G. constellatus, G. lipokarenos, G. mekinos, G. missioneiro, G. pseudolabiatus and G. tiraparae), only G. mekinos and G. tiraparae are found syntopically in a few places, and this may reflect habitat specificity constrains for these species.
Gymnogeophagus labiatus and G. pseudolabiatus have hyperthrophied lips, but both morphological and molecular evidences indicate this is a convergence.Lip hypertrophy is often associated with grazing rocky surfaces and with incipient species in lentic cichlids (Elmer et al., 2010;Burress et al., 2013).Whereas lip hypertrophy is common in lentic cichlids (Elmer et al., 2010), it is known in just a few lotic species, e.g., Gymnogeophagus labiatus, G. pseudolabiatus, and Crenicichla tendybaguassu.Besides the two Gymnogeophagus species, this distinct lip morphology is also seen in the South American Crenicichla tendybaguassu (rio Uruguay drainage), in Amphilophus citrinellus and A. labiatus from Central America, and Abactochromis labrosus, Chilotilapia euchilus, Haplochromis chilotes, Lobochilotes labiatus, Otopharynx pachycheilus, Placidochromis milomo, and Promelas ornatus from the East African Great Lakes.According to Burress (2015), among the sensorial and mechanical functions (Arnegard & Snoeks, 2001;Fryer, 1959;Fryer & Iles, 1972) attributed to this morphology, the most accepted hypothesis supposes an improvement of suction by sealing cracks and grooves.Others have suggested that it can also be used to extend the substrate for taste buds (Arnegard & Snoeks, 2001), mechanoreceptors (Fryer, 1959;Fryer & Iles, 1972), or protection from mechanical shocks during foraging on rocks (Greenwood, 1974).Hypertrophied lips have evolved separately and several times in cichlids in Africa, Central and South America (Burress, 2015), and this seems to be the case also for G. labiatus and G. pseudolabiatus that are found respectively inhabiting rocky bottom rivers from the laguna dos Patos and rio Tramandaí drainages and from the rio Quaraí and tributaries.Interestingly, G. constellatus, G. lipokarenos, and G. missioneiro are all found in rocky bottom environments, but do not show hyperthrophied lips.

Fig. 3 .
Fig. 3. Measurements and scale counts taken on examined specimens (modified from Reis& Malabarba, 1988, and Reis et  al., 1992): 1 -Standard length (SL), measured from anterior tip of upper lip to the hypural joint. 2 -Body depth, measured at the maximum depth.3 -Head length, measured from anterior tip of upper lip to posterior bony margin of opercle.4 -Dorsalfin base length, measured from the first spine insertion to the last soft-ray insertion.5 -Pectoral-fin length, measured from the pectoral-fin base to the tip of the longest ray.6 -Caudal peduncle depth, measured from the dorsal to the ventral margins of the caudal peduncle at the least depth.7 -Caudal peduncle length, measured horizontally from the base of the last anal-fin ray to the caudal-fin base.8 -Eye diameter, measured horizontally between orbital bony margins.9 -Interorbital width, measured at the point of least bony width.10 -Upper jaw length, measured from the anterior margin of the upper lip to the posterior tip of the maxilla.11 -Pre-orbital length, measured from the lower margin of the lachrymal (just above the maxilla) to the orbital rim.12 -Snout length, measured horizontally from the upper lip to anterior orbital rim.UL -Upper lateral line.LL-Lower lateral line.E1 -Scales in the row immediately above the row that includes the lower lateral line.DL -Scales between dorsalfin origin and upper lateral line.AL -Scales between anal-fin origin and upper lateral line.
), lack the segment from the nape to the upper orbital rim, with only the mark on the cheek persisting, which represents one synapomorphy for this clade.The second synapomorphy that allows the recognition of a monophyletic clade including G. australis, G. constellatus, G. caaguazuensis, G. gymnogenys, G. lipokarenos, G. mekinos, G. missioneiro, G. pseudolabiatus and G. tiraparae is the possession of a black bar originating in the dorsal contour near dorsal-fin origin and directed downward and backward in the flank.The last character is easily observable in juveniles and usually in females of all species of the G. gymnogenys clade and allows their immediate recognition from the remainder Gymnogeophagus species.

Table 3 .
Morphometrics for Gymnogeophagus constellatus.Specimens are from MCP 10499 (holotype) and MCP 10827 (16 + 3 c&s).Ranges include holotype.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.

.
Missioneiro, a Portuguese noun meaning from the Missões region, the Jesuitic Missions of the Eighteenth century in southern Brazil and Argentina, in allusion to the distribution of this species.A noun in apposition.