Three new species of the ‘ Geophagus ’ brasiliensis species group from the northeast Brazil ( Cichlidae , Geophagini )

Morphological characters and phylogenetic trees generated by analyses of segments of two mitochondrial genes cytochrome b and cytochrome c oxidase I support recognition of three new species of the ‘Geophagus’ brasiliensis species group from coastal basins of northeast Brazil. All new species were diagnosed by exclusive morphological characters and exclusive nucleotide transformations. Geophagus rufomarginatus sp. n., from the Rio Buranhém Basin, is distinguished from all other species of the group by dorsal-fin lappets with red edges, the presence of longitudinal series of small light blue spots between the anal-fin spines and rays, and non-denticulated gill-rakers; it is closely related to G. brasiliensis and G. iporangensis. Geophagus multiocellus sp. n., from the Rio de Contas Basin, is distinguished from all other species of the group by having small pale blue spots with minute bright blue dots at their centres, that are often vertically coalesced to form short bars on the caudal fin. Geophagus santosi sp. n., from the Rio Mariana Basin, is distinguished from all other species of the group by having blue stripes parallel to the dorsal and anal fin rays on their longest portions. Geophagus multiocellus and G. santosi belong to the same clade of G. itapicuruensis. The clade composed by the Rio Paraguaçu Basin species was recovered as the sister group of the other species of the ‘G.’ brasiliensis species group.


Introduction
The Atlantic Forest is a biodiversity hotspot biome which has suffered degradation and drastic reduction throughout the history of human occupation and development of economic activities (Myers et al. 2000).Consequently, many components of its endemic biodiversity are currently under threat of extinction.This South American natural province (Morrone 2006) shows a high rate of endemism in its remaining fragments (Myers et al. 2000), harboring some endemic species of freshwater fishes, including cichlids (Kullander 2003, Lucena and Kullander 2006, Ottoni 2013, Ottoni and Costa 2008).
The cichlid tribe Geophagini is broadly distributed in South America and presents the greatest diversity among tribes of Neotropical cichlids, comprising 15 genera (López-Fernández et al. 2010).Included species occupy a wide range of ecological niches and exhibit remarkable morphological and behavioural adaptations (López-Fernández et al. 2013, Arbour andLópez-Fernández 2014).The type genus Geophagus Haeckel, 1940 has been diagnosed by the morphology of vertebrae, comprising the presence of epipleural ribs on caudal vertebrae, which are associated with expansions of the swim bladder, and caudal vertebrae more numerous than abdominal (Kullander 1986).However, these morphological features are not shared by all species of the genus.Presently, the genus has been divided into three species groups (Kullander 1998;López-Fernández and Taphorn 2004).Species that fit Kullander's (1986) generic diagnosis were assembled into the Geophagus sensu stricto species group, which includes the type species of the genus Geophagus altifrons Haeckel, 1840 and other species distributed in northern South America, including the Amazonas, Orino-co and Parnaíba river basins.Nevertheless, two species groups do not have those morphological characteristics: the 'Geophagus' steindachneri species group, with a trans-Andean distribution between southern Panama and Maracaibo lake region in Venezuela, and the 'Geophagus' brasiliensis species group, geographically widespread in eastern South America, mostly in the Atlantic Forest (Kullander 2003, Mattos et al. 2015).Recent phylogenetic studies (López-Fernández et al. 2010, Ilves et al. 2017) indicate that these three species groups together do not form a monophyletic lineage, and consequently, authors when describing new species of the last two groups have tentatively assigned them to 'Geophagus', thus using the genus name between apostrophes to designate their uncertain position (Kullander 1998, López-Fernández et al. 2010, Ilves et al. 2017).
Currently, the 'G.' brasiliensis species group comprises five valid species (Kullander 2003;Mattos et al. 2015): G. iporangensis Haseman, 1911, from the Rio Ribeira do Iguape Basin; G. itapicuruensis Haseman, 1911, from the Rio Itapicuru Basin;G. obscurus (Castelnau, 1855), from the coastal section of the Rio Paraguaçu Basin (Lucena and Kullander 2006); G. diamantinensis Mattos, Costa & Santos, 2015 from the upper section of the Rio Paraguaçu Basin; and 'G.' brasiliensis, occurring in a broad area along the coastal basins between Bahia state, northeast Brazil, and the La Plata province, northeast Argentina (Kullander 2003, Mattos et al. 2015).The distribution of this species group covers a broad area of the Atlantic Forest and a small area of the Caatinga, a semiarid northeast Brazilian biome (Mattos et al. 2015).This study is the first analysis in which all valid species of the 'G.' brasiliensis species group were sampled and analysed in a molecular phylogenetic framework, besides including populations of three unidentified species from the Atlantic Forest of northeast Brazil exhibiting unique morphological features, which are herein recognised and described as new.

Material
Measurements and counts follow Kullander (1986Kullander ( , 1990) ) and Kullander & Nijssen (1989).Measurements are presented as percentages of standard length (SL), except subunits of head, which are presented as percentages of head length (HL).Osteological preparations (C&S) were made according to Taylor and Van Dyke (1985).Osteological nomenclature follows Costa (2006).Material examined is deposited in the following ichthyological collections: Ichthyology collection of the Center for Agrarian and Environmental Sciences, Chapadinha (CICCAA); Museu Nacional, Rio de Janeiro (MNRJ); Institute of Biology, Federal University of Rio do Janeiro, Rio de Janeiro (UFRJ); Museum of Zoology of the State University of Feira de Santana, Feira de Santana (UEFS).Comparative material is listed in Mattos et al. (2015).The distribution map was generated using QGIS Geographic Information System, Open Source Geospatial Foundation Project, and the information of this map was based on our examined material and data provided by Mattos et al. 2015.Specimens were euthanized by immersion in a buffered solution of tricaine methane sulphonate (MS-222) at a concentration of 250 mg/L, for a period of 10 minutes, following the guidelines of the Journal of the American Veterinary Medical Association (AVMA Guidelines) (Leary et al. 2013) and European Commission DGXI consensus for fish euthanasia (Close et al. 1996(Close et al. , 1997)).Tissue specimens for molecular analysis (DNA) were fixed and preserved in absolute ethanol just after collection.

Species delimitation
The species delimitation methodology followed in this study aims to fulfil goals of integrative taxonomy.The character-based methodology for species delimitation was the Population Aggregation Analysis.It employs a unique combination of morphological character states to diagnose species.This method of species delimitation was formally described by Davis and Nixon (1992).
The PAA applied for molecular data in this study aimed the unique substitution nucleotide for each gene analysed (Costa and Amorim 2014, Costa et. al. 2014, Costa et. al. 2017).The character-state optimization among the 'G.' brasiliensis species group and another included genus were performed using PAUP4 by most parsimonious reconstruction method (Swofford 1993).The relative numeric position was determined for each transformation through sequence alignment with the complete mitochondrial genome of Astronotus ocellatus (Agassiz, 1831) (Mabuchi et al. 2007).Plesiomorphic state for each species was presented before arrow and apomorphic state after the arrow.
The tree-based approach used for molecular data was proposed by Wiens and Penkrot (2002), in which species are delimited through well supported clades of haplotypes with concordant geographic distribution.The significance of the branches for species delimitation was evaluated by the support values, bootstrap values equal or higher than 70% as significant (Hillis and Bull 1993) and posterior probability of the branches values equal or higher than 0.95 as significant (Alfaro and Holder 2006).

DNA extraction, amplification and sequencing
Total genomic DNA was extracted from muscular tissue of the right side of the caudal peduncle using the DNeasy Blood & Tissue Kit (Qiagen).Sequence fragments of cytochrome b (CYTB) with 1,100 bp and cytochrome c oxidase I (COI) with 680 bp were obtained.To amplify these DNA fragments, we used primers available in the literature (Farias et al. 2001).Polymerase chain reaction (PCR) was performed in 50 µl reaction mixtures containing 5× Green GoTaq Reaction Buffer (Promega), 3.2 mM MgCl2, 1 µM of each primer, 75 ng of total genomic DNA, 0.2 mM of each dNTP and 1U of Taq polymerase.The thermocycling profile was: (1) 1 cycle of 4 minutes at 95 °C; (2) 35 cycles of 1 minute at 92 °C, 1 minute at 48-50 °C and 1 minute at 72 °C; and (3) 1 cycle of 4 minutes at 72 °C.Negative controls were used to check DNA contamination in all PCR reactions.Amplified PCR products were purified using the Wizard SV Gel and PCR Clean-Up System (Promega).Sequencing reactions were made using the BigDye Terminator Cycle Sequencing Mix (Applied Biosystems).Cycle sequencing reactions were performed in 10 µl reaction volumes containing 1 µl BigDye 2.5, 1.55 µl 5× sequencing buffer (Applied Biosystems), 2 µl of the amplified products (10-40 ng), and 2 µM of primer.The thermocycling profile was 30 cycles of 10 seconds at 96 °C, 5 seconds at 54 °C and 4 minutes at 60 °C.The sequencing reactions were purified, and the samples were run on an ABI 3130 Genetic Analyzer.

Phylogenetics analysis
Sequences were edited using MEGA 6.0 (Tamura et al. 2013) and aligned using ClustalW (Chenna et al. 2003); subsequently sequences were translated into amino acids residues to verify the absence of premature stop codons or indels.The best-fit model of sequence evolution was calculated by JModelTest 2.1.7(Darriba et al. 2012), which provided the same evolutive model for both genes fragments, General Time Reversible (Nei and Kumar 2000), with 5 rate categories and by assuming that a certain fraction of sites is evolutionarily invariable.
Phylogenetic analyses were performed using PAUP4 for maximum parsimony (MP), MrBayes v.3.2.1 (Ronquist et al. 2012) for Bayesian inference (BI) and GAR-LI v.2.0 (Zwickl 2006) for maximum likelihood (ML) methods for the mitochondrial concatenated dataset.MP was performed with branch-and-bound search algorithm; and tree branch support was given by bootstrap analysis, using a heuristic search with 1000 replicates and the same settings used in the MP search.ML searches for the best tree were performed in five independent replications with at least 10,000 generations, since no topology improvement was observed by adding more generations.ML tree branch support was calculated with 1000 nonparametric bootstrap replicates (Felsenstein 1985).BI was performed with the following settings: two Markov chain Monte Carlo (MCMC) runs of four chains each for 30 million generations, a sampling frequency of 1000.All parameters between partitions except topology and branch lengths were unlinked.The convergence of the MCMC chains were graphically assessed by evaluating the stationary phase of the chains using Tracer v. 1.5 (Rambaut et al. 2014).Consensus topology and posterior probabilities were obtained after applying a burn-in of the first 25% of the generated trees.
The molecular data matrix includes 27 terminal taxa of in-group terminals representing twelve populations scattered throughout the eastern range of the 'G.' brasiliensis specie group distribution, including topotypes of all species.List of ingroup specimens and respective Gen-Bank accession numbers are shown in Table 1.Outgroups comprise seven species of five Geophagini genera closely related to the 'Geophagus' brasiliensis species group (Smith et al. 2008, López-Fernández et al. 2010)
In addition, G. rufomarginatus is also distinguished from all other species of 'G.Side of head covered with cycloid scales, ventral surface of head and snout without scales.Chest, trunk and caudal peduncle covered with ctenoid scales.Scales on head smaller than scales on chest and flank.Dorsal and anal fins without scales.About one fourth of caudal fin covered with small, delicate scales.Two scale rows between lateral lines.Scales of dorsal-fin origin row 5; scales of anal-fin origin row 6; longitudinal series of scales 26; cheek scale row 5; upper lateral line scales 18, lower lateral line scales 11 + 2; circum-peduncular scale rows 16.
Premaxillary teeth conical, hyaline with red tip, slightly curved posteriorly; one regular outer row of teeth, increasing in size on symphysis; proximal teeth smaller and irregularly arranged.Dentary teeth with similar arrangement, but slightly smaller.Five branchiostegal rays.Urohyal with strong anterior constriction.Gill-rakers on first branchial arch: first ceratobranchial 12, articulation 1, first epibranchial 9. Ceratobranchial rakers short, blunt and denticulated, except on fourth ceratobranchial proximal margin and fifth ceratobranchial distal margin, conical and non-denticulated.Anterior teeth of third pharyngobranchial and fifth ceratobranchial small, thin and slightly curved anteriorly, proximal posterior teeth large, robust and circular in cross section.Distal posterior teeth of the fifth ceratobranchial laterally compressed and with one or two cuspids.Five dentigerous plate on fourth pharyngobranchial.Fifth ceratobranchial subtriangular, with concave posterior margin.One supraneural.Prox-imal radial of dorsal fin 25 + 1; proximal radial of anal fin 10 + 1; pleural ribs 13, epipleural ribs 12; vertebrae 14 + 14.

Colouration in life.
Flank yellowish brown with seven broad dark brown bars and one dark brown longitudinal stripe; dark brown bars and stripe often overlapped and without visible limits in live specimens, conspicuously delimited in preserved specimens.Pale blue iridescence on anteroventral portion of flank and small metallic blue dots on centre of scales of middle portion of flank and caudal peduncle.Rounded dark brown spot on fifth trunk bar, sometimes inconspicuous in live specimens; similar and smaller spot on middle of posterior portion of caudal peduncle.Oblique iridescent blue zone between humeral region and anterior portion of dorsal-fin base.Dorsum yellowish brown, chest and belly pinkish white.
Head greyish brown with ventral region lighter, branchiostegal region light red.Infra-orbital area with small metallic blue dots, most of them coalesced.Opercular region background colour yellowish brown.Opercular and temporal regions with few elliptical, small and large metallic blue spots spread through opercle.Iris golden brown, with dark brown bar through orbit not aligned to any portion of supra-orbital and infra-orbital stripes.Dark brown supra-orbital stripe extending from nape to posterodorsal margin of orbit, and dark brown infra-orbital stripe, approximately vertical, running between ventral margin of orbit and preopercle angle.Dorsal fin brownish yellow on basal portion, becoming reddish orange on distal and posterior portions, with metallic blue dots aligned between rays; marginal lappets with red edges; dark brown pigmentation concentrated at first two dorsal-fin spines.Anal fin reddish orange with small metallic blue spots, to brownish yellow with metallic blue lines parallel to rays and spine on anteriormost portion of fin; intense blue iridescence on distal portion of anal fin.Caudal fin reddish orange, to brownish yellow on posterodorsal corner, with small metallic blue rounded dots, vertically coalesced to form metallic blue bars on anterior portion; posterior margin dark bluish grey.Pectoral fin yellowish hyaline.Pelvic-fin spine light yellowish brown, anterior pelvic-fin rays light yellowish brown with metallic bluish stripes parallel to rays, region around last rays hyaline.
Colouration in alcohol.Similar to colouration in life, except for metallic marks becoming dark brown on flank and light grey on fins; red and dark brown pigmentation fainted.
Distribution.Known only from the middle and lower sections of the Rio Buranhém Basin, at altitudes of about 65 m above sea level or less, Bahia state, northeast Brazil (Fig. 3).

Etymology.
From the Latin marginatus (edge, border, margin) and rufo (red), an allusion to the colour pattern in life of the dorsal-fin lappets.Diagnosis.Geophagus multiocellus is distinguished from all other species of the 'G.' brasiliensis group by having small pale blue spots with minute bright blue dots on its centre, often vertically coalesced to form short bars on the caudal fin (vs.never a similar pattern).In addition, it is distinguished from G. rufomarginatus, G. obscurus and G. santosi by the absence of an oblique iridescent blue zone between humeral region and anterior portion of dorsal-fin base (vs.iridescent blue zone present); from G. rufomarginatus by having dorsal-fin lappets with grey or dark brown edges (vs.red); presence of denticles on gill-rakers of the first branchial arch (vs.absence); absence of longitudinal series of small light blue spots between anal-fin spines and rays (vs.presence); from G. santosi by having blue bands crossing anal-fin rays (vs.blue bands parallel to fin rays); from G. itapicuruensis by having XIV dorsal-fin spines (vs.XIII); lateral spot rounded (vs.elliptical); absence of a horizontal dark brown band on snout (vs.presence); and from G. brasiliensis by having longitudinal blue bands crossing the anal-fin rays (vs.transversal blue bands crossing the analfin rays); mouth subterminal (vs.subdorsal).
Geophagus multiocellus is also distinguished from all other species of the 'G.' brasiliensis group by ten unique  3. Medium sized species, largest specimen examined 102.9 mm SL.Body relatively slender and compressed.Dorsal profile slightly convex on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle; no adipose nuchal protuberance.Ventral profile convex from lower jaw to pelvic-fin insertion, nearly straight between belly and insertion of first anal-fin spine, about straight on anal-fin base, gently concave on caudal peduncle.Caudal peduncle approximately as deeper as long.Greatest body depth slightly anterior to first dorsal-fin spine insertion.Snout moderately pointed; nostrils located between tip of snout and anterior margin of orbit.Mouth subterminal, distal tip of maxilla not reaching vertical through anterior margin of orbit.Lower lip fold Tip of pelvic fin pointed, short, reaching insertion of 3rd anal-fin spine in larger specimens; shorter and rounded in specimens 50.0 mm SL or smaller, reaching between urogenital papilla and insertion of first anal-fin spine.Pelvic-fin filaments absent.Anal-fin origin at vertical between insertion of 13th dorsal-fin spine and 1st dorsal-fin ray.Dorsal fin XIV-XV + 11-12 (26); anal fin III + 8-9 (26); pectoral-fin rays 14-15 (26); pelvic fin I + 5 (26).Caudal-fin rays vi + 16 + iii (4).

Description. Morphometric data appear in Table
Side of head covered with cycloid scales, ventral surface of head and snout without scales.Chest, trunk and caudal peduncle covered with ctenoid scales.Scales on head smaller than scales on chest and flank.Dorsal and anal fins without scales.About one fourth of caudal fin covered with small delicate scales.Two scale rows between lateral lines.Scales of dorsal-fin origin row 5; scales of anal-fin origin row 6; longitudinal series of scales 26; cheek scale row 5; upper lateral line scales 18, lower lateral line scales 11 + 2; circum-peduncular scale rows 16.
Premaxillary teeth conical, hyaline with red tip, slightly curved posteriorly; one regular, outer row of teeth, increasing in size on symphysis; proximal teeth smaller and irregularly arranged.Dentary teeth with similar arrangement, but slightly smaller.Five branchiostegal rays.
Urohyal with strong anterior constriction.Gill-rakers on first branchial arch: first ceratobranchial 11, articulation 1, first epibranchial 8. Ceratobranchial rakers short, blunt and denticulated, except on fourth ceratobranchial proximal margin and fifth ceratobranchial distal margin, conical and non-denticulated.Anterior teeth of third pharyngobranchial and fifth ceratobranchial small, thin and slightly curved anteriorly, posterior teeth larger, robust and circular in cross section.Distal posterior teeth of the fifth ceratobranchial laterally compressed and with one or two cuspids.Five or six dentigerous plate on fourth pharyngobranchial, with three or four fused.Fifth ceratobranchial subtriangular, with concave posterior margin.One supraneural.Proximal radial of dorsal fin 25 + 1; proximal radial of anal fin 8 + 1; pleural ribs 12; epipleural ribs 12; vertebrae 14 + 14.

Colouration in life.
Flank greyish brown with seven broad dark brown bars and one dark brown longitudinal stripe; dark brown bars and stripe often overlapped and without visible limits in live specimens, conspicuously delimited in preserved specimens.Longitudinal rows of golden spots on ventral part of flank, between pectoral-fin insertion and caudal-fin base; spots approximately occupying ventral half-length of scales.Rounded dark brown spot on fifth trunk bar, similar and smaller spot on middle of caudal peduncle.Humeral region with three metallic blue spots arranged in oblique row.Dorsum greyish brown, chest and belly greyish white.
Head greyish brown, ventral region lighter, branchiostegal region greyish white.Infra-orbital area with oblique row of small metallic greenish blue spots.Opercular region background colour greyish brown.Absence or up to five small elliptical metallic greenish blue spots spread through opercle.Iris golden brown, with greenish blue iridescence on anterior and posterior portions, and dark brown bar through orbit aligned with sub-orbit-  al stripe.Pale brown supra-orbital stripe extending from dorsal profile to postero-dorsal margin of orbit, and dark brown infra-orbital stripe, approximately vertical, running from ventral margin of orbit to sub-opercle.Dorsal fin brownish red; anterior portion with short, oblique metallic blue stripes, posterior region with transverse rows of small pale blue spots; dark brown pigmentation con-centrated at first two dorsal-fin spines and distal half of third spine.Anal fin brownish red, with oblique metallic blue stripes, posterior-most region with longitudinal rows of small, elongated pale blue spots.Caudal fin brownish red with small pale blue spots with minute bright blue dots on its centre, often vertically coalesced to form short bars.Pectoral fin pale yellowish hyaline.Pelvic-fin spine light yellowish brown, anterior pelvic-fin rays light yellowish brown with metallic bluish stripes parallel to rays, region around last rays hyaline.
Colouration in alcohol.Similar to colouration in life, except for metallic blue marks becoming dark brown on flank and light grey on fins; red and dark brown pigmentation faded.
Distribution.Known only from the middle section of the Rio de Contas Basin, in altitudes between about 270 and 545 m above sea level, Bahia state, northeast Brazil (Fig. 3).

Etymology.
From the Latin multum (several) and ocellus (little eyes, jewels), an allusion to the presence of small pale blue spots with minute bright blue dots on its centre on the caudal fin.

Geophagus santosi sp. n.
http://zoobank.org/AEAE1FF0-0A2C-4F98-B9C3-8F5EBAC8AA6DDiagnosis.Geophagus santosi is distinguished from all other species of the 'G.' brasiliensis group by having dorsal and anal fins with blue stripes parallel to fin rays on their longest portion (vs.transverse blue bands crossing rays or fins with dots), and basal portion of caudal-fin with short, longitudinal bluish-white lines (vs.dots or bars).Geophagus santosi is similar to G. rufomarginatus and G. obscurus, and distinguished from all other species of the 'G.' brasiliensis group, by the presence of an oblique iridescent blue zone between the humeral region and the anterior portion of the dorsal-fin base (vs.absence of an iridescent blue zone).Furthermore, it is also distinguished from G. obscurus by the presence of an oblique suborbital row of aligned, small iridescent blue marks, not extending to cheek (vs.suborbital iridescent blue marks irregularly arranged extending to the cheek) and chest profile straight in lateral view (vs.convex); from G. rufomarginatus by possessing dorsal-fin lappets with grey or dark brown edge (vs.red) and presence of denticles on the first branchial arch gill-rakers (vs.absence); from G. itapicuruensis by having XIV spines on dorsal fin (vs.XIII) and lateral spot rounded (vs.elliptical); from G. diamantinensis by the absence of a dark brown mark on the humeral region (vs.presence), absence of a horizontal dark brown band on the snout (vs.presence), and urohyal bone with strong constriction (vs.with gentle anterior constriction); and from G. brasiliensis by having a terminal mouth (vs. sub-dorsal).

Description. Morphometric data appear in
Side of head covered with cycloid scales, ventral surface of head and snout without scales.Chest, trunk and caudal peduncle covered with ctenoid scales.Scales on head smaller than scales on chest and flank.Dorsal and anal fins without scales.About one fifth of caudal fin covered with small delicate scales.Two scale rows between lateral lines.Scales of dorsal-fin origin row 4; scales of anal-fin origin row 5; longitudinal series of scales 26-27; cheek scale row 5; upper lateral line scales 18, lower lateral line scales 9-11 + 2; circum-peduncular scale rows 16.
Premaxillary teeth conical, hyaline with red tip, slightly curved posteriorly; one regular, outer row of teeth, increasing in size on symphysis; proximal teeth smaller and irregularly arranged.Dentary teeth with similar arrangement, but slightly smaller.Five branchiostegal rays.Urohyal with strong anterior constriction.Gill-rakers on first branchial arch: first ceratobranchial 10, articulation 1, first epibranchial 8. Ceratobranchial rakers short, blunt and denticulated, except on fourth ceratobranchial proximal margin and fifth ceratobranchial distal margin, conical and non-denticulated.Anterior teeth of third pharyngobranchial and fifth ceratobranchial small, thin and slightly curved anteriorly, posterior teeth large, robust and circular in cross section.Distal posterior teeth of the fifth ceratobranchial laterally compressed and with one or two cuspids.Five or six dentigerous plate on fourth pharyngobranchial, two of them could merge.Fifth ceratobranchial subtriangular, with concave posterior margin and robust.One supraneural.Proximal radial of dorsal fin 24 + 1; proximal radial of anal fin 10 + 1; pleural ribs 12, epipleural ribs 11; vertebrae 14 + 14.

Colouration in life.
Flank orangish brown with seven broad dark brown bars and one dark brown longitudinal  Head side dark orange, ventral surface white; branchiostegal region dark orangish grey.Infra-orbital area with row of four to six small metallic greenish blue dots, sometimes two or three dots coalesced.Opercular region background orangish brown; opercular and temporal regions with scattered metallic greenish blue spots.Iris yellowish brown, with greenish blue iridescence on anterior and posterior portions, and dark brown bar through orbit not aligned to supra-orbital and infra-orbital stripes.Dark brown supra-orbital stripe extending from nape to postero-dorsal margin of orbit, and dark brown infra-orbital stripe, approximately vertical, running between ventral margin of orbit and pre-opercle angle.Dorsal fin pale brown on anterior portion, pale yellow on middle, pale orange on posterior region; oblique series of elongate drop-shaped metallic green spots on anterior two thirds of fin, light blue stripes parallel to fin rays on longest region of fin, and longitudinal rows of rounded light blue spots on posterior portion of fin; dark brown pigmentation most concentrated at first two dorsal-fin spines and distal half of third spine.Anal fin reddish orange, to yellowish orange on basal portion, with longitudinal metallic blue stripes between rays, and metallic blue spots on posterior region.Caudal fin reddish orange with transverse rows of small bluish white spots often coalesced to form narrow bars; basal portion of fin light yellowish orange with short, longitudinal bluish white lines.Pectoral fin pale orangish hyaline.Pelvic-fin spine light orangish brown, anterior pelvic-fin rays light orangish brown with metallic greenish blue stripes parallel to rays, region around last rays hyaline.
Colouration in alcohol.Similar to colouration in life, except for metallic marks becoming dark brown on flank and light grey on fins; red and dark brown pigmentation fainted.
Distribution.Known only from the Rio Mariana, an isolated small coastal river of Bahia state, northeast Brazil (Fig. 3).
Etymology.The name santosi is in honour of Alexandre Clistenes Alcântara Santos, ichthyologist and friend, who is dedicated to the study of aquatic ecosystems of northeast Brazil.

Discussion
This study demonstrated that short fragments of the mitochondrial genome, with a total of 1780 bp, were enough to produce phylogenetic trees strongly supporting mutually exclusive lineages designated as species, as well as recognizing species clades with high support values (Fig. 1).However, presently no morphological character is known to unambiguously diagnose those clades.
Among the three main clades of the 'G.' brasiliensis species group, the two species endemic to the Rio Paraguaçu Basin, G. diamantinensis and G. obscurus, form a well-supported basal clade (clade A), restricted to semiarid areas of northeastern Brazil (Figs. 1 and 3).Interestingly, the analyses support another clade endemic to northeastern Brazil, between about 11° and 15° S, comprising G. itapicuruensis + G. santosi + G. multiocellus (clade B) that is sister to a geographically disjunct clade comprising G. brasiliensis + G. rufomarginatus + G. iporangensis (clade C), occurring in a vast area between about 16° and 35° S.Although a biogeographic analysis is beyond the scope of this study, the occurrence of two distinct basal lineages in northeastern Brazil, highly suggests that the most recent common ancestor of the 'G.' brasiliensis species group was geographically restricted to northeastern Brazil.
The analyses also indicated that the main clades of the 'G.' brasiliensis species group cannot be associated with specific biomes or phytogeographical provinces, in contrast to that recently reported for fish groups inhabiting temporary pools (Costa et al. 2017).Although the two species of the clade A being endemic to a semi-arid Caatinga area, only G. itapicuruensis inhabits a typical Caatinga area among species of the clade B. The other species of the clade C, G. santosi and G. multiocellus, are found in a transitional area of the Atlantic Forest known as Agreste.On the other hand, species of the clade C are found in different biomes such as Atlantic Forest, Cerrado and Pampas.Palynological studies have demonstrated a succession of different vegetation formations along the Pleistocene/Holocene of northeastern Brazil (Oliveira et al. 1999).Since members of different lineages of the 'G.' brasiliensis species group are presently found in habitats such as rain forests and semi-arid regions, we conclude that vegetation changes following different climatic periods may have not affected fishes inhabiting rivers.

Figure 1 .
Figure 1.Tree topology estimated by Bayesian inference analysis for the 'Geophagus' brasiliensis species group.Numbers before terminal species names are voucher numbers.Numbers above branches indicates Bayesian posterior probabilities and below bootstrap values of the Maximum Parsimony and Maximum Likelihood analyses, respectively, separated by bar.Dashes indicate values below 50 and asterisks indicate maximum support values.
' brasiliensis group by 13 unique nucleotide substitutions: COI 285 (T > C), COI 330 (T > C), COI 333 (T > C), COI 591 (A > C), COI 642 (C > T), CYTB 60 (C > T), CYTB 129 (C > T), CYTB 186 (C > T), CYTB 309 (C > T), CYTB 324 (A > G), CYTB 886 (T > C), CYTB 906 (A > G), CYTB 958 (C > T); it is similar to G. iporangensis and G. brasiliensis and distinguished from all other species of the 'G.' brasiliensis group by four unique nucleotide substitutions: COI 700 (T > C), CYTB 165 (C > T), CYTB 582 (A > G), CYTB 1078 (A > C).Description.Morphometric data appear in Table 2. Medium sized species, largest specimen examined 104.2 mm SL.Body relatively slender and compressed.Dorsal profile slightly convex on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle; no adipose nuchal protuberance.Ventral profile straight to slightly convex from lower jaw to pelvic-fin insertion, slightly convex between belly and end of anal-fin base, nearly straight on caudal peduncle.Caudal peduncle approximately as deeper as long.Greatest body depth at level of first dorsal-fin spine.Snout moderately pointed; nostrils located between tip of snout and anterior margin of orbit.Mouth subterminal, distal tip of maxilla not reaching vertical through anterior margin of orbit.Lower lip fold moderately deep.Lower jaw slightly shorter than upper one.Eye near dorsal profile of head.Opercle not serrated.Insertion of first dorsal-fin spine slightly anterior to vertical line through posterior-most margin of opercle.Tip of dorsal-fin pointed, reaching 30-90% of caudal-fin length, shorter and rounded in specimens 40.0 mm SL or smaller.Tip of anal fin pointed, reaching 30-50% of caudal-fin length, shorter and rounded in specimens 43.0 mm SL or smaller.Caudal fin subtruncate.Pectoral fin trapezoidal with rounded extremity, posterior margin posteriorly surpassing flank blotch.Tip of pelvic-fin pointed, short, reaching insertion of 1st anal-fin spine in larger specimens, shorter and rounded in specimens 50.0 mm SL or smaller, reaching between urogenital papilla and insertion of first anal-fin spine.Pelvic-fin filaments absent.Anal-fin origin at vertical between insertion of 13th dorsal-fin spine and 1st dorsal-fin ray.Dorsal fin XIV + 12-13 (23); anal fin III + 9-10 (23); pectoral-fin rays 15 (23); pelvic fin I + 5 (26).Caudal-fin rays iv + 16 + iv (5).

Table 1 .
Vouchers and GenBank accession numbers for new sequenced material of Geophagus.

Table 2 .
Morphometric data of G. rufomarginatus.H, holotype; SD, standard deviation.Values of holotype included in range.

Table 3 .
Morphometric data of G. multiocellus.H, holotype; SD, standard deviation.Values of holotype included in range.

Table 4 .
Medium sized species, largest specimen examined 164.3 mm SL.Body relatively slender and compressed.Dorsal profile slightly convex on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle; no adipose nuchal protuberance.Ventral profile convex from lower jaw to pelvic-fin insertion, gently straight between belly and insertion of first anal-fin spine, nearly straight on anal-fin base, nearly concave on caudal peduncle.Caudal peduncle slightly longer than deep.Greatest body depth at level of first dorsal-fin spine insertion.Snout moderately pointed; nostrils located between tip of snout and anterior margin of orbit.Mouth subterminal, distal tip of maxilla not reaching vertical through anterior margin of orbit.Lower lip fold moderately deep.Lower jaw slightly shorter than upper one.Eye near dorsal profile of head.Opercle not serrated.

Table 4 .
Morphometric data of G. santosi.H, holotype; SD, standard deviation.Values of Holotype included in range.