A new species of Gymnogeophagus Miranda Ribeiro from Uruguay ( Teleostei : Cichliformes )

We describe a new species of a substrate-brooding Gymnogeophagus, based on coloration characters. The new species can be distinguished from the remaining substrate-brooding species in the genus by the unique pigmentation of the dorsal fin which consists of light blue, diagonal stripes over a red background in the spiny section and a combination of round, elliptic, and elongated bright blue spots over a red background in the soft section. It can be further distinguished from all other species of Gymnogeophagus by the following combination of characters: a discontinuous bright blue band above the upper lateral line in the humeral area, light blue roundish spots over a red to orange background on the anal fin, and conspicuous bright blue horizontal bands on body. The new species inhabits a wide range of freshwater habitats in the lower rio Uruguay basin, Rio de la Plata coastal drainages and Atlantic Ocean coastal drainages in Uruguay.


Introduction
Neotropical cichlids are among the most diverse fish taxa in the Neotropics (Kullander, 2003) and represent an ecologically diversified clade (López-Fernández et al., 2005a, 2005b, 2010).New phylogenies of teleosts, which changed the position of cichlids within the acanthomorph tree (i.e.Near et al., 2012;Betancur-R. et al., 2013), have increased interest in their evolutionary innovations and homologies.Moreover, due to their high evolutionary and ecological diversification rates (López-Fernández et al., 2013;Astudillo-Clavijo et al., 2015;Seehausen, 2015) cichlids are useful models to study ecomorphological diversification mechanisms (Winemiller et al., 1995;Burress, 2015).Among Neotropical cichlids the Geophagini is the most diversified clade, not only in species number but also in morphology, ecology, and behavior.However, as in many other freshwater fish clades, knowledge of species diversity remains incomplete (Kullander, 2003), and phylogenetic and evolutionary hypotheses remain open.Neotropical cichlids form a monophyletic clade of which one of the most southerly distributed taxa is the geophagine genus Gymnogeophagus Miranda Ribeiro, with most species endemic to the La Plata basin, laguna dos Patos system, and rio Tramandaí drainage (Reis & Malabarba, 1988;Malabarba et al., 2013Malabarba et al., , 2015)).The only exception is a record of G. balzanii (Perugia, 1891) (CAS 48828) from the rio Guaporé in the Amazon basin, that is connected to the headwaters of the rio Jauru of the rio Paraguay drainage (Lowe-McConnell, 1975: 47).
Gymnogeophagus species are distinguished from other cichlids by the presence of a forward-directed spine on top of the first dorsal-fin pterygiophore and by the absence of bony supraneurals (Gosse, 1976;Reis & Malabarba, 1988;Wimberger et al., 1998).The monophyly of the genus has been largely corroborated by morphological and molecular data (Reis & Malabarba, 1988;Wimberger et al., 1998;Pereyra & García, 2008;López-Fernández et al., 2010;Malabarba et al., 2010).However, species-level taxonomy and phylogenetic relationships, distribution patterns, and the evolutionary history of differences in reproductive behavior are still unclear.Gymnogeophagus species show contrasting reproductive strategies, with species being either mouth brooding or substrate brooding, the latter possibly forming a paraphyletic group (Wimberger et al., 1998).The substrate brooding species group is known informally as the "G.rhabdotus species group" and contains four described species: G. rhabdotus (Hensel, 1870), G. meridionalis Reis & Malabarba, 1988, G. setequedas Reis, Malabarba & Pavanelli, 1992, and G. che Casciotta, Gómez & Toresanni, 2000.The mitochondrial haplotypes of several populations of G. rhabdotus and G. meridionalis from rio Uruguay and laguna dos Patos drainages, however, do not cluster as two separate species (Wimberger et al., 1998), suggesting the existence of cryptic species in that region and/or past introgression through hybridization.
In this article we describe a new species of substratebrooding Gymnogeophagus from the middle and lower rio Uruguay basin and coastal drainages of the Río de la Plata estuary and Atlantic Ocean in Uruguay and provide a diagnosis separating it from other substrate-brooding species.This species has been previously identified as G. rhabdotus (Stawikowski, 1983), provisionally identified as "G.rhabdotus" (Yafe et al., 2002) or misidentified as G. meridionalis (Reis et al., 1992: 268, fig. 4).

Material and Methods
We examined material of the new species and comparative material from other Gymnogeophagus species belonging to the fish collections of the California Academy of Sciences, San Francisco (CAS), Departamento de Zoologia, Universidade Federal do Rio Grande do Sul (UFRGS), Facultad de Ciencias de la Universidad de la República, Montevideo (ZVC-P), Museo Nacional de Historia Natural, Montevideo (MNHN), and Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul (MCP).Additional comparisons were done using published data from Reis & Malabarba (1988), Reis et al. (1992), andCasciotta et al. (2000); coloration comparisons with G. setequedas and G. che employed color photographs provided generously by J. Casciotta and Ariel Puentes, and those available on the website Paraguay Biodiversidad (http://www.pybio.org/).Counts and measurements were taken according to Reis & Malabarba (1988) and González-Bergonzoni et al. (2009); E1 scale count refers to scales in the row immediately above that containing the lower lateral line.Cleared and stained (c&s) specimens were prepared according to Dingerkus & Ulher (1977) or Taylor & Van Dyke (1985).Differences in meristic and morphometric measures were tested using Mann-Whitney U Tests, at α=0.05 level using PAST 3.06 software (Hammer et al., 2001).

(Figs. 1-2A)
Gymnogeophagus rhabdotus, non Hensel, 1870.Stawikowski, 1983 (photo).Gymnogeophagus meridionalis, non Reis & Malabarba, 1988. Reis et al., 1992: 268 (fig. 4, same specimen figured by Stawikowski, 1983 as G. rhabdotus).Gymnogeophagus rhabdotus, non Reis & Malabarba, 1988. Yafe et al., 2002 (feeding ecology).Gymnogeophagus cf.meridionalis, non Reis & Malabarba, 1988. Pereyra & García, 2008 (mitochondrial phylogeny).Gymnogeophagus sp.Serra et al., 2014:123 (photo, distribution); 182 (diagnosed in key).Diagnosis.The number of E1 scales, (23-25 vs. 26-30), and the substrate-brooding behavior distinguishes the new species from all other Gymnogeophagus species except for G. rhabdotus, G. meridionalis, G. setequedas, and G. che.It can be differentiated from those four species by the unique pigmentation of the dorsal fin, which consists of diagonal bright blue stripes (light brown in preserved specimens) over a red background (brown in preserved specimens) in the spiny section, and a combination of round, elliptical, and elongated bright blue spots (light brown in preserved specimens) in the soft section, vs. whitish light blue round spots (white to light brown in preserved specimens) over a red background (brown in preserved specimens) in the whole fin in G. meridionalis, or diagonal whitish light blue stripes (white to light brown in preserved specimens) over a red background in the whole spiny section of the fin and the distal ¾ of the soft section in G. rhabdotus, G. setequedas, and G. che (Fig. 3).Gymnogeophagus terrapurpura can be further distinguished from G. rhabdotus by the termination of the bright blue band that runs above the upper lateral line before reaching a bright blue spot placed above the first perforated scale vs. band continuous with that spot.It can be further distinguished from G. meridionalis, G. setequedas, and G. che by the anal fin pigmentation pattern which consists of light blue rounded spots (light brown in preserved specimens) over a red to orange background (brown in preserved specimens) vs. white irregularly shaped spots over a dark red back ground in G. meridionalis (Fig. 4) or diagonal light stripes in G. setequedas and G. che (Reis et al., 1992;Casciotta et al., 2000).It is also distinguished from G. meridionalis by the absence of small clear spots between anal fin rays that reach the distal edge of the fin vs. presence of these spots (Fig. 2).Description.Meristic and morphometric data summarized in Table 1 and Table 2. Body compressed, moderately elongated.Predorsal contour slightly convex; body contour at dorsal-fin base convex, decreasing in depth to caudal peduncle.Caudal peduncle rectangular, deeper than long, dorsal and ventral profiles slightly concave.Body contour slightly convex between lower lip and last anal-fin ray, with straight segment between pelvic and anal fins.Snout pointed, nearly straight dorsally and ventrally in lateral aspect; short and anteriorly rounded in dorsal aspect.Eye small, close to dorsal profile of head; eye near middle of head length.Interorbital area convex, more strongly so in larger specimens; interorbital width larger than eye diameter.Posterior tip of maxilla not reaching vertical through anterior margin of eye.Mouth terminal, jaws isognathous.
Body scales ctenoid except for small cycloid scales mixed with ctenoid scales in preventral area.Small ctenoid scales on opercle; scales on preopercle small and cycloid.Caudal fin with small scales in single row between rays, from 5 to 7 series at level of lower lateral line and covering proximal third of fin on dorsal and ventral borders of fin.Other unpaired fins without scales.
Dorsal-fin origin anterior to vertical line through posterior bony margin of opercle, posterior end of depressed fin reaching caudal-fin base.Pectoral-fin edge at anal-fin origin.Anal-fin edge at caudal-fin base.Caudal fin truncate or slightly concave.

Geographic distribution.
Gymnogeophagus terrapurpura is distributed from the rio Arapey (in the middle rio Uruguay basin) to all tributaries of the lower rio Uruguay basin and in the eastern coastal drainages of the Río de la Plata estuary and Atlantic Ocean in Uruguay (Fig. 6).Ecological notes.Gymnogeophagus terrapurpura has been found in a large variety of habitats including shallow lakes, floodplain lakes, rivers, and streams, mainly associated with cobble, sandy or muddy substrates.Gymnogeophagus terrapurpura is an omnivore, feeding on zooplankton, macroinvertebrates, and periphyton (to a lesser extent), reducing greatly its feeding activity during autumn and winter when water temperature decreases, as described in a low-impacted lowland stream in Florida Department by González-Bergonzoni et al. (2016, named therein as "Gymnogeophagus sp.") and in a eutrophic shallow lake of Montevideo by Yafe et al. (2002, named therein as G. rhabdotus).Gymnogeophagus terrapurpura has been observed to brood on the substrate and exhibits substantial parental care, including aggressive territorial behavior in both males and females during the reproductive season, from November to January.
Etymology.The specific epithet refers to the G. E. Hudson novel "La Tierra Purpúrea" (as it is known in the Spanish translation), in which the main character makes a trip through the same region where the new species occurs.A noun in apposition.
Conservation status.Gymnogeophagus terrapurpura is relatively frequent and abundant in the rio Negro, the middle and lower rio Uruguay basin, and in the oriental coastal drainages of Río de la Plata estuary and Atlantic Ocean in Uruguay.No specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria (International Union for Conservation of Nature (IUCN), 2011).

Discussion
The new species possesses the diagnostic characters of the genus (Reis & Malabarba, 1998).Its body shape, E1 scale count, body coloration, and brooding behavior, easily place it within the substrate brooding species group.Hypothesizing affinities within the group is less straightforward.Apart from the unique elements of the coloration pattern of the dorsal fin, it shares different character states with different species.For example, it shares the pigmentation pattern of the spiny dorsal fin, consisting of diagonal light blue stripes over red background, with G. rhabdotus, G. setequedas and G. che.Although the original descriptions of the latter two species lack information on dorsal fin coloration, comparison of photos of living specimens from type localities showed that the color of their dorsal fin is indeed similar to that of G. terrapurpura and G. rhabdotus.Conversely, G. terrapurpurea shares with G. setequedas, G. che, and G. meridionalis a humeral area lacking a light blue band, while the intensity of the horizontal bright blue bands on the flanks of the new species resembles the coloration of G. rhabdotus.
Pigmentation pattern of the anal fin of the new species consists of bright blue spots over red background, which is similar to some, but not all individuals of G. rhabdotus.In G. rhabdotus, this character can even vary among individuals from the same locality.Although the anal fin in most specimens typically has diagonal stripes, round spots can be observed.Furthermore, both G. terrapurpura and G. rhabdotus vary in the shape of the blue markings of the caudal fin.In most specimens of G. rhabdotus these marks take the form of stripes, however, some individuals from different regions present round to elongated spots.The opposite pattern occurs in G. terrapurpura, in which most individuals display round spots and few individuals possess horizontal stripes.According to the original description, the anal fin pattern of G. setequedas always consists of diagonal stripes and the caudal fin lacks both stripes or rounded spots (Reis et al., 1992), while the anal fin of G. che has diagonal stripes and the caudal fin has stripes (Casciotta et al., 2000).
Because all the species in this group are very similar, complete information on fin coloration is still lacking for some of them, and several cryptic species are thought to exist (Wimberger et al., 1998).A complete morphological revision accompanied by a molecular phylogeny is needed to build a robust hypothesis of relationships of Gymnogeophagus.
There are two additional names referred to the Gymnogeophagus rhabdotus species group, G. arcoiris and G. artiguensis, described as new species from Uruguay in a manuscript first distributed as a pdf file sometime after 2004 and before 2006.Both names, however, are unpublished and unavailable because they do not satisfy the criteria from Articles 8. 1.3; 8.4; 8.5 and 78.2.4 of the International Code of Zoological Nomenclature.It is important to note that the reference to these names herein does not render them available (ICZN Article 11.5.2).
The new species has been found coexisting with G. meridionalis and G. rhabdotus throughout the rio Negro basin (Serra et al., 2014).Gymnogeophagus terrapurpura also coexists with G. meridionalis in the lower rio Uruguay drainage.It is interesting that the northern and eastern limits of the distribution of G. terrapurpura are congruent with the distribution of the characid Ectrepopterus uruguayensis (see Malabarba et al., 2012: fig.7).The northern limit of G. terrapurpura is the rio Arapey, and the species disappears abruptly in the tributaries further to the north in the rio Uruguay basin.It is also found in all the eastern tributaries of the lower rio Uruguay basin and coastal drainages of the Río de la Plata Estuary, to the laguna Castillos basin (Atlantic Ocean drainage).This distribution range is presently disrupted by the salinity barrier of the Río de la Plata estuary and Atlantic Ocean.However, during the Pleistocene the sea level was much lower (Ayup-Zouain, 2006;Bracco Boksar et al., 2011) and these systems were probably connected through an extended coastal plain allowing dispersal of freshwater fish species.In this context, most of the laguna Castillos ichthyofauna belongs to the "Patos" Ecoregion (Loureiro & García, 2006).However, G. terrapurpura, along with another "platense" Geophagine, Crenicichla scotti, share the same distribution in the basin, suggesting a complex historical biogeographic scenario and making the area potentially interesting for studying the evolution of areas of endemism.

Table 2 .
Morphometric data of Gymnogeophagus terrapurpura, G. meridionalis, and G. rhabdotus.Measurements expressed as percentages of standard length, except those marked with *, which are percentages of head length.G.terrapurpura (n = 36) G. meridionalis (n = 37) G. rhabdotus (n = 33) Color in life.Background color of dorsal region of body and head in adults light brown to olivaceous with up to seven diffuse and darker bars; first bar traversing eye from nape to ventral edge of preopercle.Black vertically elongated mid-lateral spot at third or fourth vertical band, surrounded by bright, yellow area in some specimens.Six to eight horizontal bright blue bands from behind pectoral-fin base to caudal-fin base; uppermost band interrupted in humeral region.Scales between bands red.Ventral portion of body and head light yellow to white; isthmus and branchiostegal region black in adult males and females during reproductive season.Numerous small bright blue, rounded or elongated dots usually present on cheeks, forming interrupted nearly straight line from