A new glass tetra species of Phenacogaster from the rio Salitre , rio São Francisco drainage , Brazil ( Characiformes : Characidae )

A new species of Phenacogaster is described from the rio Salitre, a tributary of the lower middle rio São Francisco drainage. The new species can be clearly distinguished from all its congeners in having a conspicuous, broad caudal peduncle spot reaching the upper and lower margins of the peduncle with a short extension onto the middle caudal fin rays and another weaker extension over the lower lobe of the caudal fin.


Introduction
The monophyletic genus Phenacogaster Eigenmann currently comprises 22 species distributed throughout the river basins of Amazon, Orinoco, Tocantins, Paraguay, and São Francisco; the coastal rivers of northern and northeastern Brazil and the Guianas (Lucena, Malabarba, 2010;Antonetti et al., 2018); and the middle rio Paraná basin (Casciotta et al., 2003).
To date, the only species of the genus mentioned from the rio São Francisco drainage is Phenacogaster franciscoensis, which was described by Eigenmann (1911) based on specimens obtained from "Boqueiras, near mouth of Rio Porto (=Preto)" (Lucena, Malabarba, 2010).In this paper, we describe the second species of the genus from that drainage based on samples collected 21 years ago from the rio Salitre basin.

Material and Methods
Examined specimens belong to the Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre (MCP), Museu Nacional, Rio de Janeiro (MNRJ), and Museu de Zoologia da Universidade de São Paulo, São Paulo (MZUSP).Morphometric and meristic data are described following the methods described by Fink, Weitzman (1974) and Malabarba, Lucena (1995).The measurements were taken using a digital caliper on the left side of each specimen always straight-line projections between two points.Counts of vertebrae, dentary teeth, and supraneurals were taken from cleared and stained specimens (c&s) prepared using the protocol specified by Taylor, van Dyke (1985).Vertebrae of the Weberian apparatus were counted as four elements and the fused PU1+U1 considered a single element.All measurements are expressed as percentages of standard length (SL), except subunits of the head, which are expressed as percentages of head length.In the Description the frequency of each count is provided in parentheses and the count of the holotype is indicated by an asterisk.In the Results section, the catalog number of the paratypes is followed by the total number of specimens in the lot, the range of standard lengths the number of specimens that were counted and measured, and the respective range of standard lengths (in parentheses).Holotype.MZUSP 123642, 27.4 mm SL, unsexed;Brazil, Bahia, Campo Formoso, rio Salitre, on  Paratypes.MCP 53629, 5 (2 c&s), 18.2-27.5 mm SL (2, 25.5 and 26.7 mm SL), and MZUSP 51375, 63, 13.0-29.5 mm SL (8, 24.7-29.5 mm SL), same data as holotype.

Phenacogaster julliae, new species
Diagnosis.The presence of a conspicuously deep caudal peduncle spot, which reaches the upper and lower margins of the caudal peduncle, with a short extension onto the middle caudal fin rays and another weaker extension over the lower lobe of the caudal fin (Figs.1-2) helps clearly distinguish Phenacogaster julliae from all its congeners, which lack the caudal peduncle spot or the extension over the lower lobe of caudal fin.Two species of the genus inhabit areas near the distribution of Phenacogaster julliae: P. franciscoensis,   Description.Morphometric data presented in Tab. 1. Body compressed.Dorsal profile of head convex from anterior tip of upper jaw to vertical through anterior border of orbit; straight to end of supraoccipital, or slightly convex in interorbital region, and convex to origin of dorsal fin.Dorsal profile between dorsal fin origin and origin of dorsal procurrent caudal-fin rays straight or slightly concave in peduncle.Ventral profile slightly convex from tip of mandible to anal-fin origin, or straight between pelvic-fin insertion and anal-fin origin.Body profile along anal-fin base straight or slightly convex.Ventral profile of caudal peduncle straight to slightly concave.Preventral area flattened.
Mouth slightly subterminal; posterior tip of maxilla reaches midway or immediately posterior to midway along infraorbital 2. Third infraorbital small, ventral and posterior margins of third infraorbital separated from preopercle by a broad space, and ventral margin separated by a larger space.Pseudotympanum extends from region immediately ahead of first rib to posterior border of second rib.
Total vertebrae 33(2): precaudal 14(1) or 15(1), caudal 18(1) or 19(1).Supraneurals 4(2).Color in alcohol.General coloration of the body is yellowish.Laterodorsal region with brown chromatophores on the edge of scales near back and more scattered below.Lateroventral region, between origins of pectoral fins until region in the front of anal fin, is less pigmented.Chromatophores are spread and/or arranged in the form of ">" throughout the region between lateral line and anal fin, demarcating myosepta.Dorsal region of head and back of the body pigmented; pigments are principally present on the border of scales in the anterior region of smaller individuals (around 20 mm SL).Humeral spot large, conspicuous, ovate, with a pale area around it, positioned above 5th or 6th to 9th scale of lateral line, extending from the end of pseudotympanum, or immediately before, to right after 6th or 7th rib.Center of humeral spot slightly below or at horizontal line through the dorsal border of pseudotympanum.
Dark midlateral line on the body from immediately after humeral spot until the origin of caudal peduncle spot.Band of chromatophores are present throughout and above midlateral line, and below is a pale hypopigmented band.Conspicuous, deep caudal peduncle spot reaches upper and lower margins of the caudal peduncle, extending on middle caudal-fin rays and more weakly on the lower lobe of caudal fin (Figs.1-2).Anal fin with scarcer pigments, less intense in the medial region of the fin starting from 6th or 7th branched ray, leaving a pale area between the margin and the base; holotype relatively more pigmented in this area.Pectoral fin with pigments along ray margins.Pelvic fin with pigments along the rays, extremely pale, last ray pale or has significantly little pigment.Adipose fin is pale.
Sexual dimorphism.Eight specimens of 21.1-26.3mm SL exhibit retrorse bony hooks on anal-and pelvic-fin rays.Hooks on last unbranched to 7th or 11th branched anal-fin rays.One, rarely two, hooks per segment of lepidotrichia.First unbranched ray to last or penultimate branched ray of pelvic fin bearing retrorse bony hooks located along medial border of second branch and on the principal branch.One hook per segment of lepidotrichia.
Geographical distribution.Known only from the type locality (Fig. 4).
Etymology.The species name is julliae, named in honour of our granddaughter Jullia, who was born during the description of this species.
Conservation status.Phenacogaster julliae is described based on 69 specimens collected in January 1997 from the middle rio Salitre basin, about 40 km from Lage, Bahia.The rio Salitre basin is considered intermittent and is located in the lower middle rio São Francisco in an area with low rainfall index, irregular rains, and water deficit because of elevated evaporation rates (Oliveira et al., 2010).In an email from Flávio Lima in July 2018, we were informed that the species was found in a narrow stretch of the river with a noticeable aquatic vegetation, transparent water, and slow flow, alternating between shallow areas with rapid flow and other slower, deeper areas reaching a depth of about 2 m.We do not have information on current conditions of the locality; however, the rio Salitre basin, which has a history of conflict over water use, faces various threats: incompatible irrigation methods, development of soil cultivation on the banks of the rivers and lakes of dams, superficial water with a high level of salinity and pollution caused by anthropic activity (untreated sewage, among others) (FEP, 2003).Furthermore, there are transposition projects, specifially the Sertão Baiano or Eixo-Sul Canal [transposition of the rio São Francisco] that runs from the rio São Francisco, starting from the Sobradinho Reservoir to the rio Itapicuru and Jacuípe water basins, influencing some basins along this path, including the Salitre (Nemus, 2015).Considering these threats faced by the rio Salitre basin and the apparent rarity of the species, Phenacogaster julliae can be categorized as Data Deficient according to the IUCN criteria (IUCN, 2017).

Discussion
Phenacogaster julliae seems not to exceed 29.5 mm SL, the smallest size recorded among the species of the genus which can reach from 36 mm SL (P.carteri) to 61 mm SL (P.megalostictus Eigenmann).Male examined specimens of 21.1 mm SL or larger exhibit hooks on their fins, indicating that they reach sexual maturity at this size.The association between hooks and sexual maturity is recorded for various taxa in Characiformes (Lampert et al., 2004;Gonçalves et al., 2005).
Phenacogaster julliae has a pectoral fin in the larval form only in individuals less than 16 mm SL, differing from most of species of the genus, in which larval pectoral fin is present in individuals up to 20 mm SL, or even in individuals larger than 25 or 30 mm SL.Only P. franciscoensis, P. retropinna Lucena & Malabarba,and P. tegata Eigenmann (17.5,17.9,and 18.2 mm SL, respectively) have presented a totally developed fin in individuals less than 20 5 e180134 [5] mm SL.Although retention of the larval form of pectoral fin in P. julliae occurs in individuals less than 16 mm SL, distinct from other species of the genus, it still supports the proposal of the permanence of the larval fin in specimens of relatively large size as a potential synapomorphy for a clade composed of Acanthocharax Eigenmann, Acestrocephalus Eigenmann, Charax Scopoli, Cynopotamus Valenciennes, Galeocharax Fowler, Phenacogaster, and Roeboides Günther in accordance with that suggested by Lucena (1998).According to Weitzman, Vari (1987), many Characidae convert from the larval form of pectoral fin to an adult form when they reach 6 to 9 mm SL.
New Phenacogaster from the São Francisco drainage