A new species of Bryconamericus (Characidae: Stevardiinae) with breeding tubercles from the upper rio Paraná basin

Five species of Bryconamericus are known from the upper rio Paraná basin: ‘ B. ’ aff. iheringii , ‘ B. ’ coeruleus , B. stramineus , ‘ B. ’ turiuba and the non-native B. exodon . The new species can be easily distinguished from them by its body depth (27.8– 31.8% SL) and the teeth aligned in the outer row of the premaxilla (except ‘ B. ’ aff. iheringii ). The new species is distributed in tributaries to the Piquiri, Ivaí and Tibagi rivers, at altitudes between 498 and 900 m a.s.l. The geographic distribution of the new species is similar to the congener ‘ B. ’ coeruleus . Other species with similar distribution are Apareiodon vladii and Planaltina kaingang , although they only occur in the Piquiri and Ivaí river basins. Furthermore, this work records the new species with the presence of breeding tubercles. These tubercles are located on the dorsal and lateral portions of the head and on the posterior margin of the scales of mature males; and in females, when present, they are smaller and restricted to the posterior margin of the scales. Comments are made on the presence of breeding tubercles in other groups of fishes, and also on some dimorphic characters present in the new species.

As presently understood, Bryconamericus does not have a morphological diagnosis.Thus, in the absence of phylogenetic evidence supporting the inclusion of a new species in the genus, that inclusion must be based on the possession of the combination of characters proposed by Eigenmann (1927), and modified by Vari, Siebert (1990): premaxilla with two rows of teeth, the inner row with four teeth, which are larger than those in the external row, zero to six teeth distributed along the anterior margin of the maxilla, complete lateral line, caudal fin naked, single tooth row on the dentary, setiform gill rakers, absence of a glandular pouch on the caudal fin of males, and third infraorbital expanded and in contact with the preopercle.Recent sampling efforts in the upper rio Paraná basin have yielded specimens fitting the aforementioned definition, which do not correspond to any other described species and are herein formally described as a new species of Bryconamericus.
Description.Morphometric data presented in Tab. 1. Dorsal profile of head convex from tip of snout to vertical through anterior border of nostrils, slightly convex from nostrils to dorsal-fin origin; straight from that point to adipose-fin origin, slightly concave along caudal peduncle.Ventral profile convex from tip of dentary to anal-fin origin; straight from that point to end of anal-fin, slightly concave along caudal peduncle.

Coloration in alcohol.
Ground color yellow to dark-brown (Fig. 1).Dorsal portion of head with dark brown coloration from tip of snout to posterior margin of supraoccipital, extending posteriorly as dorsal band to end of caudal peduncle; great concentration of melanophores around orbit and along posterior margin of maxilla; fewer melanophores scattered on infraorbitals, interopercle and opercle, and anterior portion of lower jaw; melanophores also on distal margin of scales, more concentrated on scales above lateral line, forming reticulated pattern; vertically elongated black humeral spot across second to fourth lateral line scale, reaching three scale rows above and one scale row below lateral line, tapering downward.Second, inconspicuous humeral spot separated from first spot by two scales; dark midlateral stripe from second humeral spot to end of caudal peduncle; caudal-fin with narrower stripe along median rays and melanophores concentrated on middle portion of lobes; dorsal and anal fins with melanophores concentrated on distal border; first unbranched dorsal-fin ray completely covered by melanophores; pectoral, pelvic and adipose fins with few scattered melanophores.
Sexual dimorphism.Pelvic-fin slightly longer and more rounded in males (Tab.1), covering completely urogenital opening in ventral view, and usually reaching anal-fin origin; pelvic-fin slightly shorter and more pointed in females, not covering urogenital opening in ventral view (Figs.4C-D).Distal border of anal-fin straight in males, slightly concave in females (Figs.4A-B).Anal-fin base slightly longer in males, preanal distance slightly longer in females (Tab.1).Sexually mature males with bony hooks on anal and pelvic fins; anal-fin hooks on last unbranched ray through fifth to ninth branched ray; pelvic-fin hooks on all rays except first; bony hooks absent in females.Sexually mature males with breeding tubercles along dorsal and lateral portion of head, and on distal border of scales (Fig. 3A).Tubercles absent in females or, if present, few and concentrated only on distal border of scales.Geographical distribution.Bryconamericus misei is known from the rio Bonito and from two small tributaries to the rio Capivara, in the rio Piquiri basin; from the rio Laranjeiras, a tributary to the rio Formoso, in the rio Ivaí basin; and from the rio Apucarana, a tributary to the rio Tibagi (Fig. 5).

Ecological notes.
At the sampling localities of Bryconamericus misei, the two tributaries to the rio Capivara, rio Piquiri basin (Figs.6A-B) are about 1-2 m wide and 0.2 m deep, and lie about 800-900 m a.s.l.One of these (Fig. 6A) is the type-locality.The rio Laranjeiras, rio Ivaí basin (Fig. 6C) is about 4 m wide and 0.3 m deep, and lies about 498 m a.s.l. at the sampling location.The bottom of both streams is composed of small stones and pebbles, and some stretches with sandy bottom.The vegetation is mainly shrubs with some grasses, and stretches of the river are protected by canopies of small trees.
Etymology.The specific name misei is a patronymic, given in honor of Fábio Teruo Mise, for his contributions to the ichthyological education of THP and for collecting part of the type-specimens of Bryconamericus misei.A noun in a genitive case.
Conservation status.Bryconamericus misei is known from tributaries to the Piquiri, Ivaí and Tibagi rivers and was collected from six different sites distributed along these basins.No threats to this species have been detected, therefore it has been classified as Least Concern (LC) according to the International Union for Conservation of Nature (IUCN) criteria and categories (IUCN Standards and Petitions Committee, 2022).

DISCUSSION
Ideally, the classification of any given species should be supported by a phylogenetic analysis, preferably including molecular data.However, that is not always possible, even for newly described species, and we have to use pre-cladistic classificatory schemes, such as that of Eigenmann (1927), which allow us to assign a species to a given genus based on combination of character states.Given that the phylogenetic position of Bryconamericus misei is still unknown, its generic allocation is justified by the possession of the character combination established by Eigenmann (1927) and modified by Vari, Siebert (1990) for Bryconamericus.
The subterminal mouth with aligned teeth in the outer row of the premaxilla and dentary teeth decreasing more regularly in size in an anteroposterior sense places Bryconamericus misei apart from Bryconamericus sensu stricto, and closer to 'B. ' agna, 'B.' ecai, 'B.' eigenmanni, 'B.' iheringii, 'B.' ikaa, 'B.' lambari, 'B.' patriciae, 'B.' rubropictus, 'B.' sylvicola, 'B.' uporas and 'B.' ytu, as well as to Hypobrycon and Odontostoechus.The phylogenetic relatedness of these species is confirmed by Mirande ( 2019), who shows that the "Nantis clade", "Hypobrycon clade", Odontostoechus lethostigmus and 'B.' microcephalus (hereafter referred to collectively as the "Odontostoechus clade") are relatively distant from the clade containing the type-species Bryconamericus exodon.This relationship is also reflected in morphology, as the species included in the "Odontostoechus clade" differ radically from Bryconamericus exodon in many aspects, such as the general shape of the body and the pattern of dentition.Thus, species in the "Odontostoechus clade" must be transferred to another genus (or other genera) eventually.Odontostoechus is an eligible genus-level name for that assemblage, although the maintenance of Hypobrycon and Nantis as valid genera cannot be rejected as of yet.Nonetheless, much of its alpha taxonomy and phylogeny of the "Odontostoechus clade" needs clarification before such an arrangement involving the description of additional genera can be proposed.
Most of the species from the Northern South America that remain in Bryconamericus due to the lack of proper phylogenetic investigation differ from B. misei and similar species by a clearly terminal mouth.The few exceptions are 'B.' bolivianus Pearson, 1924, 'B.' grosvenori Eigenmann, 1927(synonym of 'B.' bolivianus), and 'B.' pinnavittatus Dagosta & Netto-Ferreira, 2015.'Bryconamericus' bolivianus has 15-16 total anal-fin rays and teeth of the outer premaxillary row about as large as those in the inner series (Pearson, 1924), which, along with its general appearance and geographic distribution suggests that in reality it could be a species of Ceratobranchia.'Bryconamericus' grosvenori is very similar to female Attonitus irisae Vari & Ortega, 2000 (both species are described from Peru), with whom it shares similar dentition (especially the slender, tricuspid teeth), number of anal-fin rays and scales, and coloration.Dagosta, Netto-Ferreira ( 2015 A new species of Bryconamericus species by the body depth (27.8-31.8%SL), from all but 'B.' aff.iheringii by teeth aligned in the outer row of premaxilla, and still differs from 'B.' aff.iheringii by having a smaller orbit diameter , and also by having breeding tubercles in sexually mature males, a character absent in individuals attributed to 'B.' aff.iheringii.The fact that B. misei was overlooked by previous inventories of the Ivaí and Piquiri ichthyofauna (Frota et al., 2016;Reis et al., 2020) reflects its overall similarity with 'B.' aff.iheringii, but also the fact that even in heavily sampled driver basins undescribed species may remain unknown until in-depth taxonomic studies are performed.
Among the other congeners, the species most similar to Bryconamericus misei are 'B.' microcephalus.That species is known from the Ribeira do Iguape basin, which has a high degree of isolation relative to drainages in the Inland Slope of State of Paraná (Reis et al., 2020).Indeed, the Ivaí, Piquiri and Tibagi sub-ecoregions share only 6.5-6.9% of their ichthyofaunas with the Ribeira de Iguape ecoregion (Reis et al., 2020:478-79, tabs. 4-5).It is likely that 'B.' microcephalus and B. misei are closely related, due to their phenotypic similarity and biogeographical proximity, but phylogenetic approaches are needed to provide a more conclusive answer in this regard.Furthermore, 'B.' microcephalus differs from B. misei by having a smaller body depth , and by having unpigmented fins (Bizerril, Peres-Neto, 1995), while B. misei has pigments in all fins.
The geographic distribution of Bryconamericus misei, restricted to the rio Piquiri, Ivaí and Tibagi basins, is similar to 'B.' coeruleus, which may indicate that those basins have been exchanging fauna via drainage rearrangement.Other species with a similar distribution are Apareiodon vladii Pavanelli, 2006and Planaltina kaingang Deprá, Graça, Pavanelli, Avelino & Oliveira, 2018(Reis et al., 2020), although they only occur in the Piquiri and Ivaí basins.
Comments on breeding tubercles and sexual dimorphism.Breeding tubercles are epidermal structures perceived as tiny white bumps on the body surface of preserved fish (Wiley, Collette, 1970).Their function is still not completely clear, but according to the same authors, the tubercles may facilitate body contact between the sexes during spawning and stimulate females during breeding.
In Bryconamericus misei, the tubercles occur in both sexes, but in different sizes and body regions.Males have well-developed tubercles on the dorsal and lateral portions of the head, and slightly less developed ones on the distal border of the scales, both on the dorsal and ventral portions of the body.In females, when present, the tubercles are smaller and restricted to the distal border of the scales, i.e., they are absent from the head.No tubercles were found on the fins in either sex.Tubercles and fin hooks in B. misei were found only in sexually mature specimens over 34 mm SL captured during the reproductive period, whereas sexually dimorphic character states related to the shape of the anal and pelvic fins were observed in adult specimens at gonadal resting stage and in juvenile specimens (smaller than 34 mm SL).Males in gonadal resting were collected in March and August.This indicates that tubercles and fin hooks are reabsorbed at the end of the reproductive period, as in Knodus nuptialis Menezes & Marinho, 2019.
The presence of breeding tubercles has been discussed in Wiley, Collette (1970) and revised in Menezes, Marinho (2019), who presented an updated table with the species that have the tubercles.According to these latter authors, the presence and distribution of tubercles may vary intra and interspecifically.Two other species of the "Odontostoechus clade" are described as having breeding tubercles: 'B'.microcephalus and Hypobrycon poi.These two species have tubercles on the fins of sexually mature males, instead of on the head and scales.This tubercle distribution is similar to that found in the Stethaprioninae Deuterodon iguape Eigenmann, 1907, but Hildebrand, 1916), Astyanax aramburui Protogino, Miquelarena &López, 2006 andPiabina thomasi (Fowler, 1940) (see Protogino et al., 2006), which have tubercles on the head and scales, but only in male specimens.The presence of breeding tubercles was also recorded in other groups of fishes, in some species of Parodontidae, Lebiasinidae and Distichodontidae (Pavanelli, Britski, 2003;Vari, Ferraris, 2004;Pavanelli, 2006 FIGURE 1 | Bryconamericus misei.A. NUP 24255, holotype, 54.8 mm SL, male, unnamed stream, tributary to the rio Capivara, rio Piquiri basin, Campina do Simão, Paraná State, Brazil; B. NUP 24149, paratype, 54.9 mm SL, female.C. NUP 24155, paratype, 26.4 mm SL.

FIGURE 4 |
FIGURE 4 | Sexual dimorphism in Bryconamericus misei.A. In males, the distal margin of the anal-fin is straight.B. In females, the distal margin of the anal-fin is slightly concave.C. In males, the pelvicfin reaches distinctly past the urogenital opening.D. In females, the pelvic-fin reached at most the urogenital opening.A, C. NUP 24150, holotype, 54.8 mm SL.B, D. NUP 24149, paratype, 54.9 mm SL.
FIGURE 5 | Geographic distribution of Bryconamericus misei (red marks).The star represents the type-locality.The red rectangle on detail indicates the position of the map in relation to Brazilian borders.
) investigated the phylogenetic position of 'B.' pinnavittatus based on morphological characters, recovering the species as sister to Bryconacidnus pectinatus Vari & Siebert, 1990.Whereas the allocation of the latter in Bryconacidnus Myers, 1929 by Thomaz et al. (2015) is questionable, there is no evidence that B. pectinatus or 'B.' pinnavittatus is closely related to B. exodon or other species from the Southern Neotropics.Five species of Bryconamericus have been recorded in the area of occurrence of Bryconamericus misei: 'B.' aff.iheringii (Fig. 7), 'B.' coeruleus, B. aff.stramineus, 'B.' turiuba and the non-native B. exodon.Bryconamericus misei can be easily distinguished from all those 14/19 ni.bio.br| scielo.br/ni
Pseudocorynopoma Perugia, 1891 by having only a few, unmodified scales on the very base of the caudal fin (vs.presence of modified scales associated with glandular tissue on the ventral caudal-fin lobe of males and females of Planaltina and Diapoma pyrrhopteryx Menezes & Weitzman,