Phylogenomic analysis of the Neotropical fish subfamily Characinae using ultraconserved elements (Teleostei: Characidae).

Characinae is one of the most species-rich subfamilies of Characidae and holds special taxonomic importance because it includes Charax, type-genus of Characidae and Characiformes. Currently, the monophyly and the hypotheses of intergeneric and interspecific relationships of Characinae are based on a few morphological and molecular studies but all with low species coverage. Given their diversity, taxonomic importance, and the lack of a taxon-dense phylogeny, we sought to buttress the systematic understanding of Characinae collecting DNA sequence data from ultraconserved elements (UCEs) of the genome from 98 specimens covering 57 species (61%) plus 17 characiforms as outgroups. We used maximum likelihood, Bayesian inference, and coalescent-based species tree approaches and the resulting phylogeny with 1,300 UCE loci (586,785 characters) reinforced the monophyly of the subfamily as well as of six genera: Acestrocephalus, Charax, Cynopotamus, Galeocharax, Phenacogaster, and Roeboides. The phylogeny provides a hypothesis of intergeneric and interspecific relationships for the subfamily with Phenacogaster sister to all genera, and Acanthocharax sister to Cynopotamini (Cynopotamus (Acestrocephalus Galeocharax)) and Characini (Charax Roeboides). We propose a new tribe Acanthocharacini to allocate Acanthocharax, two subclades for Phenacogaster, two for Cynopotamus, three for Charax, and reinforced the four subclades for Roeboides previously identified by morphological studies. Additionally, we generated a time-calibrated phylogeny for Characinae that suggested an initial diversification during the Miocene at around 19 million years ago and discussed historical biogeographic events for major subclades. The results obtained here will contribute to the development of further research on the evolutionary processes modulating species diversification in Characinae.

Eye development in the four-eyed fish Anableps anableps: cranial and retinal adaptations to simultaneous aerial and aquatic vision.

The unique eyes of the four-eyed fish Anableps anableps have long intrigued biologists. Key features associated with the bulging eye of Anableps include the expanded frontal bone and the duplicated pupils and cornea. Furthermore, the Anableps retina expresses different photoreceptor genes in dorsal and ventral regions, potentially associated with distinct aerial and aquatic stimuli. To gain insight into the developmental basis of the Anableps unique eye, we examined neurocranium and eye ontogeny, as well as photoreceptor gene expression during larval stages. First, we described six larval stages during which duplication of eye structures occurs. Our osteological analysis of neurocranium ontogeny revealed another distinctive Anablepid feature: an ossified interorbital septum partially separating the orbital cavities. Furthermore, we identified the onset of differences in cell proliferation and cell layer density between dorsal and ventral regions of the retina. Finally, we show that differential photoreceptor gene expression in the retina initiates during development, suggesting that it is inherited and not environmentally determined. In sum, our results shed light on the ontogenetic steps leading to the highly derived Anableps eye.

Freshwater fish scale database.

Scales of the ray finned fishes can be used for multiple purposes. Beside others by their specific structure and elemental composition they are usable for age determination and food-web researches. Additionally, just their presence, absence, shape, location, or numbers could provide a reliable taxonomic information. The fish scales show remarkable size variation also, which characteristics provide reliable information about the environmental needs of freshwater fish. But till now this information was not interpretable and comparable in the absence of a sufficiently large and detailed database. In this study we provide a database which can facilitate the further complex comparative studies. Our dataset consists of 2954 scale photos characterising 193 freshwater fish species. All photos have a uniquely identification code showing exactly which species the scale belongs to. In addition to the photos, our database includes a table showing the exact taxonomic classification of the studied species, the average body profile-index, and the relative scale size, as well as the ecological (flow and feeding habitat preferences) and life strategic characteristics (feeding and breeding guild memberships) of each species. The sampled species have diverse origin, covering five biogeographical regions. An average of five adults from each species were selected for sampling. Three-to-four scales were collected from the anterior part of the body between the dorsal fin and the lateral line. The removed scales were cleaned and prepared to microscope slides, and after this process they were photographed or scanned. Our database can be used for both research and educational purposes. A large number of scale photos assigned of species can be an opportunity to create an automatic species identification system. Moreover, the subjectivity in morphometric measurements can be eliminated by analysing the database with artificial intelligence.

Molecular species delimitation and description of a new species of Phenacogaster (Teleostei, Characidae) from the southern Amazon basin.

Phenacogaster is the most species-rich genus of the subfamily Characinae with 23 valid species broadly distributed in riverine systems of South America. Despite the taxonomic diversity of the genus, little has been advanced about its molecular diversity. A recent molecular phylogeny indicated the presence of undescribed species within Phenacogaster that is formally described here. We sampled 73 specimens of Phenacogaster and sequenced the mitochondrial cytochrome c oxidase subunit I (COI) gene in order to undertake species delimitation analyses and evaluate their intra- and interspecific genetic diversity. The results show the presence of 14 species, 13 of which are valid and one undescribed. The new species is known from the tributaries of the Xingu basin, the Rio das Mortes of the Araguaia basin, and the Rio Teles Pires of the Tapajós basin. It is distinguished by the incomplete lateral line, position of the humeral blotch near the pseudotympanum, and shape of the caudal-peduncle blotch. Meristic data and genetic differentiation relative to other Phenacogaster species represent strong evidence for the recognition of the new species and highlight the occurrence of an additional lineage of P.franciscoensis.

Taxonomic review of the pipefish genus Pseudophallus Herald, with the description of a new species (Syngnathiformes: Syngnathidae).

We present a taxonomic review of the genus Pseudophallus, based on morphological characters, originally described to include two freshwater pipefish species from the Pacific coastal drainages of the neotropics: P. starksii and P. elcapitanensis, with the later addition of P. mindii, described from Atlantic coastal drainages. Pseudophallus mindii was formerly recognized as a single species ranging from the Brazilian state of São Paulo to Belize in Central America. Five species are recognized in the present study: P. elcapitanensis and P. starksii from the Pacific drainages; P. mindii and P. brasiliensis, the latter so far considered a junior synonym of P. mindii, and a new species. Pseudophallus mindii is redefined to include specimens with higher meristic values and narrow range of variation compared to P. brasiliensis and is restricted to the northern coastal drainages from Venezuela to Central America including the Caribbean region. Pseudophallus brasiliensis is revalidated and occurs from the drainages east of the mouth of the Orinoco to southern Brazil. The new species, Pseudophallus galadrielae sp. nov. is endemic to Lago Izabal in Guatemala. An updated identification key to the currently recognized species is provided.

Osteology of Priocharax and remarkable developmental truncation in a miniature Amazonian fish (Teleostei: Characiformes: Characidae).

Establishing phylogenetic relationships of miniature fishes is challenging in taxa with developmental truncation. Within the Characiformes, developmental truncation appears to be relatively rare, with the Neotropical genus Priocharax being an example. Priocharax includes three miniature species among the smallest of the order and has been hypothesized to belong to the Heterocharacinae. The pronounced reduction in its skeleton, however, prevented a clearer evaluation of its relationships. The present detailed osteological study was designed to address this question and revealed that 21 bones are absent and nine other skeletal structures are simplified in Priocharax when compared to other characids. Comparison of the skeleton of adult Priocharax with early developmental stages of other characids demonstrated that most of the absences and simplifications can be interpreted as developmental truncations. The most striking developmental truncations are in the pectoral girdle, in which the endoskeleton remains entirely cartilaginous. Other interesting truncations are in the ethmoid region of the skull, infraorbital series, and Weberian apparatus, in which the claustrum is absent. Our study also revealed some unusual sexual dimorphisms in the pelvic girdle. Two cladistic analyses were performed to assess the relationships of Priocharax within the Heterocharacinae. The first consisted of a traditional analysis in which all absences and reductions of Priocharax were coded in the same way as in the remaining taxa. This resulted in three equally most parsimonious topologies, all of which have Priocharax as the most basal taxon of the Heterocharacinae. The second analysis incorporated ontogenetic information, and most absences and reductions of Priocharax were reinterpreted as apomorphic conditions and thus, coded differently from similar conditions in outgroups. This resulted in a single phylogenetic hypothesis with Priocharax and Gnathocharax as sister groups based on seven synapomorphies. Our approach demonstrates the importance of developmental studies to better understand morphological evolution of miniaturized, truncated taxa, and to generate hypotheses of their relationships.

Ontogenetic development of heterocharax macrolepis eigenmann (Ostariophysi: characiformes: characidae) with comments on the form of the yolk sac in the heterocharacinae

Fishes in early developmental stages frequently have morphological features that differ from those of adult stages, and many characters found later in ontogeny are not available in initial stages. Hence, morphological descriptions of early stages are useful to provide information for the identification of eggs and larvae, a knowledge still restricted among Neotropical fishes. We studied the development of Heterocharax macrolepis, a heterocharacine whose adult specimens from the aquarium trade were kept and spawned at around 23-24ºC. A developmental series of 51 specimens was preserved, ranging from 3.2 mm notochord length to 18.6 mm standard length, covering approximately the first 73 days post-hatching. We described the development of main morphological features emphasizing those useful in the identification of H. macrolepis larvae (i.e., appearance of preopercle spine and development of the pseudotympanum). We also compared H. macrolepis with photographs taken of live larval specimens of Gnathocharax steindachneri, recently included in the Heterocharacinae. Both species have a yolk sac with a small rounded projection directed posteroventrally. Although this information is not yet available for all pertinent taxa, the different yolk sac shape in other representatives of the Characiformes may indicate that this peculiar yolk sac represents an additional synapomorphy of the Heterocharacini.

Peixes em estágios iniciais de desenvolvimento frequentemente apresentam características morfológicas distintas dos adultos e muitos caracteres presentes em estágios avançados não são disponíveis em estágios iniciais. Assim, descrições morfológicas dos estágios iniciais de desenvolvimento de peixes são úteis por fornecerem subsídios para a identificação de ovos e larvas, um conhecimento ainda escasso entre peixes Neotropicais. Estudamos o desenvolvimento de Heterocharax macrolepis, espécie de Heterocharacinae cujos exemplares adultos provenientes do aquarismo foram mantidos e reproduzidos entre 23-24ºC. Uma série de desenvolvimento de 51 exemplares foi preservada, medindo entre 3,2 mm de comprimento da notocorda e 18,6 mm de comprimento padrão, incluindo os primeiros 73 dias pós-eclosão. Descreveram-se detalhadamente os principais aspectos morfológicos, enfatizando características úteis na identificação de larvas de H. macrolepis (i.e., surgimento do espinho do pré-opérculo, desenvolvimento do pseudotímpano). Comparamos H. macrolepis com fotografias de larvas vivas de Gnathocharax steindachneri, recentemente incluída em Heterocharacinae. Ambas espécies possuem saco vitelínico com pequena projeção arredondada póstero-ventral. Ainda que a informação não esteja disponível para os táxons pertinentes, o distinto formato do saco vitelínico em outras linhagens de Characiformes pode indicar que esta forma do saco vitelínico peculiar represente sinapomorfia adicional de Heterocharacini.

Priocharax nanus, a new miniature characid from the rio negro, Amazon basin (ostariophysi: characiformes), with an updated list of miniature neotropical freshwater fishes

Priocharax nanus, new species, is described from the rio Negro, Brazil. It is a miniature fish that retains as an adult the larval rayless pectoral fin, a diagnostic character of the genus. Priocharax nanus possesses fewer reductive features compared to congeners, P. ariel and P. pygmaeus, from which it can be distinguished by the presence of i,6 pelvic-fin rays (vs. i,5), the presence of the claustrum (vs. claustrum absent) and the presence of two postcleithra (vs. postcleithra absent). An updated list of 213 species of miniature Neotropical freshwater fishes is presented. The greatest diversity among them is represented by the Characiformes with 87 miniature species.

Priocharax nanus, espécie nova, é descrita do rio Negro, Brasil. É um peixe miniatura que retém no adulto a forma larval da nadadeira peitoral, um caráter diagnóstico do gênero. Priocharax nanus possui um número menor de caracteres redutivos quando comparado aos congêneres, P. ariel and P. pygmaeus, dos quais pode ser distinguida pela presença de i,6 raios na nadadeira pélvica (vs. i,5), presença do claustrum (vs. claustrum ausente) e presença de dois pós-cleitros (vs. pós-cleitros ausentes). Uma lista atualizada de 213 espécies de peixes miniatura de água doce neotropicais é apresentada. A maior diversidade entre eles é representada pelos Characiformes, com 87 espécies miniatura.

Taxonomic study of hoplias microlepis (Günther, 1864), a trans-andean species of trahiras (ostariophysi: characiformes: erythrinidae)

The Hoplias malabaricus species group represents one of the most complexes taxonomical problems in the systematics of Neotropical fishes, including specimens widely distributed in most drainages of South America and part of Central America with great variation or overlap of putative diagnostic characters. The large number of nominal species, many of which without known type material, renders the problem more complicated. Currently, at least three nominal species can be included in the Hoplias malabaricus species group based on the form of the medial margins of dentaries and presence of tooth plates on the tongue: Hoplias malabaricus, H. teres, and H. microlepis, the latter representing the only exclusively trans-Andean known species of the genus. We present herein a taxonomic study of Hoplias microlepis based on examination of syntypes and recently collected specimens, including a redescription of the species. Hoplias microlepis occurs in the Pacific drainages of Panama and Southwestern Costa Rica, in addition to the río Guayas basin in Ecuador and the region near its mouth (río Tumbes, Northwestern Peru). Records of the species on the Atlantic coast of Panama are restricted to the Canal Zone, suggesting dispersal through the Panama Canal. We also designate lectotype and paralectotypes.

O grupo de espécies Hoplias malabaricus representa um dos problemas taxonômicos mais complexos na sistemática de peixes Neotropicais, com ampla distribuição em quase todas as bacias da América do Sul e parte da América Central e grande variação ou sobreposição de prováveis caracteres diagnósticos. O grande número de espécies nominais, muitas delas sem material-tipo conhecido, é um fator complicador nessa questão. Atualmente, pelo menos três espécies nominais podem ser incluídas no grupo de espécies Hoplias malabaricus, com base no formato das margens mediais dos dentários e presença de dentes na língua: Hoplias malabaricus, H. teres e H. microlepis, a última sendo a única espécie exclusivamente trans-andina do gênero conhecida até o momento. Apresentamos aqui um estudo taxonômico de Hoplias microlepis, com exame dos síntipos e exemplares coletados mais recentemente, incluindo uma redescrição da espécie. Hoplias microlepis distribui-se nas bacias da costa Pacífica do Panamá e sudoeste da Costa Rica, além da bacia do río Guayas no Equador e região próxima à sua foz (río Tumbes, noroeste do Peru). Registros da espécie na costa Atlântica do Panamá são restritos à Zona do Canal, sugerindo dispersão através do Canal do Panamá. São designados também lectótipo e paralectótipos.

Revision of the Neotropical trahiras of the Hoplias lacerdae species-group (Ostariophysi: Characiformes: Erythrinidae) with descriptions of two new species

Hoplias lacerdae was originally described from the rio Ribeira de Iguape, Iporanga, São Paulo State. The Hoplias lacerdae group is defined as containing generally large trahiras with the medial margins of dentaries running parallel to each other and lacking teeth on the basihyal compared to the H. malabaricus group in which the medial margins of the dentaries converge towards the mandibular symphysis and which have teeth on the basihyal. A taxonomic revision of the group based on meristic and morphometric data identified five distinct species: H. lacerdae distributed in the rio Ribeira de Iguape and rio Uruguai; H. intermedius from the rio São Francisco, upper rio Paraná basin, and rio Doce; H. brasiliensis from rivers of the Atlantic Coastal drainage from the rio Paraguaçu to the rio Jequitinhonha; H. australis new species, endemic to the rio Uruguai; and H. curupira new species present in northern South America, including the rios Negro, Trombetas, Tapajós, Xingu, Tocantins and Capim in the Amazon basin, upper rio Orinoco near the rio Casiquiare (Venezuela), and coastal rivers of Guyana and Suriname. A lectotype for Hoplias intermedius and a neotype for H. brasiliensis are designated.

Hoplias lacerdae foi descrita originalmente do rio Ribeira de Iguape, Iporanga, São Paulo. O grupo Hoplias lacerdae foi definido como um conjunto de espécies para abrigar as traíras geralmente de grande porte, com as margens mediais dos dentários dispostas paralelamente e sem dentes no basi-hial, em oposição às traíras do grupo Hoplias malabaricus, cujas margens mediais dos dentários convergem em direção à sínfise mandibular e possuem dentes no basi-hial. A revisão taxonômica do grupo baseada em dados merísticos e morfométricos identificou cinco espécies distintas: Hoplias lacerdae distribuída nos rios Ribeira de Iguape e Uruguai; H. intermedius no rio São Francisco, alto rio Paraná e rio Doce; H. brasiliensis nos rios costeiros da drenagem Atlântica, desde o rio Paraguaçu até o rio Jequitinhonha; H. australis espécie nova, endêmica ao rio Uruguai; e H. curupira espécie nova no norte da América do Sul, incluindo os rios Negro, Trombetas, Tapajós, Xingu, Tocantins e Capim na bacia Amazônica; alto rio Orinoco próximo ao rio Casiquiare (Venezuela) e rios costeiros da Guiana e Suriname. São designados um lectótipo para Hoplias intermedius e um neótipo para H. brasiliensis.