Ontogenetic changes in mouth morphology triggers conflicting hypotheses of relationships in characid fishes (Ostariophysi: Characiformes)

Abstract

Bryconamericus lethostigmus is the type-species of the monotypic genus Odontostoechus, diagnosed in part based on the presence of a unique tooth series in the premaxilla. Recently a new proposal of classification of the Stevardiinae placed Odontostoechus as a junior synonym of a monophyletic genus Bryconamericus sensu stricto, a genus characterized by the presence of two tooth series. Bryconamericus lethostigmus is redescribed herein and the single tooth series in the premaxilla is demonstrated to originate from merging of the external tooth row with the inner row during ontogeny refuting primary hypothesis of homology between the mouth morphology of B. lethostigmus and the genera Bryconacidnus, Ceratobranchia, Monotocheirodon, Othonocheirodus, Rhinopetitia and Rhinobrycon. A phylogeographic analysis indicated that the pattern described for the sympatric species Diapoma itaimbe is not mirrored by B. lethostigmus. The results also do not support the hypothesis of a new species in the rio Araranguá drainage. Keywords: Atlantic Forest, Cyanocharax itaimbe, Phylogeography, Tooth series, Tramandai-Mampituba ecoregion.Bryconamericus lethostigmus é a espécie tipo do gênero monotípico Odontostoechus, diagnosticado em parte pela presença de uma única série de dentes na pré-maxila. Recentemente uma nova proposta de classificação de Stevardiinae considerou Odontostoechus como sinônimo júnior do gênero monofilético Bryconamericus sensu stricto caracterizado pela presença de duas séries de dentes. Bryconamericus lethostigmus é redescrito e demonstra-se que a única série de dentes no premaxilar se origina pela junção da série externa de dentes com a série interna durante a ontogenia, refutando a hipótese de homologia primária entre a morfologia da boca de B. lethostigmus e os gêneros Bryconacidnus, Ceratobranchia, Monotocheirodon, Othonocheirodus, Rhinopetitia e Rhinobrycon. A análise filogeográfica indica que o padrão descrito para a espécie simpátrica Diapoma itaimbe não se repete em B. lethostigmus. Os resultados também não suportam a hipótese de uma nova espécie para a bacia do rio Araranguá.

Common barriers, but temporal dissonance: Genomic tests suggest ecological and paleo‐landscape sieves structure a coastal riverine fish community

“…For example, one of the oldest and one of the youngest divergence estimates (i.e., the northern division in H. boulengeri and the southern division in Hollandichthys, respectively; Figure 3) correspond to the proposed boundaries of putative species recognized by morphological data (Bertaco & Malabarba, 2013;Carvalho, 2006). In addition, for Bryconamericus, one species boundary corresponds to the southern division inferred in our study (Hirschmann, Fagundes, & Malabarba, 2017); however, we note the lack of a correspondence between the designation of two other species within this taxon and the regional structure inferred here (i.e., north clusters: populations 40 and 41 for B. ornaticeps and population 42 for B. tenuis -see Supporting Information S1), which results in a paraphyletic species under the currently proposed nomenclature. It is also notable that the old divergences associated with the central division are not correlated with any obvious morphological differentiation (Bertaco & Malabarba, 2013;Camelier, Menezes, Costa-Silva, & Oliveira, 2018).…”

Anatomy and ontogenetic changes of the facial and gular musculature of the tetra Astyanax brucutu: A remarkable case of adaptation to durophagy

“…Therefore, such exacerbated features seem to be result of a specific type of heterochrony, peramorphosis, in which additional steps are included at the end of development. To our knowledge, peramorphosis has been rarely recorded in characids (Menezes & Weitzman, 2009; Hirschmann et al ., 2017). Curiously, the opposite heterochronic event, paedomorphosis, has been more widely documented in the family and thought to have occurred multiple times during the characid radiation (Weitzman & Malabarba, 1998; Menezes & Weitzman, 2009; Pastana et al ., 2020).…”

A new characid species with remarkable sexual dimorphism (Characiformes: Characidae: Stevardiinae) from the upper Guayabero River, Orinoco basin, Colombia

“…In the precursor group of Stevardiinae, known as "clade A," the condition of four teeth in the inner row of the premaxilla was proposed as a synapomorphy of this group (Malabarba & Weitzman, 2003; see also Mirande, 2018). Four genera in Stevardiinae are recognized to have a single series in the premaxilla with multicuspid teeth: Aulixidens Boehlke, 1952, Monotocheirodon Eigenmann & Pearson, 1924, Odontostoechus Gomes, 1947, and Othonocheirodus Myers, 1927 In Odontostoechus, the single tooth series in the premaxilla is demonstrated to originate from the merging of the external tooth row with the inner row during ontogeny, with adults presenting seven teeth in this single row (differing from the four teeth condition in Aulixidens, Monotocheirodon, and Othonocheirodus [Böhlke, 1952;Hirschmann et al, 2017;Menezes et al, 2013;Myers, 1927]). This single series of somewhat spatulate teeth with five cuspids in Odontostoechus is apparently related to an adaptation to a diet composed of periphyton, which combines with the regression of the upper lip in this species (Hirschmann et al, 2017).…”

“…In Odontostoechus , the single tooth series in the premaxilla is demonstrated to originate from the merging of the external tooth row with the inner row during ontogeny, with adults presenting seven teeth in this single row (differing from the four teeth condition in Aulixidens , Monotocheirodon , and Othonocheirodus [Böhlke, 1952; Hirschmann et al, 2017; Menezes et al, 2013; Myers, 1927]). This single series of somewhat spatulate teeth with five cuspids in Odontostoechus is apparently related to an adaptation to a diet composed of periphyton, which combines with the regression of the upper lip in this species (Hirschmann et al, 2017).…”