Anatomy, ecology, and behavior of a new species of Scleronema Eigenmann, 1917 (Siluriformes: Trichomycteridae) from coastal drainages in the southern Brazilian Atlantic Rainforest, with comments on the monophyly and phylogeny of the genus

A new species of Scleronema (Trichomycteridae) is described from the lowlands of three coastal river basins in the Atlantic Forest of the Santa Catarina state, Southern Brazil. Aspects of the anatomy, reproduction, diet, feeding behavior and habitat of the new species are described and discussed in comparison with related taxa. The conservation status of the new species, which currently faces several threats due to environmental impacts on its region of occurrence, is established. Based on characteristics observed in the new species, as well as in most of its congeners, the phylogenetic position and monophyly of Scleronema are discussed and traits considered synapomorphic for the subgenera Plesioscleronema and Scleronema are reviewed. The monophyly of the genus Scleronema is supported by a new synapomorphy. In addition, two new synapomorphies, one of which based on behavior, are suggested for the subgenus Scleronema, justifying the inclusion of the new species. Within the subgenus Scleronema, the new species is assigned to the S. minutum group, which currently includes the majority of species of the genus, due to the presence of synapomorphic traits related to the body shape, maxillary barbel, skin flap of the opercle, caudal and pectoral fins, as well as osteological features of the lower jaw, hyoid arch, and postcranial axial skeleton. The species herein described differs from all its congeners by a combination of characters from various morphological complexes, which are described in detail using different methodologies, including radiography, whole-specimen clearing and double-staining procedures, and tridimensional computer nanotomography (3D nano-CT).

Phylogeny and historical biogeography of neotropical catfishes Trichomycterus (Siluriformes: Trichomycteridae) from eastern Brazil

The catfish subfamily Trichomycterinae is widely distributed in South America inhabiting several habitats, but specially mountain streams. Trichomycterus is the most speciose trichomycterid genus and recently due to his paraphyletic condition has been restricted to a clade from eastern Brazil called Trichomycterus sensu stricto comprising around 80 valid species distributed in seven areas of endemism of eastern Brazil. This paper aims to analyse the biogeographical events responsible for the distribution of Trichomycterus s.s., by reconstructing the ancestral data based on a time-calibrated multigene phylogeny. A multi-gene phylogeny was generated using 61 species of Trichomycterus s.s. and 30 outgroups, with divergence events calculated based on the estimated origin of Trichomycteridae. Two event-based analyses were applied to investigate the biogeographical events responsible the present distribution of Trichomycterus s.s. and suggest that the modern distribution of the group is a result of different vicariance and dispersal events. The diversification of Trichomycterus s.s. subgenera occurred in the Miocene, except for Megacambeva, with different biogeographical events shaping its distribution in eastern Brazil. An initial vicariant event split up the Fluminense ecoregion from the Northeastern Mata Atlantica + Paraíba do Sul + Fluminense + Ribeira do Iguape + Upper Paraná ecoregions. Dispersal events occurred mainly between Paraíba do Sul and neighboring river basins, with additional dispersal events from Northeastern Mata Atlantica to Paraíba do Sul, from São Francisco to Northeastern Mata Atlântica, and from Upper Paraná to São Francisco.

Chromatic polymorphism in Trichomycterus jacupiranga from eastern Brazilian Coastal basins (Siluriformes: Trichomycteridae)

Trichomycterinae catfishes often have high intraspecific variability in colour patterns that may be associated with ontogenetic changes or habitat preferences. In species of the eastern South American genus Trichomycterus s.s., some cases of chromatic polymorphism have been reported but colour pattern is still considered an important tool for species identification. Herein, we first describe chromatic polymorphism in the geographically widespread T. jacupiranga, comparing populations from Tijuca National Park and Ribeira do Iguape basin, identifying four syntopic colour morphs. In addition, we performed a phylogenetic analysis using partial sequences of the mitochondrial gene 12Ss gene for 16 individuals of T. jacupiranga, with a maximum of 0.2% of genetic distance, corroborating T. jacupiranga as a single widespread species. Finally, based on our results and field observations, we concluded that it is not possible at the present to associate chromatic polymorphism in T. jacupiranga with habitat preferences, since specimens with different colouration in variable ontogenetic stages were found at the same microhabitats.

Two new miniature translucent catfish species of the rare genus Tridens (Siluriformes: Trichomycteridae) from the Madeira River basin, northern Brazil

Two new miniature species of the trichomycterid genus Tridens are described from the Madeira River drainage, Acre and Rondônia States, Brazil. Until this work, Tridens was a monotypic genus composed solely of Tridens melanops, from the Putumayo/Içá River drainage, upper Amazonas River basin. Tridens vitreus sp.n. is known from upper and middle Madeira River drainage and differs from all other congeners by the lack of pelvic fins and girdle and by vertebra and dorsal-fin ray counts. Tridens chicomendesi sp.n. is known from Abunã River, middle Madeira River drainage and is distinguished from all other congeners by the number of vertebrae, dorsal-fin ray count and anal-fin base colouration pattern. Tr. chicomendesi sp.n. is further distinguished from T. vitreus by a combination of character states regarding the position of urogenital opening, dorsal-fin position, anal-fin position, maxillary barbel length, number of premaxillary teeth, number of dorsal-fin rays, number of anal-fin rays, number of lateral-line system pores, frontal bone anatomy, degree of ossification of maxilla, anatomy of quadrate-hyomandibular joint, size of posterodorsal process of hyomandibula, length of opercular patch of odontodes, number of interopercular odontodes, proportion of upper hypural plate cartilage relative to its area ; by the absence of a proximal, distal and ventral cartilages on ventral hypohyal; by the absence of a lateral process on basibranchial 4; by the presence of a cartilage block on the lateral process of autopalatine, the presence of a well-developed ossification on proximal margin of ventral hypohyal, the presence of hypobranchial foramen; and by the presence of an anterior cartilaginous joint between quadrate and base of posterodorsal process of hyomandibula. This work represents the first species description for the subfamily Tridentinae in more than 30 years and for the genus Tridens since its original description in 1889.

Chromatic polymorphism in Trichomycterus albinotatus (Siluriformes, Trichomycteridae), a mountain catfish from south-eastern Brazil and the role of colouration characters in trichomycterine taxonomy

Colouration is an important tool for systematists inferring species limits and phylogenetic relationships of teleost fishes, but the use of colouration variation in trichomycterine catfish systematics has generated some controversy. We first report and describe the occurrence of four, geographically disjunct colour morphs in Trichomycterus albinotatus, endemic to south-eastern Brazil, as well as ontogenetic colouration change in each morph. A phylogenetic analysis using a cytb fragment (1098 bp) for 23 specimens representing all colour morphs and four outgroups did not support any correlation between colour morphs and lineages, with different colour morphs sharing identical haplotypes. This study indicated that young adult specimens found in lighter habitats had white and brown to black spots on the flank, whereas similar-sized specimens inhabiting darker habitats had white spots inconspicuous or absent and dark brown or black spots expanded. Individuals above about 65 mm SL of all populations had flank white marks less conspicuous or absent and cryptic habits during daylight, contrasting with smaller individuals with white marks and actively swimming above the substrate. Literature data indicate that ontogenetic colouration and habit changes occur in different trichomycterid lineages. Our data thus show that colouration may be problematic in taxonomical studies, although often being consistently used to diagnose species and clades. We conclude that colouration should not be discarded a priori as evidence of trichomycterine relationships and species limits, but should be used with caution in systematic studies, being necessary additional evidence, such as osteological characters or molecular data.

Perils of Underestimating Species Diversity: Revisiting Systematics of Psammocambeva Catfishes (Siluriformes: Trichomycteridae) from the Rio Paraíba do Sul Basin, South-Eastern Brazil †

Psammocambeva, a subgenus of Trichomycterus s.s., includes a clade endemic to south-eastern Brazil, the Psammocambeva alpha-clade (PAC), containing species with similar colour pattern and fin morphology, making difficult their identification without accurate examination. The greatest diversity of PAC species occurs in the Rio Paraíba do Sul basin area (RPSA), situated within the Atlantic Forest, one of the most important and endangered biodiversity centres in the world. Herein, we: perform a multigene phylogeny focusing on species of PAC; revise morphological characters diagnosing species of PAC from the RPSA, with special attention to those equivocally synonymised in a recent study; describe two new species, and provide a key for species identification. Molecular and morphological evidence supported the recognition of eight valid species belonging to four species complexes. Data indicated that T. auroguttatus, T. travassosi, and T. longibarbatus are valid species. Finally, we discuss the negative impacts of underestimating species diversity in regions under the intense process of natural habitat loss, concluding that integrative approaches are important tools to estimate species diversity, but they should include a range of morphological characters informative to delineate and diagnose groups and their respective species, in association with phylogenies generated by robust molecular datasets.

A new catfish species of the genus Cambeva (Siluriformes: Trichomycteridae) from the Rio Iguaçu drainage, southern Brazil, with a remarkable unique colour pattern

Cambeva melanoptera sp. nov. is described from stream tributaries of the Rio Iratim, Rio Iguaçu drainage, southern Brazil. This new species is remarkable with a colour pattern not found elsewhere among trichomycterid catfishes, consisting of a broad distal black zone in all unpaired and pectoral fins, strongly contrasting with a pale-yellow proximal zone. C. melanoptera also differs from all other trichomycterids from eastern South America by the presence of the nasal barbel about thrice longer than the maxillary and rictal barbels. Due to the presence of a similar bicolour caudal fin, the new species is tentatively considered closely related to Cambeva castroi and Cambeva diabola, as well as more closely related to C. castroi than to C. diabola, with the first two species sharing the presence of a curved lateral process of the parurohyal and a trapezoidal projection on the lateral margin of the lateral ethmoid. The great morphological diversity found in Cambeva species endemic to the Rio Iguaçu drainage, including numerous exclusive characteristics not occurring in congeners and in any other species of closely related trichomycterine genera, indicates the need for more studies focusing on possible causal factors responsible for such unique diversification pattern.

Phylogenetic relationships of a new catfish of the genus Trichomycterus (Siluriformes, Trichomycteridae) from the Brazilian Cerrado, and the role of Cenozoic events in the diversification of mountain catfishes

The Brazilian Cerrado highlands shelter the headwaters of the three largest South American hydrographic basins, where a great species diversity is concentrated, but some biological groups are still insufficiently known. The focal taxa of this study are trichomycterid catfishes of the subgenus Cryptocambeva, genus Trichomycterus, endemic to mountain areas of south-eastern Brazil. The primary objective of this study is to test through a molecular phylogeny if a new species collected in streams of the upper Rio Paraná basin draining the Serra da Canastra is sister to T. macrotrichopterus, endemic to the upper Rio São Francisco at another facet of the Serra da Canastra, as suggested by morphological data. The analysis corroborated sister group relationships between these two species, besides supporting four main clades in Cryptocambeva, each of them endemic to distinct mountain regions. A time-calibrated analysis supported the divergence timing between the new species and T. macrotrichopterus at the Pliocene, which is chronologically compatible with the final period of intense fluvial configuration re-arrangement, when São Francisco headwater streams were captured by the Paraná basin. The new species herein described is similar to T. macrotrichopterus and distinguished from all other species of Cryptocambeva by having a long pectoral-fin filament. These two species are distinguished from each other by characteristics of the latero-sensory system, colour pattern and bone morphology.

Phylogenetic position of Trichomycterus astromycterus (Siluriformes: Trichomycteridae), an enigmatic trichomycterid from eastern Brazil, inferred from molecular data

Recently in this journal, a new trichomycterine from eastern Brazil, Trichomycterus astromycterus, was described and considered possibly related to the Chilean Bullockia maldonadoi due to morphological similarities. Subsequently, osteological data supported T. astromycterus in the subgenus Psammocambeva of Trichomycterus, from eastern Brazil. Phylogenetic analyses, performed here, using a multigene data set for a broad trichomycterine sample, corroborate T. astromycterus as a member of Psammocambeva, reinforcing the importance of molecular data for inferring trichomycterine relationships but showing that osteological data alone may infer correctly phylogenetic placements when using broad comparative databases.

A new catfish of the genus Trichomycterus from the Rio Paraíba do Sul Basin, south-eastern Brazil, a supposedly migrating species (Siluriformes, Trichomycteridae)

A new species of the catfish genus Trichomycterus is described from the Rio Paraíba do Sul, south-eastern Brazil. This species exhibits some morphological character states that are unique amongst congeners, including a robust opercle and a long interopercle with numerous odontodes (50–60 opercular and 90–100 interopercular), a black bar on the basal portion of the caudal fin and a dark brown flank with a well delimited dorsal yellow stripe. It also exhibits some morphological traits that are uncommon amongst congeners, such as the presence of nine pectoral-fin rays. The presence of a shallow hyomandibular outgrowth and a ventrally expanded pre-opercular ventral flap suggests that this species is closely related to T. melanopygius, T. pradensis and T. tete. The new species also differs from T. melanopygius, T. pradensis and T. tete by having an emarginate caudal fin and a single median supra-orbital pore S6. Anecdotal evidence suggests that T. largoperculatus and T. pradensis have migratory habits, a condition not previously reported for eastern South American trichomycterines.

A new candiru of the genus Paracanthopoma (Siluriformes: Trichomycteridae) from the Araguaia River basin, central Brazil

A new species of the candiru genus Paracanthopoma is described from the floodplains of the Bananal Island, a transition area between the Cerrado and Amazon, in the Araguaia River basin, central Brazil. Paracanthopoma cangussu sp. nov. is distinguished from its congeners, Paracanthopoma parva and Paracanthopoma saci, by the presence of seven opercular odontodes, five dentary teeth, five median premaxillary teeth, and first dorsal-fin pterygiophore in a vertical through the centrum of the 23th or 24th vertebra. It is further distinguished from each congener by an exclusive combination of character states, comprising the number of vertebrae, number of precaudal vertebrae, number of dorsal procurrent caudal-fin rays, number of ventral procurrent caudal-fin rays, number of dorsal-fin rays, disposition of pores on the cephalic portion of the latero-sensory system, absence of an anterior process on the anterior margin of parieto-supraoccipital, number of dorsal-fin pteryigiophores and number of interopercular odontodes. Although vandelliines are known for being exclusively hematophagous, with guts gorged with blood, two cleared and stained specimens of P. cangussu sp. nov. had Chironomidae larvae (Insecta) on their guts. Because most specimens of P. cangussu sp. nov. were collected with stomachs filled with blood, it was hypothesized that the species feeds accidentally or occasionally on insects.