Filling distribution gaps: Two new species of the catfish genus Cambeva from southern Brazilian Atlantic Forest (Siluriformes, Trichomycteridae)

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.

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.

Uncertainties and risks in delimiting species of Cambeva (Siluriformes: Trichomycteridae) with single-locus methods and geographically restricted data

Abstract Cambeva contains species with complex taxonomy or poorly delimitated in terms of morphology and geopraphic distribution. We conducted an extensive review of Cambeva populations from coastal drainages of Southern to Southeastern Brazil to evaluate species geographic limits with an integrative analysis including morphological and molecular data (COI). We test if two single-locus methods, Bayesian Poisson Tree Processes (bPTP) and Generalized Mixed Yule Coalescent (GMYC), are efficient to delimit species boundaries in Cambeva by the comparison with the diagnosable morphological units. Using GMYC, we also evaluated the combination of tree and molecular clock priors to reconstruct the input phylogeny and assessed how well the implemented model fitted our empirical data. Eleven species were identified using a morphological diagnosability criterion: Cambeva balios, C. barbosae, C. botuvera, C. cubataonis, C. davisi, C. guaraquessaba, C. iheringi, C. tupinamba, and C. zonata and two treated as undescribed species. In contrast with previous knowledge, many of them have wider distribution and high intraspecific variation. Species delimitation based on single-locus demonstrated incongruences between the methods and strongly differed from the morphological delimitation. These disagreements and the violation of the GMYC model suggest that a single-locus data is insufficient to delimit Cambeva species and the failure may be attributable to events of mitochondrial introgression and incomplete lineage sorting.

A new species of Cambeva (Siluriformes, Trichomycteridae) from the Rio Iguaçu basin, Paraná State, Brazil and redescription of Cambeva stawiarski (Miranda Ribeiro 1968)

This work aimed to describe Cambeva cauim, sp. nov., endemic to the Rio Iguaçu basin, Brazil and redescribe Cambeva stawiarski using external and internal morphological data through the revision of specimens deposited in fish collections, including the type material. In this process, we have also added comments on the possible type locality of C. stawiarski. C. cauim, sp. nov. and C. stawiarski are mainly diagnosed by the anatomy and number of procurrent caudal-fin rays in addition to colouration and several meristic and morphometric characters. Both species are compared with other possibly related species and their synapomorphic characters are discussed. C. cauim, sp. nov. and C. stawiarski along with eight other congeners are endemic to the Rio Iguaçu basin, a high impacted freshwater region which could be considered as a biodiversity hotspot to the genus.

Comparative Osteology, Phylogeny and Classification of the Eastern South American Catfish Genus Trichomycterus (Siluriformes: Trichomycteridae)

Trichomycterus has been considered for a long time to be the most problematic genus of the diverse neotropical subfamily Trichomycterinae. Recently, Trichomycterus was restricted to a clade from eastern South America supported by molecular data, but no unique morphological character state was found to distinguish it, making it difficult to allocate new species based on morphology alone. The objectives of this study were to conduct an osteological comparative analysis comprising a large sample of valid species of Trichomycterus, to conduct a total evidence phylogenetic analysis, combining osteological characters and a multigene database, and to propose an intrageneric classification based on the results of the phylogenetic analysis. Fifty-two osteological characters were combined with a multigene molecular data set of 2974 bp for 44 species of Trichomycterus, and 21 outgroups generated a well-supported phylogenetic tree, making it possible to delimit and diagnose intrageneric lineages, of which six subgenera are recognized. The high morphological diversity of osteological structures herein first reported for Trichomycterus from eastern South America is possibly related to some ecological specializations. This study shows that osteological characters combined with molecular data may be useful to consistently delimit and distinguish between trichomycterines, shedding light on the still persistent problems in trichomycterine systematics.