Historically, there are divergences in the species allocation between Centromochlus and Tatia. This study aimed to generate the first cytogenetic data about Centromochlus and, by analyzing a population of Centromochlus heckelii from the Amazon River basin, to contribute as evidence to a historical taxonomic dilemma. Diploid number of 46 chromosomes and a heteromorphic pair was found in the female karyotypes, thus characterizing a ZZ/ZW sex chromosome system. Pale blocks of heterochromatin were located in centromeric regions of some chromosomes; however, the exclusive female chromosome (W) is almost entirely heterochromatic. AgNORs were detected in terminal position on the short arms of one acrocentric pair in males and two chromosome pairs in females, the acrocentric plus the sex chromosome pair. Notable differences between Centromochlus heckelii and previous data about species of Tatia are: lower diploid number, presence of a sex chromosome system and multiple AgNORs in Centromochlus, while species of Tatia have simple AgNORs and the absence of acrocentric chromosomes. Results in this study show that chromosomal markers could contribute as evidence to taxonomic delimitation studies.

This study evaluates the long-term effects of swine wastewater (SWW) on relevant parameters for soil fertility, including calcium (Ca), magnesium (Mg), potassium (K) cations, cation exchange capacity (CEC), and organic matter (OM) in an agricultural area with 9 years of crop cultivation. Three types of SWW (raw, after leaving the biodigester, and after the manure plant) were analyzed with four application rates of SWW (0, 100, 200, and 300 m³.ha⁻¹), associated or not with mineral fertilization, resulting in eight treatments. The study found that the long-term use of SWW had significant effects on soil parameters. Principal component analysis (PCA) was used to summarize the data. The soil’s calcium (Ca), magnesium (Mg), and cation exchange capacity (CEC) levels were higher in soybean compared to other crops and natural soil. Similarly, the treatment with 0 m³.ha⁻¹ of pig manure and without mineral fertilization showed higher levels of these nutrients. In contrast, potassium (K) was found in greater quantities in oats, SWW from the biodigester, higher doses of manure, and with mineral fertilization. The crops had a higher organic matter (OM) content compared to the natural soil, with corn and raw SWW showing the most significant increase.

According to Auchenipteridae initial morphological data, Auchenipterus and Entomocorus have been considered phylogenetically close, and cytogenetic analyses are limited only to Auchenipterus osteomystax. Herein, we provide the first cytogenetic results about Auchenipterus nuchalis from Araguaia River and Entomocorus radiosus from Paraguay River. These data were generated in order to contribute to the investigation of the Auchenipterus chromosomal diversity and to attempt to better understand the phylogenetic relationship of these Auchenipterinae genera, mainly due to the existence of incongruous characters between Entomocorus and Centromochlinae. The two species presented 2n=58 chromosomes and had different karyotype formulas. The heterochromatin distribution was primarily shown in terminal regions, along with interstitial and/or pericentromeric blocks in submetacentric/subtelocentric pairs in A. nuchalis and E. radiosus. Single and terminal AgNORs were confirmed by 18S rDNA for the analyzed species, differing from A. osteomystax (cited as A. nuchalis) from Upper Paraná River. The variation in the number of 5S rDNA between species and its equilocality in E. radiosus suggest that the dispersion of the gene associated with the amplification of heterochromatic regions in the interphase, possibly promoted by the Rabl model system. The differences found between the species of Auchenipterus can work as species-specific characters and assist in studies of these taxa, which historically have been wrongly identified as a single species with wide distribution throughout the Neotropical region, when they are actually different species. Furthermore, there are cytogenetic similarities between E. radiosus and members of Centromochlinae like pointed out by recent morphological and molecular analyses in the family.