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The present study analyzes the effects of freezing and alcohol preservation in geometric morphometric data, using 15 individuals of the peacock fish Cichla kelberi (12.9–26.4 cm SL) divided into freezing and alcohol groups, conserved in each preservation method for 90 days. Discriminant analysis revealed significant difference between before and after treatments, and principal component analysis also showed separation between treatments, for both conservation methods. These results introduce a significant preservation influence that should be considered in biological, ecological and evolutionary interpretations of fish data in geometric morphometric approaches.

Background Evolutionary Theory (ET) is a central framework in the biological sciences, guiding understanding across diverse fields. Despite its foundational importance, knowledge and acceptance of ET remain uneven, often influenced by socioeconomic and cultural factors. Misconceptions about ET have been widely documented and are frequently linked to students’ backgrounds, including their political views, gender, race/ethnicity, and economic status. Socioeconomic disparities, particularly within culturally and politically polarized societies, can shape students’ perceptions and understanding of scientific concepts, potentially leading to gaps in scientific literacy. We investigate how these factors relate to ET knowledge among Brazilian undergraduates, aiming to highlight the role of social characteristics in shaping science education outcomes. Results Our survey of 812 undergraduates revealed significant correlations between ET knowledge and each assessed variable. Students identifying as men achieved higher scores than students identifying as women, and White students outperformed Black and Brown students. Political orientation also influenced performance, with left-leaning students scoring higher than those on the right. Family income positively correlated with ET knowledge, with students from wealthier backgrounds achieving better scores. Regarding religious affiliation, Christian students obtained lower scores when compared to other religious affiliations. Conclusions Gender, ethnicity, political orientation, religious affiliation, and family income are significant predictors of ET knowledge among Brazilian undergraduates, underscoring the role of socioeconomic disparities in scientific understanding. Marginalized groups may face educational barriers that impact their comprehension of core scientific concepts like ET. Addressing these disparities through culturally inclusive teaching strategies could foster more equitable learning settings. By prioritizing inclusive educational approaches, institutions can support diverse learners in achieving greater scientific literacy, which is essential for informed decision-making and active participation in societal and environmental issues.

Geometric morphometric analysis has increased in the recent years, turning into a powerful tool to explore shape and size variation. Several biological studies use specimens that have been through some kind of preservation, mainly formalin preservation, commonly used in biological collections. This study analyzed the effect of preservation in shape on two fish species: Eucinostomus argenteus and Pomadasys corvinaerformis . Twenty-nine individuals of E. argenteus and twenty-five of P. corvinaeformis were collected, photographed twice, preserved in 10 % formalin for 1 week, and then transferred to 70 % ethanol for 83 days. We evaluated three levels of error: (1) error of landmark digitalization, (2) error of taking the picture and storage in JPEG format, and (3) the formalin and ethanol fixation error using Procrustes ANOVA, Discriminant Analysis, and Principal Component Analysis. Significant difference between treatments was observed on both species with Procrustes ANOVA and Discriminant Analysis. In addition, Principal Component Analysis showed a separation between groups of treatment on both species. These results represent the first evidence of preservation effects in studies of geometric morphometrics and show that according to the statistical test utilized, the fixation could affect the shape variations in different ways and could lead the researcher to false results or wrong conclusions. Other methods to explore the shape variation of organisms previously fixed should be tested in order to assess their influence in geometric mophrometric studies.

Fish constitute a paraphyletic and profusely diversified group that has historically puzzled ichthyologists. Hard efforts are necessary to better understand this group, due to its extensive diversity. New species are often identified and it leads to questions about their phylogenetic aspects. Cytogenetics is becoming an important biodiversity-detection tool also used to measure biodiversity evolutionary aspects. Molecular cytogenetics by fluorescence in situ hybridization (FISH) allowed integrating quantitative and qualitative data from DNA sequences and their physical location in chromosomes and genomes. Although there is no intention on presenting a broader review, the current study presents some evidences on the need of integrating molecular cytogenetic data to other evolutionary biology tools to more precisely infer cryptic species detection, population structuring in marine environments, intra- and interspecific karyoevolutionary aspects of freshwater groups, evolutionary dynamics of marine fish chromosomes, and the origin and differentiation of sexual and B chromosomes. The new cytogenetic field, called cytogenomics, is spreading due to its capacity to give resolute answers to countless questions that cannot be answered by traditional methodologies. Indeed, the association between chromosomal markers and DNA sequencing as well as between biological diversity analysis methodologies and phylogenetics triggers the will to search for answers about fish evolutionary, taxonomic, and structural features.

Fish of the genus Selene, known as lookdowns or moonfish, are one of the most morphologically derived groups of the family Carangidae, whose phylogenetic relationships are still largely unknown. In this study, we discuss karyoevolutionary aspects of three representatives of this genus from the Western Atlantic: Selene brownii (2n = 48; FN = 48), Selene setapinnis (2n = 46; FN = 48), and Selene vomer (2n = 48; FN = 50). Their body patterns were also investigated and compared to one another and in relation to two other species of different genera. Two mechanisms of karyotypic evolution seem to have acted in the diversification of this genus, namely pericentric inversions and centric fusions. Mapping of rDNA sequences showed that chromosome pairs bearing 5S rDNA sites are similar, whereas those bearing 18 rDNA sites are morphologically distinct while apparently also exhibiting interspecies synteny. Although the nucleolar organizer-bearing chromosomes are extremely efficient cytotaxonomic markers among Selene species, others cytogenetic patterns of these species are relatively conserved. Hybridization with telomeric probes (TTAGGG)ₙ did not exhibit interstitial telomeric sites (ITS), especially in S. setapinnis, where, along with a reduction in diploid number, a large metacentric pair derived from centric fusion is present. Data obtained by geometric morphometrics enable a clear morphological distinction among the three species, as well as in relation to two other species of the genus Caranx and Oligoplites. Data obtained suggest that morphologic evolution in Selene species was primarily dissociated from visible changes that occurred at the chromosomal level.

Isolated oceanic islands constitute interesting model systems for the study of colonization processes, as several climatic and oceanographic phenomena have played an important role in the history of the marine ichthyofauna. The present study describes the presence of two morphotypes of Caranx lugubris, in the St. Peter and St. Paul Archipelago located in the mid-Atlantic. Morphotypes were compared in regard to their morphological and cytogenetic patterns, using C-banding, Ag-NORs, staining with CMA₃/DAPI fluorochromes and chromosome mapping by dual-color FISH analysis with 5S rDNA and 18S rDNA probes. We found differences in chromosome patterns and marked divergence in body patterns which suggest that different populations of the Atlantic or other provinces can be found in the Archipelago of St. Peter and St. Paul.