Opsin genes: research perspectives with Neotropical cichlids (Perciformes: Cichlidae) and their relevance in floodplain studies

Vision not only plays an important role in the behavior and exploration capacity of new ecology niches but also influences the evolution of species exposed to the heterogeneity of light. Floodplain environments have high habitat heterogeneity and, thus, different light gradients. Cichlids are a group of vertebrates that has stirred interest in evolutionary studies due to their morphological and behavioral diversity and their widely used vision. The molecular basis of vertebrates’ vision occurs through the interaction of opsin proteins and retinal chromophores. Proteins are expressed by opsin genes where each is responsible for absorbing certain light wavelengths.  Current review analyzes the main characteristics of opsin genes family and the possibility of using them in floodplain and Neotropical cichlids studies. Opsins may have different levels of expression and molecular polymorphisms according to the dispersion of the species. They are also related to such behavior as sexual selection, nourishment and exploration of new habitats. Floodplains are natural experiments and dynamic environments that provide a wide range of habitats. In fact, the integration of studies in floodplains and the opsin genes in Neotropical cichlids seems to be a promising and still unexplored area in Neotropical regions.

Molecular markers in studies on fish parasites (Platyhelminthes): Review

Studies with molecular markers are currently more common for all groups of living organisms. Molecular techniques used in Platyhelminthes parasites of fishes do not merely reveal complex life cycles, but are important for species distinction and the elucidation of the phylogenetic hypothesis. Current research verified which molecular markers were mainly used phylogenetic studies on Platyhelminthes parasites of fish so that subsidies for further phylogenetic studies in Icthyoparasitology could be provided. Data base of CAPES Journals platform was employed for bibliometric analysis comprising the keywords “fish” and “phylogeny” associated with “Cestoda”, “Digenea” or “Monogenea”. Information retrieved was quantified and tabulated. Most studies were on Monogenea (43%), followed by Digenea (37%) and Cestoda (18%). Ribosomal molecular markers were the most used in the phylogenetic studies for fish parasites. Due to the advance of molecular biology techniques and of bioinformatics, with more robust phylogenetic analysis, the use of these techniques in other areas such as Ichytioparasitology is on the increase. In fact, molecular phylogenetics and morphological structures analysis have efficiently contributed towards the understanding of phylogenetic relationships among the groups.