Diversidade das linhagens de siris do gênero Callinectes (STIMPSON, 1860) no Golfão Maranhense a partir dos marcadores de DNA mitocondrial e nuclear

Abstract

Crabs belonging to the genus Callinectes Stimpson, 1860 are an ecologically and socioeconomically significant group of benthic organisms. Knowledge of the phylogenetic relationships and diversity of their lineages is an important parameter for their conservation and management. Thus, the objective of this work was to describe the diversity of crab lineages of the genus Callinectes present at the eastern limit of the Brazilian Amazonian coast. The dissertation is structured into three chapters. Chapter I examines the primary objective of this study. In contrast, the other chapters provide supplementary and novel information on cannibalism and document the first occurrence of a taxon in the region. Chapter I addresses cryptic diversity in Callinectes swimming crab species on the Brazilian Amazon coast using phylogenetic analyses based on four mitochondrial markers (Cytochrome c oxidase subunit I: COI; 12S rRNA: 12S; 16S rRNA: 16S; and Cytochrome b: Cyt b) and one nuclear marker (ATP/ADP translocase). Different species delimitation methods (ABGD, ASAP, PTP, and GMYC) and haplotype networks were also used for population analyses. A total of 117 specimens were captured and identified, of which 50 were included in the analyses: 25 identified as Callinectes bocourti Milne-Edwards, 13 as Callinectes danae Smith, 1869, six as Callinectes exasperatus Gerstaecker, 1856, three as Callinectes ornatus Ordway, 1863, and three identified as Callinectes marginatus A. Milne-Edwards, 1861. A total of 43 sequences were produced for mitochondrial DNA and four for nuclear DNA, some of which are novel for Brazil and the Brazilian Amazonian coast. Most of the markers analyzed were able to recover monophyletic groups for each species, except for C. marginatus and Callinectes larvatus Ordway, 1863, which clustered into a single clade, suggesting a recent speciation process. The delimitation models were able to recover MOTUs, which in most cases corresponded to the species and the identification assigned to the sequences extracted from the databases. The results revealed that species from the east coast of the Amazon exhibit unique and contrasting genetic patterns. At the population level, the only species that showed divergence were C. bocourti and C. ornatus, suggesting the possible existence of cryptic diversity in these species. Chapter II presents the first record of C. marginatus in the state of Maranhão, with three individuals collected in the eastern region of the Brazilian Amazon coast, expanding the distribution map of this species along the Brazilian coast. Chapter III describes, for the first time, a case of cannibalism between two individuals of C. ornatus under natural conditions, providing new information on the behavior of this species and suggesting a possible mechanism of population regulation. Our study not only fills a historical gap in the knowledge of Callinectes on the Amazonian coast, being the first phylogenetic work carried out in the region,but also presents the first record of C. marginatus occurrence in Maranhão and the unprecedented description of natural cannibalism in C. ornatus. This information is of extreme relevance, as it expands the knowledge about the aquatic biodiversity of the Brazilian Amazonian coast and serves as a basis for effective management and conservation measures for this important fishery resource.