Hábito alimentar de Pachygrapsus transversus (Gibbes, 1850) (Brachyura: Grapsidae) em um ambiente recifal na praia de Gaibú (Pernambuco-Brasil)

Abstract

The aim of this study was to discribe feeding behavior of Pachygrapsus transversus (Gibbes, 1850, in the beach of Gaibú, verifying the occurence frequence, abundance and relative contribution of each food item in total volume of ingested food, comparing data between different aspects such as sex, stage of moltcicle, sample locals and seasonality on collected sample group in Gaibú beach, considering that this is one of the most common species of the Grapsidae Family in brazilian and northeanstern coast which have known influence in different trophic levels, potentiated factor by their abundance and omnivorous habit. The samplings were realized monthly during the sizygy tides between the period of september/2018 and september/2019, there were determinated two points of sampling, point 1 beying near the beach and point 2 beying closer to the sea. There was used the point method to calculate the occurence frequence, relative contribution and food index of each item. The chi-square test (X²) with significance level at 5% (a = 0,05), for analyze possible diferences between both sexes. The ER (stage of repletion) is related to how much each stomach is full, there were defined 3 stages for ER, which are: low fullness (E1), medium fullness (E2), total fullness (E3) and empty (E0). Each repletion stage recives one value to be integrated to the calculations of the poiting method, for calculate the food index, relative contribution and the relative frequence of each food item. The results showed one variety of 15 food itens: algae, mond, shell fragments, sea urchin thorn, amphipoda, sedment, eggs, microplastic, gastropoda, mite, isopoda, stomatopoda, copepoda, chironomidae larva, coleóptera, beying these vegetable and animals food, characterizing, thus, their omnivory also in the local of this study. Mond and algae were the most representative itens showing, respectively, 59.73% and 55.75% of volume in the stomach contente. The presence of sedment and other food itens rich in minerals showed changes according to the moltcicle stage, indicating that can variate accordingly the bigger necessity of minerals, as a result of the formation of the carapace in cases of individuals in the pre molt and post molt phases. There were verified the presence of microplastic in 22.79% of stomachs, in the form of blue and red fibers. There were not found significant difference in relation to the food index between male and female, as in referente to the feeding in general as in ingestion of microplastic. However, in a smaller scale, looking to the relative frequence, there was found more microplastic in ovigerous females, indicating a bigger susceptibility to the contamination by them, what can be explained by the bigger quantity of food ingested by ovigerous females, because of the bigger energy demand.