Morfologia das tocas do caranguejo fantasma ocypode quadrata (brachyura: ocypodidae) em duas praias com morfodinâmicas distintas no Litoral do Estado do Ceará, Brasil

Abstract

Crabs of the genus Ocypode (ghost crabs) are outstanding representatives of macrofauna in tropical and subtropical regions of sandy beaches being Ocypode quadrata the representative species of the genus in Brazil. Studies on the morphology of the burrows of Ocypode are still scarce and its burrowing activity of considerable importance for the modification of the complexity of sandy beaches, productivity and physical modification of the environment. In northeastern Brazil, research on ghost crab are still recent and scarce. Thus, this study intends to identify the burrows morphology patterns of two populations of O. quadrata at beaches with different morphodynamic characteristics on Ceará coast. Sampling was carried out on the beaches of Icaraí and Redonda during the dry season, in July and August, in 2014. Two beach profiles were performed to characterize the morphodynamics of the beaches. Random burrows of O. quadrata were selected along an area in the upper shore of the beach environment. Expansive polyurethane foam was used to obtain burrows casts. The beaches classification by Dean's parameter (Ω) and relative tidal range (RTR) showed that Icaraí beach is a low tide bar/rip and Redonda is an ultra-dissipative beach. Burrows were obtained in simple shapes, in Y, Y-winding, Y-multiple arms and in J. Where was observed the existence of a greater burrow complexity on Redonda's beach and a greater depth of the same in Icaraí. Statistical analysis between measurements obtained in casts and biometrics of the crabs showed a significant difference between the two beaches and the different burrow shapes, however, the Tukey’s test showed no significant differences in most formats. Only burrows in simple shape were the ones that show some significant difference. The simple shape burrows may indicate to be an intermediate stage between the formation of the burrows in Y and J. The morphodynamics of beach influences on the burrow construction and complexity, where in reflective beaches, the crab tend to build deeper burrows, in search of more stable conditions and dissipative beaches the crabs do not need to prioritize the construction of deeper burrows, therefore they have energy reserves to increase the degree of complexity of the same.