Evaluation of the Territorial Dispute by the Freshwater Crab Dilocarcinus pagei Stimpson, 1861 (Crustacea, Brachyura, Trichodactylidae), in Laboratory

The knowledge on freshwater decapods behavioral aspects is scarce, mainly, with respect to representatives of the family Trichodactylidae from South American. Thus, this study aimed to describe the territory dispute behavior of the freshwater crab DilocarcinuspageiStimpson; that is a common decapod from the “Pantanal” in Brazil; and it has been used as bait in amateur fishery. Experiments were carried out with seven repetitions using only with male crabs of similar sizes (CW= 39.26± 3.46mm), which were put in pairs inside the enclosures. Experiments were conducted two situations as follows: first treatment - a pair of crabs inserted at the same time into a circular vessel containing bottom sand, gravel, and brick with two holes and a small fish muscle piece; second treatment - a pair of crabs inserted at different times (30 minutes after the introduction of the first crab), with the same variables as in the first treatment. Experiments summed twenty behavioral acts, classified in six categories as follow: feeding, vessel exploration, stopped, social interaction, aggressive acts and self-grooming. The results suggested their aggressive behavior is directly related with the presence of food or shelter. The observed interactions might represent dispute for shelter preventing predation in its natural environment. The natural predators of this crab are known as follow: Rostrhamussociabilis (the snail kite, familyAccipitridae) and fishes of the region, i. e., Pseudoplatystomapunctifer, Brycon sp. and Piaractumesopotamicus; which were fished using living crabs as baits by fisherman. Further detailed studies should be accomplished to estimate the natural density of this crab species, which may provide more robust answers in relation to territoriality degree, besides an evaluation of its conservation status in the nature.

Keywords: freshwater, aggressive behavior, male’ crabs, brachyuran, BrazilianPantanal.