Vol. 52, 2013

Assessing the importance of burrows through behavioral observations of Parastacus brasiliensis, a Neotropical burrowing crayfish (Crustacea), in laboratory conditions

Alexandre V Palaoro, Marcelo M Dalosto, Cadidja Coutinho and Sandro Santos*

Laboratório de Carcinologia, Programa de Pós-Graduação em Biodiversidade Animal, Univ. Federal de Santa Maria, Avenida Roraima 1000, Camobi, Santa Maria 97105-900, Rio Grande do Sul, Brazil

Abstract
Background: Crayfish from the Neotropical region comprise a unique group among crustaceans. Their burrowing habits have severe consequences for many ecological, morphological, and behavioral traits. Although they are all considered true burrowers, the degree of these adaptations and their relationships to the behavioral repertoires of these crustaceans have been discussed for a long time, although with no consensus.
Results: To address this situation, we performed behavioral observations of Parastacus brasiliensis in a laboratory environment. Animals (n = 7) were isolated and acclimated in experimental aquaria according to their size (two large and five smaller aquaria) and observed for seven days at four different times of the day (twice during the day and twice at night). Their behaviors were qualified and quantified. The time spent inside and outside the burrow was also observed and analyzed with a t test for paired samples. Their circadian activity was analyzed using Rayleigh's Z test. Animals spent 54.9% of the time hiding within the burrow and also remained longer in it during the day than at night. They spent more time active outside the burrow during the night.
Conclusions: These results suggest that these crayfish are nocturnal and are definitely not a part of the lotic species group. This species appears to be closely associated with its burrow but can exhibit considerable activity outside of it and can therefore be classified as a secondary burrower. Although this is a laboratory study, the results may stimulate further studies on the importance of burrows to these animals and provide basic background information for new studies on these cryptic crustaceans.

Key words: Parastacidae; Ethogram; Parastacus; Circadian activity; Decapoda.

*Correspondence: E-mail: sandro.santos30@gmail.com