Growing in different substrates, and election of substrate, in juveniles of cherax quadricarinatus.

VIAU, V.E.; RODRÍGUEZ, E.M.

Kuopio

Simposio; 17 th Symposium of the International Association of Astacology; 2008

International Association of Astacology

The effect of different substrates on growing was assayed in both early (0.02 g of body weight: BW) and advanced (1 g BW) juveniles of C. quadricarinatus.  Glass aquaria (0.09 m2 bottom) were used, with the addition of: a) plastic mesh, b) stones (0.3-0.4 cm), c) fine sand (0.3-0.5 thickness), or d) no substrate added (control). Twelve early or ten advanced juveniles were placed in each aquarium, in triplicate. Small PVC pipes were added in excess as refuges. A temperature 25 ± 2 °C and a photoperiod of 14:10 (L:D) were maintained throughout. Each aquarium was filled with  8 L of freshwater, replaced twice a week. All juveniles were daily fed ad libitum (40 % protein). After 12 weeks, they were weighed (+ 0.1 mg precision). Early juveniles maintained in substrates c) or d) showed a BW higher than the control group, while no differences were noted among advanced juveniles. In a second experiment, 10 early and 10 advanced juveniles were individually placed in a circular glass aquarium (25 cm diameter) divided in four sections, each one containing one of the substrates used in the first experiment. Time of permanence in each section after 24 hours was registered. For both early and advanced juveniles, a marked preferenced to stones was observed. A same pattern was noted when juveniles that had just ended the first experiment were submitted to the preference assay, indicating that the election of substrate is independent of both body size and previous acclimation to different substrates.