Energetic reserves and growth of advanced juveniles of the freshwater crayfish Cherax quadricarinatus, fed on an ecdysone-enriched diet.

CHAULET, A.; CAHANSKY, A.V.; VIAU, V.E.; GUTIÉRREZ, M.L.; TURCATO OLIVEIRA, G.; RODRÍGUEZ, E.M.

Coquimbo

Congreso; The Crustacean Society mid-year meeting; 2007

The Crustacean Society

Ten advanced juveniles of the crayfish C. quadricarinatus (1.00 ± 0.30 g of body weight) were fed for 4 months on each of two diets, i.e., K: krill flour (with Tetra Pond® in a 6:4 proportion, final protein percentage: 48.2 %), and KE: same diet as K, but with α-ecdysone (Sigma Co.) added at a dose of 3.33x10-9 mol/g of food. Each animal was isolated in a glass recipient, with dechlorinated fresh water. Each experimental group was fed three times a week on the corresponding diet. Since suministered food represented 3% of juvenile biomass, the dose of ecdysone received by juveniles treated with this hormone was 10-10 mol /g of body weight, in every feeding session. As a complement, the remaining days of the weeks all animals were fed on Tetra Diskus® and fresh leaves of Elodea sp. A temperature of 26 ± 1 ºC, and a photoperiod of 14:10 (L: D) were maintained throughout.  Animals were weighed every 2 weeks. At the end of the assay, a sample of hemolymph was withdrawn from each animal and the hepatopancreas was dissected for further analysis of energetic reserves. Glucose and glycogen were measured by means of an enzymatic kit (Labtest); proteins were measured according to Lowry method, while total lipids and cholesterol were determined through the Folch´s method. KE group showed significant (p<0.05) lower levels of both total lipids and cholesterol in hemolymph than the other group. Besides, increased levels of both proteins and glycogen were observed in the hepatopancreas of the KE group that also showed a higher weight gain than K group. No differences in molting frequency were noted between experimental groups. Taken together, these preliminary results are suggesting that an anabolic effect of the ecdysone could be taking place during the intermolt period of juvenile crayfish.