Ions, carbohydrates and amino acid levels in juveniles of the freshwater crayfish Cherax quadricarinatus exposed to different combinations of temperature and salinity.

PRYMACZOK, N.; CHAULET, A.; MEDESANI, D.A.; RODRÍGUEZ, E.M.

Kuopio

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

International Association of Astacology

The possible stress caused by relatively low temperatures and high salinities was evaluated in juveniles of Cherax quadricarinatus (5-6 g of body weight). Ten animals were maintained for 30 days in each one the following combinations of temperature and salinity: 27 ºC (optimum for the studied species) or 20 ºC, at a salinity of 0 (freshwater), 5 or 10 g/L. They were fed every day on commercial fish food (40 % protein) and fresh leaves of Elodea sp. Photoperiod was maintained at 14:10 (L:D) throughout. At the end of the assay, levels of sodium, potassium, glucose and free aminoacids (FAA) were determined in hemolymph of all animals, levels of glycogen were measured in abdominal muscle and hepatopancreas, while FAA was also determined in abdominal muscle. No significant differences (p>0.05) were detected at 27 ºC in the hemolymphatic sodium level by effect of salinity, but a significant (p<0.05) increase was observed at 20 ºC with respect to 27 ºC, at any salinity, suggesting that ionic regulation would be affected at the lowest temperature. Besides, the  increase of hemolymphatic sodium was highly correlated with an increase of FAA in muscle, probably as a mechanism to adjust cell osmolarity. Moreover, glycemia was significantly (p<0.05) higher at 20 ºC than at 27 ºC, regardless of salinity, while a concomitant decrease of glycogen in abdominal muscle was observed. Obtained results are indicating a marked stress by effect of a relatively low temperature (20 ºC), while no apparent effects of the assayed salinities were seen.