Effect of temperature on molt increment and intermolt period of a juvenile Australian fresh-water crayfish, Cherax destructor

The effect of 3 temperatures (22, 25, and 28 degrees C) on molt increment and intermolt period in juvenile C. destructor (the yabby) was investigated under laboratory conditions. Newly independent juveniles were grown individually in 1-1 polyethylene containers for 6 molts from molt stages 3-9. Both the intermolt period and molt increment decreased with increasing temperature. The mean intermolt periods were 6.7, 5.5, and 5.0 days and mean molt increments were 102, 98, and 93% at 22, 25, and 28 degrees C, respectively. Regression models derived by combining molt increment and intermolt period data indicated that overall growth increased with increasing temperature. Pairwise comparisons of regression coefficients indicated that the growth rate of juvenile C. destructor at the two higher temperatures (25 and 28 degrees C) did not differ, but was significantly reduced at 22 degrees C. Thus, a shorter intermolt period, in spite of a reduced molt increment, is responsible for superior growth of juveniles of this species at elevated temperatures.