Dietary effects on growth, reproduction, body composition and stress resistance in the terrestrial isopods Oniscus asellus and Porcellio scaber

The effect of differences in food composition on growth, body composition a nd cold tolerance of the isopods Porcellio scaber (Latreille) and Oniscus a sellus (L.) has been studied. The effect on reproduction of P. scaber was i ncluded. Total lipid and protein content remained the same in O. asellus, g iven food with a nitrogen content of 2.4, 2.5, 2.8 or 3.1% for 8 weeks. Tho se fed on 3.1% N gained significantly more weight than those fed on 2.4, 2. 5 or 2.8% N. Cold tolerance after a period of low temperature acclimation c ould not be tested, due to high mortality at the subzero treatment. Haemoly mph osmolality increased after the winter acclimation for all food treatmen ts. Juvenile P. scaber, given food of 1.8, 2.5 or 3.1% N, showed no differe nce in growth over 18 weeks, nor in body composition over 14 weeks. Diet di d not influence cold tolerance ability and haemolymph osmolality remained t he same with changing cold tolerance of the animals. Gravid females of P. s caber were separated to examine the effect of diet on reproduction. Diet di d not influence the number of juveniles, nor their weight. In all food trea tments, a significant correlation was found between the weight of the femal e and the number and weight of her offspring.