Specific dynamic action (SDA) in the supralittoral isopod, Ligia pallasii: Relationship of growth to SDA

Abstract

1. 1. The relationship of Specific Dynamic Action (SDA) to growth was examined in the supralittoral isopod Ligia pallasii using a seaweed diet fed at different rations. 2. 2. Animals increased in live weight by 33% on an ad libitum or 100% diet and by 2% on a 20% ration over a 10-week period. 3. 3. Weight-specific VO 2 was significantly higher in animals eating the 100% diet than in ones eating the 20% diet. Decline in VO 2 with time in animals on the 20% diet was probably due to poor health associated with a maintenance ration. 4. 4. SDA per unit weight of food eaten was 18% higher in the 20% diet group than in the 100% one, and values remained constant over time in both groups. 5. 5. k 1 growth efficiencies (production/consumption) were higher in animals on 100% ration than in ones on 20% ration. Efficiencies declined with time in both diet-groups and fell below zero in the 20% ration-group, coincidental with weight-loss in some of the animals. 6. 6. Overall SDAs for the 10-week period were positively correlated with growth ( r 2 = 0.77), but there was no way to separate this from amounts eaten as an effect on SDA.