EFFECT OF THE CASTRATING TREMATODE PARASITE RHIPIDOCOTYLE-FENNICA ON ENERGY ALLOCATION OF FRESH-WATER CLAM ANODONTA-PISCINALIS

1. If host survival is important to a parasite, it should avoid the us e of the host's maintenance energy. Selective use of the host's energy is possible by selecting which part of the host to penetrate and when to be active. 2. We study the effects of the castrating trematode par asite Rhipidocotyle fennica on energetics of fresh-water clam Anodonta piscinalis. 3. Before production of offspring, uninfected clams alloc ate energy to shell growth and glycogen storage. During offspring prod uction shell growth slows down, clams lose weight and consume the stor ed glycogen. Concurrently the fat content of clams increases indicatin g the collection of long-term storage for maintenance during the winte r. 4. Infected clams lack glycogen reserves and are lighter, but conta in more fat than uninfected clams. Parasite reproduction occurs concur rently with the development of offspring in uninfected clams. During t heir reproduction, parasites use the energy that would otherwise be di rected to host reproduction, without interfering with the maintenance energy of the host. Using only the reproductive energy is an efficient way to use the host without causing increased risk of mortality.