Metabolic integration during the host associations of multicellular animal endoparasites.

The nature of metabolic interaction during parasitic infection was discussed and the concept of metabolic integration outlined. The subjective nature of the integrative argument was noted. The parasite-host relationships of larval trematodes of the genus Schistosoma with their intermediate molluscan hosts, the nematode Trichnella spiralis and cestode Hymenolepis diminuta, with their definitive hosts, as well as the hymenopterous insect parasite, Hyposoter exiguae, with its insect host, Trichoplusia ni, were examined. The significance of the immune system in the establishment of the parasite-host association and the means by which parasites evade host defense were discussed. The involvement of microorganisms or "hyperparasites" during the host associations of multicellular parasites was described. The importance of evolutionary considerations in assessing the nature of metabolic interaction and its significance to the success of the parasite-host relationship was emphasized. The use of teleological assessment and anthropomorphic description was discussed.