Summary
General aspects of Amazonian fish pathology were discussed, and some of the governing principles were presented, such as: a) Amazonian fishes are little exposed to industrial polution, but sometimes die in large numbers because of reduced oxygen in the water brought on by a combination of a rapidly lowered ambient temperature and the decomposition of vegetable matter, b) The fish most likely to die are those with gill infections, c) Little overt pathology is to be expected in wild-caught fishes since sick fish are soon eliminated by predators, & d) Pathology can be studied by surveying wild fish for parasites, and other pathogens, and then observing the effects of these agents on captive fish. The defense mechanisms used by Amazonian fish against: 1) foreign bodies, 2) fungi, 3) myxosporidians, 4) monogeneoidea, 5) trematodes, 6) cestodarians, 7) cestodes, 8) acanthocephalans 9) nematodes, 10} crustaceans and 11) pentastomids were discussed. Amazonian examples of these pathogens were reported, as were "black-spot disease" and three kinds os "yellow-spot disease". The ascaroid nematode, Goezia spinulosa, which is known to be a hazard to pisciculture, was reported from Amazonia. The "eye-fluke" Diplostomum, which can be pathogenic to fish and fatal to man, was reported from two host species. A case of fatty degeneration of the heart was reported in a large pirarucu, Arapaima gigas, that had been confined to a relatively small aquarium for over a year. It was suggested that insufficient exercise caused this anomaly.