DEPENDENCE OF THE PARASITIC FAUNA OF FISH AND AMPHIBIA UPON ECOLOGICAL PECULIARITIES OF THE HOST

Abstract

This chapter describes the dependence of the parasitic fauna of fish and amphibia upon ecological peculiarities of the host. Many external parasites such as Trichodina and Gyrodactylus are tolerant of wide variations of inorganic salt content of the water. In marine estuaries, species diversity is least pronounced at intermediate points where fluctuations of salinity are greatest. The diet of fishes and amphibians is the most important of all biotic features in determining the nature of their parasite faunas. As a rule, feeding activity and parasite numbers are greatest during the warmer months. Seasonal changes in the flow of water, concentration of salts, and nutrients, and deposition of inorganic and organic materials on the bottom of ponds, lakes, and streams can markedly change the numbers and kinds of vertebrates and invertebrates, in addition to their parasites. Those frogs and salamanders that move between land water but are predominantly aquatic possess more kinds of parasites than to the more terrestrial species because of the more varied habitats encountered by the former group.