Seasonal Occurrence of Helminths in Freshwater Fishes: Part III. Larval Cestoda and Nematoda

Abstract

Publisher Summary This chapter discusses the life cycles and seasonal occurrence of larval cestodes and nematodes. The life cycles of all the larval cestodes and nematodes are complex, and mostly require three hosts, an invertebrate first intermediate host, the fish second intermediate host, and a suitable definitive host, which, according to parasite species, can be a fish, an amphibian, a bird, or a mammal. Many of the larval stages in fishes are of economic importance, for example, Triaenophorus crassus, Diphyllobothrium dendriticum, Ligula intestinalis, Digramma interrupta, and Eustrongylides species, or present a public health problem if eaten by man in uncooked fish, for instance, Diphyllobothrium latum. Studies on helminths in lakes and reservoirs with thermal pollution from power stations have shown that in the heated areas there were increases in abundance of L. intestinalis, speeding up of the reproductive processes. There is an unfortunate scarcity of information about seasonal variations of helminths of freshwater fishes in the tropical regions of the world.