Studies on the biology of the gyrodactyloidea (monogenea)

Abstract

This study has examined the interaction between the viviparous rnonogenean GyrodactYlus and sticklebacks. Six species of Gyrodactylus were collected from Gasterosteus aculeatus and Pungitius pungitius in Britain. Each was narrowly host specific, and was restricted to either the gills or the body surface of the fish. A difference in attachment mechanism was noted between gill parasites (e.g. G. rarus), in which the hamuli were more important, and skin parasites (e.g. G. gasterostei), which relied upon the marginal hooks .. The observed growth rate of G. gasterostei populations upon Gasterosteus aculeatus was considerably slower than the calculated potential rate. In the later stages of infestation the population declined, possibly as a result of an increase in the probability of the ~. parasites becoming detached. This may have been related to an observed increase in the number of goblet mucus cells in the skin of infected fish. Although detached parasites were able to reinfect other fish, infection more frequently resulted from transmission during host-host contact. The abundance of Gyrodactylus spp. in the river Ver, Herts., England, was found to be limited by the annual life cycle of the hosts, which restricted transmission between adults and fry to a short period in midsummer. A comparison was made with the biology of the related Gyrdicotylus gallieni, from the amphibian Xenonus laevis. This parasite, which has a suctorial attachment mechanism, inhabits the mouth of its host, entering this habitat via the nostrils. The slow population growth, and preponderance of older flukes in the population suggests that this parasite may be adapted for persistence in individual hosts. Q. gallieni has a wider host specificity than GyrodactYlus spp., and has been recorded from five species and sub-species of Xenopus. An oviparous monogenean, closely related to the viviparous genera, has been described from the catfish Farlowella amazonum. The origin and evolution of the gyrodactylids from a form similar to this parasite has been discussed