Effect of Temperature on Oviposition of Dacylogyrus extensus Mueller & Van Cleave, 1932 (Monogenea, Dactylogyridae)

Abstract

Dactylogyrus extensus is a common, economically significant pathogenic monogenean ectoparasite of Cyprinus carpio. It attaches itself to its host by means of an opisthaptor containing two hamuli, a connecting bar and 14 marginal hooks. Smaller D. extensus which are found in higher numbers in fish presumably represent the recently invaded individuals. Large worms are found in lower numbers. D. extensus does not need to attach itself to the host tissue to initiate egg laying. The rate of egg laying varies with the environmental temperature. The first eggs that are produced in-vitro are of larger size but as oviposition continues the size of the egg becomes smaller. The mean oviposition rates were 2.03, 1.97, 1.45 eggs-1worm-1 at 11°C, 13°C and 19°C respectively. The time taken to lay an individual egg was calculated as 29.60 mins, 30.45 mins and 41.38 mins at 11°C, 13°C and 19°C respectively.