Description of the development of the attachment and copulatory apparatus of Dactylogyrus extensus from Cyprinus carpio var. koi

In July 2005 a Koi carp from a private pond in Bavaria was investigated. The aim of the presently reported study was to determine the composition of the monogenean fauna of Koi carp, Cyprinus carpio var. koi and to observe the development of Dactylogyrus extensus, under natural conditions, on the fish gills. A total of three species were recovered, namely: Dactylogyrus extensus Müller et Van Cleave, 1932, Dactylogyrus minutus Kulwieć, 1927, and Gyrodactylus cyprini Diarova, 1964. The dominant species was D. extensus, while the remaining monogeneans were not abundant. Six developmental stages of D. extensus were defined and they were compared with those previously observed by Prost (1963), under experimental conditions. The differences observed in size of the sclerotised structures of the haptor and the copulatory apparatus were discussed.