The morphology and life-cycle of the oviparousOögyrodactylus farlowellaegen. et sp.nov. (Monogenea, Gyrodactylidea)

Publisher Website
Google Scholar
Abstract
Summary: Oögyrodactylus farlowellaegen. et sp.nov., an oviparous monogenean, is described from the skin and fins ofFarlowella amazonum, a South American loricarid catfish. The Oögyrodactylidae fam.nov., containingO. farlowellae and Phanerothecium caballeroiKritsky and Thatcher, 1977, is placed with the Gyrodactylidae in the Gyrodactylidea. Although oviparous, the Oögyrodactylids are closely related to the viviparous gyrodactylids. Both families share a combination of characters, including haptor morphology, articulated marginal hooks and spike sensilla, which is not seen in other monogeneans.O. farlowellaeis similar to a hypothetical ancestor of the gyrodactylids and shows that the family arose from monopisthocotylean rather than polyopisthocotylean stock. There is a close resemblance between the reproductive system of the immatureOögyrodactylusand that of the matureGyrodactylus, suggesting that progenesis, involving the precocious maturation of oocytes, may have been important in the evolution of the viviparous genera.O. farlowellaeretains eggs individually in the ootype until embryonation is comparatively advanced. After oviposition the eggs adhere to the substrate and hatch to give a crawling, unciliated larva. These are adaptations to a host which inhabits fast-flowing streams, where the eggs and infective larvae are exposed to a constant, uni-directional water current. The life-cycle (egg to adult) is completed in 11–13 days at 27 °C.
Keywords