Efficacy of Praziquantel Bath Treatments for Monogenean Infections of theRhinobatos typus

Abstract

Abstract The efficacy of the anthelmintic Praziquantel in removing monocotylid monogeneans (Platyhelminthes) from the branchial tissue (Neoheterocotyle rhinobatidis, N. rhynchobatis, and Troglocephalus rhinobatidis) and nasal tissue (Merizocotyle icopae) of juvenile giant shovelnose rays Rhinobatos typus from Heron Island, Australia, was studied. Although effective in removing monogeneans in vivo from the skin and gills of the teleost yellow stripey Lutjanus carponotatus from the same locality, two 2-h treatments using 20 mg/L Praziquantel was ineffective for the giant shovelnose ray. Adult monocotylids were removed, but many post-oncomiracidia and some juveniles remained attached. Juvenile and adult N. rhinobatidis and T. rhinobatidis reacted similarly when exposed to 20 mg/L Praziquantel during in vitro experiments, exhibiting muscle contractions and dying after 12 and 14 h, respectively. We attribute the failure to remove small monogenean stages in vivo to the structure of the branchial and nasal tissu...