[Okinawa Churaumi Aquarium] Development of a New Treatment Method for Fish Parasites Applying 'Shark Artificial Amniotic Fluid'

Okinawa Churaumi Aquarium (Location: Motobu, Kunigami District, Okinawa Prefecture; Director: Keiichi Sato) announces the development of a new treatment method for parasitic infections in captive fish. This technology was developed by partially applying techniques from the 'shark artificial uterus' research that the aquarium has been conducting since 2017.

Background of the Research Monogeneans are parasites of several millimeters in size that attach to the skin and gills of fish, and a heavy infestation significantly affects the host's health. In aquariums, a method called 'freshwater bath,' where the infected fish are soaked in freshwater for a short time, is widely used to remove these parasites. However, this method cannot be applied to fish that are extremely sensitive to freshwater environments, such as some agnathans (hagfish) and elasmobranchs (sharks and rays). Aquariums that house diverse fish species needed a treatment applicable to fish for which freshwater baths cannot be used.

Development History As part of the 'shark artificial uterus' development, the aquarium developed a solution (artificial amniotic fluid) in 2021 for raising shark fetuses outside the mother's body. This solution is a mixture of freshwater, seawater, and urea in specific ratios, and it has chemical properties similar to shark plasma. Subsequent research suggested that this solution could be effective not only for raising shark fetuses but also for eliminating parasitic monogeneans.

By adjusting the mixing ratios of freshwater, seawater, and urea, the aquarium successfully developed a solution (urea water) that can safely and efficiently eliminate monogeneans while remaining safe for the host agnathans and elasmobranchs.

Overview of the Parasite Removal Method Fish infected with parasitic diseases are soaked for a short time (about 5 minutes) in a solution of mixed seawater, freshwater, and urea (urea water) to eliminate the monogeneans attached to the body surface. This technology has been patented as a safe method for removing parasites in agnathans and elasmobranchs where freshwater baths cannot be applied. - Invention Title: Method for removing epidermal monogenean parasites - Applicant: Okinawa Churashima Foundation - Date of Registration: May 20, 2026 - Patent Number: Patent No. 7866821 This technology is already being used to treat hagfish at the aquarium. The aquarium will continue to develop new husbandry techniques through research to realize better welfare for captive animals.