Animal Health & Research, S.E.A. Aquarium, Marine Life Park, Resorts World Sentosa, Singapore
Open Ocean Habitat (OOH) is the biggest exhibit in S.E.A. Aquarium, Resorts World Sentosa (RWS) in Singapore. Its total volume is 20,800 m3 of tropical seawater. The system is a biological marine water system with mechanical filtration, ozone disinfection and water temperature of 26–27°C. This mixed-species exhibit housed approximately 40,000 tropical fish and elasmobranches [e.g., Manta rays (Manta sp.), spotted eagle rays (Aetobatus narinari), shark rays (Rhina ancylostoma), zebra sharks (Stegostoma fasciatum), black-blotched stingrays (Taeniura meyeni), etc.].
In August 2013, it was reported that all three manta rays were developing multiple diffused white patches on the skin and cephalic lobes. Subsequently, one manta ray was caught for physical examination. During examination, skin scrapes, blood and morphometric were performed. All initial indications and cytological descriptions pointed to Caligoid copepods infestation as a cause of the lesions.1,2
Considering the size and composition of OOH habitat, diflubenzuron (Dimilin®) was considered as an effective and safe treatment at 0.02 mg/L through bio-testing at our quarantine facility with different species of elasmobranches and as described in reviewed literature.1,3,4 The target exposure time was calculated for a minimum of 8 hours, and the regime was as follows: at 0830 hours, Ozone, FF venturi pump turned off during treatment and turned on all components at 1630 hours, making an eight hours prolonged immersion treatment. Food was reduced 25% during treatment day. The drug was re-dosed after 40 hours after finishing the last dosing for a total of 10 treatments (3 weeks). No parasites were observed after complete treatment. No adverse effects on water-quality parameters. In addition, water samples were collected pre-treatment, during treatment and post-treatment and submitted for organophosphate analysis at Agri-Food & Veterinary Authority (AVA), Singapore, to measure the levels of diflubenzuron residual concentration.
The authors wish to thank Dr. Tonya Clauss of Georgia Aquarium and Tim Graham of Aqua Design and Management for their assistance in this case. The authors thank the staffs of Animal Health & Research and Life support system team of S.E.A. Aquarium at Resorts World Sentosa.
* Presenting author
1. Benz GW, Bullard SA. Metazoan parasites and associates of chondrichthyans with emphasis on taxa harmful to captive hosts. In: Smith M, Warmolts D, Thoney D, Hueter R, eds. The Elasmobranch Husbandry Manual: Captive Care of Sharks, Rays and their Relatives. Ohio Biological Survey; 2004:325–415.
2. Boxshall G. Copepoda (copepods). In: Rohde K, ed. Marine Parasitology. CSIRO Melbourne and CABI Wallingford; 2005:123–138.
3. Hadfield CA, Jones TG, Clayton LA. Successful treatment of fish lice (Argulus sp.) in a 30,000-gallon mixed-species exhibit. In: Proceedings of the International Association for Aquatic Animal Medicine 43th Annual Conference, Atlanta, GA; 2012:20–21.
4. Noga EJ. Copepod infestation/infection. In: Noga EJ. Fish Disease: Diagnosis and Treatment. St. Louis, MO: Mosby; 1996:79–85.