In reef aquaria, fish may need to be removed for quarantine, medical treatment, or husbandry reasons. Sedation of resident fish may facilitate capture and eliminate the need to expose sensitive invertebrate inhabitants to physical manipulation and potentially hazardous medical treatments.1-3 Tricaine methanesulfonate (MS-222) is currently the only FDA-approved sedative or anesthetic for fish.4 MS-222 has also been used in cnidarians, including medusozoans (jellies) and even actinarians (sea anemones).5,6 However, no studies have been conducted to determine the drug's effects on coral health to date.
The objective of this study was to evaluate morbidity and mortality of the green star polyp coral (Pachyclavularia violacea) when exposed to a common anesthetic dose of MS-222 (150 mg/L) for one hour.2,3 Pachyclavularia violacea was chosen for this study because it is a popular addition to many reef aquariums and is readily available. Pachyclavularia violacea is a soft coral that grows by spreading over rocks and substrate, and it is easily propagated.7 The genus Pachyclavularia has a behavioral response to withdraw its polyps when threatened, which serves as an observable indicator of stress.7 For this study, 16 circular frag rocks (32 mm in diameter) covered with P. violacea were evenly divided among 8, 10-gallon aquariums. The aquariums were stand-alone systems, each outfitted with a 50-watt heater, thermometer, hang on the back filter, and LED lighting. Instant Ocean synthetic sea salt was added to well water to create 33 ppt salinity. With regular "top-offs" of fresh well water, water parameters (temperature, pH, and salinity) were consistent throughout the study, at 24°C, pH 8.0, and 33 ppt salinity. Literature suggests that 150 mg/L is a useful anesthetic dose for many reef fishes, so treatment aquariums (n = 4) were exposed to 150 mg/L of buffered MS-222 (2:1 w/w sodium bicarbonate to Tricaine-S) and control aquariums (n = 4) were treated with sodium bicarbonate alone.2,3 One hour following treatment, activated carbon was added to the filters and left for the remainder of the experiment to remove the MS-222.8 The corals were observed for polyp extension, as well as polyp and base mat color and texture 10, 30, and 60 minutes after treatment, and every 24 hours after treatment for 7 days. There were no observable changes between the two groups within one week of treatment. One coral sample was taken from each aquarium 24 hours and 7 days after exposure, fixed in Z-Fix®, and processed for histopathology. There was no microscopic evidence of tissue damage or loss in either group of corals throughout the experiment.9,10
These results suggest that Pachyclavularia violacea can be exposed to 150 mg/L of MS-222 without significant compromise. This study is an important first step in determining whether MS-222 may be an appropriate tool to facilitate capture of fish from living reef aquaria.
The authors want to thank Tim Plafcan of United Pet Group and Tamara Marshall of Ocala Reef.
* Presenting author
+ Student presenter
1. Crosby TC, Hill JE, Martinez CV, Watson CA, Pouder DB, Yanong RP. Preparation of ornamental fish for shipping. University of Florida IFAS Extension [Internet]. 2011 [cited 2016 January 26]. Available from: http://edis.ifas.ufl.edu/fa120.
2. Neiffer DL, Stamper MA. Fish sedation, anesthesia, analgesia, and euthanasia: considerations, methods, and types of drugs. Institute for Laboratory Animal Research Journal. 2009;50(4):343–360.
3. Noga EJ. Fish Disease: Diagnosis and Treatment. 2nd ed. New York: John Wiley & Sons; 2010:519.
4. U.S. Food and Drug Administration [Internet]. Approved drugs for aquaculture. 2014 [cited 2016 January 23]. Available from: http://www.fda.gov/AnimalVeterinary/Development ApprovalProcess/Aquaculture/ucm132954.htm (VIN editor: Link could not be accessed as of 3-31-16).
5. Lewbart GA. Invertebrate Medicine. 2nd ed. New York: John Wiley & Sons; 2011:507.
6. Siddiqui S, Goddard RH, Bielmyer-Fraser GK. Comparative effects of dissolved copper and copper oxide nanoparticle exposure to the sea anemone, Exaiptasia pallida. Aquatic Toxicology. 2015;160:205–213.
7. Borneman EH. Aquarium Corals: Selection, Husbandry, and Natural History. Charlotte, VT: Microcosm Limited; 2001:464.
8. Dawson VK, Marking LL, Bills TD. Removal of toxic chemicals from water with activated carbon. Transactions of the American Fisheries Society. 2011;105(1):119–123.
9. Work TM, Aeby GS, Hughen KA. Gross and microscopic lesions in corals from Micronesia. Veterinary Pathology. 2016;53(1):153–162. doi: 10.1177/0300985815571669.
10. Galloway SB, Work TM, Bochsler VS, Harley RA, Kramarsky-Winters E, McLaughlin SM, Meteyer CU, Morado JF, Nicholson JH, Parnell PG, Peters EC, Reynolds TL, Rotstein DS, Sileo L, Woodley CM. Coral disease and health workshop: coral histopathology II. NOAA Technical Memorandum NOS NCCOS 56 and NOAA Technical Memorandum CRCP 4. Silver Spring, MD: National Oceanic and Atmospheric Administration; 2007:84 p.