Abstract
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.
Acknowledgements
The authors want to thank Tim Plafcan of United Pet Group and Tamara Marshall of Ocala Reef.
* Presenting author
+ Student presenter
Literature Cited
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