Abstract
Moray eels (family Muraenidae) are commonly exhibited in aquariums; however, relatively little has been published about the common causes of morbidity and mortality in these fish.1-6 The objective of this study was to determine the most significant causes of morbidity and mortality in aquarium-maintained green and purple mouth moray eels. Medical records and pathology reports for forty purple mouth morays (Gymnothorax vicinus) and eight green morays (Gymnothorax funebris) housed at Mystic Aquarium over a ten year period were retrospectively reviewed. Mortality in this examination period consisted of seven purple mouth (P) and four green (G) morays. Assessment of morbidity came from a total of 73 examinations of purple mouth morays and 37 examinations of green morays. The most common cause for veterinary evaluation in both species was traumatic wounds from conspecifics and other fish in the system (P = 20, G = 14). Purple mouth morays additionally demonstrated frequent self-trauma from rubbing within the exhibit (P = 16, G = 1). Clinical manifestation of lipid deposition diseases (including lipid keratopathy, lipogranulomatous dermatitis, fatty dermal nodules, and hepatic lipidosis) was the next most common cause for veterinary evaluation in both species (P = 17, G = 5). Purple mouth morays exhibited coelomic distension and complications from egg retention (P = 7); nasal issues including blunting of the nasal papilla (P = 5) and bacterial rhinitis (P = 4); lethargic behavior of unknown etiology (P = 2, G = 1); and an epidermal papilloma (P = 1). Green morays exhibited gastric and intestinal issues including gastric and intestinal hyperplasia (G = 4), gastric and intestinal polyps (P = 1, G = 3), gastritis/colitis (G = 2), and chronic regurgitation (G = 1); bacterial dermatitis (G = 5); and buoyancy problems associated with swim bladder disease (G = 1). Causes of mortality included: trauma (P = 2, G = 1); bacterial rhinitis and septicemia (P = 2); cutaneous ulceration, hepatic lipidosis, and myocyte degeneration possibly indicative of essential fatty acid or vitamin/mineral deficiency (P = 2); bacterial coelomitis (P = 1); chronic papillomatous gastric mucosal hyperplasia, hepatic lipidosis, and systemic lipid deposition (G = 2); and one euthanasia due to swim bladder dysfunction (G = 1). Data from a survey of four cooperating aquaria that also house purple mouth and green morays was compared to determine whether similar causes of moray morbidity and mortality were observed across facilities. Predominant causes of morbidity and mortality of purple mouth and green morays at these facilities were consistent with our findings and included lipid keratopathy, traumatic wounds, bacterial skin issues, septicemia, and gastric hyperplasia and polyps. This investigation demonstrates that trauma and diseases related to lipid storage and metabolism are frequent causes of morbidity in both managed purple mouth and green morays. Complications from egg retention and bacterial rhinitis appear to be significant in purple mouth morays whereas gastrointestinal hyperplasia and polyps appear to be significant in green morays. A more complete understanding of important morbidity and mortality issues in these moray species can guide aquarists and clinicians in their husbandry, and preventative and clinical medicine. Tank population and diet management (including addressing feeding frequency, volume, type of food, and supplementation practices) have been implemented and appear to be useful in reducing the occurrences of trauma and the clinical manifestations of lipid accumulation.
Acknowledgements
The authors would like to thank the following clinicians at other facilities housing purple mouth and green morays who completed and returned the surveys: Dr. Mike Hyatt of Adventure Aquarium, Dr. Craig Harms of the North Carolina Aquariums, Drs. Charlie Innis and Julie Cavin of the New England Aquarium, and Drs. Tres Clark and Robert MacLean of the Audubon Nature Institute Aquarium of the Americas. Drs. Inga Sidor and Salvatore Frasca, Jr., the pathologists who assessed the biopsies on live eels, and tissue sets on eel mortalities during this period, are also acknowledged for their exceptional contribution.
* Presenting author
+ Student presenter
Literature Cited
1. Clode AB, Harms C, Fatzinger MH, Young F, Wert D. 2012. Identification and management of ocular lipid deposition in association with hyperlipidemia in captive moray eels, Gymnothorax funebris Ranzani, Gymnothorax moringa (Cuvier) and Muraena retifera Goode and Bean. J Fish Dis 35:683–693.
2. Erlacher-Reid C, Hoffman W, Priede M, Pulver R, Tuttle AD. 2011. Plasma biochemistry values of recently wild-caught purple mouth moray eels (Gymnothorax vicinus). J Zoo Wildl Med 42:671–679.
3. Erlacher-Reid C, Tuttle AD, Frasca Jr. S. 2012. Xanthogranulomatous panniculitis of the head of an aquarium-maintained California moray. J Aquat Anim Health 24:171–177.
4. Francis-Floyd R, Roth L, Ardelt TC, Andrew M, Reed P, Rose E. 1992. Contact dermatitis in green moray eels (Gymnothorax funebris) exposed to fiberglass. J Zoo Wildl Med 23: 328–335.
5. Herbst LH, Costa SF, Weiss LM, Johnson LK, Bartell J, Davis R, Walsh M, Levi M. 2001. Granulomatous skin lesions in moray eels caused by a novel Mycobacterium species related to Mycobacterium triplex. Infect Immun 69: 4639–4646.
6. Meegan J, Sidor IF, Field C, Roddy N, Sipenski G, Dunn JL. 2012. Endoscopic evaluation and biopsy collection of the gastrointestinal tract in the green moray eel (Gymnothorax funebris): application in a case of chronic regurgitation with gastric mucus gland hyperplasia. J Zoo Wildl Med 43:615–620.