Abstract

Moray eels are commonly on display at commercial aquariums, zoological parks, and in large home aquariums. As the demand increases for exhibiting moray eels, there should also be an increased responsibility and awareness for their health and wellbeing in captivity. Contact dermatitis, gastric mucus gland hyperplasia, lipid keratopathy, and cutaneous granulomatous and xanthomatous lesions are conditions that have been documented in captive moray eels.^1-2,4-8 Of particular interest is the development of lipid keratopathy which, when severe, can cause visual impairment resulting in difficulty navigating an enclosure.⁴ The prevalence of lipid keratopathy has been associated with the apparent predisposition for increased serum triglyceride and cholesterol values in moray eels; however, adjustments to the dietary regime may improve lipid keratopathy in some cases.¹

The primary purpose of this study was to establish plasma biochemistry reference intervals for healthy recently wild-caught purple mouth moray eels (Gymnothorax vicinus) to enhance medical care in captivity. These data can also provide baseline values for cholesterol and triglycerides in recently wild-caught moray eels to aid in monitoring elevations to these values in captivity over time. With this knowledge, precautionary measures including dietary modifications could be instituted in aquarium-maintained moray eels to possibly prevent the development of lipid keratopathy.

Thirty-one clinically healthy purple mouth moray eels of unknown age and sex were caught from the wild, maintained at an average salinity of 31ppt and temperature between 23-24 degrees Celsius, and anesthetized fifty days following capture for blood collection and microchip placement. The moray eels were fasted for one week prior to blood collection. The eels were anesthetized with an immersion bath of tricaine methanesulfonate (MS-222) at a concentration of 80ppm and maintained at a concentration of 50ppm delivered by a water-circulating, flow-through anesthetic machine and the blood was collected from the ventral coccygeal vein.

The median packed cell volume (PCV) for purple mouth moray eels in this study (median 21%, range 14-31%) is similar to the PCV documented in captive green moray eels (Gymnothorax funebris).³ Furthermore, plasma triglyceride values (median 206 mg/dl, range 113-435 mg/dl) and cholesterol values (median 334 mg/dl, range 233-433 mg/dl) in wild-caught purple mouth moray eels are similar to other documented wild-caught moray eels but are much lower compared to captive moray eels.¹ The remaining plasma biochemistry reference values obtained from this study have not been previously documented in moray eels for comparison but can be utilized by future studies in moray eels to monitor changes in values as diet is modified or if health status is altered.

Acknowledgements

The authors thank employees and volunteers at Mystic Aquarium including Amy DelMonaco, Jill Reeves, Gayle Sirpenski, Chris Sodergren, Ainsley Smith, Amanda Wacasey, Dawn Holman, and Rebecca Bray for their incredible assistance during the moray eel blood collection procedure. The authors also thank Pfizer Global Research & Development for processing the blood samples.

References

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2.  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.

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4.  Greenwell MG, Vainisi SJ 1994. Surgical management of lipid keratopathy in green moray eels (Gymnothorax funebris). Abstr Proc Association of Reptilian and Amphibian Veterinarians; Pp. 155-157.

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.

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7.  Reavill DR, Schmidt R 2006. Xanthomatous lesions in three eels. Abstr Proc International Association for Aquatic Animal Medicine; Pp. 85.

8.  Richard MJ, Gentz EJ, Snyder SB, Casman H 2001. Cutaneous granulomas in morays (Gymnothorax sp.). Abstr Proc Internation Association for Aquatic Animal Medicine; Pp. 45.