Abstract

Head and Lateral Line Erosion, or HLLE, is a clinical syndrome seen frequently in captive marine ornamental fish. It has been documented in fishes from private collections and public aquaria but not in fishes in wild habitats. This syndrome is characterized by progressive epithelial erosion and depigmentation. Lesions often begin on the head, gradually enlarge, and develop along the lateral line.¹ Surgeonfishes (family Acanthuridae) appear to be especially susceptible, although the syndrome has been documented in other fish families. While the disease is usually nonfatal, it often renders fish unsuitable for display purposes.

Multiple hypotheses surround the etiology of this syndrome including: infectious agents, water quality deterioration, diet, use of copper medications, stray electrical voltage, and presence of activated carbon in the filter system. In one study a unique reovirus was isolated from a moribund marine angelfish (Pomacanthus semicirculatus) with initial HLLE lesions.⁹ Other papers report resolution of lesions with dietary supplementation of vitamin C¹ or removal of activated carbon from the filtration system.⁵

This project utilized ninety wild-caught juvenile ocean surgeonfish. A randomized block experimental design was followed with three fish housed in each of the thirty twenty-gallon rectangular glass aquaria. All thirty aquaria were incorporated into a single recirculating system to eliminate water quality and environmental variables. Following a four-week quarantine, initial weights and measurements were obtained on all the fish and they were tagged with elastomer (Northwest Marine Technologies, Shaw Island, Washington) for identification purposes.

Approximately 50 mg/kg vitamin C has been reported as the minimum dietary requirement for many important aquaculture species to prevent deficiency signs, assuming optimal environmental conditions and 100% nutrient bioavailability.⁸ The dietary requirement for vitamin C varies according to species, age, environmental conditions, stress levels, and initial ascorbic acid levels in tissues. Also, higher levels of dietary vitamin C have been shown to have beneficial effects on the immune system, stress response, and reproduction.^2-4,6 Six different diets were fed throughout the course of the study. Four diets were specially manufactured from a commercially available food base to have set levels of ascorbic acid (0, 100, 500, and 1,000 ppm). Two control diets were used as well: the unaltered food base, as it is sold commercially, and another commercial food popular with marine fish hobbyists. The Nutritional and Environmental Analytical Services (NEAS) laboratory at Cornell University analyzed nutritional contents of all six feeds. Fish were fed 5% of their body weight per day (adjusted following each weigh session), 6 days a week. Algae was scrubbed from tanks and debris was siphoned daily to prevent fish from acquiring nutrients from other sources than the feed provided.

Fish were anesthetized with MS-222 every other week, then weighed and measured. At this time the fish were closely examined for HLLE lesions (depigmentation and/or loss of epithelium around nares, eyes, opercula or along lateral line) or other signs of vitamin C deficiency including structural deformities in fins, gill operculum and support cartilage, vertebrae (scoliosis and/or lordosis), and blood vessels (hemorrhages).⁷ Lesions were documented pictorially and photographed to allow for monitoring progression of lesions over the course of the experiment.

At the time of this writing of this abstract no significant differences in HLLE development or other deficiency signs were noted among different vitamin C feed groups. However, other studies³ indicate that it can take at least nine weeks for signs of vitamin C deficiency to be manifested. The proposed observational study period of 16 weeks should allow for development of lesions. Preliminary gross findings and conclusions will be presented.

Acknowledgements

We would like to thank Florida Sea Grant and Disney's Animal Programs, The Living Seas, Epcot®, Walt Disney World® Resort for their generous financial support of this research.

References

1.  Blasiola GC. 1989. Description, preliminary studies and probable etiology of head and lateral line erosions (HLLE) of the palette tang, Paracanthurus hepatus (Linnaeus, 1758) and other Acanthurids. Deuxième Congrès International d'Aquariologie (1988) Monaco, 1989. Bulletin de l-Institut océanographique, Monaco, n° spécial 5: 255-263.

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3.  Chen R, et al. 2003. Alternative Complement Activity and Resistance to Heat Stress in Golden Shiners (Notemigonus crysoleucas) Are Increase by Dietary Vitamin C Levels in Excess of Requirements for Prevention of Deficiency Signs. Journal of Nutrition, 133: 2281-2286.

4.  Dabrowski K, et al. 2004. Effects of dietary ascorbic acid on oxygen stress (hypoxia or hyperoxia), growth and tissue vitamin concentrations in juvenile rainbow trout (Oncorhynchus mykiss). Aquaculture, 233: 383-392.

5.  Frakes TA. 1988. Report on head and lateral line erosion. SeaScope, 5: 1, 3

6.  Li Y, Lovell RT. 1985. Elevated levels of dietary ascorbic acid increase immune responses in channel catfish. Journal of Nutrition, 115: 123-131.

7.  Lim C, Lovell RT. 1978. Pathology of the vitamin C deficiency syndrome in channel catfish (Ictalurus punctatus). Journal of Nutrition, 108: 1137-1146.

8.  National Research Council. 1993. Nutrient Requirements of Fish. National Academy Press. Washington, D.C.

9.  Varner PW, Lewis DH 1991. Characterization of a Virus Associated with Head and Lateral Line Erosion Syndrome in Marine Angelfish. Journal of Aquatic Animal Health. 3: 198-205.