Abstract
Hyperplasia in teleosts may be traditionally linked with neoplasia and pathogens, but fishes in public aquaria can also experience hyperplasia associated with trauma, age, nutrition, water quality, and exhibit interaction.1-3 Aesthetics and public reaction may cause fish with uncorrected external lesions to be removed from display which makes surgical debridement and cryotherapy important tools in palliative treatment when root causes of proliferative conditions cannot be addressed. Some unique teleost anatomical features will be highlighted as it pertains to the following cases.
Case 1: Mackerel scad (Decapterus macarellus) developed hyperplastic adipose lids that were significantly restrictive for display purpose at two different public aquaria (South Carolina Aquarium and North Carolina Aquarium at Fort Fisher). Fish presented with bilaterally symmetrical, firm, clear gel around the eyes that were later identified as hyperplastic adipose lids composed primarily of a cartilage-like matrix. Surgical debridement of the matrix was simple but not curative. In severe cases, impairment to feeding led to a loss of body condition.
Case 2: Hyperostosis is a proliferation of cellular bone that is common in the ribs, haemal spines, intramuscular bones, supraoccipital crest, cleithrum, etc., depending on the species.4 The condition is almost unique to marine teleosts and commonly affects the Carangidae.4 Hyperostosis occurs in the wild and does not appear to affect fish longevity or display quality. The cause is unknown although hard water (calcium rich) appears to be a minimum criterion for its occurrence.4
Case 3: While the majority of fish adapt to captive conditions, tank walls and substrate barriers are a common cause of nonneoplastic dermal proliferation due to irritation. Pelagic species are logically more prone to develop lesions associated with physical interactions with tank walls, but even inshore species exhibit traumatic proliferative lesions from the confines of captivity. Cheilitis was noted on the mandible of a tripletail (Lobotes surinamensis) which was treated with over-the-counter freeze wart remover.5 The proliferative fibrous tissue responded poorly until the lesion self-resolved when the animal was moved to a larger tank. Tarpon (Megalops atlanticus) exhibited large, maxillary, proliferative bony growths which were suspected to be the result of trauma with conspecifics or exhibit walls. The masses were refractory to debridement and over-the-counter wart remover cryotherapy. Fish were removed for aesthetic reasons and treated with aggressive debridement and liquid nitrogen cryotherapy which were curative.6
Case 4: A suspected prolapse of reproductive tissue through the lateral body in a lined seahorse (Hippocampus erectus) became a large, external proliferative mass with an angioma like-architecture. Repeat use of liquid nitrogen cryotherapy and surgical debridement in eight anesthetic procedures were able to maintain display quality over a year.
Acknowledgements
We thank Tom Waltzek at the University of California, Davis, School of Veterinary Medicine; Hap Fatzinger of the North Carolina Aquarium at Fort Fisher; Mike Garner at NorthWest Zoopath; McHugh Law at North Carolina College of Veterinary Medicine; Lee Yarbrough at Mount Pleasant Dermatology; Rachel Kalisperis, and all the staff/volunteers at the South Carolina Aquarium for their participation in the cases.
References
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