Characterization of Multiple Ulcerative and Proliferative Masses in a Colony of Lookdowns (Selene vomer)
Wild caught Lookdowns (Selene vomer) were shipped to the Aquarium
Restaurant from Florida in the summer of 1998. The animals have been since housed in a large
cylindrical aquarium of 10,000 gallons. The Lookdowns have developed raised and ulcerative nodular
masses along the head and face and mandible. The masses are also observed frequently on the tail
fins. The lesions are often white but can have a flesh colored appearance near the dorsal surface.
The masses can spontaneously regress and can also recur. The tank is known to have monogenetic
trematodes and also the protozoan Cryptocaryon sp. Water chemistry is within normal limits
but the nitrates can be in the high range, and sometimes the salinity is lowered. The tank has
been treated with copper sulfate on occasion.
The white and sometimes reddish brown nodular masses have a size range from
1-2mm to 3-4mm in diameter. The masses tend to be soft and pliable. Several biopsies were
obtained, fixed in 10% buffered neutral formalin, embedded in paraffin and processed for staining
(hematoxylin and eosin). The microscopic evaluation characterized the masses as nodular
proliferations of moderately cellular fibrous connective tissue with areas of neovascularization
and mild chronic nonsuppurative inflammation predominantly around blood vessels. The overlying
epidermis is mildly to moderately hyperplastic with areas of vesicle formation. Some of the
epithelial cells have intracellular edema and occasionally cells were observed to have cytoplasmic
inclusions. Areas of ulceration were observed on some surfaces.
Further characterization of the masses will be presented with supporting data
of transmission electron microscopic evaluations. In addition, a differential diagnosis list as to
the etiology of the masses will also be presented.