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Diseases of Aquatic Organisms

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DAO 24:81-91 (1996)  -  doi:10.3354/dao024081

Pathology of fin erosion in goldfish Carassius auratus

Sharples AD, Evans CW

This paper describes the pathology of fin erosion in a feral population of goldfish Carassius auratus (L.) exposed to bleached kraft mill effluent in the Waikato River, New Zealand. Acute fin erosion is initially characterised by hyperplasia of the epidermis, loss of the cuticle and of the epidermal microridges, and the rounding and eventual sloughing of the outermost squamous cells. It typically involves an increase in the number of pigment cells, particularly in the marginal zones of the affected fins, thus accounting for the characteristic black edge of eroded fins. A lymphocytic reaction of variable extent and epidermal oedema are also evident in the acute phase of fin erosion as are increased numbers of mucous cells and decreased numbers of alarm cells in the epithelium. The stratum germinativum and basement membrane of an acutely eroded fin are typically thickened. As fin erosion progresses, increased sloughing of the epidermal cells thins the epidermis. Cells in the stratum germinativum become enlarged and vacuolar and may lift from the basement membrane. Dermal oedema and fibrosis develop early in the progression of the disease with the later stages involving loss of the dermis and erosion of the lepidotrichia. Healed erosion is characterised by dermal fibrosis and the presence of a node of thickened lepidotrichia that is largely unsegmented. New fin rays are formed distally, but they are not continuous initially with the old fin ray stumps. Longitudinally oriented lepidotrichia-forming cells are apparent at the distal tip of the node and in foci distal to the nodal area. Melanophores and basophilic fibroblasts are also abundant and surround each area of fin ray deposition during the healing process. Only in the final stages of healing do the fin rays became continuous with the old fin ray stumps at the node, and the newly formed rays acquire segmentation. Fin erosion as described here is a unique and definitive pathological condition which may have potential as a bio-indicator for a variety of pollutants including pulp mill effluents.

Carassius auratus . Goldfish . Fin erosion . Pathology

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