Epidermal Response to pH, Aluminum, and Calcium Exposure in Brook Trout (Salvelinus fontinalis) Fry

Abstract

Eyed brook trout eggs were exposed to various combinations of pH (4.3–6.3), aluminum (0–1000 μg/L), and calcium (0.5 to 8.0 mg/L) for 40 d through hatching until the swim-up life stage. High resolution light microscopy, image analysis, and stereological techniques were used to quantitatively determine morphological changes in the epidermis of fry surviving this exposure. Exposure to increased acidity resulted in both mucous cell hypertrophy (increase in size) and hyperplasia (increase in number); exposure to low calcium resulted in mucous cell hyperplasia. Aluminum did not significantly affect mucous cell size or number. Epidermal thickness was not consistently affected by exposure to pH, aluminum, or calcium. The changes observed in epidermal mucous cells may be a compensatory mechanism used by brook trout fry to counter ionoregulatory stress resulting from extended exposure to acidic conditions.