Skin mucous cell response to acid stress in male and female brown bullhead catfish, Ictalurus nebulosus (Lesueur)

Exposure of brown bullhead catfish Ictalurus nebulosus (Lesueur) to water made acid in pH by addition of dilute sulfuric acid, removed a sexual dimorphism observed in mucosubstance-containing cells of control epidermis. When stained by the alcian blue-periodic acid Schiff's reagent technique for acidic and neutral mucosubstances, positive cells in control males are seen primarily at the external surface. A few mucosubstance-containing cells are observed in basal regions. By contrast, skin of control female brown bullheads appears to contain far more mucosubstance. Morphometric analysis of skin reacted by the above technique for mucosubstance revealed the following: 1) mucous cells of control females are more than twice as large as those of control males; 2) 48 h after initiation of acid stress (pH 5.7-3.8) both sexes respond with hyperplasia of mucous cells; 3) more severe acid stress (pH 5.2-3.8) leads to hypertrophy of mucous cells in epidermis of males. Preliminary observations concerning development of the response indicate that an initial increase in mucosubstance occurs throughout the entire epidermis by 48 h. This increase is followed by movement of mucous cells toward the surface and eventual release of mucosubstance. After 3 or 4 days of exposure, the majority of mucous cells appear within the upper one-third of the epidermis. Endocrine factors possibly mediating mucosubstance in control and acid-stressed epidermis are discussed.