Temporal dynamics of epidermal responses of guppies Poecilia reticulata to a sublethal range of waterborne zinc concentrations

Authors

  • C. Gheorghiu,

    Corresponding author
    1. Institute of Parasitology, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste-Anne de Bellevue, QC, H9X 3V9 Canada
      Author to whom correspondence should be addressed at present address: Department of Biology & Chemistry, Faculty of Science, Wilfrid Laurier University, 75 University Avenue West Waterloo, ON, N2L 3C5 Canada. Tel.: +1 519 884 0710, ext. 2347; email: cris_ghe@yahoo.com
    Search for more papers by this author
  • D. J. Marcogliese,

    1. Fluvial Ecosystem Research Section, Aquatic Ecosystem Protection Research Division, Water Science and Technology Directorate, Science and Technology Branch, Environment Canada, St Lawrence Centre, 105 McGill, 7th Floor, Montreal, QC, H2Y 2E7 Canada
    Search for more papers by this author
  • M. E. Scott

    1. Institute of Parasitology, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste-Anne de Bellevue, QC, H9X 3V9 Canada
    Search for more papers by this author

Author to whom correspondence should be addressed at present address: Department of Biology & Chemistry, Faculty of Science, Wilfrid Laurier University, 75 University Avenue West Waterloo, ON, N2L 3C5 Canada. Tel.: +1 519 884 0710, ext. 2347; email: cris_ghe@yahoo.com

Abstract

This study assessed the histological changes in the epidermis of guppies Poecilia reticulata induced by waterborne zinc (Zn). Laboratory-reared P. reticulata fry were maintained individually in separate vessels containing artificial water (8 µg l−1 Zn) to which 0, 15, 30, 60 or 120 µg l−1 Zn was added. Their epidermal response to Zn was monitored regularly over 4 weeks. Compared with controls, mucus was rapidly released and mucous cell numbers decreased at all concentrations. Thereafter mucous release, epidermal thickness, numbers and size of mucous cells fluctuated at a rate that varied with Zn concentration, but fluctuations declined after day 18. Results clearly highlight the dynamic nature of the epidermal response to sublethal concentrations of waterborne Zn. In general, low concentrations of Zn induced a rapid response with reduced numbers and size of mucous cells and shift in mucin composition, and a subsequent thickening of the epidermis. Epidermal thickness and mucous cell area fluctuated over time but were normal after a month of exposure to low Zn concentrations. The number of mucous cells, however, remained low. Virtually all mucous cells from fish maintained in 15 and 60 µg l−1 Zn contained acidic mucins throughout the month, whereas fish maintained at 30 µg l−1 Zn responded by production of neutral mucins during the first 12 days followed by a mixture of neutral and acidic mucins. At 120 µg l−1 Zn, the most dramatic effects were the gradual but sustained decrease in numbers and area of mucous cells, and the shift to acidic mucins in these cells. Thus, as concentration of Zn increased, the epidermal responses indicated a disturbed host response (dramatic decline in mucous cell numbers, with mixed composition of mucins), which may have been less effective in preventing Zn uptake across the epithelium.

Ancillary