Morphological examination of x-cell affected gills from Pagothenia borchgrevinki

During the 83-84 season, several Pagothenia borchgrevinki fish were collected which had damaged gills. The gill filaments were white, instead of the usual red colour due to blood perfusion and also appeared to be very swollen. Fish with the same condition were captured in the 85-86 season making up approximately 15% of the captured population. Preliminary work was conducted on the anatomy of these affected gills using scanning and transmission electron microscope. Morphological work found that the affected gill tissue is packed with a foreign cell type, called x-cell. In the 87-88 season, gills from both normal and x-cell affected fish were dissected and examined under a microscope. Filament numbers and lengths were measured as well as secondary lamellar density in order to determine the surface area of the gills and thus the reduction of surface area brought about by x-cell proliferation. Gill samples were fixed in glutaraldehyde and returned to New Zealand for biochemical analysis. In the 90-91 season, plastic resin casts of the gills was made. The cast of the blood system down to the capillary level was viewed under a scanning electron microscope. The casts of the blood system of x-cell diseased gills was compared with healthy gills.