THE HISTOPATHOLOGY ASSOCIATED WITH THE JUVENILE STAGES OF LEPEOPHTHEIRUS-SALMONIS ON THE ATLANTIC SALMON, SALMO-SALAR L

Abstract. Atlantic salmon infected with juvenile stages of Lepeophtheirus salmonis were obtained from sea loch cage sites on the West coast of Scotland. Attached parasites on the skin were studied using light and electron microscopy. Behavioural activity was observed in attached stages maintained on skin in vitro. Pathological changes were associated with four main areas of interaction between the parasite and the host, namely second antennal attachment, filament attachment, maxilliped activity and feeding activity. The skin changes involved were initial mechanical disruption followed by epidermal hyperplasia. The filament material was secreted into the epidermis and spread laterally without breaching the basement membrane. Surprisingly little reaction to the filament occurred, but chalimus activity resulted in chronic changes which were more marked as the later chalimus stages were reached. Fibroplasia was a feature of lesions induced by redundant filaments resulting in small nodular lesions. After erosion of these nodules, all that remained were the melanized rings characteristic of old chalimus sites. Copyright © 1990, Wiley Blackwell. All rights reserved