Annual variation of parasite communities of deep-sea macrourid fishes from the western Mediterranean Sea and their relationship with fish diet and histopathological alterations

Abstract

Parasite communities of three abundant benthopelagic macrourid species (Hymenocephalus italicus, Nezumia aequalis and Trachyrincus scabrus) of the upper slope from the western Mediterranean were analysed seasonally. Histopathological, dietary and environmental information (temperature, salinity, O2 and turbidity) were also obtained. The three fish hosts shared only three parasite species (the nematodes Raphidascaris macrouri and Hysterothylacium aduncum and the acanthocephalan Echinorhynchus trachyrinci). H. italicus, the most benthopelagic fish, showed low parasite richness and diversity. The highest total mean abundance of parasites was found in spring for H. italicus and T. scabrus, coinciding with the highest prevalence/abundance of the majority of parasites whereas parasites of N. aequalis exhibited the highest richness, mean abundance and diversity in winter. Parasites related with benthic or infaunal preys were linked to autumn and summer samples off Besós (Barcelona). Some parasites were also linked to high turbidity, which may be due to higher abundances of the intermediate hosts, such as near-bottom zooplaktonic or suprabenthic preys. Few histopathological alterations (e.g. cysts of unknown aetiology) were observed restricted to the two most benthic-feeding fish species inhabiting more closely the near-bottom/sediment level, especially in autumn.