Living Together: The Parasites of Marine Mammals

Abstract

The reader may wonder why, within a book of biology and conservation of marine mammals, a chapter should be devoted to their parasites. There are four fundamental reasons. First, parasites represent a substantial but neglected facet of biodiversity that still has to be evaluated in detail (Windsor, 1995; Hoberg, 1997; Brooks and Hoberg, 2000. Perception of parasites among the public are negative and, thus, it may be hard for politicians to justify expenditure in conservation programmes of such organisms. However, many of the reasons advanced for conserving biodiversity or saving individual species also apply to parasites (Marcogliese and Price, 1997; Gompper and Williams, 1998). One fundamental point from this conservation perspective is that the evolutionary fate of parasites is linked to that of their hosts (Stork and Lyal, 1993). For instance, the eventual extinction of the highly endangered Mediterranean monk seal Monachus monachus would also result in that of its host-specific sucking louse Lepidophthirus piriformis (Fig. 1b). Second, parasites cause disease, which may have considerable impact on marine mammal populations (Harwood and Hall, 1990). Scientists have come to realise this particularly after the recent die-offs caused by morbilliviruses (see Domingo et al., this volume). However, these epizootic outbreaks represent the most dramatic, but by no means the only, example of parasite-induced mortality in marine mammal populations (see Section 3 below).