Ecology and Biogeography, Future Perspectives: Example Marine Parasites

Aguiar et al. discussed global speciation and diversity, and Appletans et al. the magnitude of marine species diversity. The latter authors conclude that “between one-third and two-thirds of marine species may be undescribed” and that” If the current trends continue, most species will be described this century”. Recent reviews of parasite diversity in general are given by the various contributors in Morand and Krasnov and Morand et al.. Detailed discussions of marine parasite diversity can be found in Rohde and Leung et al. These reviews show that even hosts (and particularly invertebrate hosts) of parasites are incompletely know, i.e., many species have not been described. Leung et al.  gave estimates of known species and those estimated to exist, of some important groups of marine invertebrates using the Catalog of Life database (www.species2000org) and the World Registry of Marine Species (www.marinespecies.org). 

Some examples are: Cnidaria 11 433 species known, 40 318 estimated to exist; Echinodermata: 7286 vs. 19040; Mollusca: 48 648 vs. 169 840;Crustacea: 66 250 vs. 130 855. Parasites are far less known. Much work on parasites remains to be done even for well-known marine host animals such as seabirds. Hoberg reports that more than 700 species of digenean trematodes, eucestodes, nematodes and acanthocephalans have been described from about 165 marine bird species. 50% of all bird species have never been examined. Protistan parasites of marine invertebrates and vertebrates are less well known, and studies have been mainly restricted to economically important species. For example, there are thousands of marine fish species in Australia, but probably less than 5% of them have been examined for protistan parasites.