Meeting Abstract
Despite the substantial impact of parasites on modern marine ecosystems, the evolution of parasitism in deep time is poorly known. The best-known record of parasites in fossil crustaceans are swellings attributed to isopods in the gill chambers of decapod crustaceans. This 180-million-year record allows us to (a) assess infestation patterns through time, (b) test whether the degree of infestation and specimen abundance per taxon are correlated, and (c) evaluate whether infested specimens are statistically smaller than non-parasitized conspecific specimens. We studied a variety of European decapod assemblages consisting of over 4000 specimens associated with Late Jurassic – Miocene sponge-coralgal habitats. Infestation percentages are highest in the Late Jurassic – Early Cretaceous interval (2.9 – 9.2%), while decapods with parasitic swellings are absent in the studied Late Cretaceous – Miocene assemblages. This decline may in part be explained by a drop in the abundance of commonly infested taxa such as homolodromioid brachyurans and galatheoid squat lobsters. The study of the two largest assemblages yielded mixed results regarding the influence of host abundance on the degree of infestation: a Late Jurassic assemblage shows no significant correlation, while an Early Cretaceous assemblage yields a positive correlation. Finally, infested specimens of two Late Jurassic species are significantly larger than conspecific specimens without a visible infestation, as opposed to studies on modern infested decapod species.
