ASSESSING CRUSTACEAN PARASITE PRESERVATION POTENTIAL; COMPARING MODERN AND FOSSIL EVIDENCE

Parasitism is an extremely common biotic interaction in the modern, yet fossil evidence of parasitism is rare, and robust quantitative data on fossil parasites is even rarer. The exact mechanisms driving this scarcity of fossil parasite evidence remain understudied, and may include taphonomic and sampling biases that vary widely between taxa and timescales. Here, modern and fossil evidence of crustacean parasitic interactions are synthesized from the literature, to assess a number of modern interactions for fossilization potential. Specimen and taxonomic data from 110 peer-reviewed publications were compiled, and quantitative data was used when available to compare modern and fossil parasite prevalence. Of the 33 crustacean-parasite host relationships described in the literature, just six have undisputed fossil records, though others have disputed fossil evidence. Preserved evidence of parasitism among crustaceans appears to be restricted almost exclusively to sites of exceptional preservation, and remains rare even in these contexts, with fossil parasite prevalence ranging from 0.05% to 30% of modern prevalence values. Fossil evidence of crustacean parasitic interactions is concentrated in the Mesozoic relative to the Paleozoic or the Cenozoic. The fossil record of parasitism remains poorly resolved, seemingly in contrast to an overwhelming modern prevalence of parasitic ecologies, even in cases of exceptional preservation conditions. Although a number of co-occurring biases appear to have some impact on the scarcity of parasitic ecologies in the fossil record, the poor preservation potential of the small, soft-bodied, and/or endoparasitic parasites suggests a strong taphonomic bias against many of the most ecologically significant parasitic taxa. The extent of these biases must be addressed before palaeoecological and evolutionary questions regarding the history of parasitism can be answered.