Evolutionary History of Cephalopod Pathologies Linked with Parasitism

Extant cephalopod soft tissues are commonly infested by various lineages of parasites making it plausible that extinct cephalopods also had a variety of parasites. Direct evidence of such a relationship is rare, due to the low preservation potential of soft tissues of fossil cephalopods and parasites alike, and the relatively scarce infestation of mineralized tissue by parasites. Evidence for infestations in the fossil record is, therefore, overall rare and limited to shell pathologies. Comparative studies on these structures in extant cephalopods are also not very numerous. Based on similar bauplans and biomineralization pathways, parasite-induced pathologies in bivalves and gastropods can inform about their causes. The position of these features might reveal their parasitic nature. The restriction of these structures to certain cephalopod lineages might indicate the influence of phylogeny, anatomy and potential role of ecology (feeding, mode of life) on infestation risks. However, preservation and research biases might also contribute to differences between externally and internally shelled cephalopods. Other long-term associations with detriment to cephalopods such as epizoa and bioerosion as well as other malformations, which can be confused with parasitic causes, are briefly discussed.