Parasites and diseases of worldwide cephalopods: an update

Cephalopods are known to harbor parasitic organisms in almost every organ of their body. The growing importance of cephalopods for both commercial and research purposes requires a better understanding about their health and welfare, which includes a detailed characterization of their parasites and diseases, especially of those infectious agents that are able to affect the physiology of cephalopod hosts or their marketability as fishery products. Information about the parasitic fauna of cephalopods also prove very useful for scientists since it may help elucidating some aspects of cephalopod biology and ecology in natural environment. During the last decades, the development of new investigation techniques, such as the increased use of molecular tools, allowed the identification of new parasite species and helped to solve the taxonomic uncertainty resulting from difficulties associated with morphological identification of small-sized and often cryptic organisms, which had produced, over time, a high synonymy rate among parasitic taxa. The present work intends provide an update of the last 25 years of research about cephalopod infectious agents, by considering over two hundred new publications, since they were first extensively surveyed in 1990. The number of new parasite descriptions, new host records and new infection reports was reviewed as well as the geographic distribution of reports in order to characterize the worldwide pattern of research efforts in cephalopod parasites. The total amount of literature available so far was also considered and analyzed in order to detect potential variations in parasite biodiversity among cephalopod groups as well as among geographic areas and to identify parasitic groups, host groups and geographic areas that require more investigation. Special attention is paid to potentially pathogenetic agents and to treatments available or attempted so far.