Modus vivendi: invasive host/parasite relations—Charybdis longicollis Leene, 1938 (Brachyura: Portunidae) and Heterosaccus dollfusi Boschma, 1960 (Rhizocephala: Sacculinidae)

Abstract

Parasitic castrators, specifically rhizocephalan barnacles, considered as important regulators of host population density, were proposed as control agents for invasive decapod crustaceans. The temporal variability of the invasive parasitic barnacle Heterosaccus dollfusi prevalence was examined a decade after its introduction into the Mediterranean, with the purpose of elucidating whether it is indeed an efficient control agent of its invasive host, the swimming crab, Charybdis longicollis. Despite the high prevalence of the parasite and its injurious impact on the host reproduction, the Erythrean invasive host-parasite pair reached a modus vivendi with no noticeable reduction in the host population, and high rates of infestation and multiple infestation. It is suggested that high fecundity, “size refuge” formed by parasite-free larger males, and “open” recruitment dynamics, keep the population density of C. longicollis high enough to allow H. dollfusi, with its “closed” recruitment dynamics, to maintain its pandemic infection rates.