A host, a parasite, and a predator: the dynamics of successive invasions in the eastern Mediterranean

The eastern Mediterranean shelf ecosystem has been profoundly disrupted by the influx of invasive alien species introduced through the Suez Canal. Yet, the role of retaining or shedding co-evolved parasitofauna in the success of the invading biota has been scarcely monitored, with the exception of the lesser swimming crab Charybdis (Archias) longicollis Leene, 1938 parasitized by the rhizocephalan Heterosaccus dollfusi Boschma, 1960. Host size, sex ratio, prevalence of ovigerous females, parasitization, and multiple parasitization, were studied over 30 years to determine long-term host-parasite variation. Our results reveal that C. longicollis crabs have shifted their temporal activity pattern shortly following the domination of their preferred depth niche by the invasive diurnal predator, the silver-cheeked toadfish Lagocephalus sceleratus (Gmelin, 1789), which preferentially feeds on C. longicollis locally. A unique set of predator-host-parasite interactions among three successive Erythraean invasive aliens is considered herein.