Sometimes, the invasion of these parasites may have the effect of reducing the competitive advantages that Red Sea invaders have in the Mediterranean. For example, the Indo-Pacific swimming crab Charybdis longicollis was first recorded in the Mediterranean in the mid-1950s and became dominant in silty and sandy substrates off the coast of Israel, making up to 70% of the total biomass in these habitats. Until 1992, none of the specimens collected was infected with the parasite Heterosaccus dollfusi, but in that year, a few infected crabs were collected. The parasite is a barnacle which desexes its host. Within three years, the parasite had spread to southern Turkey and 77% of the crabs collected in Haifa Bay were infected. This rapid increase and high infection rate is attributed to the extremely high population density of the host and the year-round reproduction of the parasite. One effect of this was that the population of the Mediterranean native swimming crab Liocarcinus vernalis recovered somewhat.
