Host specificity of Sacculina carcini, a potential biological control agent of the introduced European green crab Carcinus maenas in California

Abstract

The European green crab, Carcinus maenas, is an introduced marine predator established on the west coast of North America. We conducted laboratory experiments on the host specificity of a natural enemy of the green crab, the parasitic barnacle Sacculina carcini, to provide information on the safety of its use as a possible biological control agent. Four species of non-target, native California crabs (Hemigrapsus oregonensis, H. nudus, Pachygrapsus crassipes and Cancer magister) were exposed to infective larvae of S. carcini. Settlement by S. carcini on the four native species ranged from 33 to 53%, compared to 79% for green crabs. Overall, cyprid larvae tended to settle in higher numbers on individual green crabs than on either C. magister or H. oregonensis. However, for C. magister this difference was significant for soft-shelled, but not hard-shelled individuals. Up to 29% of the native crabs arrested early infections by melanizing the rootlets of the parasite. Most native and green crabs settled on by S. carcini became infected, especially when settled on by >3 cyprids. Infected green crabs died at more than twice the rate of uninfected green crabs. In contrast to green crabs, all infected native crabs died without producing an externa (reproductive sac). At high settlement intensities, infected native crabs frequently exhibited neurological symptoms (twitching, loss of movement) before death. These results indicate that use of S. carcini as a biological control agent could result in the death of native crabs. The magnitude of this effect would be proportional to the density of infected green crabs in the environment and the probability that cyprids would contact native crabs in the wild. Potential benefits of biological control should be assessed in relation to these potential non-target effects.

Invasive alien Crustacea: dispersal, establishment, impact and control

“…A potential control agent of C. maenas is the parasitic barnacle Sacculina carcini Thompson. This species, however, can settle on, infect, and kill a number of native crab species (Goddard et al 2005) and thus the application of this method necessitates a thorough cost-benefit analysis.…”

Tissue changes in the shore crab Carcinus maenas as a result of infection by the parasitic barnacle Sacculina carcini

“…The species is harvested for recreational angling bait and directly for human consumption in continental Europe (Vale & Sampayo 2002). Shore crabs are also invasive pests in the USA and Australia because of damage to bivalve fisheries by predation (Goddard et al 2005). Therefore, there are several economical and ecological incentives to study disease processes in this species of crab.…”

Effects of Season, Size and Parasitism by the Acanthocephalan, Profilicollis altmani, on the Carotenoid Concentration and Composition of the Pacific Mole Crab, Emerita analoga

“…Sacculina larvae inject a germinal cell mass into the crab that form microscopic root-like structures that tap into the host nervous system. Eventually, the abdominal organs and gonads are completely infiltrated and destroyed as the parasite develops (Goddard et al 2005). The parasitic isopod Hemioniscus balani has a similar effect on sessile adults of many free-living barnacle species, and infection by a single H. balani adult causes complete castration of the barnacle (Blower and Roughgarden 1989).…”

“…Also, physical changes in the reproductive tissues of infected males were not measured. Some parasites such as Sacculina species may castrate their hosts, using gonads as a nutrient sources and perhaps reducing reproductive behavior that is risky to host survival (Goddard et al 2005). In the future, additional E. analoga males could be collected and studied for these effects.…”