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

We studied the effect of parasitic invasion by the barnacle Sacculina carcini on shore crabs Carcinus maenas collected from the Menai Straits in North Wales, UK. A significant reduction in serum protein and circulating granular, semi-granular and hyaline blood cells was observed in parasitised individuals, while serum ammonium and glucose concentrations were significantly increased. No difference in hepatopancreatic glycogen concentration was found between healthy and parasitised crabs. Histological analysis showed the apparent removal of fibrillar protein from infected muscle by the parasite. Hepatopancreas tubule necrosis was also routinely observed in infected individuals. Parasitisation by S. carcini dramatically affects the haemocyte population and serum chemistry of infected crabs.