Histopathology and host response in lithodid crabs parasitized by Briarosaccus callosus

Abstract

Two red (Paralithodes camtschatica) and 26 golden (Lthodes aequispina) king crabs parasitized by the rhzocephalan Briarosaccus callosus were examined microscopically for histopathological effects of and host response to the parasite. Although numerous organs were invaded and tissues displaced, replaced or compacted, there was little necrosis or degeneration of tissues other than gonads. Host response to healthy B. callosus was negliqble, but degenerating rootlets of the parasite elicited heavy hemocytic response in a typical crustacean foreign-body reaction. Boschma (1962) described Briarosaccus callosus and suggested it may be a cosmopolitan parasite of lithodid crabs, reporting it from Lithodes aequispina in the Bering Sea, L. agassizii off southeastern United States, and L. antarcticus and Paralomis granulosa in the Antarctic and sub-Antarctic regions. Subsequently, Boschma & Haynes (1969) reported it from Pardithodes camtschatica in southeastern Alaska. Hawkes et al. (1985a) first reported B. callosus from Paralithodes platypus, again from southeast Alaska. Prevalences of infection have been investigated in blue king crab Paralithodes platypus (Hawkes et al. 1985a, b), red king crab P. camtschatica (Hawkes et al. 1986), and golden king crab Lithodes aequispina, as have gross observations on the effect on growth, reproduction and migratory behavior of parasitized crabs (Sloan 1984, 1985, Bower & Sloan 1985, Hawkes et al. 1986), but heretofore the histopathological effects have been only briefly mentioned (Sparks 1985, Sparks & Morado 1985). MATERIALS AND METHODS Two red king crabs Parahthodes camtschatica with Briarosaccus callosus externa were shipped alive to our laboratory where necropsies were performed and random samples of the major organ systems were O Inter-Research/Printed in F. R. Germany excised, fixed, and processed by standard histotechniques. All other crabs were collected during crab population surveys by the Resource Assessment and Conservation Engineering Division (RACE) of the National Marine Fisheries Service (NMFS) or Alaska Department of Fish and Game (ADF & G). Necropsies were performed aboard ship by personnel of our laboratory, the NMFS Kodiak Laboratory or the ADF&G. The fixed tissues were processed in our laboratory where microscopical observations were made on the histopathological effects of B. callosus and host response to the parasite in parasitized crabs.