Comparison of antibacterial activity in the hemocytes of different crustacean species

Antibacterial activity in hemocytes of the squat lobster, Galathea strigosa, the Norway lobster, Nephrops norvegicus, the common shrimp, Crangon crangon, and the giant Antarctic isopod, Glyptonotus antarcticus, was investigated in vitro. For all species, the marine bacterium, Psychrobacter immobilis, was used as the test organism, although with G. antarcticus, the Gram positive bacteria, Planococcus citreus and BS 68 (an isolate from Antarctic waters), were also used. Hemocyte lysate supernatants (HLS) from all four species reduced the viable count of test bacteria over a period of 4 hr showing that their hemocytes contain factors able to neutralize bacteria in vitro. However, comparison of responses produced by serially diluted samples of HLS from G. strigosa, N. norvegicus and C. crangon, revealed that activity (per unit protein) is weaker than for Carcinus maenas. Using G. antarcticus, positive activity was also observed against P. citreus and BS 68; with the response effective against all of the bacteria at both 0°C and 20°C. These results show that: (1) the hemocytes from a range of crustacean species contain factor(s) able to neutralize bacteria in vitro; (2) antibacterial potency varies from species to species; and (3) antibacterial immunity in at least one polar invertebrate functions at low temperature.