Different bacterial lipopolysaccharides as toxicants and stressors in the shrimp Palaemon elegans

This study compares the in vivo haemocytic response of shrimp, Palaemon elegans (Rathke) to different types of LPS injection. In particular it investigates to what degree and speed the haemocytopenia varies between LPSs from different sources. It further compares the tolerated doses of different LPSs in these animals and finds substantial differences in the various toxicity types. The work then relates this to blood glucose levels and stress-linked variations in glycaemic status. The order of LPS decreasing toxicity determined by LD50 at 96 h was: Salmonella enteritidis, Serratia marcescens, Pseudomonas aeruginosa 10, Escherichia coli K-235 and E. coli 0111:B4. Eyestalkless animals were more sensitive to LPS. The effects of injected LPS on circulating total blood cell count (THC) was tested. The results show that LPS caused a decrease in THC 8 h after injection and then the THC returned to the initial level and this effect depended on the LPS tested. E. coli K-235 was the most effective in causing haemocytopenia followed by E. coli 0111:B4, S. enteritidis, S. marcescens, and P. aeruginosa 10. Moreover, LPS-induced increases in the blood glucose level and the time and dose related curves of response obtained depended on the type of LPS tested. E. coli K-235 LPS was again the most effective in elevating blood glucose followed by E. coli 0111:B4, S. marcescens, S. enteritidis and then P. aeruginosa 10. No significant hyperglycaemia was induced in eyestalkless animals. An inverse order relationship between toxicity (LD50) and stress responses (hyperglycaemia and THC decrease) may suggest a defensive and adaptive role of the latter in occasional septicaemia.