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Uca tangeri is a marine fiddler crab found commonly in the West African coast and is often exposed to Gram-negative pathogens upon injury. The aim of this study was to document the patterns of endotoxin-induced protein coagulation and phenoloxidase (PO) activity in hemolymph fractions of Uca tangeri. Hemolymph from live crabs was obtained by carapace puncture, pooled. and then separated into plasma, hemocyte Lysate (HL), hemocyte lysate supernatant (HLS) and hemocyte lysate debris (HLD). The effect of Escherichia coli (O1111:B4) endotoxin and calcium ion (Ca(2+)) on protein coagulation in the presence/absence of endotoxin and the endotoxin dose-dependence of coagulation and PO activity were each studied in the plasma, HL, HLS and HLD. The results showed Ca(2+) was required to induce coagulation, and was endotoxin concentration-dependent in the plasma. PO activity was highest in the HLS but PO specific activity was highest in HLD. PO activity remained relatively constant with increased LPS concentration in the range studied 0-10 EU/ml. From the data we conclude that endotoxin-induced protein coagulation occurs in the plasma alone and might be mediated by trans-glutaminases, while PO activity is localized inside hemocytes and cell membranes in Uca tangeri.

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