Crustacean defense strategies II. Recognition, clearance, accumulation and externalization of soluble foreign proteins by the mud-crab Scylla serrata.

ABSTRACT

The Defense reactions of Scylla serrata have been investigated by challenging crabs with two metalloproteins, horse radish peroxidase (HRPM.W. 40,000) and hemoglobin (Hb64,000). The defense response analyzed include 1) recognition of foreign proteins; 2) clearance from the haemocoel; 3) accumulation in tissues and 4) externalization. Protein clearance was similar to dye clearance in several respects 1) clearance rate increased with higher a) molecular weight and concentration and b) at night and 2) decreased with crab size. HRP clearance rate was significantly increased after repeated injections of HRP but not saline. Clearance was not enhanced after repeated injections of Hb. About 70% of HRP accumulates in gills within 2 hours after injection, when there were no signs of HRP accumulation in the hepatopancreas. But about the same percent of injected Hb accumulated in both gills and hepatopancreas after 2 hours of injection. When 300 ug HRP declined in gills after 8 hour, similar amounts of HRP accumulated in the hepatopancreas. Moreover when 325 ug of Hb was lost from gills after 4 hours, the hepatopancreas accumulated about 300 ug, suggesting that foreign proteins may undergo antigenic alteration in the gills prior to mobilization to the hepatopancreas. There is no evidence of degradation of proteins in gills. When HRP and Hb level declined in the hepatopancreas, the levels of these proteins increased in gut contents indicating externalization of injected proteins via gut.