Immunohistochemical localization of phenoloxidase in heptopancreas, muscle and epidermis of grass shrimp (Penaeus monodon F.)

The in vivo sites of melanogenesis in grass shrimps (black tiger shrimp, Penaeus monodon F.), unirradiated and irradiated (5 kGy), was investigated by determining the location of phenoloxidase in heptopancreas, muscle and epidermis using an immunocytochemical technique with electron microscopy. Specific labelling by gold-IgG complex particles was observed over the microvillar border, apical surface and endoplasmic reticula in hepatopancreas, sarcoplasmic reticula in muscle and chromatophores in epidermis. These results suggest that phenoloxidase is synthesized in R-cells of heptopancreas, or chromatophores in epidermis and transferred to muscle. There was no difference in the location of phenoloxidase in shrimp tissues that were nonirradiated and irradiated. Consequently, R-cells in heptopancreas and chromatophores in the epidermis were considered to be important in studying melanogenesis in shrimps