The free amino acid pool of the haemocytes of Carcinus maenas (L.).

The functions of the blood cells of crustaceans have received little investigation. The majority of the work reported in the literature to date has been concerned with the involvement of the haemocytes in the phenomenon of plasma coagulation. In several crustacean species highly fragile blood cells have been described ' Hardy's explosive corpuscles' which are generally believed to contain substances which can induce plasma coagulation (Hardy, 1892). This is supported by the observation that materials which can decrease, delay, or prevent alterations in the explosive corpuscles have also been found to interfere with plasma coagulation. Crustacean blood cells have also been shown to contain a tyrosinase which is liberated during coagulation and which is capable of the oxidation of adrenaline and also of catechol. It is thought to be involved in pigment formation and quinone tanning (Bhaguart & Richter, 1938; Pinhey, 1930; Roche & Latreille, 1934). Recently, however, a possible hepatic function has been proposed for crustacean blood cells (Johnston, Spencer Davies & Elder, 1971). These investigators found that the haemocytes of Carcinus could maintain stores of both glycogen and non-glycogen polysaccharides which were quantitatively more important than those found in the hepatopancreas of the crab. Preliminary biochemical and histochemical analyses have have also shown that the Carcinus haemocytes contain the enzyme glucose-6-phosphatase, a pre-requisite for the glycogenolysis of glycogen to glucose, which could then be liberated from the cells. The present investigation is concerned with the discovery of a large pool of free amino acids within Carcinus haemocytes. It sets out to measure the relative contributions of the individual amino acids to this pool and to make a comparison with the results for other tissues from Carcinus. Some possible functions for the amino acids are suggested, and the significance of the results is discussed with respect to other investigations concerning the free amino acids of crustacean blood.