Spectrophotometric studies on the iron linked respiratory protein haemoglobin in arcid clam Scapharca was discussed in earlier communication (Patel and Patel, 1968). The present paper discusses further investigations on the effect of ionizing radiations on the haemoglobin of Scapharca deyrollei sub. sp. crispi.

Oxyhaemoglobin solutions when exposed to Cobalt-60 source delivering 4,600 y per minute showed decrease in absorption maxima at 280,415, 540 and 576-78 m;* and an increase around 510 and 630 m/µ. No difference in spectral behaviour was observed when various Hb-fractions obtained by calcium phosphate gel were irradiated separately. Exposure to dose exceeding 1150 T'- resulted in precipitation of the pigment. Changes occurring during irradiation were similar to those produced when oxyhaemoglobin was treated with hydrogen peroxide, suggesting that H₂ O₂ produced during radiolysis of aqueous solutions may be the species responsible for the damage. Haemoglobin of Scapharca was found to be extremely radiosensitive as it could not be exposed to dose exceeding 1150 y