Survival of the edible crab, Scylla serrata Subjected to endocrinological and pharmacological procedures, was examined after exposing them to 4o°0 C for 3 hr. Only normal, intact crabs could withstand the thermal shock but not reserpinized intact, eyestalkless, sinus glandectomised (SGE), SGE and reserpinized (RSP), SGE injected with sinus gland homogenate and SGE injected with SG homogenate and reserpinized crabs. The possible involvement of endocrine centres in S. serrata in sustaining the environmental thermal shock is discussed.