ENDOCRINE CONTROL OF METABOLISM IN THE LAND CRAB, GECARCINUS LATERALIS (FRÉMINVILLE). I DIFFERENCES IN THE RESPIRATORY METABOLISM OF SINUSGLANDLESS AND EYESTALKLESS CRABS ,

Abstract

1. A volumetric macrorespirometer and gas analyzer are described. Procedures and precautions for their use are discussed.2. Determinations of respiratory rates and respiratory quotients before and after surgical removal of both sinus glands from the eyestalks of the land crab, Gecarcinus lateralis, indicated that, except in one respect, the crabs were fundamentally unaffected by the loss of organs which had been thought essential for maintenance of normal metabolism.3. The exception lay in an operated crab's eventual loss of its normal ability to vary the type and rate of metabolism. Indications of this loss were a constant respiratory quotient at the normal mean value and a low and relatively invariable respiratory rate. Fluctuations in rate of oxygen consumption and level of respiratory quotient were recorded from normal crabs.4. Eyestalkless crabs showed a sudden and pronounced alteration from normal respiratory rates and respiratory quotients, a change indicative of a pre-molt metabolism and culminating in a second, even more marked metabolic shift at the time of molt.5. It is clear that removal of eyestalks does, but removal of sinus glands does not, deprive these crabs of the molt-inhibiting and respiration-regulating hormone. Previous bilateral sinus gland removal does not alter the capacity of a crab to respond to subsequent bilateral eyestalk removal in the manner described above. The same is true when unilateral eyestalk removal is followed by removal of the other eyestalk.6. These metabolic data supplement and confirm morphological observations reported in an earlier paper (Bliss and Welsh, 1952). One may conceive of a brachyuran neurosecretory system composed of neurosecretory cell bodies as synthesizing elements, axons as transporting elements, and the sinus glands as storing and releasing organs. This is an extension of a concept developed originally by Scharrer and Scharrer (1944) for vertebrates and insects.