ABSTRACT
The influence of water-loading and low-temperature stress on the physiology of the antennal gland was studied in specimens of the freshwater crayfish, Orconectes virilis.
The results of experiments on water-loading suggested that the crayfishes were able to excrete water injected into them, but they did so at the expense of an abnormal loss of salts (sodium). Heavy water-loads caused large and prolonged increases in inulin clearances and urine flow.
Low temperature had its primary effect in reducing urine flow and inulin clearance. Low temperature apparently had little effect on the rate of sodium excretion or intensity of water excretion.
The urine flow (at 16 ° C.) of specimens of O. virilis was determined to be 3 % of the body weight per 24 hr. This value agreed with the urine flow calculated from average inulin clearances and inulin U/B ratios obtained independently upon specimens of the same species.
The results presented in the present paper throw further light upon the function of the crayfish antennal gland. They agree fairly closely with results obtained in other animals where filtration is known to play a role in primary urine formation. However, because of limitations imposed, principally by the lack of morphological evidence for a filtration site in the crayfish kidney, it cannot be stated unequivocally that the crayfish antennal gland is a filtration kidney.
The use of the term ‘filtration’ in this paper follows the restrictions outlined by Riegel & Kirschner (1960). This use of the term implies that urine is formed by the passive movement of fluid from which particles larger than an unknown critical size are restrained, but the cause of the fluid movement is not stated. Where the term is used without quotations, the usual sense of the word is meant—that is, movement of fluid through a porous membrane under the impetus of hydrostatic pressure.
No precedent for the use of the reciprocal of the inulin urine/blood ratio was found in the literature. Since the inulin U/B ratio is commonly used as an indicator of the intensity of water reabsorption, it was felt that the reciprocal of that value could be used to indicate the degree to which water is not reabsorbed, i.e. the intensity of water excretion.
