Compensation to high temperature in the loss and cctive absorption of chloride in the fresh-water field-crab, Paratelphusa sp.

Comp. Biochem. Physiol., 1962, Vol. 5, pp. 65 to 67. Pergamon Press Ltd., London. Printed in Great Britain

SHORT COMMUNICATION COMPENSATION TO HIGH TEMPERATURE IN THE LOSS AND ACTIVE ABSORPTION OF CHLORIDE IN THE FRESH-WATER FIELD-CRAB, P A R A T E L P H U S A SP. K. PAMPAPATHI RAO and V. VENKATAREDDY Department of Zoology, Sri Venkateswara University, Tirupati, A.P., India (Received 29 May 1961)

Abstract--1. When crabs are transferred from 28C to 36~C, they lose and gain chloride ions more rapidly. 2. After 12-15 days at the higher temperature, the rate of chloride change diminishes. The animals compensate so that in fact the chloride flux is now lower at 36°C than at 28°C. INTRODUCTION

TEMPERATURE influences to a very great extent the metabolic activity of the animal. Many poikilotherms exhibit in their metabolism and activity some degree of independence of their environmental temperature (Bullock, 1955; Precht, Christophersen & Hensel, 1955; and Prosser, 1958). In spite of this extensive work little is known about the influence of such compensation on permeability and active transport which assist in osmoregulation in dilute media. These factors are important in an understanding of the physiology of colonization of fresh waters (Pampapathi Rao, 1959). T h e experiments reported below demonstrate for the first time that compensation to temperature change occurs in such processes as chloride loss (permeability) and chloride uptake against a gradient (active transport) in a fresh-water poikilotherm when it is acclimatized to high temperature. T h e chloride uptake and output of the crabs were determined by estimating the concentration of chloride present in the water in the experimental vessels. T h e crabs were acclimatized to 36°C for 12-15 days. RESULTS

T h e results are plotted Fig. 1 (a-f) and each set of points is fitted with a regression line by the method of least squares. F r o m the graphs it is evident that chloride loss is less than chloride gain at any given temperature. This is due to the fact that loss is a passive process and gain is an active process. Fig. 1 (g) and (h) show that in normal crabs chloride loss as well as active uptake of chloride increases at the higher temperature (36°C). But the process of chloride uptake is less sensitive to temperature change compared to the process of chloride loss. 65

66

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PAMPAPATHI

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Comparing Fig. 1 (b) with Fig. 1 (f) it is seen (Fig. 1 (g)) that chloride loss at 36°C is remarkably lowered after acclimatization to 36°C. Chloride loss at 36°C after acclimatization is very near the level at 28°C (Fig. 1 (g)). A similar trend is seen in the process of active uptake of chloride (chloride gain). Thus, comparing Fig. 1 (e) with Fig. 1 (d) it is seen (Fig. 1 (h)) that the rate of chloride uptake at 36°C in crabs acclimatized to 36°C is lower than that in normal crabs H

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FIG. 1. (a) Chloride loss at 28°C. (b) Chloride loss at 36°C before acclimatization. (c) Chloride uptake at 28°C. (d) Chloride uptake at 36°C before acclimatization. (e) Chloride uptake at 36°C after acclimatization. (f) Chloride loss at 36°C after acclimatization. (g) Comparison of chloride loss at 28°C and 36°C before acclimatization with the rate at 36°C after acclimatization: lines taken from (a), (b) and (f). (h) Comparison of chloride uptake at 28°C and 36°C before acclimatization with the rate at 36°C after acclimatization: lines taken from (c), (d) and (e).

at 36°C. This lowered rate of gain at 36°C in high temperature acclimatized crabs is very close to the rate of gain at 28°C in normal crabs (Fig. 1 (h)). Both chloride loss and chloride gain tend to be equal to the 28°C level at 36°C after acclimatization. Actually there appears to be some degree of over-compensation as in Type I of Precht et al. (1955). DISCUSSION

The outward permeability to chloride in a fresh-water crab, Paratelphusa, increases with a rise in temperature. Likewise the active inward uptake of chloride against a concentration gradient also increases with an increase in temperature.

TEMPERATURE COMPENSATION IN CHLORIDE ABSORPTION

67

When the crab gets acclimatized to the high temperature, the rate of outward flow of chloride at that high temperature diminishes and reaches (actually in this particular instance goes below) the level it originally exhibited at the lower temperature (28°C) before transfer to the higher temperature (36°C). The outward permeability which was enhanced due to high temperature is reduced to its original level on prolonged sojourn at the high temperature. Hence the process of acclimatization to high temperature involves some mechanism which reduces the outward permeability of the crab. Likewise it is seen that on acclimatization the rate of active inward movement of chloride is also reduced, from an initial high level on transfer to 36°C, to a level as low or even slightly lower than the original rate at 28°C, although the temperature continues to be high. The rate of the active uptake, which was speeded up on account of increase in temperature, is slowed down to compensate for the rise in temperature. Since a process like active transport requires metabolic energy, this compensation contributes in part to the overall metabolic compensation to temperature in such poikilotherms. The importance of such a compensation to temperature in the permeability to chloride and in active uptake of chloride, especially for tropical and temperate fresh-water poikilotherms, needs no emphasis. Both the osmotic problems and the wide range of temperatures in shallow fresh waters faced by tropical fresh-water poikilotherms are quite well known (Pampapathi Rao, 1959) and a homeostatic mechanism in relation to chloride loss and uptake, as demonstrated above, would be of great survival value in such environments. SUMMARY 1. The chloride loss and uptake are studied at 28 + I°C and 36 + 1°C in the freshwater field crab Paratelphusa, before and after acclimatization to 36 + I°C. 2. It is shown that both chloride loss and gain are temperature sensitive and increase at the higher temperature (36°C). 3. A comparison of acclimatization curves at 36 + I°C with the curves of chloride loss and gain at 36 _+l°C before acclimatization indicates that there is less chloride loss and gain after acclimatization. 4. This change in the rate of chloride loss and gain compensates for the increase in temperature (from 28 to 36°C). REFERENCES BULLOCKT. H. (1955) Compensation for temperature in the metabolism and activity of poikilotherms. Biol. Rev. 30, 311-342. PAMPAPATHI RAO K. (1959) Some contributions towards an understanding of the metabolism of poikilotherms in fresh water. Syrup. Zool. Soc., India Bulletin No. 3, 6-8. PRECHT H., CHRISTOPHERSENJ. & HENSEL I~. (1955) Temperatur und Leben. SpringerVerlag, Berlin. PROSSER C. L. (Ed.) (1958) Physiological Adaptation. American Physiological Society, Washington, D.C.