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Effects of temperature on Drosophila—I. respiration of D. melanogaster grown at different temperatures
Comp. Biochem.Physiol., 1964, Vol. 11, pp. 411 to 417. PergamonPressLtd. Printedin Great Britain
EFFECTS OF TEMPERATURE ON D R O S O P H I L A - - I . RESPIRATION OF D. M E L A N O G A S T E R GROWN AT DIFFERENT TEMPERATURES* A L I C E S. H U N T E R Department of Biology, University of the Andes, Bogota, Colombia
(Received 14 August 1963) Abstract--1. The oxygen consumption in pl/hr per adult fly and per mg wet weight is reported for the following stocks of Bogotll D. m~/anogastsr: two stocks grown at 15°C, two stocks grown at 25°C and one stock grown at 30°C, all measured at 15°C, 20°C, 25°C and 30°C. 2. In general there are no differences in the rate of respiration of the males grown at the different temperatures. 3. Females grown at 25°C and 30°C have a significantly lower rate of respiration at 20°C, 25°C and 30°C than do females which have been grown at 15°C. 4. Qz0 values have been calculated and are lower for all stocks at the higher temperatures. 5. The data are interpreted as suggesting that temperature adaptation has taken place in the females of D. melanogaster grown for many generations at different temperatures. INTRODUCTION STUDIES of seasonal frequency (Patterson & Wagner, 1943) and geographic distribution of Drosophila show that some species are distributed widely relative to environmental temperature (eurytherms) while others are more restricted (stenotherms). Drosophila grown u n d e r laboratory conditions differ morphologically and physiologically with differences in ambient temperature. Eigenbrodt (1930) f o u n d that in a homozygous race of Drosophila the weight of the flies varies inversely as the temperature. Ray (1960) demonstrated that Bergmann's and Allen's rules apply to four Drosophila species. Differential resistances of " t e m p e r a t u r e races" of D. funebris from different geographic regions are correlated with the temperature of their respective habitats (Timofe6ff-Ressovsky, 1940). T a n t a w y & Mallah (1961) found that stenokous and euryokous populations of D. melanogastersimulans from different regions of the Middle East vary in their viability u n d e r laboratory conditions. T h e euryokous population was more viable over a wide range of temperature while the stenokous population was superior only at one temperature. T h i s suggests that a eurythermal species such as D. melanogaster
* Acknowledgement is made to the U.S. Department of Agriculture and the Rockefeller Foundation for support of this work. 411
412
ALICE S. HUNTER
may have a superior capacity for adaptation to different temperatures than do stenothermal species such as D. willistoni or D. pseudo-obscura. In this paper the oxygen consumption of D. melanogaster, chosen as an example of a eurythermal species, will be reported for adults grown at different temperatures. In subsequent studies the comparisons will be extended to various stenothermal species. MATERIALS AND METHODS The specimens of D. melanogaster were collected in nature m Bogota, Colombia, during February-May of 1959. A sample of about 1000 flies was randomly divided into two groups. From that time to the present, one group has been maintained at 14-16°C and the other group at 24-26°C. For all stooks, 1 lb culture jars stoppered with cotton are used. Since there is no humidity control in the incubators, the culture medium for the flies growing at 15°C contains less agar to counteract the problem of dehydration during the long period of development. The media are prepared as follows: 15° 25 Water Crude agar cut and ground Banana mash 10% Tegosept m alcohol
1000 ml 15 g 1000 ml 14 ml
1000 ml 30 g 1000 ml 14 ml
In the jars at 25 °, 80 ml of the medium is used, while 120 ml is put into the 15 ° jars. Afew drops of a solution of live Fleischman's baker's yeast are addedwhen the adults are removed. Two types of cultures of flies have been maintained at each of the two temperatures: 25° five pair stock. Five males and five females of 2-4 days of age since hatching from pupae are left in a jar for 2 days to copulate and lay eggs. Twelve to fourteen days after removing the parents from the jars the offspring are collected and sexed. 25 ° twenty pair stock. Twenty males and twenty females of 2-6 days of age are left in a jar for 5 days to copulate and lay eggs. Twelve to sixteen days after removing the parents the offspring are collected and sexed. 15 ° ten pair stock. Ten males and ten females of 2-3 weeks of age are left m a jar for 1 week to copulate and lay eggs. The offspring are collected 4-5 weeks after removing the adults. 15 ° 120 stock. One hundred and twenty flies (not sexed) are left m a jar for a week to copulate and lay eggs. The offspring are collected 4-5 weeks after removing the adults. 30 ° stock. In September 1962 a fifth stock was established from the five pair 25°C adults. This is maintained in the same way as the parent stock, but at 30°C instead of 25°C. Each type of stock is set up three times a week. The adults from five to ten jars of a particular stock are grouped and sexed, and the flies for new jars are taken from these. All stocks are exposed to light during the day and kept in the dark at night. In all experiments young adults are used.
413
EFFECTS OF TEMPI~ATURE ON D R O S O P H I L A - - I
T h e measurements of oxygen consumption were made in a W a r b u r g respirometer, using vessels of 5-7 ml capacity. T h e flies were weighed and placed in capsules having a total volume of about 0"1 ml. In preliminary experiments gelatin capsules with pin-pricked holes were used, but apparently the humidity inside the W a r b u r g vessels was sufficient to soften the gelatin and the holes closed up and reduced the rate of gas exchange. T e n females or twelve males were placed in a glass capsule which was closed with a cotton plug pushed in just far enough to prevent flying and limit walking. Gas exchange in these capsules is equal to that in tiny hand-sewn gauze bags which obviously in no way prevent movement of gases. In the side-arm of the vessel 0.1 ml of 25% K O H was added to absorb the CO 2. Readings were recorded every 15 min and the data from a 3 hr period were used to determine the rate of oxygen consumption per hour. RESULTS T h e oxygen consumption, in ~l/hr per fly and also per mg of fresh weight, is reported in Table 1 for the flies grown at 15°C, in T a b l e 2 for those grown at T A B L E 1 - - M I C R O L I T E R S OXYGEN CONSUMED PER HOUR BY
10 Pair S.D. N
15°C
FLIES
120 Flies S.D. N
At 15°C Per fly--female Per mg--female Per fly--male Per mg--male
1"9 1"6 1"4 16
0"3 0"1 0"2 0"3
23 23 22 22
1'8 1"6 1"4 1"8
0"3 0"3 0"3 0"3
19 19 19 19
At 20°C Per fly--female Per mg--female Per fly--male Per mg--male
3-4 2'7 2"4 2"7
0"4 0"2 0"3 0'3
19 19 19 19
3"2 2"8 2"3 2"8
0'5 0"2 0"3 0"3
23 23 23 23
At 25°C Per fly--female Per rag--female Per fly--male Per mg--male
4"0 3"4 3.0 3"4
0"6 0"4 0"5 0"7
25 25 25 25
3"8 3"5 2-9 3"7
0"7 0"5 0.5 0'5
34 34 32 34
At 30°C Per fly--female Per mg--female Per fly--male Per mg--male
5-9 4-7 4"4 4.8
0"8 0"5 0"6 0.4
12 12 12 11
5'3 47 3"4 4.7
0"8 0"3 0"5 0.4
19 20 19 19
25°C and in T a b l e 3 for those grown at 30°C. T h e average wet weights of single adult flies in milligrams are as follows: ten pair 15 ° stock females, 1.22, and males,
414
ALICE S. HUN'm~
0"89; 120 fly 15 ° stock females, 1-12, and males 0.78; five pair 25 ° stock females, 1.09, and males, 0'78; twenty pair 25 ° stock females, 0.88, and males 0"63; five pair 30 ° stock females, 1.04, and males, 0.71. T h e r e are no statistically significant differences in the respiration of the males grown at different temperatures. However, the females grown at 15°C have a higher rate of respiration than those grown at 25°C and at 30°C w h e n measured at TABLE 2 - - M I C R O L I T E I t ~
OXYGEN CONSUMED PER HOUR BY
5 Pair S.D.
N
25°C
FLIES
20 Pair S.D.
N
At 15°C Per fly--female Per rag---female Per fly--rnale Per rag--male
1.6 1 "5 1"2 1"7
0.3 0"2 0.2 0"1
18 18 15 15
1.3 1"5 1'0 1 "7
0.2 0-2 0.2 0"3
14 14 14 14
At 20°C Per fly--female Per rng--female Per fly--male Per rag--male
2.8 2"4 2"0 2'6
0-6 0.3 0"4 0"4
18 18 18 18
2.2 2"3 1"8 2"5
0.5 0.2 0-5 0"4
18 18 17 17
At 25°C Per fly--female Per mg--female Per fly--male Per mg--male
3.5 3"3 2"6 3-6
0"6 0"5 0"5 0"5
18 17 17 15
2"6 3.0 2"1 3'4
0"4 0.3 0"4 0"6
20 20 20 20
At 30°C Per fly--female Per mg--fernale Per fly--male Per nag--male
4"5 4-2 3"7 4"7
0"9 0"4 0"9 0"6
13 13 13 13
3"4 40 2'7 4"4
0-6 0.4 U4 0"7
13 13 13 13
20 °, 25 ° and 30°C ( P = 0.001). Although no relationship can be f o u n d between respiration per m g and weight of the male, there is a positive correlation between the wet weight of the females and the oxygen c o n s u m p t i o n at 20°C (r = 0-77), at 25°C (r = 0.90) and at 30°C (r = 0"84). Within the two stocks growing at 15°C there are no differences in the oxygen c o n s u m p t i o n per m g wet weight between the males and females. C o m p a r i n g the sexes grown at 25°C and 30°C, the value for the males is higher than that for the females at all t e m p e r a t u r e s ( P ranging between 0.1 and 0.001).
tseaqsC'l'8OF TKI~-maATUREON D R O S O P H 1 L A - - I
415
T.~z.e 3 - - M x c a o L r r n s oxcom~ coh'szvmm ~ a Hcam m¢ 30°C m . . ~ S.D.
N
At 15°C Per fly---female Per rag--female Per fly--male Per rag--male
1.6 1"6 1.3 1.8
0"4 0"2 0"5 0"3
9 9 9 9
At 20°C Per fly--female Per mg--female Per fly--male Per rag---male
2. ~ 2.5 2.0 2.9
0.7 0"3 0"5 0-4
9 9 9 9
At 25°C Per fly--female Per mg--female Per fly--mah Per mg---male
3"3 3"2 2"6 3"7
0-8 0"3 0"6 0"4
9 9 9 9
At 30°C Per fly--female Per rag--female Per fly---male Per mg--male
4"5 4"3 3"4 4"8
0"8 0"3 0"6 0"3
9 9 9 9
TABLE 4.--.-~ o VALUESl~OnOX~O~ C O ~ O N
Or D. mdanogas~r
15-20°C
20-25°C
25-30°C
15°C Stocks 10 pair females 120 pair females 10 pair males 120 pair males
2.8 3"1 2.9 2.4
1"6 1"6 1.6 1.7
1"9 1"8 2.0 1-6
15°C Stocks 5 pair females 20 pair females 5 pair males 20 pair males
2.6 2.3 2.3 2.2
1.9 1.7 1.9 1.9
1"6 1-8 1-7 1.7
30°C Stocks 5 pair females S pair males
2-5 2-4
1"6 1"7
1"9 1.7
416
AxicE S. Htma'ER
The Qlo values have been calculated for 5 ° intervals using the means presented in the tables. In Table 4 it can be seen that the Qlo is higher at the lower temperatures for all the stocks compared. DISCUSSION In terms of the overall purpose of this project, a comparison of the metabolism of stenothermal and eurythermal species of Drosophila, the values reported here for D. melanogaster serve as a base-line and as an example of a species which may be considered eurythermal. Comparison of the data reported in Tables 1, 2 and 3 with those in the literature reveals some differences. Kucera (1934) and Orr (1937) have reported a higher rate of respiration for D. melanogaster females than for the males. Although their values are comparable in magnitude to ours we did not find the same sex difference. D. melanogaster pupae were studied by Poulson (1935) and he found that the oxygen consumption per unit weight is greater in males than in females, while Vernberg & Meriney (1957) found no significant sex differences in oxygen consumption of the strains of D. melanogaster which they studied. Perhaps some of these inconsistencies will be resolved by a consideration of the temperature at which the flies have been growing. The data reported in the present paper can be interpreted as indicative of no sex difference in the oxygen consumption of flies grown at 15°C when measured at 15-30°C. However, in the stocks which have been grown at higher temperatures the respiration of the males is always slightly higher than that of the females. In general the data reported here agree with the values obtained by Vernberg & Meriney (1957) 44.46/d/min/g or 2.67/~l/hr/mg as corrected in a personal communication from F. J. Vernberg. With respect to the hypothesis that eurythermal species of Drosophila may have a greater capacity for temperature adaptation the results are positive for the females only. In the terminology of Precht (1958), the females studied here show a partial compensation at 20-30°C, but the difference or the translation of the rate/ temperature curve is small. In these studies it is important to compare animals of the same weight, since it has been shown that larger organisms within a species may show a greater rate change with temperature than smaller ones (Bullock, 1955). This presents a problem with Drosophila since the size and form (Ray, 1960) vary considerably with the temperature at which they have grown. By keeping the flies quite crowded as in the 120 stock we have obtained an adult at 15°C which is not too different in wet weight from the five pair flies growing at 25°C. Therefore, this seems to be the most valid comparison to make. There is much evidence in the literature which indicates that cold-adapted animals respire faster than warmadapted ones when compared at an intermediate temperature (Bullock, 1955). The 120 stock females grown at 15°C have a rate of respiration which is 17 per cent higher than that of the five pair females grown at 25°C, when it is measured at the intermediate temperature of 20°C. This difference is comparable to that obtained by Dehnel & Segal (1956) with the adult cockroach. They found that an animal of 0.9 g weight acclimated to 16°C consumes 18 per cent more oxygen than its counterpart from 26°C.
EFFECTS OF TEMPERATURE ON D R O S O P H 1 L A - - I
417
I f this difference does indicate a temperature adaptation of the adult D. melanogaster female, then what is the basis for its occurrence in one sex only ? Perhaps only certain organs specific to the females are adapting while the rest of the female, like the male, does not adapt. For example, it has been shown in amphibians (Rieck et al., 1960) that skeletal muscle and stomach have a rate of respiration which differs with the t e m p e r a t u r e of acclimation, while liver does not. It should also be noted that in this study no distinction has been made between short-term adaptation, environmentally induced, as a p h e n o m e n o n separate from the long-term genetic adaptation. It is highly possible that the latter could have taken place, since these stocks have been growing at the same t e m p e r a t u r e for m a n y generations. Studies of reversibility in progress m a y clarify this point. REFERENCES BULLOCK T. H. (1955) Compensation for temperature m the metabohsm and activity of poikilotherms. Bzol. Rev. 30, 311-342. DEHNEL P. A. & SEOALE. (1956) Acclimauon of oxygen consumption to temperature m the American cockroach (Periplaneta americana). Biol. Bull., Woods Hole 111, 53-61. EmENBRODT H. J. (1930) The somatic effects of temperature on a homozygous race of Drosophila. Physiol. Zool. 3, 392. KucERA W. G. (1934) Oxygen consumption in :he male and female fly, Drosophila melanogaster. Physiol. Zool. 7, 449-457. ORR P. R. (1937) Physiological studies on respiratory metabolism of Drosophila melanogaster. Physiol. Zool. 10, 235. PATTERSON J. T. & WAGNER R. P. (1943) Geographical Distribution of Species of the Genus Drosophila in the U.S. and Mexico, University of Texas Pub. 4313, pp. 217-281. POULSON D. F. (1935) Oxygen consumption of Drosophila pupae--I. Drosophila melanogaster. Z. vergl. Physiol. 22, 466-472. PRECHT H. (1958) Concepts of the temperature adaptation of unchanging reaction systems of cold-blooded animals. In Physiological Adaptation (Edited by PROSSER C. L.), pp. 50-78. American Physiological Society, Washington, D.C. RAY C. (1960). The application of Bergmann's and Allen's rules to the poikilotherms. J. Morph. 106, 85-10~. RIECK A. F., BUELl J. A. & BLASKOVlCSM. E. (1960) Oxygen consumption of whole animal and tissues in temperature acclimated amphibians. Proc. Soc. Exp. Biol. Med. 103, 436-439. TANTAWY A. O. & MALLAH G. S. (1961) Studies on natural population of Drosophila--I. Heat resistance and geographical variation m Drosophila melanogaster and D. simulans. Evolution 5, 1-14. TIMOFE~FE-REssovsKY N. W. (1940) Mutations and geographical variation. In The New Systematics (Edited by HUXLEYJ.). VERNBERC, F. J. & MERINEYD. K. (1957) The influence of temperature and humidity on the metabolism of melanistic strains of Drosophila melanogaster. J. Elisha Mitchell Sci. Soc. 73, 351-362.
EFFECTS OF TEMPERATURE ON D R O S O P H I L A - - I . RESPIRATION OF D. M E L A N O G A S T E R GROWN AT DIFFERENT TEMPERATURES* A L I C E S. H U N T E R Department of Biology, University of the Andes, Bogota, Colombia
(Received 14 August 1963) Abstract--1. The oxygen consumption in pl/hr per adult fly and per mg wet weight is reported for the following stocks of Bogotll D. m~/anogastsr: two stocks grown at 15°C, two stocks grown at 25°C and one stock grown at 30°C, all measured at 15°C, 20°C, 25°C and 30°C. 2. In general there are no differences in the rate of respiration of the males grown at the different temperatures. 3. Females grown at 25°C and 30°C have a significantly lower rate of respiration at 20°C, 25°C and 30°C than do females which have been grown at 15°C. 4. Qz0 values have been calculated and are lower for all stocks at the higher temperatures. 5. The data are interpreted as suggesting that temperature adaptation has taken place in the females of D. melanogaster grown for many generations at different temperatures. INTRODUCTION STUDIES of seasonal frequency (Patterson & Wagner, 1943) and geographic distribution of Drosophila show that some species are distributed widely relative to environmental temperature (eurytherms) while others are more restricted (stenotherms). Drosophila grown u n d e r laboratory conditions differ morphologically and physiologically with differences in ambient temperature. Eigenbrodt (1930) f o u n d that in a homozygous race of Drosophila the weight of the flies varies inversely as the temperature. Ray (1960) demonstrated that Bergmann's and Allen's rules apply to four Drosophila species. Differential resistances of " t e m p e r a t u r e races" of D. funebris from different geographic regions are correlated with the temperature of their respective habitats (Timofe6ff-Ressovsky, 1940). T a n t a w y & Mallah (1961) found that stenokous and euryokous populations of D. melanogastersimulans from different regions of the Middle East vary in their viability u n d e r laboratory conditions. T h e euryokous population was more viable over a wide range of temperature while the stenokous population was superior only at one temperature. T h i s suggests that a eurythermal species such as D. melanogaster
* Acknowledgement is made to the U.S. Department of Agriculture and the Rockefeller Foundation for support of this work. 411
412
ALICE S. HUNTER
may have a superior capacity for adaptation to different temperatures than do stenothermal species such as D. willistoni or D. pseudo-obscura. In this paper the oxygen consumption of D. melanogaster, chosen as an example of a eurythermal species, will be reported for adults grown at different temperatures. In subsequent studies the comparisons will be extended to various stenothermal species. MATERIALS AND METHODS The specimens of D. melanogaster were collected in nature m Bogota, Colombia, during February-May of 1959. A sample of about 1000 flies was randomly divided into two groups. From that time to the present, one group has been maintained at 14-16°C and the other group at 24-26°C. For all stooks, 1 lb culture jars stoppered with cotton are used. Since there is no humidity control in the incubators, the culture medium for the flies growing at 15°C contains less agar to counteract the problem of dehydration during the long period of development. The media are prepared as follows: 15° 25 Water Crude agar cut and ground Banana mash 10% Tegosept m alcohol
1000 ml 15 g 1000 ml 14 ml
1000 ml 30 g 1000 ml 14 ml
In the jars at 25 °, 80 ml of the medium is used, while 120 ml is put into the 15 ° jars. Afew drops of a solution of live Fleischman's baker's yeast are addedwhen the adults are removed. Two types of cultures of flies have been maintained at each of the two temperatures: 25° five pair stock. Five males and five females of 2-4 days of age since hatching from pupae are left in a jar for 2 days to copulate and lay eggs. Twelve to fourteen days after removing the parents from the jars the offspring are collected and sexed. 25 ° twenty pair stock. Twenty males and twenty females of 2-6 days of age are left in a jar for 5 days to copulate and lay eggs. Twelve to sixteen days after removing the parents the offspring are collected and sexed. 15 ° ten pair stock. Ten males and ten females of 2-3 weeks of age are left m a jar for 1 week to copulate and lay eggs. The offspring are collected 4-5 weeks after removing the adults. 15 ° 120 stock. One hundred and twenty flies (not sexed) are left m a jar for a week to copulate and lay eggs. The offspring are collected 4-5 weeks after removing the adults. 30 ° stock. In September 1962 a fifth stock was established from the five pair 25°C adults. This is maintained in the same way as the parent stock, but at 30°C instead of 25°C. Each type of stock is set up three times a week. The adults from five to ten jars of a particular stock are grouped and sexed, and the flies for new jars are taken from these. All stocks are exposed to light during the day and kept in the dark at night. In all experiments young adults are used.
413
EFFECTS OF TEMPI~ATURE ON D R O S O P H I L A - - I
T h e measurements of oxygen consumption were made in a W a r b u r g respirometer, using vessels of 5-7 ml capacity. T h e flies were weighed and placed in capsules having a total volume of about 0"1 ml. In preliminary experiments gelatin capsules with pin-pricked holes were used, but apparently the humidity inside the W a r b u r g vessels was sufficient to soften the gelatin and the holes closed up and reduced the rate of gas exchange. T e n females or twelve males were placed in a glass capsule which was closed with a cotton plug pushed in just far enough to prevent flying and limit walking. Gas exchange in these capsules is equal to that in tiny hand-sewn gauze bags which obviously in no way prevent movement of gases. In the side-arm of the vessel 0.1 ml of 25% K O H was added to absorb the CO 2. Readings were recorded every 15 min and the data from a 3 hr period were used to determine the rate of oxygen consumption per hour. RESULTS T h e oxygen consumption, in ~l/hr per fly and also per mg of fresh weight, is reported in Table 1 for the flies grown at 15°C, in T a b l e 2 for those grown at T A B L E 1 - - M I C R O L I T E R S OXYGEN CONSUMED PER HOUR BY
10 Pair S.D. N
15°C
FLIES
120 Flies S.D. N
At 15°C Per fly--female Per mg--female Per fly--male Per mg--male
1"9 1"6 1"4 16
0"3 0"1 0"2 0"3
23 23 22 22
1'8 1"6 1"4 1"8
0"3 0"3 0"3 0"3
19 19 19 19
At 20°C Per fly--female Per mg--female Per fly--male Per mg--male
3-4 2'7 2"4 2"7
0"4 0"2 0"3 0'3
19 19 19 19
3"2 2"8 2"3 2"8
0'5 0"2 0"3 0"3
23 23 23 23
At 25°C Per fly--female Per rag--female Per fly--male Per mg--male
4"0 3"4 3.0 3"4
0"6 0"4 0"5 0"7
25 25 25 25
3"8 3"5 2-9 3"7
0"7 0"5 0.5 0'5
34 34 32 34
At 30°C Per fly--female Per mg--female Per fly--male Per mg--male
5-9 4-7 4"4 4.8
0"8 0"5 0"6 0.4
12 12 12 11
5'3 47 3"4 4.7
0"8 0"3 0"5 0.4
19 20 19 19
25°C and in T a b l e 3 for those grown at 30°C. T h e average wet weights of single adult flies in milligrams are as follows: ten pair 15 ° stock females, 1.22, and males,
414
ALICE S. HUN'm~
0"89; 120 fly 15 ° stock females, 1-12, and males 0.78; five pair 25 ° stock females, 1.09, and males, 0'78; twenty pair 25 ° stock females, 0.88, and males 0"63; five pair 30 ° stock females, 1.04, and males, 0.71. T h e r e are no statistically significant differences in the respiration of the males grown at different temperatures. However, the females grown at 15°C have a higher rate of respiration than those grown at 25°C and at 30°C w h e n measured at TABLE 2 - - M I C R O L I T E I t ~
OXYGEN CONSUMED PER HOUR BY
5 Pair S.D.
N
25°C
FLIES
20 Pair S.D.
N
At 15°C Per fly--female Per rag---female Per fly--rnale Per rag--male
1.6 1 "5 1"2 1"7
0.3 0"2 0.2 0"1
18 18 15 15
1.3 1"5 1'0 1 "7
0.2 0-2 0.2 0"3
14 14 14 14
At 20°C Per fly--female Per rng--female Per fly--male Per rag--male
2.8 2"4 2"0 2'6
0-6 0.3 0"4 0"4
18 18 18 18
2.2 2"3 1"8 2"5
0.5 0.2 0-5 0"4
18 18 17 17
At 25°C Per fly--female Per mg--female Per fly--male Per mg--male
3.5 3"3 2"6 3-6
0"6 0"5 0"5 0"5
18 17 17 15
2"6 3.0 2"1 3'4
0"4 0.3 0"4 0"6
20 20 20 20
At 30°C Per fly--female Per mg--fernale Per fly--male Per nag--male
4"5 4-2 3"7 4"7
0"9 0"4 0"9 0"6
13 13 13 13
3"4 40 2'7 4"4
0-6 0.4 U4 0"7
13 13 13 13
20 °, 25 ° and 30°C ( P = 0.001). Although no relationship can be f o u n d between respiration per m g and weight of the male, there is a positive correlation between the wet weight of the females and the oxygen c o n s u m p t i o n at 20°C (r = 0-77), at 25°C (r = 0.90) and at 30°C (r = 0"84). Within the two stocks growing at 15°C there are no differences in the oxygen c o n s u m p t i o n per m g wet weight between the males and females. C o m p a r i n g the sexes grown at 25°C and 30°C, the value for the males is higher than that for the females at all t e m p e r a t u r e s ( P ranging between 0.1 and 0.001).
tseaqsC'l'8OF TKI~-maATUREON D R O S O P H 1 L A - - I
415
T.~z.e 3 - - M x c a o L r r n s oxcom~ coh'szvmm ~ a Hcam m¢ 30°C m . . ~ S.D.
N
At 15°C Per fly---female Per rag--female Per fly--male Per rag--male
1.6 1"6 1.3 1.8
0"4 0"2 0"5 0"3
9 9 9 9
At 20°C Per fly--female Per mg--female Per fly--male Per rag---male
2. ~ 2.5 2.0 2.9
0.7 0"3 0"5 0-4
9 9 9 9
At 25°C Per fly--female Per mg--female Per fly--mah Per mg---male
3"3 3"2 2"6 3"7
0-8 0"3 0"6 0"4
9 9 9 9
At 30°C Per fly--female Per rag--female Per fly---male Per mg--male
4"5 4"3 3"4 4"8
0"8 0"3 0"6 0"3
9 9 9 9
TABLE 4.--.-~ o VALUESl~OnOX~O~ C O ~ O N
Or D. mdanogas~r
15-20°C
20-25°C
25-30°C
15°C Stocks 10 pair females 120 pair females 10 pair males 120 pair males
2.8 3"1 2.9 2.4
1"6 1"6 1.6 1.7
1"9 1"8 2.0 1-6
15°C Stocks 5 pair females 20 pair females 5 pair males 20 pair males
2.6 2.3 2.3 2.2
1.9 1.7 1.9 1.9
1"6 1-8 1-7 1.7
30°C Stocks 5 pair females S pair males
2-5 2-4
1"6 1"7
1"9 1.7
416
AxicE S. Htma'ER
The Qlo values have been calculated for 5 ° intervals using the means presented in the tables. In Table 4 it can be seen that the Qlo is higher at the lower temperatures for all the stocks compared. DISCUSSION In terms of the overall purpose of this project, a comparison of the metabolism of stenothermal and eurythermal species of Drosophila, the values reported here for D. melanogaster serve as a base-line and as an example of a species which may be considered eurythermal. Comparison of the data reported in Tables 1, 2 and 3 with those in the literature reveals some differences. Kucera (1934) and Orr (1937) have reported a higher rate of respiration for D. melanogaster females than for the males. Although their values are comparable in magnitude to ours we did not find the same sex difference. D. melanogaster pupae were studied by Poulson (1935) and he found that the oxygen consumption per unit weight is greater in males than in females, while Vernberg & Meriney (1957) found no significant sex differences in oxygen consumption of the strains of D. melanogaster which they studied. Perhaps some of these inconsistencies will be resolved by a consideration of the temperature at which the flies have been growing. The data reported in the present paper can be interpreted as indicative of no sex difference in the oxygen consumption of flies grown at 15°C when measured at 15-30°C. However, in the stocks which have been grown at higher temperatures the respiration of the males is always slightly higher than that of the females. In general the data reported here agree with the values obtained by Vernberg & Meriney (1957) 44.46/d/min/g or 2.67/~l/hr/mg as corrected in a personal communication from F. J. Vernberg. With respect to the hypothesis that eurythermal species of Drosophila may have a greater capacity for temperature adaptation the results are positive for the females only. In the terminology of Precht (1958), the females studied here show a partial compensation at 20-30°C, but the difference or the translation of the rate/ temperature curve is small. In these studies it is important to compare animals of the same weight, since it has been shown that larger organisms within a species may show a greater rate change with temperature than smaller ones (Bullock, 1955). This presents a problem with Drosophila since the size and form (Ray, 1960) vary considerably with the temperature at which they have grown. By keeping the flies quite crowded as in the 120 stock we have obtained an adult at 15°C which is not too different in wet weight from the five pair flies growing at 25°C. Therefore, this seems to be the most valid comparison to make. There is much evidence in the literature which indicates that cold-adapted animals respire faster than warmadapted ones when compared at an intermediate temperature (Bullock, 1955). The 120 stock females grown at 15°C have a rate of respiration which is 17 per cent higher than that of the five pair females grown at 25°C, when it is measured at the intermediate temperature of 20°C. This difference is comparable to that obtained by Dehnel & Segal (1956) with the adult cockroach. They found that an animal of 0.9 g weight acclimated to 16°C consumes 18 per cent more oxygen than its counterpart from 26°C.
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I f this difference does indicate a temperature adaptation of the adult D. melanogaster female, then what is the basis for its occurrence in one sex only ? Perhaps only certain organs specific to the females are adapting while the rest of the female, like the male, does not adapt. For example, it has been shown in amphibians (Rieck et al., 1960) that skeletal muscle and stomach have a rate of respiration which differs with the t e m p e r a t u r e of acclimation, while liver does not. It should also be noted that in this study no distinction has been made between short-term adaptation, environmentally induced, as a p h e n o m e n o n separate from the long-term genetic adaptation. It is highly possible that the latter could have taken place, since these stocks have been growing at the same t e m p e r a t u r e for m a n y generations. Studies of reversibility in progress m a y clarify this point. REFERENCES BULLOCK T. H. (1955) Compensation for temperature m the metabohsm and activity of poikilotherms. Bzol. Rev. 30, 311-342. DEHNEL P. A. & SEOALE. (1956) Acclimauon of oxygen consumption to temperature m the American cockroach (Periplaneta americana). Biol. Bull., Woods Hole 111, 53-61. EmENBRODT H. J. (1930) The somatic effects of temperature on a homozygous race of Drosophila. Physiol. Zool. 3, 392. KucERA W. G. (1934) Oxygen consumption in :he male and female fly, Drosophila melanogaster. Physiol. Zool. 7, 449-457. ORR P. R. (1937) Physiological studies on respiratory metabolism of Drosophila melanogaster. Physiol. Zool. 10, 235. PATTERSON J. T. & WAGNER R. P. (1943) Geographical Distribution of Species of the Genus Drosophila in the U.S. and Mexico, University of Texas Pub. 4313, pp. 217-281. POULSON D. F. (1935) Oxygen consumption of Drosophila pupae--I. Drosophila melanogaster. Z. vergl. Physiol. 22, 466-472. PRECHT H. (1958) Concepts of the temperature adaptation of unchanging reaction systems of cold-blooded animals. In Physiological Adaptation (Edited by PROSSER C. L.), pp. 50-78. American Physiological Society, Washington, D.C. RAY C. (1960). The application of Bergmann's and Allen's rules to the poikilotherms. J. Morph. 106, 85-10~. RIECK A. F., BUELl J. A. & BLASKOVlCSM. E. (1960) Oxygen consumption of whole animal and tissues in temperature acclimated amphibians. Proc. Soc. Exp. Biol. Med. 103, 436-439. TANTAWY A. O. & MALLAH G. S. (1961) Studies on natural population of Drosophila--I. Heat resistance and geographical variation m Drosophila melanogaster and D. simulans. Evolution 5, 1-14. TIMOFE~FE-REssovsKY N. W. (1940) Mutations and geographical variation. In The New Systematics (Edited by HUXLEYJ.). VERNBERC, F. J. & MERINEYD. K. (1957) The influence of temperature and humidity on the metabolism of melanistic strains of Drosophila melanogaster. J. Elisha Mitchell Sci. Soc. 73, 351-362.