The Effect of Temperature on Physiological Processes in Daphnia Magna

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Abstract The physiological procedures of many beings are sensitive to temperature. In order to see this consequence of temperature, we examined the bosom rate of a Daphnia magna over a scope of different temperatures. Bing an poikilothermic animate being, the Daphnia ‘s organic structure temperature is dependent on H2O temperature. It was hypothesized that since most physiological procedures are quicker at higher temperatures, the Daphnia ‘s bosom rate will be faster at higher temperatures and slower at low temperatures. This was, in fact, true and a form was apparent which showed that bosom rate increased as temperature increased. The Q10 was high at higher temperatures which show elevated sensitiveness at higher temperatures. Clearly, Daphnia have an optimum temperature scope outside which they do non work to their full potency. A Daphnia ‘s bosom rate, so, was proved to be dependent on temperature.

Introduction Daphnia magna is a widespread fresh water zooplankton. Since Daphnia are poikilothermic animate beings, their organic structure temperature fluctuates with environmental temperature. Hence, these animate beings are ideal to analyze the effects of temperature. Most such animate beings function good at certain specific temperatures. They have an optimum temperature scope, outside which they are unable to execute physiological procedures efficaciously ( Lamkemeyer et al. 2003 ) . It is believed that most physiological procedures take topographic point more quickly at higher temperatures and that alterations in temperature can act upon physiological rates ( Ziarek et al. 2010 ) . In order to look into this, we questioned whether the bosom rate of a Daphnia is different at different temperatures. Q10, which is the temperature sensitiveness of a reaction, was a utile tool. We hypothesized that the Daphnia will hold different bosom rates at different temperatures and hence that temperature will impact bosom rate. It was besides hypothesized that Q10 will differ at different temperatures. This hypothesis was tested by exposing the Daphnia to different H2O temperatures, allowing it equilibrate to the H2O temperature and numbering its bosom round in a systematic manner. Since most physiological procedures addition at higher temperatures, we predicted that if the temperature is higher ( close to 35A°C ) so the bosom rate of the Daphnia will be faster and if the temperature is low ( close to 5A°C ) so it would be slower. In add-on, we predicted that Q10 will be higher at low temperatures and lower at high temperatures. In position of the fact that Daphnia had an optimum temperature scope, it would be apprehensible if the Daphnia was more sensitive to temperatures outside this scope and accordingly reacted by changing its bosom rate.

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Methods A Daphnia was placed on a little vilification of Vaseline on the underside of a civilization dish ( Olaveson and Rush 2011 ) . Aged H2O at room temperature was added to the dish. Five proceedingss were allowed for the Daphnia to set to the H2O temperature and the temperature of the H2O was measured and recorded. Under a dissecting microscope, the Daphnia was placed and the 4X lens were used to turn up the bosom and number the pulses. The figure of beats was counted over a 10 2nd period which was followed by a 10 2nd intermission in numeration and so 10 seconds of numbering once more. In order to acquire 9 measurings of the bosom rate, this form was repeated for 3 proceedingss. Then, ice and H2O were assorted in a beaker to do a H2O mixture between 5A°C to 10A°C. To replace the pat H2O in the civilization dish with chilled H2O, a Pasteur pipette was used. Five proceedingss were allowed for the Daphnia to make equilibrium and so the bosom round was counted to obtain 9 steps of bosom rate ( heartbeats/ 10 seconds ) . The values were recorded. The temperature was so increased in 5A° increases till 35A°C and bosom rate was measured at each point. Small sums of the colder H2O were replaced with the heater H2O ( obtained from a H2O bath ) till the coveted temperature had been reached. Five proceedingss were ever allowed for equilibration and utilizing the same method, 9 steps of bosom rate were recorded. The 9 estimations of bosom rate taken at each temperature were used to happen the mean bosom rate at each temperature. These values were entered into an excel papers by all pupils and subsequently used for analysis.

Consequences Statistical analysis and information processing shed light upon the consequence of temperature on the bosom rate of a Daphnia. The Statistical T trial analysis proved that the Ho could be rejected for all the three trials turn outing that temperature does hold a important consequence on the bosom rate of a Daphnia. The Q10 every bit good as the mean bosom rates at different temperatures provided grounds that supported the hypothesis that temperature would impact Daphnia bosom rate excessively.

At the temperature interval of 4A°C to 14A°C, the Q10 was found to be 1.31 ( Table 1 ) . Although this was non the highest Q10 value and therefore non the most sensitive temperature interval, a lessening in bosom rate was apparent at the lower temperature of 4A°C compared to other higher temperatures ( figure 1 ) . The bosom rate at 4A°C was found to be 106.74 beats per minute where as the bosom rate at 14A°C was 140.10 beats per minute. The important lessening in bosom rate at 4A°C compared to bosom rate at the ambient temperature ( 24A°C ) was supported by the t trial analysis ( sample T statistic: 14.3938 ; critical T statistic:1.978 ; df:136 ; p = 0.05 ) . The temperature interval from 14A°C to 24A°C showed increased sensitiveness ( Q10:1.40 ) . This indicated the addition in bosom rate at 24A°C compared to lower temperatures ( figure 1 ) and was supported by the t trial analysis as the Ho ( hypothesis that no alteration in bosom rate would be apparent ) was rejected ( t statistic: 8.6519 ; critical T statistic:1.978 ; df:136 ; p = 0.05 ) . During the temperature interval from 24A°C to 34A°C, the highest Q10 was noted ( table 1 ) .

Figure 1. The mean bosom rate ( beats per minute ) of a Daphnia over scope of temperatures ( A°C )

Table 1. Q10 values of Daphnia bosom rates across different temperature intervals

Temperature Interval ( A°C )


34A°C- 24A°C

( High and Ambient Temperatures )


24A°C- 14A°C

( Ambient and Moderate Temperatures )



( Moderate and Low Temperature )


This sensitiveness to high temperatures was obvious when bosom rates at the two temperatures were compared ( bosom rate at 24A°C: 196.32 beats/min ; at 34A°C: 277.92 beats/ min ) . The H0 was therefore rejected ( t statistic: 9.7792 ; critical T statistic: 1.978 ; df: 136 ; P = 0.05 ) .

All the three trials provided grounds that suggested that temperature had an consequence on the Daphnia ‘s bosom rate. At higher temperatures, the bosom rate was faster and at lower temperatures, it was slower. By and large, as temperature increased so did the Daphnia ‘s bosom rate ( figure 1 ) .

Discussion All beings have an optimal temperature scope over which they function best. Consequently, at certain temperatures, the physiological procedures of a Daphnia magna are at its extreme potency. Some hypothesized that Daphnia optimize their fittingness by apportioning the clip spent in the different home grounds depending on the temperature gradient ( Kessler & A ; Lampert, 2004 ) . Hence, obviously temperature has an consequence on the public presentation of a Daphnia. Specifically, as hypothesized, temperature affected the bosom rate of Daphnia. It was noticed that the Daphnia ‘s bosom rate increased at higher temperatures ( shut to 34A°C ) and decreased at lower temperatures ( shut to 5A°C ) . Since Daphnia are poikilothermic, their organic structure temperature varies with environmental temperature. Since Daphnia can non thermoregulate, their organic structure temperature experiences discrepancy following i¬‚uctuations in the environment ( Ziarek et al. 2010 ) . Hence as the temperature of the H2O increased, so did the Daphnia ‘s bosom rate. The information supported this anticipation. This is merely because most physiological procedures take topographic point more quickly at higher temperatures. In add-on, research has shown that additions of bosom rate by important values were measured in D. Magna as a map of temperature ( Paul et al. 2004 ) . One ground why the bosom rate of Daphnia additions with temperature would be because less O is present in the warmer H2O. Consequently, deficiency of O could ensue in deficient sum of oxygenated blood and therefore the bosom would hold to work harder to pump blood around the organic structure. For this intent, it makes sense that the bosom rate would increase. Very small research has been done about O degrees at different temperatures and Daphnia bosom rates and possibly more such research will supply more lucidity on this subject. The small research that has been done, though, suggests that a decreased aerophilic range allows merely time-limited endurance at temperatures outside the optimum scope ( Lamkemeyer et al. 2003 ) in being such as Daphnias. Other research has besides shown that high temperatures increase a Daphnia ‘s metabolic rates by increasing their pulse rates ( MacArthur & A ; Baittie, 1929 ) , and accordingly their O demands ( Ziarek et al. 2010 ) .

It is besides of import to observe that although it was predicted that Q10 would be higher at low temperatures and lower at high temperatures, the informations did non back up this anticipation. The opposite, in fact, was apparent. At higher temperatures the Q10 was higher and at lower temperatures it was lower. This could be possible simply because the Daphnia was more sensitive to alterations in temperature at higher temperatures. It could besides be possible that Q10 was higher at higher temperatures because of other mistakes. For case, when the ice was added to the H2O in order to obtain low H2O temperatures ( 5A°C ) , it was hard to obtain the exact temperatures. Although the temperature obtained ( about 8A°C ) was lower than room temperature ( or ambient temperature ) , it is possible that it was n’t low plenty to trip major physiological alterations. A important fact to maintain in head is that since temperatures are increasing due to planetary heating, H2O temperatures are traveling to increase every bit good. This could take to jobs for beings such as Daphnia which can non work good outside of their optimum temperature scope. It has been suggested that lifting temperatures associated with planetary warming present a challenge to the destiny of many aquatic beings ( Doorslaer et al. 2009 )

In decision, Daphnia bosom rate is affected by temperature and tends to increase at high temperatures and lessening at low temperatures.

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