The Effects Of Acclimation On Oxygen Consumption In The Crayfish,
Mean oxygen consumption rates were collected for crayfish (Orconectes propinquus) acclimated to either warm (20-25°C) or cold (3-5°C) temperatures at time intervals of 30 minutes and 1 hour. Warm crayfish were placed in water at an average temperature of 19. 967 ± 0. 284 °C and cold crayfish were placed in water at an average temperature of 6. 774 ± 0. 395 °C. After omission of outlier data, the mean oxygen consumption rate of 50 warm-acclimated crayfish, averaging a mass of 8. 585 ± 0. 578 grams, was 5. 233 ± 0. 454 μg O2 min-1 g-1 for 30 minutes and 4. 559 ± 0. 434 μg O2 min-1 g-1 for 1 hour. The mean oxygen consumption rate of 47 cold-acclimated crayfish of average mass 9. 033 ± 0. 387 grams was 4. 170 ± 0. 463 μg O2 min-1 g-1 for 30 minutes and 4. 287 ± 0. 748 μg O2 min-1 g-1 for 1 hour. After performing an unpaired t-test, a P value of approximately 14% was given. The Q10 value for oxygen consumption in the crayfish was 1. 122. Figure 1. Mean oxygen consumption rates for the crayfish, Orconectes propinquus acclimated to warm and cold temperatures for two time intervals. Data presented are ± 1 SEM, N= 50 for warm and N=47 for cold.
Discussion
Over the course of the experiment, it was found that warm acclimated crayfish seemed to lower their oxygen consumption rates with time, while cold acclimated crayfish showed an increase in mean O2 consumption. Despite this difference in direction however, both groups had very similar mean consumption rates (Figure 1). This finding paired with the t-test and Q10 values hails that the hypothesis, Orconectes propinquus will show metabolic compensation when acclimated at different temperatures, could be supported. The Q10 value being so close to 1 demonstrates that the crayfish has compensated for the change in temperature. Paired with the knowledge that Medway Creek, the natural home of these crayfish, can have temperatures ranging from 0-30°C, we can deduce that the crayfish are very capable of handling temperature variation. We know for a fact that when the environmental temperature surrounding an ectotherm changes, so does the body temperature of the organism (Hill et al. , 2012). Other factors could very likely have been responsible for differences in the rates of O2 consumption. Levels of oxygen in the water were diminished as the experiment progressed, for example; the utilization of a plastic cover to block the water from interacting with the airborne oxygen would have led to decreased levels as the time passed. The amount of oxygen in the water was also lost over time due to both the crayfish consuming it, and the siphoning of water as instructed by the lab outline.
Temperature is not the only variable that can alter oxygen consumption in organisms. Consumption also increases with body mass of organisms, so in the case of the heavier cold-acclimated crayfish, the data would have ideally shown greater mean consumption rates for those specimens. There are many variations in the data that seem to disagree with literature theories and values.
These variations were likely caused by the separation of workload among many groups of students, rather than one small group or individual performing all of the experimentation. This diffusion of data led to some outliers that needed to be omitted from the mean calculations and resulted in the number of crayfishes compared being uneven. The mere 47 cold acclimated crayfish which were included may have influenced the fact that despite their greater mass, they had a lower mean consumption rate. To eliminate at least one of these variations in data, the oxygen consumption rate was measured in terms of the body mass. This made sure to put emphasis only on oxygen consumption variation in relation to external temperature. Crayfish acclimated to warm temperatures may have been at a disadvantage as cold water can hold more dissolved oxygen than warm water (Powell and Watts, 2006). This could potentially explain why the oxygen consumption rate decreased over time in the warm crayfish (Figure 1).
As a result of living in an environment with lower levels of dissolved oxygen, the crayfish may have metabolically compensated to live in colder environments with richer oxygen content. The crayfish, along with other ectotherms, have both physiological and biochemical methods to acclimate to different temperatures. A study was done with teleost fish to analyze such methods and found that cold-acclimation results in significant increases in the density of mitochondria and capillaries in skeletal muscle (Johnston and Dunn, 1987). At a physiological level, this is an important adaptive strategy in that mitochondria provide energy to the cells and chemical energy ends up degrading to heat. With these ectothermic crayfish relying on external temperatures to heat them, they rely on that extra internal heat to survive harsh cold climates.
At a biochemical level the study found differential effects on the synthesis and degradation rates of mitochondrial proteins (Johnston and Dunn, 1987). This altered degradation rate led to net increases in the mitochondria concentration. In conclusion, this experiment led students to see how Orconectes propinquus reacts to acclimation in both warm and cold environments, and how that acclimation affects their metabolic rates. While the data showed that specific acclimation temperature had no significant effect on the compensation of the crayfish, it can still be taken away that the crayfish has both physiological and biochemical mechanisms in place to adjust in either direction. Our understanding of the mechanisms can help us to know how exactly we affect the livelihood of not only this species of crayfish, but ectotherms alike. Fishing industries could benefit from this information just as well as environmental groups. It is very important to put forward one’s best effort into maintaining our earth, and that includes protecting the lesser organisms that play into the food chain.
