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Daphnia is a genus of small planktonic crustaceans, 0.2–6.0 mm ... (e.g. to study the effect of temperature on the heart rate of these ectothermic organisms).
Daphnia lumholtzi is typically found in the warm, shallow regions [6] of bodies of water with larger surface areas. [7] While most species of Daphnia see high mortality at temperatures greater than 25 °C, [8] D. lumholtzi individuals can survive and reproduce at temperatures up to 30 °C, [8] [9] [10] with a thermal optimum occurring at 29 °C. [9]
The effects of temperature on enzyme activity. Top - increasing temperature increases the rate of reaction (Q 10 coefficient). Middle - the fraction of folded and functional enzyme decreases above its denaturation temperature. Bottom - consequently, an enzyme's optimal rate of reaction is at an intermediate temperature.
Other Daphnia species than D. magna may occasionally be used, but labs mostly use D. magna as standard. Test No. 211 is a 21-day chronic toxicity test, at the end of which, the total number of living offspring produced per parent animal alive at the end of the test is assessed, to determine the lowest observed effect concentration of the test ...
For example, a study used Daphnia and a fish that was too small to prey on them (Lebistus reticulatus), found that with the introduction of the fish to the system the Daphnia remained below the thermocline, where the fish was not present. This demonstrates the effects of kairomones on Daphnia DVM. [24]
Daphnia have a compound eye, and they are known to have an optomotor response. [12] D. pulicaria generally have a body length less than 3mm. [3] Because of the clear carapace of Daphnia, it is possible to see the heart and digestive tract, which often appears to be green due to the consumption of algae. [11]
[5] [8] Although the process through which the genotypic interactions occur is unclear, environmental factors, such as temperature, play a large role in the castration of Daphnia. Studies have shown that female Daphnia are sterilized at warmer temperatures (20–25 °C (68–77 °F)), but still have the ability to reproduce at lower ...
Like all Daphnia species, D. longispina is a filter feeder, collecting particles of about 2 to 40 μm suspended in the water. [5] The main food are green algae. At 20 °C maturity is reached within about 6 to 12 days, followed by a period of regular reproduction in about 3-4 day intervals.