How do Daphnia swim?
To swim, Daphnia use a large pair of antennae to propel themselves through the water with abrupt movements, making them easy to spot in a jar of clear lake water.
Why do we experiment on Daphnia?
Daphnia are excellent organisms to use in bioassays because they are sensitive to changes in water chemistry and are simple and inexpensive to raise in an aquarium. They mature in just a few days, so it does not take long to grow a culture of test organisms.
What are the adaptations of Daphnia?
Because the Daphnia pulex is denser than the water it lives in, it has developed a unique way in which it moves in order to avoid sinking to the bottom of its freshwater environment. The organism uses its muscles to beat the second set of antennae, which actually pushes them through the water.
What are the features of the Daphnia life cycle?
The life cycle of Daphnia during the growth season is characterized by its asexual mode of reproduction (apomixis) (Figure 2.9). A female produces a clutch of parthenogenetic (amictic) eggs after every adult molt (if feeding conditions permit). Figures 2.3 to 2.5 show females with parthenogenetic eggs.
Can Daphnia swim?
We found that Daphnia clones, including those within a single species, exhibit a wide range of swimming behaviors as measured by swimming speed.
What type of water do Daphnia live in?
freshwater
Daphnia can be found in almost any permanent body of water. They are mainly freshwater and densely populate most lakes and ponds. They live as plankton in the open water of lakes, or live either attached to vegetation or near the bottom of the body of water (Miller, 2000).
How are Daphnia used in scientific research?
An organism also known as the water flea, Daphnia is an environmental model species used for the study of ecotoxicity. This freshwater crustacean is especially used in biological studies to determine aquatic toxicity.
What factors affect Daphnia?
Daphnia is poikilothermic, which means that its body temperature and therefore its metabolic rate are affected directly by the temperature of the environment. The change in metabolic rate is reflected in the rate at which the heart beats (cardiac frequency).
Why does Daphnia heart rate increase with temperature?
One reason why the heart rate of Daphnia increases with temperature would be because less oxygen is present in the warmer water. Consequently, lack of oxygen could result in insufficient amount of oxygenated blood and hence the heart would have to work harder to pump blood around the body.
What is the physiology of the Daphnia?
Daphnia are filter feeders. The setose thoracic legs act as sieves for filtering algae, bacteria, and small particles of debris from the water. Daphnia transfer food to the mouth and grind it with mandibles before it moves through the gut for digestion. Food retention is from ½ to 3 hr.
What do water Daphnia eat?
Daphnia are filter feeders. They strain microscopic food particles from the water. Daphnia pellets, an algae food source, and a baker’s or brewer’s yeast suspension are all good feeding options for cultures.
How does temperature affect Daphnia?
Specifically, as hypothesized, temperature affected the heart rate of Daphnia. It was noticed that the Daphnia’s heart rate increased at higher temperatures (close to 34°C) and decreased at lower temperatures (close to 5°C). Since Daphnia are ectothermic, their body temperature varies with environmental temperature.
What do Daphnia do?
Daphnia are oftened used to clear fish tanks of algae “bloom” because of their diet of bacteria, fine detritus, and very small algae particles.
What conditions in the laboratory are needed for Daphnia to survive?
Daphnia typically reproduce well with 12 hours of light and 12 hours of darkness a day. Be sure that any artificial light does not significantly heat the water in the container. The temperature of the water should remain near 70° F to promote successful breeding.
What is the control in the Daphnia experiment?
In the case of our Daphnia, an example of a controlled variable would be the temperature of the water in which the Daphnia are tested. This variable needs to be controlled because Daphnia hearts beat faster in warm water than they do in cold water.
What is the independent variable in the Daphnia experiment?
The control is the heart rate of Daphnia prior to exposure to caffeinated solutions. The dependent variable is the heart rate measured before and after exposure. The independent variables are the seven caffeinated solutions that are tested on the Daphnia magna.
What factors affect the heart rate of Daphnia?
How does temperature change affect Daphnia?
It was noticed that the Daphnia’s heart rate increased at higher temperatures (close to 34°C) and decreased at lower temperatures (close to 5°C). Since Daphnia are ectothermic, their body temperature varies with environmental temperature.
What kind of body plan does Daphnia have?
Daphnia’s body layout has bilateral symmetry; if you cut the daphnia in half both sides would be identical.