Daphnia spp. Water Flea
Brandon Churchill - Section 020 - Cleber Ten Caten
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Introduction
Introduction
Water fleas are small organisms found all over the world in bodies of freshwater.
Primary literature article: "The interactive effects of calcium concentration and temperature on the survival and reproduction of Daphnia pulex at high and low food concentrations" (Ashforth & Yan 2008).
Taxonomy
Taxonomy
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Branchiopoda
Order: Diplostraca
Suborder: Cladocera
Family: Daphniidae
Genus: Daphnia
Species: Daphnia spp.
Background
Background
Eukaryotic Invertebrates
Freshwater plankton
1mm to 5mm in size
Consume small particles in water
Can live in small pools of water and massive lakes
Reproduce asexually (cloning) in favorable conditions
Reproduce sexually during unfavorable conditions to promote genetic variation (Ebert 2005)
Considered a model organism for experimentation since so widespread and exposed to many stressors (Altshuler et al., 2011)
Appearance
Appearance
Most Daphnia appear red due to constantly circulating blood (Ebert 2005)
Survival and Reproduction Experiment
Survival and Reproduction Experiment
Daphnia pulex ability to reproduce at different temperatures, calcium concentrations, and food concentrations (algal density) was tested (Ashforth & Yan 2008).
Graph a shows Daphnia pulex when exposed to a high concentration of algae, meaning there was more food present during this group (Ashforth & Yan 2008).
Graph b shows Daphnia pulex when exposed to a low algal concentration, or that there was not much food for consumption in this group (Ashforth & Yan 2008).
Daphnia pulex reproduce best at high calcium concentrations (10 mg/L^-1) and moderate temperatures (24 ℃) when exposed to high algal concentration (more food) (Ashforth & Yan 2008).
Daphnia pulex reproduce best at moderate calcium concentrations (2 mg/L^-1) and moderate temperatures (24 ℃) when exposed to low algal concentration (less food) (Ashforth & Yan 2008).
Conclusion
Conclusion
Researchers found that daphnia (Daphnia pulex) are more likely to reproduce at higher quantities on average when exposed to lots of food (Ashforth & Yan 2008).
As stated earlier, daphia will reproduce asexually during non-stressful conditions (Ashforth & Yan 2008). This means that the daphnia tested may have reproduced asexually when favorable conditions were tested in the experiment as genetic variation was not needed.
However, daphnia may have reproduced sexually in group b, as there was not enough food present for constant reproduction. This could in turn promote genetic variation and cause more daphnia to survive these conditions.
The importance of this study is that daphnia are known to be model organisms for testing, therefore if they experience forms of distress that limits survival or reproductive abilities, these stressors can cause issues in many other organisms that rely on daphnia for survival in one way or another (Altshuler et al., 2011).
Further studies could test…
More species of Daphnia
With concentrations of different minerals found in freshwater
A larger scale to mimic populations
References
References
Ashforth, D & Yan N. 2008. The interactive effects of calcium concentration and temperature on the survival and reproduction of Daphnia pulex at high and low food concentrations. Limnology Oceanography 53(2): 420–432.
https://aslopubs.onlinelibrary.wiley.com/doi/pdfdirect/10.4319/lo.2008.53.2.0420.
Altshuler I, Demiri B, Xu S, Constantin A, Yan N, Cristescu M. 2011. An integrated multi-disciplinary approach for studying multiple stressors in freshwater ecosystems: Daphnia as a model organism. Integrative and Comparative Biology 51(4): 623-633.
https://doi.org/10.1093/icb/icr103.
Ebert, D. “Chapter 2. Introduction to Daphnia Biology” (On-line), U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK2042/pdf/Bookshelf_NBK2042.pdf.
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