Dietary fatty acids and temperature effects on the reproduction of Daphnia magna

• Main Authors: Albright, Mark, Yampolsky, Lev
• Format: Others
• Published: Digital Commons @ East Tennessee State University 2018
• Subjects: Lipids; Daphnia; Plasticity; Environmental Effects; Biochemistry; Cell Biology; Developmental Biology
• Online Access: https://dc.etsu.edu/asrf/2018/schedule/36

Previous research has shown variation of thermal tolerance in clones of the aquatic crustacean Daphnia magna. In general, genotypes from regions with warmer climate possess a greater tolerance to high temperatures than those from colder climates. However, the mechanism by which they achieve this thermal tolerance is unclear. One possible explanation may lie in how the animals utilize polyunsaturated fatty acids (PUFAs), which are macromolecules essential for maintaining cell membrane fluidity and to prevent transition to gel-like phase. The need for PUFAs is exacerbated further in poikilothermic animals at colder temperatures. Therefore, it can be hypothesized that D. magna originating from colder climates would more readily uptake and incorporate PUFAs into their cell membranes when in a cold environment. This study examined twenty-one D. magna clones known to differ in thermal tolerance. A life-table experiment was conducted in order to see which clones could produce viable eggs at 10°C, when given a diet low in PUFAs (green alga Scenedesmus obliquus). Since egg-laying requires a significant investment of PUFAs, fecundity was used as the measurement of cold tolerance. Separately, eggs and their mothers from select clones were collected for lipid analysis. No D. magna clone showed success in every egg clutch during the experiment, although a few showed failures in every clutch. Clones from cold climate regions were not more likely to have more successful clutches when compared to those from warm climates. Lipid analysis via gas chromatography is ongoing and will compare lipid content in eggs and mothers at 25°C and 10°C with different diets—either low in PUFAs (S. obliquus) or high in PUFAs (heterokont alga Nannochloropsis limnetica). The lipid analysis will reveal if there is a lack of PUFA investment in eggs at cold temperatures by comparing unsuccessful cold-temperature eggs to successful cold-temperature eggs and warm-temperature eggs. Adult uptake of PUFAs can also be discerned by comparing adults with a low-PUFA diet at cold temperatures to those with a high-PUFA diet at cold temperatures and those at warm temperatures. This analysis will help understand trade-offs between high performance at different temperatures and mechanisms of plastic response to temperature.