WILLIAMS, J.L.; BIESIOT, P.M.; LEE, C.E.; Univ. of Southern Miss. Gulf Coast; Univ. of Southern Miss. Hattiesburg; Univ. of Wisconsin-Madison: Differences in Lipid Composition of Three Populations of Eurytemora affinis Reared Under Constant Conditions
This study examined effects of constant rearing conditions on lipid composition of the copepod Eurytemora affinis (Poppe). Populations of different latitude along the Atlantic Coast of North America [L’Isle Verte, Canada, Maryland (MD), USA, South Carolina (SC), USA] were reared under constant laboratory conditions (13oC, 15 PSU, 15L:9D) for a period of 6 months, (at least two generations) and were fed identical diets (Rhodomonas sp.). These copepods are known to repeatedly invade freshwater habitats from saline ones and are of interest to evolutionary biologists because they provide excellent models for rapid evolution and adaptation. The three populations are morphologically and genetically similar, but occupy different latitudes and habitats. There are small genetic differences between the Quebec and the MD and SC populations (~1% at cytochrome oxidase I). The population in Quebec occurs in the L’Isle Verte salt marsh, while the MD and SC samples are from estuaries. During lab rearing , the copepods stored large amounts of lipid, as they do in the wild. Lipid analysis of the three lab-reared populations showed variation in amounts of total lipids and specific lipid classes between sexes and among populations. Dominant lipid classes were wax esters/sterol esters and triacylglycerols (TAG) for the Quebec copepods, polar lipids for the MD copepods, and TAG and polar lipids for the SC populations. Results suggest that genetically-based differences exist among populations. Data on wild populations are forthcoming and should reveal the effects of diet, temperature, and other environmental factors on lipid composition.
