Science Briefs
Contact: Joe Carr at 207-581-3571
Ancestral alewives
A genetic study of alewives living in landlocked lakes in Connecticut found that the popular baitfish evolved from a common anadromous rather than a freshwater ancestor.
The research found no evidence to uphold a common belief that all Connecticut landlocked alewife populations are nonnative, the result of intentional stocking years ago to provide forage for game fish.
The landlocked populations examined diverged from a common anadromous ancestor between 300 and 5,000 years ago, according to Eric Palkovacs, a postdoctoral researcher in the University of Maine School of Biology and Ecology, and his colleagues at Yale University. This time frame overlaps with the onset of human dam construction in Connecticut.
The study of genetic and phenotypic divergence between anadromous and landlocked alewife populations was conducted as part of Palkovacs’ dissertation at Yale. It was published in a recent issue of “Molecular Ecology.”
Like other anadromous fish such as Atlantic salmon and sturgeon, alewives make annual runs up freshwater streams to spawn, then return to the sea. They can be found in the coastal waters from Labrador to North Carolina.
But landlocked alewives have lost the marine phase of their life cycle. The researchers found that foraging traits have evolved in the landlocked populations in Connecticut to allow them to survive by eating smaller zooplankton.
Fighting cancer with vitamin D
Healthy levels of serum vitamin D provide significant protection against many types of cancers, according to University of Maine researchers, who did a literature survey of vitamin D studies conducted in the past 37 years.
“These studies find that the higher the UV exposure, dietary intake and serum level of 25(OH)D, the lower the incidence and mortality from cancers of the breast, colon, lung, pancreas, prostate, melanoma and Hodgkin’s lymphoma,” write UMaine researchers Betty Ingraham, Beth Bragdon and Anja Nohe in the journal “Current Medical Research and Opinion.“
Vitamin D, obtained from diet, supplements and sunlight, is essential in cell growth and function. In particular, calcitriol, an active form of vitamin D, has a critical role in regulating cellular mechanisms involved in cancer development.
But while epidemiological, preclinical and clinical trials provide overwhelming evidence that calcitriol can prevent cancers of the colon, breast, prostate, ovary and pancreas, as well as Hodgkin’s lymphoma, nearly all studies indicate that most people have below-normal levels of serum vitamin D.
The clinical research community is now revising upward recommendations for optimal serum levels and sensible levels of sun exposure. The last time that the recommendations were set in 1997, the Food and Nutrition Board of the Institute of Medicine recommended daily adult dietary intake of vitamin D at 400 IU. Since then, most researchers in the field believe that, for optimal health, intakes between 1,000-4,000 IU would lead to a more healthy serum level of approximately 75 nmol/L.