Tag Archives: Jim

Panda report!

(from Jim)

Male panda in a tree at Foping Panda Reserve (D. Raubenheimer photo)

Sitting at the airport, about to leave for Phoenix.  Our trip to China was a great success.  After two days visiting historic Xian (including the terracotta warriors), Monica and I headed, along with Nie Yonggang (Wei Fuwen’s PhD student), to Foping and the Foping Nature Reserve.  We hiked 7 km to the research station and spent four days hiking and “chasing” pandas.  We were lucky enough to see them on three of the four days (see pic).  We were joined by nutritional ecologist David Raubenheimer (Massey University) and were able to have extended discussions of how to proceed with new studies of the nutritional ecology of pandas.  Basically, we wish to understand how pandas achieve (or fail to achieve) a diet balanced in protein, carbohydrate, P, Ca, Na, etc given their very limited diet (which, in Foping, consists of only two bamboo species).  Great fun was had and more studies are to come during the coming years.  Thanks to our wonderful Chinese hosts for the hospitality.

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Genetic basis of P sensitivity in Daphnia

Wiley InterScience :: JOURNALS :: Ecology Letters.

Posted by Jim:

Our long-time collaborators Puni Jeysasingh, Bob Sterner, and Larry Weider have published a nifty paper showing how the genotype for Pgi (a gene controlling phosphoglucose isomerase, an enzyme involved in energy processing) is closely linked to an animal’s sensitivity to poor stoichiometric food quality (high C:P in algae).  Pgi homozygotes outcompete pgi heterozygotes because they are energetically INEFFICIENT, which is an advantage when food has high C:P ratio (C in excess).  The discovery is quite remarkable, as Pgi has long been used as some kind of “neutral” marker for identifying different populations of Daphnia.  So, it’s quite a coincidence that Pgi seems to be closely involved in how Daphnia copes with poor food quality.

Members of the Elser group should read this paper immediately.

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Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean : Abstract : Nature

Posted by Jim:

Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean : Abstract : Nature.

Here’s another paper with a lot of stoichiometry in it and of high relevance for large-scale planetary issues we are investigating in our Astrobiology project.  At the very end the authors take the heretical step of wondering if the N:P ratio in the ocean might actually in some situations be higher than the canonical 16:1.   Start the clock on their oceanographic excommunication…

And it had a nice take-home line in the abstract:

“…using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean.”