Speaker: Bas Kooijman
Date: 2009/06/28-2009/07/1
Event: Society for Experimental Biology, session Physiological Energetics
Place: Scottish Exhibition and Conference Centre, Glasgow 
Title: Perturbation as method for research on metabolic organisation of 
       individuals

Abstract: (Eco)toxicology has a traditional focus on toxic or
pharmaceutical effects of particular chemical compounds or an
environmental concern, but its methods can also be used to study the
metabolic organisation of individuals by evaluating how chemicals
change energetics: the uptake of food and its use for the various
endpoints, such as maintenance, growth, maturation and
reproduction. Coherent responses to such perturbations reveal the
hierarchy in the metabolic organisation and can be used to supplement 
effects of changes in temperature and food availability. 

The Dynamic Energy Budget (DEB) theory offers a general framework to 
evaluate effects of such perturbations from a life cycle perspective. 
I will illustrate its application with three examples:

- the effects of caloric restriction on aging; the aging module of the
  standard DEB model has just two aging parameters with the well-known
  Weibull and Gompertz models as special cases, and an important role
  for the mobilisation rate of reserve as quantifier for metabolic activity.

- the effects of an increase in the cost of structure on the reproduction
  rate (e.g. by a chemical). Such an increase reduces growth; 
  food uptake is linked to size, so the long term effect is reduction of 
  food uptake, and so of allocation to reproduction. DEB theory states that
  an egg hatches if maturity exceeds a threshold value, and accounts for
  a maternal effect by linking the reserve density of the neonate to that of
  the mother at egg formation. An increase of the cost of structure has the
  effect of a decrease in amount of structure at hatching, which reduces the
  cost of an egg to the extend that the reproduction rate can show hormesis:
  an increase in the reproduction at small effects, but a decrease at larger
  effect levels.

- temperature affects nutrient uptake by phototrophs, but hardly light-limited
  carbon fixation. The consequence is that carbohydrate reserve builds up at
  low temperatures, and changes the nutritional value of e.g. algae for 
  bivalves. The growth and reproduction of bivalves not only depends on the
  availability of (particular) algae, but also of their nutritional value.
  More models for primary production that account for reserve dynamics of
  algae can be used to study energy balances of bivalve species as function 
  of their geographic distribution.