In answer to Jonathan: Thanks for your advice about clearance of limnic crustacean digestive tracts. Only a question: do you think that these times are also suitable for marine species? , and what should be the effect of temperature (tropical vs polar species) on egestion rates? If you have references on that topic, please let me know. Regarding the possible bacterial shift (if any), I don't have any idea about it. It was just a question Pat __________________________________________________________ Patrick DAUBY Universite de Liege Laboratoire d'Oceanologie Unite de Recherche en Biogeochimie des Isotopes Stables (URBIS) B6 Sart Tilman B-4000 Liege, Belgium Phone: +32.4.3663322 - 3663307 Fax: +32.4.3663325 WWW: http://www.ulg.ac.be/oceanbio/urbis.htm __________________________________________________________