title: Metabolic changes during estivation in the common earthworm Aporrectodea caliginosa.
abstract: The common earthworm Aporrectodea caliginosa survives drought by forming estivation chambers in the topsoil under even very slight reductions in soil water activity. We induced estivation in a soil of a consistency that allowed the removal of intact soil estivation chambers containing a single worm. These estivation chambers were exposed to 97% relative humidity for 30 d to simulate the effect of a severe summer drought. Gas exchange, body fluid osmolality, water balance, urea, and alanine were quantified, and whole-body homogenates were screened for changes in small organic molecules via (1)H-nuclear magnetic resonance (NMR). Formation of estivation chambers was associated with a dramatic increase in body fluid osmolality, from 175 to 562 mOsm kg(-1), accompanied by a 20% increase in water content. Dehydration for 1 mo caused a further increase to 684 mOsm kg(-1), while the worms lost 50% of their water content. Gas exchange was depressed by 50% after worms entered estivation and by 80% after a further 30 d of dehydration. Urea concentrations increased from 0.3 to 1 micromol g(-1) dry mass during this time. Although (1)H-NMR did not provide the identity of the osmolytes responsible for the initial increase in osmolality after estivation, it showed that alanine increased to more than 80 mmol L(-1) in the long-term-estivation group. We propose that alanine functions as a nitrogen depot during dehydration and is not an anaerobe product in this case.
authors.affiliation: Zoophysiology, Department of Biological Sciences, University of Aarhus, Building 1131, DK-8000 Aarhus C, Denmark. mark.bayley@biology.au.dk
authors.forename: Mark
authors.initials: M
authors.lastname: Bayley
authors.forename: Johannes
authors.initials: J
authors.lastname: Overgaard
authors.forename: Andrea Sødergaard
authors.initials: AS
authors.lastname: Høj
authors.forename: Anders
authors.initials: A
authors.lastname: Malmendal
authors.forename: Niels C
authors.initials: NC
authors.lastname: Nielsen
authors.forename: Martin
authors.initials: M
authors.lastname: Holmstrup
authors.forename: Tobias
authors.initials: T
authors.lastname: Wang
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000737:chemistry; D004734:Energy Metabolism / Q000502:physiology*; D004956:Estivation / Q000502:physiology*; D009835:Oligochaeta / Q000502:physiology*; D009994:Osmolar Concentration; D014867:Water / Q000737:chemistry / Q000378:metabolism; D015431:Weight Loss
chemical_list: D014867:Water