TY - JOUR
T1 - Metabolic changes during estivation in the common earthworm Aporrectodea caliginosa
AU - Bayley, Mark
AU - Overgaard, Johannes
AU - Høj, Andrea Sødergaard
AU - Malmendal, Anders
AU - Nielsen, Niels Chr
AU - Holmstrup, Martin
AU - Wang, Tobias
PY - 2011
Y1 - 2011
N2 - 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.
AB - 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.
U2 - 10.1086/651459
DO - 10.1086/651459
M3 - Journal article
C2 - 20367318
SN - 1522-2152
VL - 83
SP - 541
EP - 550
JO - Physiological and Biochemical Zoology
JF - Physiological and Biochemical Zoology
IS - 3
ER -