Responses of Arthropods to Environmental Extremes
27
trehalose, has been completely removed from the tissues. Trehalose replaces
the water surrounding molecules and membranes, thereby stabilising them
under conditions of water depletion (e.g. Sct>mme 1996). At the same time,
lipids are important for the maintenance of metabolism during anhydrobiosis and are used as sources of energy during recovery. After dehydration
the glycogen level is rapidly restored.
2.S.2.2
Ecomorphosis
Like "anhydrobiosis", the term "ecomorphosis" is used to describe phenomena involving morphological, anatomical and physiological changes in animals under stress. Ecomorphosis is not linked directly to conditions of water
stress in Collembola. Nevertheless, it seems to enable species pre-adapted to
cold to adjust their development to the seasonally varying environments that
have appeared during the post glacial period (Poinsot-Balaguer 1988).
Like anhydrobiosis, ecomorphosis takes place after downward migration
and immobilisation in the organic layers of the soil. It involves morphological modifications of the cuticle and appendices, anatomical changes in the
digestive tube, and changes in the metabolism of lipids and glycogen after a
period of fasting (Cassagnau 1986). The onset of ecomorphosis is accompanied by voracious foraging which results in an increase in the lipid, glycogen
and protein contents of the body. Feeding then ceases and the midgut
becomes inactive. A reduction in the lipid and glycogen contents of the body
has been recorded at this point, while the amount of protein increases. Initiation of recovery takes place while the animals are still in the deeper soil
layers. Bodily reserves are made use of and recovery is followed by upward
migration.
27
trehalose, has been completely removed from the tissues. Trehalose replaces
the water surrounding molecules and membranes, thereby stabilising them
under conditions of water depletion (e.g. Sct>mme 1996). At the same time,
lipids are important for the maintenance of metabolism during anhydrobiosis and are used as sources of energy during recovery. After dehydration
the glycogen level is rapidly restored.
2.S.2.2
Ecomorphosis
Like "anhydrobiosis", the term "ecomorphosis" is used to describe phenomena involving morphological, anatomical and physiological changes in animals under stress. Ecomorphosis is not linked directly to conditions of water
stress in Collembola. Nevertheless, it seems to enable species pre-adapted to
cold to adjust their development to the seasonally varying environments that
have appeared during the post glacial period (Poinsot-Balaguer 1988).
Like anhydrobiosis, ecomorphosis takes place after downward migration
and immobilisation in the organic layers of the soil. It involves morphological modifications of the cuticle and appendices, anatomical changes in the
digestive tube, and changes in the metabolism of lipids and glycogen after a
period of fasting (Cassagnau 1986). The onset of ecomorphosis is accompanied by voracious foraging which results in an increase in the lipid, glycogen
and protein contents of the body. Feeding then ceases and the midgut
becomes inactive. A reduction in the lipid and glycogen contents of the body
has been recorded at this point, while the amount of protein increases. Initiation of recovery takes place while the animals are still in the deeper soil
layers. Bodily reserves are made use of and recovery is followed by upward
migration.