We have investigated water loss from, and ion regulation within, the hemolymph and tissues of five replicate populations of @entity238 that have undergone laboratory selection for enhanced desiccation resistance (i.e. the D populations). We compared the patterns and rates of water loss and the ion content of the D populations prior to and during desiccation with those of five replicate control (C) populations. The net rate of water loss in the C flies was approximately 3-fold greater than that of the D flies during the initial hours of desiccation. After 8 h, both C and D flies had considerable reductions in water loss rate. During 24 h of desiccation, the tissue water content of the D flies was conserved, while the C flies were faced with significant loss of tissue water during the initial 8 h of desiccation. We propose that the increased hemolymph volume of the D flies plays a role in buffering water loss from the tissues. One consequence of this large hemolymph pool is that the hydrated D flies contained approximately seven times more @entity1372 within the hemolymph than did the hydrated C flies. Despite a continual loss of hemolymph volume in the D flies during lengthy periods of desiccation, the @entity1372 content of the hemolymph was significantly reduced only during a single event. We provide evidence that the regulation of extracellular @entity1372 , as well as @entity2865 , occurred via excretory processes during desiccation. In addition, whole-body @entity972 was not significantly decreased in the D flies during desiccation but was reduced (i.e. excreted) in the C flies; hence, we suggest that the @entity972 content paralleled tissue water level.

Evolved patterns and rates of water loss and ion regulation in laboratory-selected populations of XXXX .

@entity972 :: ('MESH:D011188', 'Chemical') :: ['potassium'] @entity1372 :: ('MESH:D012964', 'Chemical') :: ['sodium'] @entity238 :: ('7227', 'Species') :: ['Drosophila melanogaster'] @entity2865 :: ('CHEBI:17996', 'Chemical') :: ['chloride']
@entity238 :: (7227,Species) :: ['Drosophila melanogaster']
