Divergence of water balance mechanisms in two sibling species (Drosophila simulans and D. melanogaster): effects of growth temperatures

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 183; no. 3; pp. 359 - 378
• Main Authors: Parkash, Ravi, Aggarwal, Dau Dayal, Singh, Divya, Lambhod, Chanderkala, Ranga, Poonam
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-04-2013; Springer Nature B.V
• Subjects: Acclimatization; Acclimatization - physiology; Adaptation, Biological - physiology; Animal Physiology; Animals; Biochemistry; Biological Evolution; Biomedical and Life Sciences; Biomedicine; Climate adaptation; Climate change; Dehydration; Desiccation; Drosophila melanogaster - physiology; Global climate; Hemolymph - chemistry; Human Physiology; India; Insects; Laboratories; Larva - physiology; Larvae; Life Sciences; Lipids; Lipids - analysis; Original Paper; Permeability; Physiology; Pigmentation - physiology; Plasticity; Species Specificity; Temperature; Water balance; Water conservation; Water loss; Water-Electrolyte Balance - physiology; Zoology; India; Himalaya Mountains; Pakistan, Himalayas; Cuticular lipid mass; Water balance-related traits; Developmental plasticity; Body melanisation
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-012-0714-3

Drosophila simulans
is more abundant under colder and drier montane habitats in the western Himalayas as compared to its sibling
D. melanogaster
but the mechanistic bases of such climatic adaptations are largely unknown. Previous studies have described
D. simulans
as a desiccation sensitive species which is inconsistent with its occurrence in temperate regions. We tested the hypothesis whether developmental plasticity of cuticular traits confers adaptive changes in water balance-related traits in the sibling species
D. simulans
and
D. melanogaster
. Our results are interesting in several respects. First,
D. simulans
grown at 15 °C possesses a high level of desiccation resistance in larvae (~39 h) and in adults (~86 h) whereas the corresponding values are quite low at 25 °C (larvae ~7 h; adults ~13 h). Interestingly, cuticular lipid mass was threefold higher in
D. simulans
grown at 15 °C as compared with 25 °C while there was no change in cuticular lipid mass in
D. melanogaster
. Second, developmental plasticity of body melanisation was evident in both species.
Drosophila simulans
showed higher melanisation at 15 °C as compared with
D. melanogaster
while the reverse trend was observed at 25 °C. Third, changes in water balance-related traits (bulk water, hemolymph and dehydration tolerance) showed superiority of
D. simulans
at 15 °C but of
D. melanogaster
at 25 °C growth temperature. Rate of carbohydrate utilization under desiccation stress did not differ at 15 °C in both the species. Fourth, effects of developmental plasticity on cuticular traits correspond with changes in the cuticular water loss i.e. water loss rates were higher at 25 °C as compared with 15 °C. Thus,
D. simulans
grown under cooler temperature was more desiccation tolerant than
D. melanogaster
. Finally, desiccation acclimation capacity of larvae and adults is higher for
D. simulans
reared at 15 °C but quite low at 25 °C. Thus,
D. simulans
and
D. melanogaster
have evolved different strategies of water conservation consistent with their adaptations to dry and wet habitats in the western Himalayas. Our results suggest that
D. simulans
from lowland localities seems vulnerable due to limited acclimation potential in the context of global climatic change in the western Himalayas. Finally, this is the first report on higher desiccation resistance of
D. simulans
due to developmental plasticity of both the cuticular traits (body melanisation and epicuticular lipid mass) when grown at 15 °C, which is consistent with its abundance in temperate regions.