Biochemical adaptation for dormancy in subitaneous and dormant eggs of Daphnia magna
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Daphnia can reproduce through subitaneous and dormant eggs. The production of dormant eggs is induced by stimuli associated with deteriorating growth conditions, and enable Daphnia populations to survive temporarily harsh environmental conditions. Dormant eggs are expected to have developed special biochemical adaptations to bridge this long unfavourable period, but little comparative biochemical data are available for dormant and subitaneous eggs. We compared levels of the following molecules between subitaneous and dormant eggs: (a) triglycerides, which are the most abundant energy storage molecules in Daphnia, (b) glycerol, a cryoprotectant also involved in energy storage, and (c) the heat shock protein Hsp60, a molecular chaperone that may assist in maintaining protein structural integrity and inhibiting cell metabolism during diapause. Unexpectedly, no difference in triglycerides content between egg types was found. As expected, dormant eggs contained more glycerol and relatively more Hsp60 than subitaneous eggs. The biochemical composition of dormant eggs can therefore be seen as an adaptation to the harsh environmental conditions these eggs encounter.
KeywordsCladocera Heat shock protein Hsp60 Diapause
We thank three anonymous referees for their detailed and to-the-point comments of an early version of the manuscript, and Lisa Shama for the grammatical revision. Kevin Pauwels acknowledges financial support from IWT Flanders; Robby Stoks is a post-doctoral researcher with the Fund for Scientific Research (Flanders—FWO). This research was financially supported by FWO grant G.0269.04 and K.U.Leuven Research grant OT/04/23.
- Arbaciauskas, K., 1998. Life-history traits of exephippial and parthenogenetically derived daphnids: indicators of different life-history strategies. Archiv für Hydrobiologie 52: 339–358.Google Scholar
- Caceres, C. E., 1998. Interspecific variation in the abundance, production, and emergence of Daphnia diapausing eggs. Ecology 79: 1699–1710.Google Scholar
- Clegg, J. S., J. K. Willsie & S. A. Jackson, 1999. Adaptive significance of a small heat shock/alpha-crystallin protein (P26) in encysted embryos of the brine shrimp, Artemia franciscana. American Zoologist 39: 836–847.Google Scholar
- Cousyn, C., & L. De Meester, 1998. The vertical profile of resting banks in natural populations of the pond-dwelling cladoceran Daphnia magna Strauss. Archiv für Hydrobiologie, Special Issues Advances in Limnologie 52: 127–139.Google Scholar
- Denlinger, D. L., J. P. Rinehart & G. D.Yocum, 2001. Stress proteins: a role in insect diapause? In Denlinger, D. L., J. M. Giebultowicz & D. S. Saunders (eds), Insect Tming: Circadian Rhythmicity to Seasonality. Elsevier, Amsterdam: 155–171.Google Scholar
- Lencioni, V., 2004. Survival strategies of freshwater insects in cold environments. Journal of Limnology 63(Suppl. 1): 45–55.Google Scholar
- Peters, R. H., 1987. Metabolism in Daphnia. Memorie dell’Instituto Italiano di Idrobiologia, 45: 193–243.Google Scholar
- Roff, D. A., 1992. The Eolution of Life Histories: Theory and Analysis. Chapman & Hall, New York.Google Scholar
- Stearns, S. C., 1992. The Evolution of Life Histories. Oxford University Press, New York.Google Scholar