Why do predators sometimes lay dormant eggs -- eggs which are hardy, but take a long time to hatch, and are expensive to produce?
That is the question that researchers from Singapore University of Technology and Design (SUTD) set out to answer in a recent paper published in Advanced Science , a cutting-edge research journal with an impact factor of 15.804 (2019 Journal Citation Reports).
The traditional answer is that these hardy eggs allow the population to survive harsh environmental conditions, like winter or drought. However, this does not explain why dormant eggs are laid even in non-seasonal habitats, such as tropical lakes.
The team of researchers led by Assistant Professor Kang Hao Cheong from SUTD, in collaboration with Dr Eugene V. Koonin, senior investigator at the National Institutes of Health, have discovered an alternate explanation: Dormancy is a naturally occurring response to over-predation. In non-seasonal habitats, prey organisms, such as algae in a lake, grow to very large populations. This leads their predators, such as zooplankton, to consume them at a high rate and grow in population as well. Eventually, this leads to over-consumption. As the algae population collapses, little food is left for the large amount of zooplankton, which then begin to starve and die.
It is during this period of food scarcity that dormancy makes a lot of sense. If a zooplankton had laid hardy, slow-hatching dormant eggs in advance, those eggs would likely hatch after the prey populations had recovered, allowing them to survive and reproduce. On the other hand, if the zooplankton had only laid regular fast-hatching eggs, those eggs would likely hatch in the middle of the famine, and would not aid much in the recovery of the zooplankton population. Eventually, only those zooplankton which lay dormant eggs would dominate the population.
In discovering this explanation, the researchers were inspired by a phenomenon called Parrondo's paradox. The paradox states that it is possible to alternate between a pair of losing strategies, such as losing bets in a gamble, and still end up winning. When food is plenty, the researchers realized that dormancy is similarly paradoxical. Related Stories
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