The anhydrobiotic chironomid larvae presumably experience nuclear DNA fragmentation with each cycle of desiccation and rehydration, and must have overcome this threat efficiently to survive the drought season.
But given the bdelloid's individual prolificacy, repopulating their environment after a cycle of desiccation does presumably not represent a major challenge, whilst keeping their genome functional must be one !
Terrestrial cyanobacteria are subjected to repeated cycles of dehydration, desiccation, and rehydration, and can survive under desiccated conditions for long periods.
It has been suggested that foreign genes might be incorporated into bdelloid genomes during cycles of desiccation and rehydration, during which DNA is broken and repaired [ 19– 219.
Therefore, bdelloids might make use of their ancestral tetraploid state and maintain alpha tubulin copies to perform specialist functions during cycles of desiccation [ 9].
They are able to survive extremely harsh conditions, including frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and high UV intensities.
Rotaria sordida lives on terrestrial moss [ 25] and is likely to undergo frequent cycles of desiccation and rehydration, whereas Rotaria tardigrada is found mostly in small ephemeral pools of water and therefore also experiences desiccation, but perhaps less frequently.
Lichen species are widespread and can be found from the Arctic to deserts; they can survive frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and UV light intensities.
The relationship between HGT and desiccation tolerance/frequency needs to be examined in more bdelloid species encompassing multiple shifts in habitat type, but findings from within Rotaria provide initial support for the hypothesis that the rate of HGT is increased by cycles of desiccation and rehydration in bdelloid rotifers [ 14, 20, 21].
It is plausible that the repeated cycles of desiccation and rehydration experienced by A. [Adineta] vaga in its natural habitats have had a major role in shaping its genome: desiccation presumably causes DNA double-strand breaks, and these breaks that allow integration of horizontally transferred genetic material also promote gene conversion when they are repaired.
As a rather wild prediction, I would not be surprised if certain asexual forms of life turned out to be able to adapt to those environments, using radiations instead of the cycles of desiccation used by the bdelloids, both to provoke intermittent haploidisation of some of their genome, and to destroy any infectious pathogens.
