A new study has cast doubt on leading theory for how tiny creatures have evolved for tens of millions of years – without ever having sex.
Most animals reproduce sexually, a process which shuffles genes from parent to offspring. This makes natural selection more efficient and allows animals to evolve defences against changing environmental conditions more rapidly, especially new diseases.
Bdelloid rotifers however appear to be an exception to this rule: they are all female, and their offspring are clones of their mothers. Bdelloids are microscopic animals that live in freshwater and damp habitats across the world. Despite their apparent lack of sex, we know they have evolved for tens of millions of years into more than 500 species.
By studying their genomes – the set of all the genes that define an animal’s characteristics – researchers thought they had identified an explanation for how bdelloids had ‘gotten away’ with no sex for millions of years.
However, a new study, published today in PLOS Biology and led by Imperial College London researchers, reveals this mechanism may not be the main explanation for the bdelloids’ success
Reuben W. Nowell, Pedro Almeida, Christopher G. Wilson, Thomas P. Smith, Diego Fontaneto, Alastair Crisp, Gos Micklem, Alan Tunnacliffe, Chiara Boschetti, Timothy G. Barraclough. Comparative genomics of bdelloid rotifers: Insights from desiccating and nondesiccating species. PLOS Biology, 2018; 16 (4): e2004830 DOI: 10.1371/journal.pbio.2004830
This is one of the species in the study: Rotaria macrura.Credit: Michael Plewka