Rotifers as a study system

Rotifers are microscopic, aquatic invertebrate animals with many advantages as a model system for aging and maternal effects research. The monogonont rotifer, Brachionus, has a short, two-week lifespan enabling high replication and rapid experimentation. The animals are transparent, allows easy imaging of morphology and cellular processes. Females normally reproduce asexually, so all individuals in a population are genetically identical; this permits direct examination of maternal effects without changes in genome, but inducible sexual reproduction enables crossing and traditional genetics. Tools for rotifer research include genomes, transcriptomes, and RNAi. Rotifers are thus a tractable and robust system for investigating many basic biological questions, including the evolution of mate recognition and speciation, the influence of environmental conditions on phenotypic plasticity, and the genetic and epigenetic mechanisms of aging, lifespan-extending interventions, and maternal effects. 

Brachionus manjavacas: (Top left) Amictic (asexual female) carrying a single egg; (top right) haploid male; (bottom left) amictic female egg; (bottom center) male egg; (bottom right) dormant resting egg, the product of sexual reproduction.  Photos: K. Gribble and E. Corey 

Rotifers complement existing invertebrate study systems as a model system for studies relevant to human health (like the biology of aging and maternal effects). As basal triploblast animals, rotifers provide needed evolutionary breath to existing model systems. Importantly, rotifers have not undergone the genome reduction of some other model invertebrates, and thus share more genes in common with humans. Many researchers are beginning to understand that there is value in studying a variety of species to address questions relevant for human health. It is likely that the most robust treatments for aging in humans will be those that work on the broadest range of taxa and act through evolutionarily conserved mechanisms. 

Life cycle of the monogonont rotifer Brachionus manjavacas. Left, the asexual cycle, in which a female produces clonal diploid eggs by mitosis.  Right, the sexual cycle, in which crowding conditions prompt a portion of females in the population to become mictic, producing haploid gametes via meiosis.  If haploid gametes are not fertilized, they hatch into diminutive haploid males.  Fertilized gametes develop into a dormant resting egg, able to desiccate and overwinter in the sediments.  Upon hatching, the resting egg restores the sexual cycle.   

Associated Publications