The Marine Biological Laboratory is aiming to develop new model organisms, and are looking to several microscopic animals, including one called the rotifer. They are often found in freshwater environments, but can also live in saltwater. These tiny creatures use cilia, small filaments that protrude from cells, to gather food and move it into their digestive system.
One kind of rotifer also has special DNA sequences, terminons, which act as retrotransposons. These molecules can replicate and insert themselves into the genome. But unlike normal transposons, terminons get added to the ends of chromosomes. They can give the chromosome protection against degradation, which has been associated with aging. As such, these rotifers could be a great model for learning more about the aging process.