Secretive flatworms
divide coyly in darkness
by three-stage fission.
Freshwater flatworms are able to reproduce asexually by dividing in half – the head and tail pieces then each become a new worm. This process of binary fission was previously difficult to study as it occurred in darkness, halts with any disturbance and occurs infrequently (about once a month) but researchers now have more of an understanding of how the process occurs.
Malinowski et al (2017) found that fission occurs in three steps: 1) a local constriction along the body of the flatworm as if a waist is forming, 2) pulsations that apply stress to the ‘waist’ ultimately leading to 3) a rupture at the waist and the creation of two pieces which then re-grow their missing halves. The researchers also developed a linear mechanical model of the fission enabling a better understanding of the division process and accurate predictions of where on the body of a flatworm it will occur.