Primitive co-operation

During amoeboid fission, the two daughter cells generally have few problems separating. But in 22 March Nature, David Biron and colleagues at the Weizmann Institute of Science, Israel, report that in about a third of the dividing cells of Entamoeba invadens the cleavage furrow stops developing before separation is complete and the cells remain attached by a tubular connection.

In what seems to be a striking example of primitive co-operation, neighbouring amoebae are recruited to assist this stalled separation process (Nature 2001, 410:430). The amoeba 'midwife' can travel up to 200 μm to reach the non-separated cells — usually along a straight trajectory — where it assists in rupturing of the connection, enabling all three amoebae to move on.

To test whether midwives are recruited chemotactically, Biron et al aspirated fluid from the vicinity of a dividing amoeba and discharged it near a distant amoeba. Of...