Slime mold aggregation
A striking example of pattern formation linked to the emission of a chemoattractant occurs in colonies of the slime mold Dictyostellum discoideum. When conditions (supply of nutrients, moisture, …) become critical, these unicellular organisms gather into a mound, which then develops a “fruiting body”. The latter will disperse spores which can survive in harsh conditions. At the beginning of this aggregation process, cells emit chemoattractants which lead to the appearance of target and spiral waves in the colony.