A new study has demonstrated that programmed cell death – a process by which cells deliberately destroy themselves – is key to termite evolution wherein they molt from workers, to presoldiers and finally soldiers under the effect of juvenile hormones.
This mandibular regression may be the price to pay for the formation of termites” defensive organs, according to Kouhei Toga and Kiyoto Maekawa from the University of Toyama, and Shinichi Yoda from the University of Tokyo, in Japan.
Juvenile hormones play a central role in caste differentiation – a two molt process for termite soldiers during which dramatic morphological changes occur.
Toga and colleagues collected nests of N. takasagoensis termites from the Yaeyama Islands in Japan. They artificially induced presoldier differentiation by using a juvenile hormone, which works as an insect-growth regulator, and observed the shape and structure of the right mandibles throughout the differentiation process.
Their observations showed that mandibular teeth were lost during soldier differentiation. In particular, mandibular size reduced dramatically during differentiation, and substantial regression occurred during the presoldier molt. The most significant finding was evidence of programmed cell death in the regressing mandibles of presoldiers.
The authors conclude: “Our results prove that programmed cell death is responsible for the regression of mouth parts in termite soldiers, and hence social caste differentiation in this species. The exaggerated nasus and frontal glands develop as the mandibles regress. Programmed cell death could therefore be a regulatory mechanism of trade-off for the production of defensive organs.”
The study was recently published online in Springer”s journal Naturwissenschaften – The Science of Nature.