Parasites, diseases and antibiotics
Because the fungus of fungus-growing ants reproduces clonally, it is particularly susceptible to parasites and diseases. This is because all the daughter colonies founded by new queens produced in a fungus-growing ant nest will have fungus that is genetically identical. Any parasite that is particularly well adapted to attack fungus with that particular genetic make-up will spread very quickly through the ant population and will be able to attack all the fungi.

Social insect colonies are also particularly susceptible to diseases and parasites, because the high density of individuals within a nest means that any parasites and diseases can spread quickly.

Fungus-growing ants therefore have particular problems. It is vital for them to protect both themselves and their fungus from parasites and diseases.

The picture to the right shows a queen of Acromyrmex and her young fungus garden, both of which have been overcome by a parasitic fungus.

Chemical protection by antibiotics
Ants have a special paired gland on the thorax, called the metapleural gland. The picture on the right shows the position of the metapleural gland on a major worker of Atta cephalotes.

The metapleural gland has been shown to produce substances that can act as antibiotics. This gland is particularly well developed in the fungus-growing ants.

The picture to the right shows a scanning electron micrograph of the right hand metapleural gland in Acromyrmex octospinosus. There is a large bulbous area of the cuticle (the bulla), which covers the main part of the gland. The substances produced by the gland flow out over the ant's surface through numerous pores.

Research at the University of Aarhus, in collaboration with the University of Keele, has shown that the gland produces at least 22 different chemical compounds, many of which are effective at killing a wide range of bacteria and fungi.

Research is continuing into how the genetic make-up of worker ants and their caste and age affect their production of antibiotics.

Researchers at the Universities of Copenhagen and Aarhus who are investigating antibiotic production and defence against pathogens in fungus-growing ants are:
Dr. Koos Boomsma
Dr. Diethe Ortius
Jeanette Bot
Michael Poulsen