Mycangium

The term mycangium is used in biology for special structures on the body of an animal that are adapted for the transport of symbiotic fungi (usually in spore form). This is seen in many xylophagous insects (e.g. horntails and bark beetles), which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the wood fibers. In some cases, as in ambrosia beetles, the fungi are the sole food, and the excavations in the wood are simply to make a suitable microenvironment for the fungus to grow. In other cases (e.g., the southern pine beetle, Dendroctonus frontalis), there are mites which have their own type of mycangium (for historical reasons, mite taxonomists use the term sporotheca), and the mites ride on the beetles.

Mycangium in bark and ambrosia beetles

Mycangia of bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are often complex cuticular invaginations for transport of symbiotic fungi. Several types exist. Phloem-feeding bark beetles (Coleoptera: Curculionidae: Scolytinae) have usually numerous small pits on the surface of their body, while ambrosia beetles (many Scolytinae and all Platypodinae), which are completely dependent on their fungal symbiont, have deep and complicated pouches. These mycangia are often equipped with glands secreting substances to support fungal spores and perhaps to nourish mycelium during transport. In many cases, the entrance to a mycangium is surrounded by tufts of setae, aiding in scraping mycelium and spores from walls of the tunnels and directing the spores into the mycangium.

References

• Francke-Grossmann H. (1967). Ectosymbiosis in wood inhabiting insects. In: M. Henry (ed.) Symbiosis, Vol. 2. Academic Press, NewYork. pp.141-205