Mycocepurus smithii

Mycocepurus smithii is an attine fungus-growing ant from Latin America whose species consists exclusively of females which reproduce asexually. The queen reproduces by parthenogenesis and all ants in a colony are female clones of the queen.^[1] The ants cultivate a garden of fungus inside their colony grown with pieces of dead vegetables and other insects. It is this capacity for farming which initially prompted research into the species as a basal genus member would provide insight into the natural history of the fungal-cultivating ant tribe, Attini.^[2]

Description

Ants of the genus Mycocepurus are distinctly recognizable for the crown-like cluster of horns on their promesonotum, the fused mesonotum and pronotum on the front of their alitrunk or midsection. M. smithii has sharp, protruding propodeal (posterior of the alitrunk) spines unlike M. obsoletus whose propodeal spines are blunt. Workers also do not have developed promesonotal spines in the center of their crown.^[3]

Fungal cultivation

Foundress queens shed their wings prior to colony excavation either near the site or just inside. They then excavate a tunnel to a depth of roughly 10 cm (4 in) and create a primary chamber. The dealate queen then carries the wings into the primary chamber and inserts them into the chamber ceiling where the surface of the wings is used as a platform for growing an incipient fungal garden. The female fore wings of all three Attini basal genera (Mycocepurus, Apterostigma, and Myrmicocrypta) have a crescent-shaped spot lacking any veins or pigmentation, though the spot's functionality is unknown.^[2]

Nest architecture

M. Smithii nests in Puerto Rico, Costa Rica, and Trinidad have a single entrance, though the close proximity to other nests in high colony-density areas may give the illusion of multiple entrances.^[2] M. Smithii nests consist of a mound excavated around an entrance roughly 1.2 mm in diameter.^[4] This leads to a vertical tunnel opening into the garden chamber at a depth of approximately 12.5 mm.^[4] M. Smithii maintain narrow tunnels (diameter of 1.3 mm) which do not allow two ants to pass each other in the tunnel (head size is approximately 0.7 mm for workers and 0.9 mm for queens).^[2] The tunnels also have a number of slightly larger sections (approximately 3.6 mm diameter) which would allow passing while also facilitating information exchange. Narrow tunnels are presumably easier (energetically cheaper) to construct and may also aide in leveling the humidity or temperature of the colony or preventing predatory intrusions.^[2]

Himler research

The research team was led by a graduate student at the University of Texas at Austin in the United States, Anna Himler.^[1][5] The researchers initially were interested in the ants' capability for cultivating fungus.^[5] The researchers used DNA profiling to confirm that each member of the colony was genetically identical to the queen.^[5] They also discovered through a process of dissection that the mussel organ, a female docking apparatus within the vagina used to hook the mate's genitalia,^[6] had degenerated in members of this species.^[7] A total of six separate tests were carried out, with the researchers unable to locate any male members of the species.^[1] The team's findings were then published in the journal Proceedings of the Royal Society B.^[7]

References

Further reading

• Anna Grace Himler, Ph.D. Dissertation: Evolutionary Ecology and Natural History of Fungus-Growing Ants: Host-Switching, Divergence, and Asexuality. Chapter 3. No sex in fungus-farming ants or their crops, 2007.

External links

• Media related to Mycocepurus smithii at Wikimedia Commons
• Photograph of Mycocepurus smithii at myrmecos.net