Mycocepurus smithii
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| File:Mycocepurus smithii CASENT0173989 1.jpg | |
| Specimen of Mycocepurus smithii | |
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M. smithii
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| Binomial name | |
| Mycocepurus smithii (Forel, 1893)
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| File:Mycocepurus smithii distribution.svg | |
| Distribution of Mycocepurus smithii | |
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Mycocepurus smithii is an attine fungus-growing ant from Latin America. While a widely reported study from 2009 claimed that the species consists exclusively of females which reproduce asexually a latter work in 2011 found evidence of sexual reproduction in some populations. In many colonies queen reproduces by parthenogenesis and all other 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]
Contents
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
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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 about 12.5 mm.[4] M. smithii ants maintain narrow tunnels (diameter of 1.3 mm) which do not allow two ants to pass each other in the tunnel (head size is around 0.7 mm for workers and 0.9 mm for queens).[2] The tunnels also have a number of slightly larger sections (about 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]
Reproduction
No male individuals of M. smithii have ever been identified, and when researchers examined 6 widely dispersed sites the discovered that all of the workers of each colony were genetically identical with the queen. That fact, together with evidence that the mussel organ, a female docking apparatus within the vagina used to hook the mate's genitalia, has degenerated in dissected queens led to the conclusion that M. smithii was the first ant species to reproduce entirely asexually through parthenogenesis.[5][6]
However, a follow-up study surveying additional locations identified a set of colonies along the Amazon and Rio Negro whose genetic diversity is clear evidence of ongoing sexual reproduction. Furthermore, the researchers identified stored sperm in the reproductive tracts of queens from those colonies. Thus they concluded that "M. smithii actually consists of a mosaic of asexual and sexual populations."[7]
References
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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 Lua error in package.lua at line 80: module 'strict' not found. at Wikimedia Commons- Photograph of Mycocepurus smithii at myrmecos.net
