|Actual size of electric ant|
(Roger, 1863) 
The electric ant, also known as the little fire ant, Wasmannia auropunctata, is a small (approx 1.5 mm long), light to golden brown (ginger) social ant native to Central and South America, now spread to parts of Africa (including Gabon and Cameroon), North America, Puerto Rico, Israel, Cuba, and six Pacific Island groups (including the Galápagos Islands, Hawaii, New Caledonia and the Solomon Islands) plus north-eastern Australia (Cairns),
The name, electric ant (or little fire ant) derives from the ant's painful sting relative to its size. This ant's impact in those environments and countries outside of its place of origin has been described as follows:
Wasmannia auropunctata .. is blamed for reducing species diversity, reducing overall abundance of flying and tree-dwelling insects, and eliminating arachnid populations. It is also known for its painful stings. On the Galápagos, it eats the hatchlings of tortoises and attacks the eyes and cloacae of the adult tortoises. It is considered to be perhaps the greatest ant species threat in the Pacific region.
The ant is described as follows:
"..Wasmannia auropunctata workers are monomorphic, which means they display no physical differentiation... The ants are typically small to medium-sized, with the workers ranging from 1-2mm ... [It] is light to golden brown in color. The gaster is often darker. The pedicel, between the thorax and gaster, has two segments; the petiole and postpetiole. The petiole is "hatchet-like", with a node that is almost rectangular in profile and higher than the postpetiole. The antennae have 11 segments, with the last two segments greatly enlarged into a distinct club. The antennal scape (the first segment) is received into a distinct groove (scrobe) that extends almost to the posterior border of the head. The thorax has long and sharp epinotal spines. The body is sparsely covered with long, erect hairs. This species is well-known for a painful sting, seemingly out of proportion to its size."
In, Wasmannia auropunctata, queens produce more queens through parthenogenesis. Sterile workers usually are produced from eggs fertilized by males. In some of the eggs fertilized by males, however, the fertilization can cause the female genetic material to be ablated from the zygote. In this way, males pass on only their genes to become fertile male offspring. This is the first recognized example of an animal species where both females and males can reproduce clonally resulting in a complete separation of male and female gene pools.
These ants get the benefits of both asexual and sexual reproduction - the daughters who can reproduce (the queens) have all of the mother's genes, while the sterile workers whose physical strength and disease resistance are important are produced sexually.
Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilization. Thelytoky is a particular form of parthenogenesis in which the development of a female individual occurs from an unfertilized egg. Automixis is a form of thelytoky, but there are several kinds of automixis. The kind of automixis relevant here is one in which two haploid products from the same meiosis combine to form a diploid zygote.
W. auropunctata thelytokus queens from clonal populations can reproduce by automictic parthenogenesis involving central fusion of haploid meiotic products, a process that allows conservation of heterozygosity in progeny. The same parthenogenic queens that produce progeny by automixis may also produce normally segregating meiotic oocytes, which upon fertilisation by males give rise to diploid workers.
The oocytes that undergo automixis display much lower rates of crossover recombination (by a factor of 45) than the oocytes produced by sexually reproducing queens that give rise to workers. These low recombination rates in automictic oocytes favor maintenance of heterozygosity, and allow only very low rates of transition from heterozygosity to homozygosity (0 to 2.8%). The sharp decrease in recombination rates likely allows clonal queens using automixis to benefit from thelytoky (transmission of their entire genomes to individual progeny), while also avoiding the potential for inbreeding depression that would result from random fusion of meiotic products leading to loss of heterozygosity.
In general, parthenogenesis appears to be favored in recently disturbed habitats (such as produced by floods, fires and glaciers). The clonal populations of W. auropunctata are mostly found in habitats disturbed by recent human activity.
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- Electric ant (Wasmannia auropunctata) webpage Accessed 7 March 2009
- Global Invasive Species Database - No. 100 - Wasmannia auropunctata
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