Day: February 2, 2011

The Ant that Wasn’t (Aphantochilus rogersi)

Aphantochilus rogersi (left) with prey

The most astounding arthropod I found in Ecuador last month wasn’t an ant, believe it or not, although it looks just like one from a few feet away.

Aphantochilus is a crab spider slightly over a centimeter long.  The species isn’t exactly uncommon in the Neotropics- in fact, Aphantochilus has appeared previously on Myrmecos. Rather, it is spectacular for its color, size, shape, texture, and movement. Aphantochilus is a convincing stand-in for Cephalotes atratus, the giant turtle ant, and every time I see one lurking about the margins of a turtle ant trail I do a double take and gleefully pass the next half hour watching it work.

Last month’s encounter was the first time I had a camera handy. Thus, some photographs to share with you folks.

A quiet moment

Although it may seem that the spider uses its impressive camouflage to fool its prey, I am not convinced.

The vision of most ants is rather rudimentary, enough that I think it unlikely such remarkable visual mimicry would yield enough of a payoff to be worthwhile. Ants perceive their environment predominately in a chemical medium. Instead, I suspect the spider intends to fool other visual predators- birds, maybe- that would normally pass up acidic chitinous ants but would happily take a spider. For more detailed explorations of the topic, see here and here.

Which is the spider, and which is the ant?

photo details
Canon EF 100mm f/2.8 macro lens & 12mm extension tube on a Canon EOS 7D
ISO 200, f/16, 1/250 sec. Indirect strobe bounced off white paper

Ant sex keeps getting weirder

In 2008 Jürgen Heinze penned “The Demise of the Standard Ant“, noting that the stereotyped ant nuclear family (one queen, one male, and lots of kids) was increasingly obscured by an accumulation of myrmecological data showing enormous variation among species in life history, that real ant colonies were often messy polygamous affairs, and that odd strategies like clonal reproduction were probably more common than previously thought.

Paratrechina longicornis, the black crazy ant

A study out today by Pearcy et al reveals that a common invasive ant, Paratrechina longicornis, is one of those oddballs:

from the abstract:

We discovered that the highly invasive longhorn crazy ant, Paratrechina longicornis, has evolved an unusual mode of reproduction whereby sib mating does not result in inbreeding. A population genetic study of P. longicornis revealed dramatic differences in allele frequencies between queens, males and workers. Mother–offspring analyses demonstrated that these allele frequency differences resulted from the fact that the three castes were all produced through different means. Workers developed through normal sexual reproduction between queens and males. However, queens were produced clonally and, thus, were genetically identical to their mothers. In contrast, males never inherited maternal alleles and were genetically identical to their fathers. The outcome of this system is that genetic inbreeding is impossible because queen and male genomes remain completely separate.

In other words, the DNA of males and queens are separate clonal lineages, while workers are hybrids between the two. This arrangement avoids the inbreeding problems associated with diploid males, possibly helping this species colonize new sites from small propagules.

What’s more, P. longicornis is not the only invasive ant with this reproductive quirk. Wasmannia auropunctata, the little fire ant, shares a similar system, suggesting that clonal reproductives and hybrid workers may be a more general strategy of invasive social insects.

For a better explanation than mine (as usual), Ed Yong has more.

Pearcy, M. et al 2011. Sib mating without inbreeding in the longhorn crazy ant. Proc. R. Soc. B, Published online before print February 2, 2011, doi:10.1098/rspb.2010.2562