Cerapachys biroi is a small (2–3 mm) blind subterranean ant with short antennal scapes, a distinctly two-segmented waist, a powerful sting, and a cylindrical body armored with thick cuticle. The species is very inconspicuous owing to its hypogaeic foraging, and is rarely collected. It believed to be native to Asia (Brown, 1975; Wetterer et al., 2012), where it is widely spread from Nepal, India and China to South East Asia, and has established introduced populations throughout the Pacific Islands (where it was referred to by its junior synonym C. silvestrii) and the West Indies. Outside Asia, all records of C. biroi come from islands, possibly due to reduced competition with dominant ants in island habitats (Wetterer et al., 2012). It is also the only known species within the Cerapachyinae to successfully establish populations outside its native range. The introduced populations are not known to have any adverse impacts on agricultural systems or human health. The general biology and worldwide distribution was profiled by Wetterer et al. (2012).
Like many of its congeners, C. biroi maintains colonies of up to several hundred workers that raid the brood of other ant species for food (Tsuji & Yamauchi, 1995), but will occasionally take the soft-bodied larvae of other insects (Wolcott, 1951 (1948)). The heavily sclerotized cuticle provides excellent protection against injury and dismemberment during prey raids, and the venomous sting is used to immobilize opponents (Hölldobler, 1982). The species alternates stationary and nomadic phases that are synchronized with the production of distinct brood cohorts (Ravary et al., 2006; Ravary & Jaisson, 2002). Cerapachys biroi belongs to a very small number of ant species known to reproduce through thelytokous parthenogenesis (Heinze, 2008; Ravary & Jaisson, 2004; Tsuji & Yamauchi, 1995). It has been proposed that this ability of workers to produce diploid eggs has facilitated the ability of C. biroi to establish new populations across the world (Yamauchi & Ogata, 1995). The ability of researchers to maintain colonies of C. biroi in laboratory settings (Ravary et al., 2007)also hint at its capacity as a successful tramp species.
Native range. Widely spread through Asia, from Nepal, India and China to South East Asia.
Introduced range: Pacific Islands and West Indies.
Hawaii: Kauai, Oahu, Molokai, Maui and Hawaii
Diagnosis among workers of introduced and commonly intercepted ants in the United States. Antenna 9-segmented. Antennal insertions entirely exposed, not covered even partially by frontal lobes. Antennal scapes conspicuously short; barely surpassing eye level. Eyes minute to absent (equal to or less than 3 facets). Waist 2-segmented. Petiole narrowly attached to gaster and with conspicuous posterior face. Gaster armed with sting. Pygidium flattened and armed with a row of small peg-like teeth. Body cylindrically shaped.
Cerapachys biroi is distinguished from all other introduced ants by the following characters: (1) waist with two segments; (2) eyes absent or reduced to a single ommatidia; (3) antennal insertions entirely exposed, not covered even partially by frontal lobes; (4) antennal scapes conspicuously short and barely surpassing eye level; (5) pygidium flattened and armed with a row of small peg-like teeth.
Molecular Biology and Genetics
Barcode data: Cerapachys biroi
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Cerapachys biroi
Public Records: 9
Specimens with Barcodes: 47
Species With Barcodes: 1
Cerapachys biroi, or the clonal raider ant, is a queenless clonal ant in the Ooceraea group of the genus Cerapachys. Native to the Asian mainland, this species has become invasive on tropical and subtropical islands throughout the world. Unlike most ants, which have reproductive queens and mostly non-reproductive workers, all individuals in a C. biroi colony reproduce clonally via thelytokous parthenogenesis. Like most cerapachyines, C. biroi are obligate myrmecophages and raid nests of other ant species to feed on the brood.
Clonal raider ants are small, ~2mm, but relatively stocky. Like many cerapachyines, C. biroi are heavily armored, with the short, thick antennae which give the genus its name (from Greek, keras/κέρας, meaning horn and pachys/παχυς, meaning thick). The other defining characteristic of the Cerapachyinae, a row of teeth over the pygidium (last visible abdominal segment), is very small in C. biroi and difficult to see. C. biroi can be distinguished from many other cerapachyines by the combination of highly reduced or non-existent eyes, rectangular head, and distinct post-petiole.
Cyclic life history
Like many myrmecophagous ants, C. biroi exhibit synchronized oviposition and cyclic behavior, shifting between a reproductive phase and a foraging phase. The reproductive phase begins when a cohort of larvae pupate and all the adults in the colony activate their ovaries. Thelytokously produced eggs are then laid synchronously after about four days and develop for roughly 10 days while the adults remain within the nest, cleaning and tending the eggs and pupae. Eggs hatch roughly two weeks into the reproductive phase, and then a few days later the foraging phase begins with emergence of new adults from the pupae. Adults will forage for the next two weeks, raiding the nests of other ant species to bring back food for the larvae. The cycle completes with the pupation of the new larval cohort and the resumption of the reproductive phase.
Genetics and genomics
Because C. biroi can be very easily maintained in laboratory conditions, it has attracted attention as a potential model organism for studying the molecular biology of sociality. Laboratory maintenance is made easy by the clonality of the species; a few individuals placed in an airtight box and given ant brood as food can be grown up into many large colonies. Clonal reproduction is achieved by automixis with central fusion, as is common in Hymenoptera, yet unlike most clonal Hymenoptera loss of heterozygosity is extraordinarily slow. The upshot of this is that offspring are almost genetically identical to the parents, allowing nearly complete control over the genotype of experimental subjects. Finally, since C. biroi are queenless and all workers reproduce, generation time is about two months (the developmental time of a single individual), rather than many years as is the case for most ant species.
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- F. Ravary and P. Jaisson (2002). "The reproductive cycle of thelytokous colonies of Cerapachys biroi Forel (Formicidae, Cerapachyinae)". Insectes Sociaux 49: 114–119. doi:10.1007/s00040-002-8288-9.
- P.R.O Oxley, L. Ji, I. Fetter-Pruneda, S.K. McKenzie, C. Li, H. Hu, G. Zhang, D.J.C. Kronauer (2014). "The Genome of the Clonal Raider Ante Cerapachys biroi". Current Biology 24: 451–458. doi:10.1016/j.cub.2014.01.018.
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