05DISCOVER UBDFOS Researchers Contribute Studyon Exploding Ants to BiotropicaDr Linda Lim and Dr Chan Chin Mei (UBD Chemistry Programme) identified pH-indicating chemical products filling the hypertrophied mandibular gland reservoirs of Brunei’s mysterious “exploding ants”. Rather than being confined to the worker ant’s head (as usual in ants), glandular reservoirs extend through the worker thorax and abdomen. Across more than a dozen species in this ant group, product colors range from brilliant white to yellow, orange and red with increasing pH, making these Colobopsis species literally ‘litmus paper with legs’. Species-specific product pH values are thought to perhaps influence ant associations with microbes. Common in the rainforest canopy at the Kuala Belalong Field Studies Centre, these ants graze microbial biofilms on leaves and other plant surfaces. A subset of the Colobopsis species defend their foraging territories suicidally against intruding ants which might contaminate the foraging grounds. A territorial Colobopsis worker instantaneously grasps an invader’s leg, wraps its body around the intruder and exudes sticky mandibular gland product through anterior ducts at the edges of mandibles (mouth parts). Simultaneously, it explodes the glandular reservoirs through its abdominal wall onto the opponent’s back. Glued to its attacker, the targeted ant tumbles to the ground and dies. Because only highly evolved Colobopsis species use mandibular gland products in this way, the article’s authors suggest that the chemicals evolved initially for some other role, likely in processing of microbialThe unusual behaviours of these ants display potentially novel roles in the forest ecosystem. Although voluntary self-sacrifice is known to occur in other social insects, the behaviour of exploding Colobopsis is unique in occurring on distant foraging territories, rather than in defense of queen, brood and nest site. Further, if as hypothesised, these ants alter microbial abundances on plant surfaces, this would represent a novel type of ant-plant interaction. Deterrence of herbivorous consumers (mainly insects) by ants is well-documented in tropical forests, but interactions of ants with pathogenic and beneficial microbes might be even more important in ever-wet equatorial forests like that in Brunei Darussalam.Many other species have evolved to take advantage of the Colobopsis, e.g., by mimicking foraging behaviour (an unrelated ant, a ‘grazing’ spider). Other ant species either follow Colobopsis to food or cultivate food retrieved from their nests. Tiny flies (Ceratopognonidae) are quickly attracted to mandibular gland products of ‘exploded’ Colobopsis workers, and a colorful diurnal and predacious cricket may specialise on these ants despite their sticky contents.The Bruneian studies conducted in “”Diet of Borneo’s Exploding Ants” began as a comparative investigation on the trophic levels at which ants feed in New and Old World rain forests (Borneo and Peru). It then discovered how many clade members occurred near Brunei’s Kuala Belalong Field Centre and the context in which worker ants sacrificed themselves.THE UNUSUAL BEHAVIOURS OF THESE ANTS DISPLAY POTENTIALLY NOVEL ROLES IN THE FOREST ECOSYSTEM. ALTHOUGH VOLUNTARY SELF-SACRIFICE IS KNOWN TO OCCUR IN OTHER SOCIAL INSECTS, THE BEHAVIOUR OF EXPLODING COLOBOPSIS IS UNIQUE IN OCCURRING ON DISTANT FORAGING TERRITORIES, RATHER THAN IN DEFENSE OF QUEEN, BROOD AND NEST SITE. Three current and former members of UBD’s Faculty of Science (FOS) contributed to a study recently highlighted by Biotropica, a journal focusing on tropical ecology and conservation. A Colobopsis species has grasped the antenna of a weaver ant (Oecophylla smaragdina) and exploded contents of its mandibular gland reservoirs on the opponent’s face. Photo: Courtesy of Linda Lim
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