Posts Tagged ‘Myrmecia’

Sensilla ampullacea and sensilla coeloconica in the bull ant, Myrmecia pyriformis.

Sensilla ampullacea and sensilla coeloconica in the bull ant, Myrmecia pyriformis. (A) External structure of sensilla ampullacea (white arrows) and coeloconica (black arrow). (B) Cross-section through the antennal cuticle shows the peg of a sensillum coeloconicum within the chamber. (C) Detached ampoule of the sensillum ampullaceum reveals no porosity, but a single large opening (white arrow). (D) Micrograph of an uncoated specimen reveals the sensory peg within the enclosing ampoule of sensilla ampullacea (white arrow). (E) Cross-section through the cuticle shows a sensillum ampullaceum hanging within the antennal lumen by a slender tube (white arrow) connecting to the external opening. (F) Detached sensilla ampullacea showing opening for neural innervation (white arrow). Scale bars = 1 mm.

In an ant society, olfaction and mechanoreception plays a big role for communication, recruitment and for identifying nestmates from non-nestmates. An ant’s antennae is packed with a number of detectors, sensilla, that capture different kinds of information. While ant sensilla have been previously described, there have been huge discrepancies with sensilla often being misidentified or given different names. Together with Fiorella and Jochen, using high quality scanning electron microscope images we described a range of sensilla on the antennae of the the now famous bull ant, Myrmecia pyriformis. Given the inconsistent use of sensillum nomenclature and difficulties associated in reliable identification we consolidated the ant sensilla literature to make possible interspecific comparisons in the future.

Read more here: Esquivel FR, Zeil J & Narendra A. in press. The antennal sensory array of the nocturnal bull ant, Myrmecia pyriformisArthropod Structure and DevelopmentDOI: 10.1016/j.asd.2014.07.004

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New Pictures: Myrmecia

The ant gallery gets updated with males and workers of a bunch of Myrmecia ants, the renowned Australian bullants and jackjumpers. The large eyes and ocelli (simple eyes), especially in the male ants are worth drooling.

Worker of the bull ant Myrmecia tarsata bares its jaws at the intruding photographer

The handsome males of Myrmecia pyriformis fly during the day in search of a mate, whereas its own workers are exclusively nocturnal foragers

Have a look here

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After having spent several days of nocturnal lifestyle studying the Bull ant, Myrmecia pyriformis in Canberra, I am quite pleased to report that one of our findings has been published. Our earlier discovery that these ants exhibit strong bursts of inbound and outbound activity in evening and morning twilight respectively in the summer, prompted us to ask whether the onset activity of these ants is restricted to the twilight period for the whole year and if so how do they determine the time of the day in such a dim-lit temporal niche.

By regular monitoring of activity schedules at different nests it became clear that temperature does not play a major role in this – a factor thought to play a major role in regulating ant foraging. Of course when surface temperature dropped to 6.5°C the ants decided to take a break (thankfully for us!), which indicated that this might be close to their critical minima – that’s another story.

The interesting bit here was that in overcast conditions (determined by measuring light levels) ants began their activity much earlier relative to sunset time and conversely under clear skies began activity much later. This indicated that light intensity might play a role in the timing of foraging and that the setting sun alone was not a cue to begin activity.

Inspired by Edward Hodgson’s observations in 1955 on leaf cutter ants3 we set about modifying light intensity during twilight. The challenge of was to make the twilight brighter ensuring no point light sources would be available for orientation. We did this by using a dome shaped diffuser and suspending it above the nest entrance. This also ensured that if the ants came close to the nest entrance the visual panorama was still available for them to navigate. Keeping the lights on for the first 60 minutes of the twilight did not result in ant activity. As soon as the lights were turned off, activity began within a few minutes. The necessary controls were carried out and replication at three nests provided very similar results.

Publications in Proceedings B is currently available for free download as they are celebrating their 350th anniversary. So go on and download this paper.

Narendra A, Reid SF & Hemmi JM. 2010. The twilight zone: light intensity triggers activity in primitive ants. Proceedings of the Royal Society, Biological Sciences. doi: 10.1098/rspb.2009.2324

Hodgson ES 1955. An ecological study of the behaviour of the leaf-cutting ant Atta cephalotes. Ecology 36: 293-304

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Ever wondered about what goes on in the enormous eyes of Bullants? Yup we did too, and we ended up finding that the diameter of the photoreceptor, the optical sensitivity, the number of facets and the facet sizes, all increase gradually from diurnal to diurnal/crepuscular, crepuscular/nocturnal and nocturnal species. Such adaptations in eye structure within a single genus, the primitive ant genus Myrmecia especially, is truly remarkable.
Read more here:
Greiner B, Narendra A, Reid SF, Dacke M, Ribi WA, Zeil J. 2007. Eye structure correlates with distinct foraging bout timing in primitive ants. Current Biology 17 (20): R879-R880.

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