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Comparison of nest shapes and densities of two sympatric species of Cubitermes (Isoptera: Termitidae: Termitinae) as clues for the study of their population dynamics
Solange Patricia Wango,Guy Josens
African Zoology , 2011,
Abstract: Two species of Cubitermes coexist in the grassy Loudetia Savanna of Bondoé, in the Central African Republic, namely C. sankurensis (Wasmann, 1911) and C. ugandensis (Fuller, 1923) Despite the obvious size difference between individuals their nests have the same general shape but there are significant, though small, differences in height, diameter, number of caps, surface and volume. The closest correlations between these five parameters can be seen between the surface and the volume of the nests. The regressions between these two parameters are identical for both species; the addition of a first cap decreases the volume/surface ratio but a second or third cap does not alter this ratio further. Three apparent age classes have been attributed to the nests based on their external appearance: recent, eroded, and dilapidated. The great density (1297 nests/ha) and abundance of the nests that are dilapidated but still occupied by a declining population clearly suggests that the pressure from predation is weak. This study suggests that the environmental conditions are more influential than the species in shaping the mounds and tentative population dynamics of the termite mounds of Bondoé are outlined.
Croissance en pots de quatre espèces végétales sur des substrats enrichis avec la terre de termitières de Cubitermes
Mokossesse, JA.,Lepage, M.,Josens, G.
Tropicultura , 2009,
Abstract: Growth Study in Pots of Various Plants Species on Substrates Enriched by Termite Mounds Cubitermes. The different parts of Cubitermes mounds (cap, trunk and base) from Burkina Faso were analyzed and proved to be richer in available phosphorus, carbon and NO3-N and much richer in NH4-N than the surrounding soil. Their possible stimulating effect was tested on the seedling's growth of four species: Acacia holosericea (A. Cunn. ex G. Don.), Acacia raddiana (Sav.), Crotalaria ochroleuca (G. Don.) and Sorghum sp. (L.) during 47 days. An acceleration of growth is observed for Sorghum on the substrates containing powder 50% of cap or column. This acceleration becomes significant only from 26 days. A similar growth is observed for Crotalaria but as from 40 days.
Efficient Egress of Escaping Ants Stressed with Temperature
Santiago Boari, Roxana Josens, Daniel R. Parisi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081082
Abstract: In the present work we investigate the egress times of a group of Argentine ants (Linepithema humile) stressed with different heating speeds. We found that the higher the temperature ramp is, the faster ants evacuate showing, in this sense, a group-efficient evacuation strategy. It is important to note that even when the life of ants was in danger, jamming and clogging was not observed near the exit, in accordance with other experiments reported in the literature using citronella as aversive stimuli. Because of this clear difference between ants and humans, we recommend the use of some other animal models for studying competitive egress dynamics as a more accurate approach to understanding competitive egress in human systems.
Calcium imaging in the ant Camponotus fellah reveals a conserved odour-similarity space in insects and mammals
Fabienne Dupuy, Roxana Josens, Martin Giurfa, Jean-Christophe Sandoz
BMC Neuroscience , 2010, DOI: 10.1186/1471-2202-11-28
Abstract: Using calcium imaging of specifically-stained second-order neurons, we show that these odours induce specific activity patterns in the ant antennal lobe. Using multidimensional analysis, we show that clustering of odours is similar in ants, bees and rats. Moreover, odour similarity is highly correlated in all three species.This suggests the existence of similar coding rules in the neural olfactory spaces of species among which evolutionary divergence happened hundreds of million years ago.A major aim of neuroscience is to understand how physical stimuli are represented in the animal or human brain, and to attempt to describe the main dimensions that define the perceptual spaces of these organisms [1]. As olfaction represents a key sensory modality in most animal species, numerous studies in the past have endeavoured to unravel the anatomical and functional features of olfactory centres, from the repartition of olfactory receptors at the periphery, their projection within the glomeruli of primary odour centers (olfactory bulb in vertebrates, antennal lobe in insects) and further projection to higher brain centers (olfactory cortex in vertebrates, mushroom bodies in insects) [2-5]. Neurophysiological studies, using both electrophysiological [6-11] and optophysiological techniques [12-18] have studied how different odour molecules differentially activate subsets of neurons or glomeruli. These studies have emphasized the remarkable similarities both in the general organization and in the odour coding properties of the olfactory systems of animals as remote in evolutionary terms as higher vertebrates and insects [19,20]. A general finding of these studies was that odours give rise to a combinatorial pattern of activity that can be measured across neurons of the same structure or across glomeruli in the antennal lobe (AL) or olfactory bulb. Moreover, odours sharing a chemical functional group or showing similar length of the carbon chain give rise to across-fibre patterns
Censos de aves acuáticas en sus colonias reproductivas en lagunas del sudeste de la provincia de Buenos Aires
Josens,María Laura; Pretelli,Matías G.; Escalante,Alicia H.;
El hornero , 2009,
Abstract: buenos aires province is one of the most disturbed regions of argentina due to human activities, yet has continental lagoons representing complex habitats which host abundant and diverse waterbirds, especially during the breeding season. our primary objective was to identify and survey breeding colonies of waterbirds in three continental lagoons of southeastearn buenos aires province, determining abundance, breeding phenology, and habitat selection of waterbirds. we identified four breeding colonies: one monospecific colony of cattle egret (bubulcus ibis), and three mixed-species colonies of brown-hooded gull (larus maculipennis) and grey-headed gull (larus cirrocephalus), cattle egret and white-faced ibis (plegadis chihi), and cocoi heron (ardea cocoi) and great white egret (egretta alba). los padres lagoon had the greatest species richness and most of the breeding colonies. colonies in different lagoons differed in their phenology of breeding activities, such as nest building, egg laying and chick rearing.
Faster-is-slower effect in escaping ants revisited: Ants do not behave like humans
Daniel R. Parisi,Sabrina A Soria,Roxana Josens
Physics , 2014, DOI: 10.1016/j.ssci.2014.09.014
Abstract: In this work we studied the trajectories, velocities and densities of ants when egressing under controlled levels of stress produced by a chemical repellent at different concentrations. We found that, unlike other animals escaping under life-and-death conditions and pedestrian simulations, ants do not produce a higher density zone near the exit door. Instead, ants are uniformly distributed over the available space allowing for efficient evacuations. Consequently, the faster-is-slower effect observed in ants (Soria et al., 2012) is clearly of a different nature to that predicted by de social force model. In the case of ants, the minimum evacuation time is correlated with the lower probability of taking backward steps. Thus, as biological model ants have important differences that make their use inadvisable for the design of human facilities.
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