Optical Imaging of Odor-Evoked Glomerular Activity Patterns in the Antennal Lobes of the Ant Camponotus rufipes

 Ants have a well developed olfactory sense, which they need both for the perception of environmental chemicals, and for a highly sophisticated intraspecific communication system based on pheromones. The question arises therefore as to how different odors are coded in the antennal lobe, the first central neuropil to process olfactory information. We measured odor-evoked activity patterns using in vivo neuropil calcium recording in the antennal lobe of the ant Camponotus rufipes. We found that (a) odors elicit focal activity spots (diameter ca. 20 μm) which most probably represent the olfactory glomeruli; (b) different odors are coded in odor specific patterns of such activated spots, and a particular spot can participate in the pattern for different odors; (c) calcium increased in the activated spots within the 2-s stimulation period and slowly declined thereafter. Received: 10 March 1999 / Accepted in revised form: 5 July 1999     

Metamorphic evolution of eclogite and associated garnet-mica schist in the high-pressure metamorphic Maksyutov complex, Ural, Russia

Metasedimentary garnet-mica schists are interlayered with metabasic garnet–omphacite schists and enclose eclogite boudins in the high-pressure metamorphic Maksyutov complex in the Southern Urals, Russia. These three rock types were investigated in one outcrop and compared chemographically and thermobarometrically. The Fe/Mg distributions between garnet rim–omphacite and garnet rim–phengite pairs indicate different equilibration temperatures for the three samples, with the lowest temperature (500°C, >1.5 GPa) for the eclogite boudin, an intermediate temperature (630°C, >1.7 GPa) for the foliated eclogite and the highest temperature (650°C, >1.7 GPa) for the garnet-mica schist. The garnets in garnet-mica schist enclose abundant chloritoid relics and the Fe/Mg distribution between chloritoid and garnet records an earlier high-temperature stage (650°C, >2.0 GPa) before the garnet rim–phengite temperatures were reached. Together with some minimum- and maximum-pressure estimates three different prograde pressure–temperature paths and a common retrograde metamorphic evolution are interpreted from the chemographic and thermobarometric data. The different early metamorphic evolutions and conditions confirm the variability of protoliths, which are also indicated by different U/Pb zircon and rutile ages.     

The effect of octopamine on behavioral responses of free-foraging bumblebees to a change in food source profitability

The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee.