Three-dimensional ultrastructural organization of the ommatidium of the minute parasitoid wasp Trichogramma evanescens

Existing information on insect compound eyes is mainly limited to two-dimensional information derived from histological or ultrathin sections. These allow a basic description of eye morphology, but are limited in z-axis resolution because of the section thickness or intervals between sections, so that accurate volumetric information cannot be generated. Here we use serial-sectioning transmission electron microscopy to present a 3-D reconstruction at ultrastructural level of a complete ommatidium of a miniaturized insect compound eye. Besides the general presentation of the three dimensional arrangement of the different cell types within the ommatidium, the reconstruction allowed volumetric measurements and numerical analyses to be undertaken, revealing new insights into the number, size and distribution of cell organelles in insect ommatidia. Morphological features that can be related to miniaturization, namely the dimensions and displacement of nuclei, reduction of average pigment granule volume and loss of pigment granules in the terminals of the cone cells, the impact of metabolic activity of cell types on miniaturization, as well as maintenance of rhabdomere volume and limits to its miniaturization, are all discussed.

Life as a cataglyphologist--and beyond

Rüdiger Wehner's lifelong research activities centered on Cataglyphis have rendered these thermophilic desert ants model organisms in the study of animal navigation. The present account describes how the author encountered Cataglyphis and established a study site at Maharès, Tunisia; how he increasingly focused his research on the neuroethological analysis of the ant's navigational toolkit; and finally, how he extended these studies to thermophilic desert ants in other deserts of the world, to Ocymyrmex in southern Africa and Melophorus in central Australia. By including aspects of functional morphology, physiology, and ecology in his research projects, he has favored-and advocated-an organism-centered approach. Beyond "cataglyphology," he was engaged in substantial teaching both at his home university in Zürich and overseas, writing a textbook, running a department, and working as a Permanent Fellow at the Institute for Advanced Study in Berlin.

Central projections of sensory systems involved in honey bee dance language communication

Honey bee dance language is a unique and complex form of animal communication used to inform nest mates in the colony about the specific location of food sources or new nest sites. Five different sensory systems have been implicated in acquiring and communicating the information necessary for dance language communication. We present results from neuronal tracer studies identifying the central projections from four of the five. Sensory neurons of the dorsal rim area of the compound eyes, involved in acquiring sun-compass based information, project to the dorsal-most part of the medulla. Sensory neurons of the neck hair plates, required to transpose sun-compass based information to gravity-based information in the dark hive, project to the dorsal labial neuromere of the subesophageal ganglion. Sensory neurons from the antennal joint hair sensilla and the Johnston's organ, which perceive information on dance direction and distance from mechanostimuli generated by abdomen waggling and wing vibration, project to the deutocerebral dorsal lobe and the subesophageal ganglion, and the posterior protocerebrum, respectively. We found no 'dance-specific' projections relative to those previously described for drone and queen honey bees and other insect species that do not exhibit dance communication. We suggest that the evolution of dance language communication was likely based on the modification of central neural pathways associated with path integration, the capability to calculate distance, and directional information during flight.