Insects share the same physical environment as terrestrial vertebrates. However, insects are vastly more successful in terms of their adaptive radiation and colonization. The biomass of insects alone is said to outweigh all other organisms and it can be speculated that their evolutionary success is a consequence, not only of their environmental colonization, but also of their behavioral versatility which sets them apart from other terrestrial arthopods. If this hypothesis is correct, it might be expected that there exist neural organizations that are peculiar to, or greatly elaborated in, the Insecta alone. This chapter describes the occurrence among selected arthropods of a brain region that, in eusocial insects, reaches great complexity and is implicated in learning and memory. Its identification in various taxa is assessed against the background of current theories of arthropod evolution and brain segmentation.
Mushroom bodies are prominent neuropils found in annelids and in all arthropod groups except crustaceans. First explicitly identified in 1850, the mushroom bodies differ in size and complexity between taxa, as well as between different castes of a single species of social insect. These differences led some early biologists to suggest that the mushroom bodies endow an arthropod with intelligence or the ability to execute voluntary actions, as opposed to innate behaviors. Recent physiological studies and mutant analyses have led to divergent interpretations. One interpretation is that the mushroom bodies conditionally relay to higher protocerebral centers information about sensory stimuli and the context in which they occur. Another interpretation is that they play a central role in learning and memory. Anatomical studies suggest that arthropod mushroom bodies are predominately associated with olfactory pathways except in phylogenetically basal insects. The prominent olfactory input to the mushroom body calyces in more recent insect orders is an acquired character. An overview of the history of research on the mushroom bodies, as well as comparative and evolutionary considerations, provides a conceptual framework for discussing the roles of these neuropils.
Catalysts containing nanoclusters of Ag(I) and Fe 2 O 3 as dopants with sodalite and Y zeolite supports have been investigated in order to develop a more efficient catalyst for photodecomposition of the pesticide carbaryl and to gain insight about the reaction mechanism. Ag(I)-sodalite, Ag(I)/Fe 2 O 3 -sodalite, Ag(I)-Y zeolite, and Ag(I)/Fe 2 O 3 -Y zeolite were synthesized by ion-exchange techniques and characterized by powder X-ray diffraction (XRD), solid-state luminescence, UV-visible absorption, and atomic absorption spectroscopy measurements. The luminescence activity of the sodalite-supported and Y zeolite-supported catalysts was significantly different. Catalyst performance studies were conducted using carbaryl as the target compound and specific wavelengths of UV light as photon sources for the experiments. The studies showed that each catalyst's performance was determined primarily by the specific wavelength of the UV light with which the system was irradiated. The studies also showed that inclusion of Fe 2 O 3 as dopant enhanced the reactivity of the catalysts in several instances, with the Ag(I)/Fe 2 O 3 -sodalite catalyst and 298 nm irradiation being the most reactive of the systems studied. Additional reactions using each catalyst and 298 nm irradiation, and including either sodium bicarbonate as hydroxyl radical scavenger or D 2 O as solvent, showed that hydroxyl radicals were likely intermediates in the catalyzed photodecomposition reaction.
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