We compared fluctuating asymmetry (FA) of wing vein lengths in honeybees (Apis mellifera) between heterozygotes and homozygotes at the malate dehydrogenase (MDH) locus. FA is an indirect measure of developmental homeostasis -the ability of individuals to develop normal phenotypes despite genetic and environmental stresses. Heterozygosity is thought to have a positive influence on developmental homeostasis; hence we hypothesized that honeybees heterozygous for the MDH locus would have greater developmental homeostasis and less FA than homozygotes. Our data support this hypothesis. For one of the five characters measured, MDH heterozygotes displayed less FA than homozygotes in both colonies we examined. We also detected differences in character size and character correlation between MDH heterozygotes and homozygotes, although these patterns were not consistent across colonies. A discriminant function analysis of wing vein characters revealed significant differences between homozygotes and heterozygotes.
Several studies have used auditory mismatch negativity (MMN) to study auditory stream segregation. Few of these studies, however, focused on the stream segregation that involves spatial hearing. The present study used MMNs to examine the spatial aspect of stream segregation. Traditional oddball streams were presented in a passive listening paradigm, either in isolation or in the presence of an interfering stream. The interfering streams were engineered so that the deviants were not unexpected if the two streams were heard as perceptually integrated. Interfering streams were either spectrally distant from or close to the oddball stream, and were also spatially separated from the oddball stream. The deviant stimuli differed from the standards in perceived spatial location. For comparison, the MMN paradigm developed by Lepistö et al. (2009) using intensity deviants was repeated on the same group of subjects. For both paradigms, the MMN was strongest when the oddball stream was presented in isolation, less strong but present when the two streams were spectrally separated, and not observable when the streams were spectrally close. These results demonstrate the feasibility of using the MMN to measure spatial stream segregation, especially in populations for whom task-based behavioral experiments cannot be undertaken.
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