Moving beyond convergence in the pheromone system of the moth

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Are isomeric alkenes used in species recognition among neo-tropical stingless bees (Melipona spp)

The majority of our understanding of the role of cuticular hydrocarbons (CHC) in recognition is based largely on temperate ant species and honey bees. The stingless bees remain relatively poorly studied, despite being the largest group of eusocial bees, comprising more than 400 species in some 60 genera. The Meliponini and Apini diverged between 80-130 Myr B.P. so the evolutionary trajectories that shaped the chemical communication systems in ants, honeybees and stingless bees may be very different. Therefore, the main aim of this study was to study if a unique species CHC signal existed in Neotropical stingless bees, as shown for many temperate species, and if so what compounds are involved. This was achieved by collecting CHC data from 24 colonies belonging to six species of Melipona from North-eastern Brazil and comparing this new data with all previously published CHC studies on Melipona. We found that each of the eleven Melipona species studied so far each produced a unique species CHC signal based around their alkene isomer production. A remarkable number of alkene isomers, up to 25 in M. asilvai, indicated the diversification of alkene positional isomers among the stingless bees. The only other group to have really diversified in alkene isomer production are the primitively eusocial Bumblebees (Bombus spp), which are the sister group of the stingless bees. Furthermore, among the eleven Neotropical Melipona species we could detect no effect of the environment on the proportion of alkane production as has been suggested for some other species

Odour Maps in the Brain of Butterflies with Divergent Host-Plant Preferences

Butterflies are believed to use mainly visual cues when searching for food and oviposition sites despite that their olfactory system is morphologically similar to their nocturnal relatives, the moths. The olfactory ability in butterflies has, however, not been thoroughly investigated. Therefore, we performed the first study of odour representation in the primary olfactory centre, the antennal lobes, of butterflies. Host plant range is highly variable within the butterfly family Nymphalidae, with extreme specialists and wide generalists found even among closely related species. Here we measured odour evoked Ca2+ activity in the antennal lobes of two nymphalid species with diverging host plant preferences, the specialist Aglais urticae and the generalist Polygonia c-album. The butterflies responded with stimulus-specific combinations of activated glomeruli to single plant-related compounds and to extracts of host and non-host plants. In general, responses were similar between the species. However, the specialist A. urticae responded more specifically to its preferred host plant, stinging nettle, than P. c-album. In addition, we found a species-specific difference both in correlation between responses to two common green leaf volatiles and the sensitivity to these compounds. Our results indicate that these butterflies have the ability to detect and to discriminate between different plant-related odorants

The sense of smell, its signalling pathways, and the dichotomy of cilia and microvilli in olfactory sensory cells

Smell is often regarded as an ancillary perception in primates, who seem so dominated by their sense of vision. In this paper, we will portray some aspects of the significance of olfaction to human life and speculate on what evolutionary factors contribute to keeping it alive. We then outline the functional architecture of olfactory sensory neurons and their signal transduction pathways, which are the primary detectors that render olfactory perception possible. Throughout the phylogenetic tree, olfactory neurons, at their apical tip, are either decorated with cilia or with microvilli. The significance of this dichotomy is unknown. It is generally assumed that mammalian olfactory neurons are of the ciliary type only. The existance of so-called olfactory microvillar cells in mammals, however, is well documented, but their nature remains unclear and their function orphaned. This paper discusses the possibility, that in the main olfactory epithelium of mammals ciliated and microvillar sensory cells exist concurrently. We review evidence related to this hypothesis and ask, what function olfactory microvillar cells might have and what signalling mechanisms they use

Sensilla on the antennal funiculus of the blow fly, Protophormia terraenovae (Diptera: Calliphoridae)

The morphology of the antennal funiculus and the external morphological characteristics and distribution of sensilla of blow fly, Protophormia terraenovae, have been studied using light and scanning electron microscopy. Cross section of the funiculus is roughly triangular in shape, with an anterior-medial, anterior-lateral, and posterior surface. The latter presents some large-size pits on restricted lateral and median areas of the proximal funiculus, and several smaller-size ones close to the pedicel–funiculus joint. The entire surface of the antennal sub-segment appears densely populated by microtrichia and is inhabited by seven types of sensilla: one trichoid, two basiconic, one auriculate, one coeloconic, and two basiconic-like pit sensilla. Trichoid, basiconic, auriculate and basiconic-like types display a multiporous wall, a feature characteristic of insect olfactory sensilla. It remains to be verified whether or not the coeloconic structure type has wall pores. The most abundant sensilla are the trichoid ones, which are followed by the basiconic, coeloconic and auriculate types in a decreasing density order. The basiconic-like pit sensilla are present only on the posterior funicular surface, unlike the remaining ones which populate the entire sub-segment. The blow fly’ funiculus displays a significant, even though moderate sexual dimorphism, the female sub-segment being bigger and presenting a higher number of trichoid and auriculate sensilla. The presence of multiple wall pores in most of sensilla types implies an olfactory modality for sensory neurons they accomodate, thus indicating that the blow fly’ funiculus is a plain olfactory organ