Functional brain networks underlying latent inhibition of conditioned disgust in rats

The present experiment examined the neuronal networks involved in the latent inhibition of conditioned disgust by measuring brain oxidative metabolism. Rats were given nonreinforced intraoral (IO) exposure to saccharin (exposed groups) or water (non-exposed groups) followed by a conditioning trial in which the animals received an infusion of saccharin paired (or unpaired) with LiCl. On testing, taste reactivity responses displayed by the rats during the infusion of the saccharin were examined. Behavioral data showed that preexposure to saccharin attenuated the development of LiCl-induced conditioned disgust reactions, indicating that the effects of taste aversion on hedonic taste reactivity had been reduced. With respect to cumulative oxidative metabolic activity across the whole study period, the parabrachial nucleus was the only single region examined which showed differential activity between groups which received saccharin-LiCl pairings with and without prior non-reinforced saccharin exposure, suggesting a key role in the effects of latent inhibition of taste aversion learning. In addition, many functional connections between brain regions were revealed through correlational analysis of metabolic activity, in particular an accumbens-amygdala interaction that may be involved in both positive and negative hedonic responses

Helminth diversity of two anurans: Rhinella marina and Incilius valliceps (Anura: Bufonidae) from lagunas de Yalahau, Yucatán, Mexico

En México, las comunidades de helmintos en anfibios han recibido poca atención. Durante 2005 y 2006, un total de 52 individuos del sapo marino (Rhinella marina) y 54 del sapo de la costa del golfo (Incilius valliceps) fueron recolectados en las lagunas de Yalahau (Yucatán, México) para estudiar dichas comunidades. Para comparar entre sus comunidades, se produjeron curvas de rarefacción y extrapolación basadas en el tamaño de la muestra y se estimó la diversidad usando los números de Hill. Se calcularon los 3 primeros números que se asocian a los estimadores de riqueza y dominancia de especies y se construyeron las curvas de rarefacción y extrapolación respectivas. Los resultados mostraron que con el tamaño de la muestra obtenido se registró la mayor parte de las especies de parásitos en ambos hospederos. Una mayor diversidad de helmintos y número de especies se registraron en R. marina frente a I. valliceps. Sin embargo, la extrapolación mostró que al alcanzar los 50 individuos no hay diferencias estadísticas entre ambas comunidades. Las comunidades de estos anfibios en esta región del trópico se ajustan al patrón descrito en latitudes neárticas. Igualmente, el hábitat que ocupan es un factor importante en la estructuración de sus comunidades helmínticas. ABSTRACT Helminth communities in amphibians in Mexico have received little attention. During 2005 and 2006, we collected a total of 52 individuals of the marine toad (Rhinella marina) and 54 of the southern Gulf Coast toad (Incilius valliceps) in the Lagunas de Yalahau (Yucatán, Mexico), in order to study their helminth communities. We produced rarefaction and extrapolation sample-size-based and coverage-based curves to provide asymptotic diversity estimators based on Hill numbers to compare the communities. We calculated the first 3 Hill numbers, which are associated with estimators of species richness and species dominance. In general, all results showed that the sample size was large enough to register most of the species of parasites present in both host toad species. We found more helminth species and a higher diversity in the R. marina community than that in I. valliceps. However, extrapolation analysis showed that when a sample size of 50 individuals is reached, there are no statistical differences between the helminth communities. Our results suggest that amphibian communities in this part of the tropics follow the same pattern as described for Nearctic latitudes, equally the terrestrial habitat of the hosts is an important factor in the structure of its helminth communities

Presence of the yeast Kodamaea ohmeri associated with Aethina tumida (Coleoptera: Nitidulidae) collected in Africanized honey bee colonies from two apiaries of Yucatan, Mexico

Aethina tumida (Coleoptera: Nitidulidae), comúnmente conocido como el Pequeño Escarabajo de la Colmena (PEC), se está posicionando como una plaga importante en la industria apícola fuera de su rango de distribución natural. En México, informes recientes indican que el PEC está distribuido en toda la península de Yucatán. La invasión de las colonias de abeja melífera por el PEC está químicamente mediada por compuestos volátiles producidos por la levadura Kodamaea ohmeri, considerada un simbionte secundario del PEC. Se analizó la presencia de esta levadura en colonias de abeja melífera en Yucatán con base en la premisa de que los simbiontes se encuentran frecuentemente distribuidos junto con su huésped, por lo que la presencia de K. ohmeri en colmenas estaría fuertemente asociada con la presencia del PEC. En colonias manejadas de abeja melífera africanizada (AMA), se aislaron e identificaron levaduras asociadas con escarabajos adultos y los resultados muestran que el PEC junto con su levadura asociada, K. ohmeri, ha invadido colonias de AMA en Yucatán. También se reportó por primera vez la presencia de levaduras diferentes a K. ohmeri asociadas con el PEC en esta región geográfica.Aethina tumida (Coleoptera: Nitidulidae), commonly known as the Small Hive Beetle (SHB), is becoming a significant pest in the beekeeping industry outside of its natural distribution range. In Mexico, recent reports indicate that the SHB is distributed throughout the Yucatan peninsula. The invasion of honey bee colonies by SHB it is mainly chemically mediated by volatiles produced by the yeast Kodamaea ohmeri which is regarded as a secondary symbiont of the SHB. It was analyzed the presence of this yeast in honey bee colonies of Yucatan based on the premise that symbionts are often conjointly distributed with their hosts, therefore the presence of K. ohmeri in hives will be closely associated with the presence of SHB. In managed Africanized honey bee (AHB) colonies, yeasts associated with adult beetles were isolated and identified and the results show that the SHB together with their associated yeast, K. ohmeri, have invaded AHB colonies in Yucatan. It was also reported the presence of yeasts other than K. ohmeri associated with SHB that for the first time are recorded in a geographical region where they had not been recorded before

Comparación de efectos de dos especies de levaduras florícolas Metschnikowia en el néctar

Nectar yeast communities in southern Spain are dominated by two closely-related species, Metschnikowia reukaufii Pitt & M.W. Mill. and M. gruessii Gim.-Jurado (Ascomycota, Saccharomycetales), although they tend to be distributed differentially across different host plants. We explore here the possibility that the two yeasts play different functional roles in floral nectar by differing in their impact on sugar concentration and composition of nectar. Experiments were undertaken under controlled conditions using bumblebees caught foraging on the flowers of two different host plants each of which is known to harbor predominantly one of the two yeasts. Bumblebees were used as sources of inocula to obtain two groups of samples from the nectar of Helleborus foetidus L. (Ranunculaceae): nectar samples inoculated with M. gruessii and samples inoculated with M. reukaufii. Metschnikowia gruessii was poorly represented in nectar samples, while M. reukaufii was by far the most common and had the highest cell density. Although the two yeasts caused relatively similar changes in nectar sugar composition, which involved increasing fructose and decreasing sucrose proportions, they marginally differed in their quantitative impact on total nectar sugar concentration. Results suggest that differential yeast occurrence across host plants may lead to yeast specialization and modify the outcomes of the plant-pollinator interface.Las comunidades de levaduras asociadas al néctar en el sur de España son dominadas por dos especies, Metschnikowia reukaufii Pitt & M.W. Mill. y M. gruessii Gim.-Jurado (Ascomycota, Saccharomycetales). Ambas levaduras son especies muy cercanas entre sí, pero se distribuyen diferencialmente entre las especies de plantas cuyo néctar las hospeda. En este trabajo se explora la posibilidad de que las levaduras tengan funciones distintas impactando diferencialmente la concentración y composición del néctar. Para esto se realizaron experimentos bajo condiciones controladas usando individuos de abejorros que fueron capturados cuando visitaban flores que albergan predominantemente una de las dos posibles levaduras mencionadas. Los abejorros fueron utilizados como agentes inoculantes naturales en el néctar de Helleborus foetidus L. para obtener dos grupos de muestras, unas con M. reukaufii y otras con M. gruessii. Los resultados mostraron que M. gruessii estuvo pobremente representada en las muestras; en contraste, M. reukaufii fue la más frecuente y de mayor densidad en el néctar. Aun cuando ambas levaduras tuvieron un efecto similar en la composición proporcional de los azúcares en el néctar, aumento de la fructosa y decremento de la sacarosa, las dos especies difieren marginalmente en su impacto en la concentración total de azúcares. Los resultados sugieren que la ocurrencia diferencial de las especies de levaduras entre sus plantas hospederas, puede conducir a una modificación en las interacciones entre las plantas y sus visitantes florales y también a una especialización de levaduras por hospedero

Micro-organisms behind the pollination scenes: microbial imprint on floral nectar sugar variation in a tropical plant community

† Background and Aims Variation in the composition of floral nectar reflects intrinsic plant characteristics as well as the action of extrinsic factors. Micro-organisms, particularly yeasts, represent one extrinsic factor that inhabit the nectar of animal-pollinated flowers worldwide. In this study a ‘microbial imprint hypothesis’ is formulated and tested, in which it is proposed that natural community-wide variation in nectar sugar composition will partly depend on the presence of yeasts in flowers. † Methods Occurrence and density of yeasts were studied microscopically in single-flower nectar samples of 22 animal-pollinated species from coastal xeric and sub-humid tropical habitats of the Yucata´n Peninsula, Mexico. Nectar sugar concentration and composition were concurrently determined on the same samples using high-per- formance liquid chromatography (HPLC) methods. † Key Results Microscopical examination of nectar samples revealed the presence of yeasts in nearly all plant species (21 out of 22 species) and in about half of the samples examined (51.8 % of total, all species combined). Plant species and individuals differed significantly in nectar sugar concentration and composition, and also in the incidence of nectar yeasts. After statistically controlling for differences between plant species and individuals, nectar yeasts still accounted for a significant fraction of community-wide variance in all nectar sugar parameters considered. Significant yeast × species interactions on sugar parameters revealed that plant species differed in the nectar sugar correlates of variation in yeast incidence. † Conclusions The results support the hypothesis that nectar yeasts impose a detectable imprint on community- wide variation in nectar sugar composition and concentration. Since nectar sugar features influence pollinator attraction and plant reproduction, future nectar studies should control for yeast presence and examine the extent to which microbial signatures on nectar characteristics ultimately have some influence on pollination ser- vices in plant communitiesPeer reviewe

Nectar-living yeasts of a tropical host plant community: Diversity and effects on community-wide floral nectar traits

We characterize the diversity of nectar-living yeasts of a tropical host plant community at different hierarchical sampling levels, measure the associations between yeasts and nectariferous plants, and measure the effect of yeasts on nectar traits. Using a series of hierarchically nested sampling units, we extracted nectar from an assemblage of host plants that were representative of the diversity of life forms, flower shapes, and pollinator types in the tropical area of Yucatan, Mexico. Yeasts were isolated from single nectar samples; their DNA was identified, the yeast cell density was estimated, and the sugar composition and concentration of nectar were quantified using HPLC. In contrast to previous studies from temperate regions, the diversity of nectar-living yeasts in the plant community was characterized by a relatively high number of equally common species with low dominance. Analyses predict highly diverse nectar yeast communities in a relatively narrow range of tropical vegetation, suggesting that the diversity of yeasts will increase as the number of sampling units increases at the level of the species, genera, and botanical families of the hosts. Significant associations between specific yeast species and host plants were also detected; the interaction between yeasts and host plants impacted the effect of yeast cell density on nectar sugars. This study provides an overall picture of the diversity of nectar-living yeasts in tropical host plants and suggests that the key factor that affects the community-wide patterns of nectar traits is not nectar chemistry, but rather the type of yeasts interacting with host plants.Peer Reviewe

Especies de Megacerus (Coleoptera: Bruchidae) y sus plantas hospederas en Yucatán Megacerus species (Coleoptera: Bruchidae) and their host plants in Yucatán

Se registra la incidencia de Megacerus (Coleoptera: Bruchidae) en semillas de 7 especies de Convolvulaceae de 6 sitios al norte de Yucatán. Las semillas de Ipomoea crinicalyx, I. hederifolia, I. nil, I. triloba, Jacquemontia penthanta, Merremia aegyptia y M. cissoides recolectadas en etapa de dispersión fueron colocadas en sobres limpios de papel y puestas en condiciones de laboratorio hasta la emergencia de los brúquidos. Se obtuvieron 1111 coleópteros pertenecientes a 5 especies: Megacerus (Megacerus) cubiculus, M. (M.) porosus, Megacerus (M.) sp., M. (M.) tricolor, y M. (Serratibruchus) cubiciformis. Las semillas de I. crinicalyx, M. aegyptia y M. cissoides fueron infestadas principalmente por M. (M.) porosus, las de I. hederifolia e I. triloba por M. (M.) cubiculus y las de I. nil por M. (M.) tricolor. Todos los individuos de Megacerus (M.) sp., fueron encontrados en semillas de J. penthanta. En el nivel génerico de hospedero se encontró que las semillas de Ipomoea fueron infestadas principalmente por M. (M.) cubiculus y las de Merremia por M. (M.) porosus. Estos resultados amplían el rango de plantas hospederas registrado para las especies de Megacerus y resaltan la estrecha asociación que existe entre un linaje de depredadores de semillas Bruchidae y plantas de la familia Convolvulaceae.<br>Seed-attacking by Megacerus (Coleoptera: Bruchidae) is reported for 7 Convolvulaceae species from 6 sites at the North of Yucatan. Seeds of Ipomoea crinicalyx, I. hederifolia, I. nil, I. triloba, Jacquemontia penthanta, Merremia aegyptia and M. cissoides were collected and placed in clean envelopes under laboratory conditions to collect all bruchids emerged from seeds. A total of 1111 coleopterans were hatched from seeds, and 5 taxa were identify: Megacerus (Megacerus) cubiculus, M. (M.) porosus, Megacerus (M.) sp., M. (M.) tricolor, and M. (Serratibruchus) cubiciformis. Seeds of I. crinicalyx, M. aegyptia and M. cissoides were attacked mainly by M. (M.) porosus; I. hederifolia and I. triloba ones by M. (M.) cubiculus, and I. nil ones by M. (M.) tricolor. Individuals of Megacerus (M.) sp., hatched exclusively from J. penthanta seeds. At level of host plant gender, Ipomoea was overall attacked by M. (M.) cubiculus and Merremia was by M. (M.) porosus. Our results increase the number of host plants reported for Megacerus and suggest a close interaction between one lineage of Bruchidae and species of the Convolvulaceae family

Inhospitable sweetness: nectar filtering of pollinator-borne inocula leads to impoverished, phylogenetically clustered yeast communities

Identifying the rules and mechanisms that determine the composition and diversity of naturally co-occurring species assemblages is a central topic in community ecology. Although micro-organisms represent the ‘unseen majority’ of species, individuals and biomass in many ecosystems and play pivotal roles in community development and function, the study of the factors influencing the assembly of microbial communities has lagged behind that of plant and animal communities. In this paper, we investigate experimentally the mechanisms accounting for the low species richness of yeast communities inhabiting the nectar of the bumble-bee-pollinated Helleborus foetidus (Ranunculaceae), and explore the relationships between community assembly rules and phylogenetic relatedness. By comparing yeast communities on the glossae of foraging bumble-bees (the potential species pool) with those eventually establishing in virgin nectar probed with bee glossae (the realized community), we address the questions: (i) does nectar filter yeast inocula, so that the communities eventually established there are not random subsamples of species on bumble-bee glossae? and (ii) do yeast communities establishing in H. foetidus nectar exhibit some phylogenetic bias relative to the species pool on bumble-bee glossae? Results show that nectar filtering leads to species-poor, phylogenetically clustered yeast communities that are a predictable subset of pollinator-borne inocula. Such strong habitat filtering is probably due to H. foetidus nectar representing a harsh environment for most yeasts, where only a few phylogenetically related nectar specialists physiologically endowed to tolerate a combination of high osmotic pressure and fungicidal compounds are able to develop