Seasonal stability and species specificity of environmentally acquired chemical mating signals in orchid bees

Traits that mediate reproductive isolation between species, such as those involved in mate choice and/or recognition, are predicted to experience stabilizing selection towards the species mean. Male orchid bees collect chemical compounds from many sources, such as plants and fungi, which they use as a perfume signal (pheromone) during courtship display, and are suggested to contribute to reproductive isolation between species. Environmentally acquired signals are more prone to variation as source availability can vary through space and time. If orchid bee perfumes are important for reproductive isolation between species, we expect them to exhibit stable species-specific differences in time and space. Here, we describe phenotypic patterns of inter- and intraspecific variation in the male perfumes of three sympatric species of Euglossa orchid bees across an entire year, investigating both their seasonality and species specificity. Our analysis revealed considerable within-species variation in perfumes. However, species specificity was maintained consistently throughout the year, supporting the idea that these perfumes could play an important role in reproductive isolation and are experiencing stabilizing selection towards a species mean. Our analysis also identified strong correlations in the abundance of some compounds, possibly due to shared collection sources between species. Our study suggests that orchid bee perfumes are robust in the face of environmental changes in resource availability and thus can maintain reproductive isolation between species.     

Disruption of chromosome 11 in canine fibrosarcomas highlights an unusual variability of CDKN2B in dogs

Background  

In dogs in the western world neoplasia constitutes the most frequently diagnosed cause of death. Although there appear to be similarities between canine and human cancers, rather little is known about the cytogenetic and molecular alterations in canine tumours. Different dog breeds are susceptible to different types of cancer, but the genetic basis of the great majority of these predispositions has yet to be discovered. In some retriever breeds there is a high incidence of soft tissue sarcomas and we have previously reported alterations of chromosomes 11 and 30 in two poorly differentiated fibrosarcomas. Here we extend our observations and present a case report on detail rearrangements on chromosome 11 as well as genetic variations in a tumour suppressor gene in normal dogs.     

Nematode biphasic ‘boom and bust’ dynamics are dependent on host bacterial load while linking dauer and mouth-form polyphenisms

Cross-kingdom interactions involve dynamic processes that shape terrestrial ecosystems and represent striking examples of co-evolution. The multifaceted relationships of entomopathogenic nematodes with their insect hosts and symbiotic bacteria are well-studied cases of co-evolution and pathogenicity. In contrast, microbial interactions in soil after the natural death of insects and other invertebrates are minimally understood. In particular, the turnover and succession of nematodes and bacteria during insect decay have not been well documented - although it represents a rich ecological niche with multiple species interactions. Here, we utilize developmentally plastic nematode Pristionchus pacificus and its associated scarab beetles as models. On La Réunion Island, we collected rhinoceros beetle Oryctes borbonicus, induced death, and placed carcasses in cages both on the island and in a mock-natural environment in the laboratory controlling for high spatial and temporal resolution. Investigating nematode population density and dispersal dynamics, we were able to connect two imperative plasticities, dauer and mouth form. We observed a biphasic ‘boom and bust’ dispersal dynamic of dauer larvae that corresponds to bacterial load on carcasses but not bacterial type. Strikingly, all post-dauer adults have the predatory mouth form, demonstrating novel intricate interactions on decaying insect hosts. Thus, ecologically relevant survival strategies incorporate critical plastic traits.     

Biomarkers of the metabolic syndrome: influence of selected foodstuffs,containing bioactive components

The influence of various non-nutritive bioactive foodstuffs and food components on the biomarkers of the metabolic syndrome in humans is critically reviewed. Tea, coffee, cocoa, soy, olive oil, fruit and nuts are most of the time found to be effective in improving lipid profiles, CRP and adiponectin. Spices (garlic, curcumin and cinnamon), carotenoids and the phytosterol/-stanols are frequently related to lower risk of metabolic syndrome and improved biomarkers. Since food is a complex matrix and the heterogeneity of studied population and served diets are not always well-defined, this could explain some contradictory results found in literature. Other factors jeopardizing definite conclusions are mentioned.     

Identification of coiled body-like structures in meristematic cells of Pisum sativum cotyledonary buds

This study focused on two types of nuclear bodies visible in plant cells that were previously thought to be similar to the coiled bodies (CBs) of animal cells: the nucleolus-associated body (NAB) and dense body (DB). We show that both NABs and DBs share common features with animal CBs: they consist of ribonucleoproteins, are silver-stainable, and lack DNA. Immunoelectron microscopy shows that only the NABs are rich in snRNAs and fibrillarin, two markers characteristic of animal CBs. This suggests that NABs rather than DBs are the plant counterparts of the CBs of animal cells. These structures appear most frequently in cells blocked in G0–1, their frequency gradually declining with resumption of the cell cycle and nucleolar activity. During this reactivation period, NABs are released from the nucleolus to the nucleoplasm, suggesting that they may act as nuclear transport or sorting structures. Received: 2 November 1998; in revised form: 18 January 1999 / Accepted: 1 February 1999