Removal of clay by stingless bees: load size and moisture selection

Some organisms disperse energy, associated with the transportation of resource, which is not necessarily food. Stingless bees of Central Amazonia (Melipona flavolineata and M. lateralis) collect clay in banks along streams for nest building. The moisture of the clay varies along the bank, and bees collect clay from specific location, indicating that there is some sort of preference regarding their selection. This study aims at identifying: if larger bees carry more clay; if there is a preference for moisture of substrates; and if bees are less efficient accumulating and transporting clay when it is wet. In order to do so, I measured the size of the bees and of the pellets of clay found in the corbicula. I set up a field experiment to test substrate preferences. The amount of clay transported, increased exponentially in accordance to the size of the bee, and the preferred substrate was the driest clay. The amount and the efficiency of removal of clay were not affected by the moisture of the substrate. Despite the wet clay being denser, it does not reduce the efficiency of exploitation of the resource, but suggests that bees spend more energy to carry the same quantity of wet clay, which may be the underlying mechanism explaining their preference for removing drier clay.Alguns organismos têm custos energéticos associados com o transporte de recursos, que não necessariamente são alimentos. Algumas abelhas sem ferrão da Amazônia Central (Melipona flavolineata e M. lateralis) coletam argila na margem de córregos para a construção do ninho. A umidade da argila varia ao longo do barranco e as abelhas coletam argila de pontos específicos, o que sugere que há preferência. Aqui testo se abelhas maiores transportam mais argila; se existe preferência pela umidade do substrato; e se abelhas são menos eficientes na coleta e transporte de argila com elevada umidade. Para isso, eu medi o tamanho das abelhas e das agregações de argila na corbícula. Eu realizei um experimento de campo para testar a preferência de umidade do substrato. A quantidade de argila transportada aumentou exponencialmente com o tamanho da abelha e o substrato preferido foi o de menor umidade. A quantidade de argila removida e a eficiência de remoção não foram influenciadas pela umidade do substrato. A argila com maior umidade é mais densa, o que sugere que as abelhas gastam mais energia para transportar a mesma quantidade de argila quando ela está mais úmida. Esse pode ser o mecanismo para explicar a preferência de remoção pela argila com menor umidade.Univ Fed Mato Grosso do Sul, Ecol Lab, Programa Posgrad Ecol &Conservacao, BR-79070900 Campo Grande, MS, BrazilUniv Estadual Paulista, Dept Ecol, Programa Posgrad Ecol &Biodiversidade, BR-13506900 Rio Claro, SP, BrazilUniv Estadual Paulista, Dept Ecol, Programa Posgrad Ecol &Biodiversidade, BR-13506900 Rio Claro, SP, Brazi

Assessment of the temporal variability of hydro-physical parameters in the HIROMB model

Comparison between long-term measurements carried out during POLRODEX'97 experiment and results from HIROMB is presented. Analysis based on graphical presentation and statistical measure (reliability index) shows that model reproduces current direction fairly well, while current magnitude is underestimated. Time variability of salinity, temperature and water level variation reproduced by the model indicates discrepancies from observations

Vistula River Mouth - History and Recent Problems

The history of the Vistula River mouth exhibits the development of the hydrographic system of Żuławy lowlands caused by natural phenomena and human intervention. During its history, the Vistula River has changed the location of its direct connection with the Baltic Sea three times; the first (the Gdańsk Vistula) and the second (the Brave Vistula) river outlets were created by nature, while the recent one (the Vistula Cross-Cut) was man-made. Each of these locations faced similar problems, i.e. sedimentation in the river mouth leading to flooding problem in the surrounding region, intensified in winter by ice jams. The recent outlet, made as a short cut of the river reach in 1895, requires permanent maintenance as to diminish a flood risk for the surrounding areas due to sedimentation. Since the opening, its maintenance is carried out by elongation of jetties on both sides of the river mouth, and occasional dredging of sand. Presently, further elongation of jetties is proposed, however new methods to keep the river mouth should be considered

Role of groins in river regulation

Ostrogi są konstrukcjami budowanymi poprzecznie do kierunku przepływu, które stosowane są przy regulacji rzek nizinnych. Zasadniczym celem ich budowy jest ochrona brzegów oraz zwężenie koryta rzecznego, co prowadzi do zwiększenia głębokości w korycie głównym, a w konsekwencji do przedłużenia okresu nawigacyjnego. Analizując wpływ ostróg na hydrodynamikę oraz ruch rumowiska w rzece, należy rozważyć na dwa przypadki: (1) ostrogi niezatopione, kiedy korona konstrukcji znajduje się ponad zwierciadłem wody oraz (2) ostrogi zatopione. W warunkach ostróg niezatopionych obserwuje się zwężenie koryta głównego rzeki, któremu towarzyszy zwiększenie prędkości wody, a w konsekwencji jego pogłębianie. W obszarach między ostrogami ruch wody jest znacznie wolniejszy, co powoduje odkładanie się tam niesionego rumowiska. W przypadku ostróg zatopionych ruch wody odbywa się całym korytem rzeki, jednak zwiększenie oporów ruchu w obszarze ostróg powoduje zmniejszenie przepustowości rzek, co może mieć istotne znaczenie w warunkach powodziowych. W każdym z przypadków ruchowi wody towarzyszy mniej lub bardziej intensywny ruch rumowiska. Stan wiedzy w zakresie mechanizmów wzajemnego oddziaływania rzeki z ostrogami jest nadal niewystarczający, by można było prognozować zmiany denne w korycie rzeki z dużą dokładnością. Ostrogi choć budowane od bardzo dawna, nie zawsze doprowadziły do osiągnięcia zamierzonego celu; często przysparzają dodatkowych trudności (np. wymycia, odkładanie rumowiska). W ostatnim okresie można zauważyć powrót do badań laboratoryjnych; rzadziej wykonywane są pomiary terenowe. Badania na modelach hydraulicznych pozwalają lepiej zrozumieć mechanizmy rządzące ruchem wody i rumowiska w warunkach rzeki regulowanej ostrogami. Dostarczają one również danych dla potrzeb weryfikacji modeli matematycznych, które pozwolą na rozwiązywanie problemów występujących w naturze.Groins are structures often used in lowland river regulation. The main goal of their construction is protection of coast and narrowing of the river channel to increase water depth and prolongation of the navigation period. Analysing the influence of groins on hydrodynamics and sediment transport in rivers it is necessary to consider two cases: (1) non-submerged groins, when the groins top is above the water surface, and (2) submerged groins. In case of nonsubmerged groins the narrowing of the main channel is observed; it is accompanied by increase of water velocity leading to further deepening of the main channel. In the groin fields water flows much slower, supporting sediment deposition. In case of submerged groins water flows in the whole channel, but increase of resistance due to groins causes reduction of its capacity, being an important aspect in flooding periods. Water flow is always accompanied by sediment transport, but the existing knowledge in this respect is still insufficient to allow prediction of morphological changes with high accuracy. Groins are constructed since few centuries but not always the expected results are reached; it is not unique that they create new problems (deepening, sediment deposition). Recently laboratory experiments are carried out to solve simplified problems; less common field measurements are carried out. Tests on hydraulic models allow better understanding the mechanisms governing water and sediment movement in rivers trained by groins. They also support us with data necessary to verify mathematical models. The on-going developments in numerical modelling result in better representation of changeable hydro- and morpho-dynamics; however the results are still far from being able to reproduce all phenomena observed in nature

Oligomannose-rich membranes of dying intestinal epithelial cells promote host colonization by adherent-invasive E. coli

A novel mechanism is revealed by which clinical isolates of adherent-invasive Escherichia coli (AIEC) penetrate into the epithelial cell layer, replicate, and establish biofilms in Crohn's disease. AIEC uses the FimH fimbrial adhesin to bind to oligomannose glycans on the surface of host cells. Oligomannose glycans exposed on early apoptotic cells are the preferred binding targets of AIEC, so apoptotic cells serve as potential entry points for bacteria into the epithelial cell layer. Thereafter, the bacteria propagate laterally in the epithelial intercellular spaces. We demonstrate oligomannosylation at two distinct sites of a glycoprotein receptor for AIEC, carcinoembryonic antigen related cell adhesion molecule 6 (CEACAM6 or CD66c), on human intestinal epithelia. After bacterial binding, FimH interacts with CEACAM6, which then clusters. The presence of the highest-affinity epitope for FimH, oligomannose-5, on CEACAM6 is demonstrated using LC-MS/MS. As mannose-dependent infections are abundant, this mechanism might also be used by other adherent-invasive pathogens