Pumping of nutrients to ocean surface waters by the action of propagating planetary waves

Primary productivity in the oceans is limited by the lack of nutrients in surface waters. These nutrients are mostly supplied from nutrient-rich subsurface waters through upwelling and vertical mixing, but in the ocean gyres these mechanisms do not fully account for the observed productivity. Recently, the upward pumping of nutrients, through the action of eddies, has been shown to account for the remainder of the primary productivity; however, these were regional studies which focused on mesoscale (100-km-scale) eddies. Here we analyse remotely sensed chlorophyll and sea-surface-height data collected over two years and show that 1,000-km-scale planetary waves, which propagate in a westward direction in the oceans, are associated with about 5 to 20% of the observed variability in chlorophyll concentration (after low-frequency and large-scale variations are removed from the data). Enhanced primary production is the likely explanation for this observation, and if that is the case, propagating disturbances introduce nutrients to surface waters on a global scale--similar to the nutrient pumping that occurs within distinct eddies.     

Single origin of Malagasy Carnivora from an African ancestor

The Carnivora are one of only four orders of terrestrial mammals living in Madagascar today. All four (carnivorans, primates, rodents and lipotyphlan insectivores) are placental mammals with limited means for dispersal, yet they occur on a large island that has been surrounded by a formidable oceanic barrier for at least 88 million years, predating the age of origin for any of these groups. Even so, as many as four colonizations of Madagascar have been proposed for the Carnivora alone. The mystery of the island's mammalian origins is confounded by its poor Tertiary fossil record, which leaves us with no direct means for estimating dates of initial diversification. Here we use a multi-gene phylogenetic analysis to show that Malagasy carnivorans are monophyletic and thus the product of a single colonization of Madagascar by an African ancestor. Furthermore, a bayesian analysis of divergence ages for Malagasy carnivorans and lemuriforms indicates that their respective colonizations were temporally separated by tens of millions of years. We therefore conclude that a single event, such as vicariance or common dispersal, cannot explain the presence of both groups in Madagascar.     

Ciliary proteins link basal body polarization to planar cell polarity regulation

Planar cell polarity (PCP) refers to coordinated polarization of cells within the plane of a cell sheet. A conserved signaling pathway is required for the establishment of PCP in epithelial tissues and for polarized cellular rearrangements known as convergent extension. During PCP signaling, core PCP proteins are sorted asymmetrically along the polarization axis; this sorting is thought to direct coordinated downstream morphogenetic changes across the entire tissue. Here, we show that a gene encoding a ciliary protein (a 'ciliary gene'), Ift88, also known as Polaris, is required for establishing epithelial PCP and for convergent extension of the cochlear duct of Mus musculus. We also show that the proper positioning of ciliary basal bodies and the formation of polarized cellular structures are disrupted in mice with mutant ciliary proteins ('ciliary mutants'), whereas core PCP proteins are partitioned normally along the polarization axis. Thus, our data uncover a distinct requirement for ciliary genes in basal body positioning and morphological polarization during PCP regulation.     

THM1 negatively modulates mouse sonic hedgehog signal transduction and affects retrograde intraflagellar transport in cilia

Characterization of previously described intraflagellar transport (IFT) mouse mutants has led to the proposition that normal primary cilia are required for mammalian cells to respond to the sonic hedgehog (SHH) signal. Here we describe an N-ethyl-N-nitrosourea-induced mutant mouse, alien (aln), which has abnormal primary cilia and shows overactivation of the SHH pathway. The aln locus encodes a novel protein, THM1 (tetratricopeptide repeat-containing hedgehog modulator-1), which localizes to cilia. aln-mutant cilia have bulb-like structures at their tips in which IFT proteins (such as IFT88) are sequestered, characteristic of Chlamydomonas reinhardtii and Caenorhabditis elegans retrograde IFT mutants. RNA-interference knockdown of Ttc21b (which we call Thm1 and which encodes THM1) in mouse inner medullary collecting duct cells expressing an IFT88-enhanced yellow fluorescent protein fusion recapitulated the aln-mutant cilial phenotype, and live imaging of these cells revealed impaired retrograde IFT. In contrast to previously described IFT mutants, Smoothened and full-length glioblastoma (GLI) proteins localize to aln-mutant cilia. We hypothesize that the aln retrograde IFT defect causes sequestration of IFT proteins in aln-mutant cilia and leads to the overactivated SHH signaling phenotype. Specifically, the aln mutation uncouples the roles of anterograde and retrograde transport in SHH signaling, suggesting that anterograde IFT is required for GLI activation and that retrograde IFT modulates this event.     

Intestinal uptake of ouabain and digitoxin in the milkweed bug,Oncopeltus fasciatus

Summary The absorption of ouabain and digitoxin into the gut of the milkweed bug was studied by a tissue-accumulation technique. Uptake of both compounds obeyed diffusion kinetics, was Na⁺ sensitive, and for digitoxin, was concentrative.The authors express their appreciation to Dr.James A. Slater and Ms.Flavia O'Rourke, Biological Sciences Group, University of Connecticut, Storrs, Conn. (USA) for supplying milkweed bugs. This work was supported by the University of Maine Honors Program and the University of Maine Agricultural Experiment Station.     

Importance of migrating salmon smolt in Ring-Billed ( Larus delawarensis ) and California Gull ( L. californicus ) diets near Priest Rapids Dam, Washington

Ring-billed ( Larus delawarensis ) and California Gulls ( L. californicus ) have been implicated in depredations on migrating salmon smolt in the Columbia River. As part of a gull management program conducted in 1995 and 1996, we collected L. delawarensis (n = 120) and L. californicus (n = 45) near Priest Rapids Dam, Washington, and analyzed stomach contents to determine food habits and thus the importance of fish in gull diets. Percent volume measurements and index of relative importance rankings suggested a greater reliance on fish by L. californicus than by L. delawarensis . Peak percent consumption of fish by both species occurred in May, coinciding with peak salmon outmigration through Priest Rapids Dam; and for both species number of fish consumed by gulls was higher below Priest Rapids Dam. Gulls collected prior to, and after, peak smolt migration indicated low importance rankings for fish in both L. delawarensis and L. californicus diets. However, the importance ranking of fish in gull diets changed over time and was higher for both species as the smolt migration peaked in May.     

Chemical promotion of pistillate flower formation inCucurbita

Zusammenfassung Blattspritzungen mit 1,1,5,5,-Tetramethyl-3-dimethyl Amino-dithiobiuret (MATB) induzierten die Bildung weiblicher Blüten bei Gurken (C. sativa) und Kürbis (C. maxima). Diese Wirkung von MATB wurde von Gibberellin A₃ vollständig aufgehoben. Es wurden keine Anzeichen für die Abgabe von Äthylen bei den mit MATB behandelten Pflanzen beobachtet.