Sinistral snail shells in the sea: developmental causes and consequences

The paucity of sinistral (left-coiling) relative to dextral (right-coiling) species of gastropods in the marine realm is an enigma. In Conus , one of the most diverse marine animal genera, sinistral shell coiling has evolved as a species-wide character only once. Fossils of this species, Conus adversarius , are found in Upper Pliocene and lowermost Pleistocene deposits in the southeastern USA. Conus adversarius had nonplanktonic larval development; this may have been a critical factor for the early establishment of the species, as well as sinistral marine species in other clades. Notably, most specimens of aberrantly sinistral modern Conus are derived from typically dextral species that have nonplanktonic development. If C. adversarius was reproductively isolated from dextral conspecifics, then this species may provide an example of nearly instantaneous sympatric speciation in the fossil record. Furthermore, the common and widespread – while geologically short-lived – fossil shells of C. adversarius show large amounts of variability in form and this variation may be related, at least in part, to a pleiotropic effect associated with the reversed coiling direction of this species.     

Paired pleural disks in Dicaulograptus cumdiscus n. sp.

A diplograptid graptolite with strongly introverted thecae and unusual thecal processes was isolated from limestones of the Ordovician Pratt Ferry Formation of Alabama and is described as a new species Dicaulograptus cumdiscus. The thecal processes are referred to as pleural disks. They occur in pairs above every thecal aperture and are inferred to have functioned as suspension processes receiving uplift from small-scale turbulent water motion. Such a function is compatible with a passively buoyant mode of life and is difficult to reconcile with an automobile mode of life.     

Using Echo Ultrasound from Schooling Fish to Detect and Classify Fish Types

Fish finders have already been widely available in the fishing market for a number of years.However,the sizes of these fishfinders are too big and their prices are expensive to suit for the research of robotic fish or mini-submarine.The goal of thisresearch is to propose a low-cost fish detector and classifier which suits for underwater robot or submarine as a proximity sensor.With some pre-condition in hardware and algorithms,the experimental results show that the proposed design has good per-formance,with a detection rate of 100 % and a classification rate of 94 %.Both the existing type of fish and the group behaviorcan be revealed by statistical interpretations such as hovering passion and sparse swimming mode.     

On the Stability of Clathrate Hydrates Encaging Polar Guest Molecules: Contrast in the Hydrogen Bonds of Methylamine and Methanol Hydrates

Abstract

The stability of clathrate hydrates encaging highly polar guests has been investigated in order to explain the experimental observation that some amines form clathrate hydrates but alcohols act as inhibitor to hydrate formation. We choose methylamine and methanol as guest species and examine the stable structure, at which the total potential energy has a minimum value. At the local minima of those two hydrates, the potential energies of water-water and guest-water, and their hydrogen bonded networks are compared. It is found that methanol does not retain the host lattice structure, while the host-network structure is kept in the presence of methylamine. It is shown that the difference in the magnitude of the partial charge on the hydrogen atom between the hydroxyl and amino groups plays a much more significant role on the stability of both clathrate hydrates than the difference in molecular geometry. This is supported from the result of a methylamine-like model that has the same partial charges on the atoms in the hydrophilic site as methanol.     

Constructing more informative plant–pollinator networks: visitation and pollen deposition networks in a heathland plant community

Interaction networks are widely used as tools to understand plant–pollinator communities, and to examine potential threats to plant diversity and food security if the ecosystem service provided by pollinating animals declines. However, most networks to date are based on recording visits to flowers, rather than recording clearly defined effective pollination events. Here we provide the first networks that explicitly incorporate measures of pollinator effectiveness (PE) from pollen deposition on stigmas per visit, and pollinator importance (PI) as the product of PE and visit frequency. These more informative networks, here produced for a low diversity heathland habitat, reveal that plant–pollinator interactions are more specialized than shown in most previous studies. At the studied site, the specialization index was lower for the visitation network than the PE network, which was in turn lower than for the PI network. Our study shows that collecting PE data is feasible for community-level studies in low diversity communities and that including information about PE can change the structure of interaction networks. This could have important consequences for our understanding of threats to pollination systems.     

Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin

The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca. -100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multistate pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2–1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.Abbreviations BLM Black lipid membranes - CCCP carbonyl cyanide m-chlorophenylhydrazone - DOPC dioleoyl phosphatidylcholine - PS phosphatidylserine - TPP⁺ tetraphenylphosphonium cation     

Electron-microscopic studies on the threshold value of calcium concentration for the release of storage granules and the acceleration of their degradation in the rat parathyroid gland

Summary To determine both a threshold value of calcium concentration (CC) for the release of storage granules and that for the acceleration of degradation of these granules, the rat parathyroid glands were perfused in situ with HEPES-Ringer solutions containing different concentration of Ca²⁺ for 10 min. With perfusates containing 0.83–1.21 mM Ca²⁺ (equivalent to 8–11 mg/dl serum calcium), the number of type-I storage granules (large core) [NSG-I] and that of type-II storage granules (small core) [NSG-II] remained unchanged. With perfusates containing 0.83 mM Ca²⁺ (7.5 mg/dl) or less, however, both NSG-I and NSG-II decreased remarkably and the former was larger than the latter. On the contrary, with perfusates containing 1.27 mM Ca²⁺ (11.5 mg/dl) or more, NSG-II increased and the ratio of NSG-I to NSG-II was changed reversely. We concluded that a thereshold value of CC required for the release of storage granules may be present between 0.88 and 0.83 mM Ca²⁺ (8 and 7.5 mg/dl) and that a threshold value of CC for accelerating the transformation of type-I granules into type-II, the degradation of storage granules, may be situated at about 1.27 mM Ca²⁺ (11.5 mg/dl). Additionally, it was suggested that both prosecretory and storage granules are not only formed at the innermost Golgi cisterna but also at the trans-Golgi network.