Rare, threatened and alien species in the gastropod communities in the clay pit ponds in relation to the environmental factors (The Ciechanowska Upland, Central Poland)

The objectives of the present survey were to formulate a zoocenological analysis of the gastropod communities in clay pit ponds, as well as to determine the relationships between the gastropods and their environments, and to evaluate the water habitats in terms of their ecological-conservation value. The physical and chemical parameters of water, gastropod species and macrophytes occurring in the ponds indicate mesotrophic conditions. Principal Component Analysis (PCA) reveals a correlation between gastropod density and nitrates, a correlation between gastropod density and alkalinity, and additionally shows a correlation between gastropod density and chlorides. The pond surface area, nitrates, chlorides concentrate, alkalinity, and substratum have all affected these gastropod communities. The occurrence of the first permanent population of Ferrissia clessiniana (Jickeli, 1882) was recorded in Poland. Valvata naticina Menke 1845 has become a critically rare species (CR) due to the pollution of water environments. Five other species, e.g. Anisus vorticulus (Troschel, 1834) and Planorbis carinatus O.F. Müller, 1774 are recorded on the Polish Red List of Species. The clay pit ponds of the Ciechanowska Upland, because of their distinctive environmental features, provide a refuge where a number of rare, threatened and alien gastropod species live.     

Some properties of the walls of metaxylem vessels of maize roots,including tests of the wettability of their lumenal wall surfaces

Background and Aims

Since the proposal of the cohesion theory there has been a paradox that the lumenal surface of vessels is rich in hydrophobic lignin, while tension in the rising sap requires adhesion to a hydrophilic surface. This study sought to characterize the strength of that adhesion in maize (Zea mays), the wettability of the vessel surface, and to reconcile this with its histochemical and physical nature.

Methods

Wettability was assessed by emptying the maize root vessels of sap, perfusing them with either water or oil, and examining the adhesion (as revealed by contact angles) of the two liquids to vessel walls by cryo-scanning electron microscopy. The phobicity of the lumenal surface was also assessed histochemically with hydrophilic and hydrophobic probes.

Key Results

Pit borders in the lumen-facing vessel wall surface were wetted by both sap/water and oil. The attraction for oil was weaker: water could replace oil but not vice versa. Pit apertures repelled oil and were strongly stained by hydrophilic probes. Pit chambers were probably hydrophilic. Oil never entered the pits. When vessels were emptied and cryo-fixed immediately, pit chambers facing away from the vessels were always sap-filled. Pit chambers facing vessel lumens were either sap- or gas-filled. Sap from adjoining tracheary elements entering empty vessels accumulated on the lumenal surface in hemispherical drops, which spread out with decreasing contact angles to fill the lumen.

Conclusions

The vessel lumenal surface has a dual nature, namely a mosaic of hydrophilic and hydrophobic patches at the micrometre scale, with hydrophilic predominating. A key role is shown, for the first time, of overarching borders of pits in determining the dual nature of the surface. In gas-filled (embolized) vessels they are hydrophobic. When wetted by sap (vessels refilling or full) they are hydrophilic. A hypothesis is proposed to explain the switch between the two states.     

阔叶红松混交林林隙内丘坑复合体特征及分布格局

对小兴安岭凉水国家级自然保护区红松阔叶混交林不同大小林隙及郁闭林分内丘坑复合体特征及分布格局进行了对比和分析.结果表明： 大、中、小林隙及郁闭林分中丘坑复合体的丘宽、丘高、丘厚均大于与之对应的坑宽、坑长、坑深.大林隙内丘坑复合体的丘宽、丘高、丘厚、坑宽、坑长、坑深均最大,分别为2.85、0.37、2.00、2.99、2.10、0.39 m;郁闭林分均最小,分别为2.35、0.19、1.60、2.66、1.65、0.21 m.丘的平均体积（1.66 m³）均大于坑的（1.44 m³）.同一大小林隙内绝大多数丘坑复合体之间的特征值差异显著,而郁闭林分内绝大多数丘坑复合体之间的特征值差异不显著.不同大小林隙及郁闭林分丘坑复合体之间的特征值大多差异显著.2012年样地内丘坑复合体大多数特征值显著小于2011年.89.5%和60.5%的丘坑复合体类型为铰链式,形状为半椭圆状,丘坑复合体的分布格局为相对集中.     

乙二胺四醋酸二钠对蝮蛇抗栓酶毒性的影响

对照组小鼠腹腔注射蝮蛇抗栓酶０．１ｕ／１０ｇ,实验组同时再注射０．５％ＥＤＴＡ２Ｎａ溶液０．２５ｍｌ／１０ｇ,结果表明,死亡率各组间无差别（Ｐ＞０．０５）,但对照组动物脏器有出血现象,而实验组则无出血。     

Ontogenetic perspective on mechanical and nonmechanical models of primate circumorbital morphology

Dimensions of the supraorbital torus, postorbital bar, and postorbital septum were collected in an ontogenetic series of Macaca fascicularis and compared with expectations based on models that attribute morphological variation in these features to spatial factors, allometry, anterior dental loading, and neurofacial torsion. Each model was evaluated using correlation, partial correlation, and regression techniques (model I/least squares; model II/reduced major axis) applied to log-transformed and size-corrected data. Results indicate clearly that face or skull size is the primary determinant of variation in circumorbital structures. Strong support is found for the influence of spatial influences on anteroposterior supraorbital torus development (Moss and Young, Am. J. Phys. Anthropol. 18:281-292, 1960). Only minor support is noted for the neurofacial torsion model of Greaves (J. Zool. 207:125-136, 1985), and no support is indicated for the anterior dental loading model. The sexes do not differ significantly in any relevant comparisons of ontogenetic trajectories.     

Stochastic simulations of nanoparticle internalization through transferrin receptor dependent clathrin-mediated endocytosis

Background

Receptor dependent clathrin-mediated endocytosis (CME) is one of the most important endocytic pathways for the internalization of bioparticles into cells. During CME, the ligand-receptor interactions, development of clathrin-coated pit (CCP) and membrane evolution all act together to drive the internalization of bioparticles. In this work, we develop a stochastic computational model to investigate the CME based on the Metropolis Monte Carlo simulations.

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation–refilling and freeze–thaw cycles for a whole year. Cavitation resistance was determined from ‘vulnerability curves’ showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation–refilling cycle, whereas frost fatigue was caused by a freeze–thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12‐month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes.     

Ultrastructure of the ciliary pits in the Geocentrophora group (Platyhelminthes,Lecithoepitheliata)

The ultrastructure of the paired lateral ciliary pits in several endemic species of Geocentrophora from Lake Baikal and in one cosmopolitan species, G. baltica, has been compared and the possible functional significance is discussed. The pit is composed of two distinctive parts; the bottom of the pit is an extensive sensitive area, filled with uni-and biciliary sensory receptors with reduced rootlets and numerous neurotubules. The walls of the pit are formed by several large dark cells, characterized by a dark cytoplasm with numerous mitochondria, a large nucleus, intracellular canaliculi, basal infoldings of the cell membrane, glycogen granules and a varying number of cilia. A protruding, densely ciliated ridge occurs along the anterior wall of the pit. The cilia have a strengthened rootlet system and seem to provide a strong water current into the pit. Dark cell processes penetrate the basement membrane of the pit and come into the vicinity of large cells with a cytoplasm similar to that of the dark cells of the pit. These large cells in their turn come close to the terminal parts of the protonephridial canals, containing a weir. Smaller protonephridial capillaries without a weir seem to open directly into the pit lumen. The morphological data obtained suggest that the ciliary pit in not only a sensory structure, but plays a part in osmoregulation and ion exchange as well.     

Post‐Hurricane Regeneration of Pioneer Plant Species in South Florida Subtropical Hardwood Hammocks1

After Hurricane Andrew crossed southern Florida (U.S.A.) on 24 August 1992, native and exotic pioneer species in subtropical hardwood forests (hammocks) regenerated from seed banks. Regeneration occurred in hammocks of metropolitan Dade County and the Long Pine Key region of Everglades National Park. The density of the native pioneer Trema micrantha was significantly higher in hammocks of Long Pine Key than in those of metropolitan Dade County. In contrast, the basal area of the exotic pioneer Carica papaya was greater in Dade County hammocks than Long Pine Key hammocks. Although T. micrantha tended to be restricted to areas of soil disturbance (tip‐up pits) formed by trees uprooted during Hurricane Andrew, especially in Long Pine Key, C. papaya was located throughout hammocks. These results suggest differences in the regeneration niches in which the native T. micrantha required more specific disruptions (i.e., both canopy and soil) than C. papaya (only removal of canopy) for establishment. A broad regeneration niche could in part account for the capability of an exotic species with a dormant seed bank to invade native subtropical forests following natural large‐scale disturbances.     

Structural determinants of increased susceptibility to dehydration‐induced cavitation in post‐fire resprouting chaparral shrubs

It is well established that transpiration and photosynthetic rates generally increase in resprouting shoots after fire in chaparral shrublands. By contrast, little is known about how plant hydraulic function varies during this same recovery period. We hypothesized that vascular traits, both functional and structural, would also shift in order to support this heightened level of gas exchange and growth. We examined stem xylem‐specific hydraulic conductivity (K_s) and resistance to cavitation (P₅₀) for eight chaparral shrub species as well as several potential xylem structural determinants of hydraulic function and compared established unburned plants and co‐occurring post‐fire resprouting plants. Unburned plants were generally more resistant to cavitation than resprouting plants, but the two groups did not differ in K_s. Resprouting plants had altered vessel structure compared with unburned plants, with resprouting plants having both wider diameter vessels and higher inter‐vessel pit density. For biomechanics, unburned plants had both stronger and denser stem xylem tissue than resprouting plants. Shifts in hydraulic structure and function resulted in resprouting plants being more vulnerable to dehydration. The interaction between time since disturbance (i.e. resprouting versus established stands) and drought may complicate attempts to predict mortality risk of resprouting plants.