斑须蝽生物学特性及成虫耐寒性的研究

斑须蝽Dalycoris baccarum(Linnaeus)是多种作物和苗木的重要害虫。在鲁西南一年发生3代，以成虫主要在越冬菜叶夹缝、作物根际、枯枝落叶，树皮及房屋缝隙等处越冬。其越冬成虫结冰点和过冷却点分别为-5．2℃和-8．5℃。冬季极端低温对其越冬成活率有明显影响．第一代发生较轻．第二代发生重。成虫具弱趋光性，第二代上灯量占全年总量的77．56%。     

A comparative histological and histochemical study of the post-gastric alimentary canal from three species of pleuronectid, the Atlantic halibut, the yellowtail flounder and the winter flounder

The histology and mucus histochemistry of the pleuronectid post-gastric alimentary canal was examined using light and electron microscopy. Distinct differences in goblet cell mucus histochemistry were observed between species, with the two closest taxonomic species, the winter flounder and the yellowtail flounder showing the most diversity and the halibut showing regional variation. Numbers of goblet cells within post-gastric regions did not differ significantly between species, but were significantly different between regions within species increasing toward the rectum. The post-gastric region was divisible into two areas based upon the ultrastructural features of lipid digestion and absorption in the intestine and pyloric caeca, and of exogenous protein in the rectum. The combination of species-specific histochemical differences in mucus and general histological and ultrastructural differences within the post-gastric regions between these species suggest a correlation between lumenal environmental conditions/histology and natural prey preference.     

Winter in the Ouchitas—A severe winter storm signature in Pinus echinata in the Ouachita Mountains of Oklahoma and Arkansas,USA

Each year severe winter storms (≈ice storms) damage trees throughout the southern USA. Arkansas and Oklahoma have a history of severe winter storms. To extend that history back beyond the reach of written records, a distinctive tree ring pattern or signature is needed. Storm-caused breakage, branch loss and bending stress provide that signature. We found a severe storm signature in shortleaf pine (Pinus echinata). We used three published site chronologies, a set of five new site chronologies from a growth-and-yield study conducted by Oklahoma State University and the unpublished Shortleaf Canyon chronology from a master’s thesis at the University of Arkansas. Our method is based on two ring width values for the first and second growing seasons after the storm standardized to the ring widths of the seven growing seasons after the storm. Concordance between storm years predicted by tree ring patterns and actual storm years was tested using Cohen’s Kappa. Concern about confounding of ice storm signals by droughts led us to test concordance between severe storms and drought in July, August and September; results were inconclusive but stand as a warning that these two phenomena cannot be distinguished with certainty in the tree ring record. Damaging severe storms occurred in about 2.8% of all years. Two out of three storms identified as “severe” produced glaze icing.     

Vertical and seasonal distributions of micro-organisms,zooplankton and phytoplankton in a eutrophic lake

The vertical distributions of bacteria, picoalgae,protozoan and metazoan zooplankton, and phytoplanktonin the highly eutrophic Lake Köyliönjärvi(SW Finland) were studied monthly during the period ofice-cover in January-April 1996. For comparison, wealso provide some data on the distributions of theplankton during the summer. The whole watercolumn remained oxic during the ice-covered period,although the near-bottom oxygen concentrations werealways very low. The heterotrophic nanoflagellateswere more abundant in winter than in summer, butciliates, picoalgae and bacteria were more numerous insummer. In general both zooplankton and phytoplanktonhad low biomass during the ice-covered period.However, the biomass of the diatom Aulacoseiraislandica ssp. islandica was high under the icein April. The calanoid copepod Eudiaptomusgraciloides was the dominant zooplankton species fromJanuary to March, but had almost disappeared by thebeginning of April and did not increase again until inJune. The dominant rotifer species in winterwere Keratella cochlearis, Filinia terminalis,and Filinia longiseta in the surface water andRotaria neptunia near the bottom.     

Density regulation in toad populations (Epidalea calamita,Bufotes viridis) by differential winter survival of juveniles

The size of amphibian populations varies considerably between years, so that systematic trends in dynamics are difficult to detect. Informed conservation management of presumably declining populations requires the identification of the most sensitive life stage. In temperate-zone anurans there is growing evidence that juveniles hibernating for the first time suffer from substantial winter losses. In two syntopic toads (Epidalea calamita, Bufotes viridis) we monitored survival of such juveniles during four consecutive winters in the natural habitat and in four temperature treatments (3°, 5 °C, 10°/15 °C or 20 °C, natural light-dark cycle) in temperature-controlled chambers during winter. Specifically, we tested the hypotheses that (1) winter mortality of juvenile toads which hibernate for the first time in their life is an important component of population dynamics, and that (2) mortality rates differed between the two species. Parameters quantified were size-dependent winter mortality and body condition of pre- and post-hibernating juveniles. Field data provided evidence for the important role of winter mortality of first-hibernators in population dynamics. Choice of hibernacula differed in E. calamita between small and medium-sized individuals and also between the two species suggesting distinct mortality risks. The inability of small E. calamita to reach frost-proof hibernacula by burrowing, and the exposure of small B. viridis to predators are the most probable causes of size-assortative winter mortality. In conclusion, E. calamita juveniles may benefit from rising average winter temperatures in the future by decreased risk of freezing to death, whereas predator-caused winter mortality of B. viridis juveniles will also depend on the effects of climate warming on predator phenology.     

Root development in winter wheat grown at different N/P supply: Root length patterns and N-P interactions in phosphate uptake

Effects of different N/P ratios on several root parameters and on net P uptake were studied in winter wheat, Triticum aestivum cv. Starke II, grown in water culture. In the First experiment N/P ratios of (0/4, 2/3, 4/2, 6/1 and 8/0) were used, and plants were harvested at age 3, 5, 8, 11 and 14 days. In the second experiment N/P ratios of 6/1, 10/1, 15/1, 17/1, 20/1 and 25/1 were applied at two different N,P levels. Root length and number were determined using a digitizer connected to a computer. In the first experiment. the 6/1 N/P ratio gave the largest plants at day 14, and growth decreased with decreasing N/P ratio, The same pattern was found fur lateral root length and root number (seminal and lateral). In the second experiment the root weights decreased with increasing N/P ratio within each level. Lateral root number and overall length decreased with increasing N/P ratio at both levels as did the average lateral root length at the high N,P level. At the low N.P level, average lateral root length was about the same at all N/P ratios. Increasing the N/P ratio increased net uptake of P at the low N,P level, but decreased net P uptake at the high N,P level. Net P uptake increased with increasing P concentration in the roots and then decreased with further increase in P concentration. Net P uptake based on calculated root length [m (g root)⁻¹] showed no significant deviation from weight-based uptake plots. The effect of N and P on root structure is discussed as well as the interaction of N and P in P uptake. The relevance of a proper basis for expressing root activity is stressed.     

Genome-wide CRISPR Screens Reveal Host Factors Critical for SARS-CoV-2 Infection

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Distribution and migration of Mississippi Kites in South America

Mississippi Kites (Ictinia mississippiensis) are trans‐equatorial, long‐distance migrants that breed in North America and overwinter in South America. Information about their migration routes and winter distribution in the Neotropics is mostly anecdotal. By compiling records of Mississippi Kites in South America from the literature and previously unpublished observations (1904–2010), we identified 96 locality records (a location where a flock or individual was recorded) and 146 independent records of flocks (observations of flocks irrespective of year, location, or time of year). Our locality records included 38 (39%) during southbound migration (1 September–30 November), 18 (19%) during northbound migration (15 February–30 April), 38 (39%) during austral summer (1 December–14 February), and two (3%) during austral winter (1 May–31 August). Most Mississippi Kites (84, 88%) were observed between the 11°S and 32°S latitudinal band in central South America. Of our independent records of flocks, 133 (92%) were observed between 11°S and 32°S, 12 (7%) between 11°N and 10°S, and a lone vagrant (1%) between 33°S and 43°S. Our data suggest that Mississippi Kites are common and widespread in the austral summer between 11°S and 32°S in central South America. On the basis of the number of locality records (N = 52, 54%) and number of flocks of Mississippi Kites observed between 22°S and 32°S (N = 61, 42%), the Chaco forest appears to be the main wintering grounds for the species. However, additional monitoring is needed to further test this hypothesis. A large portion of Chaco habitat is now under cultivation, and how this habitat transformation might influence the annual cycle of Mississippi Kites is unknown.     

Environmental margin and island evolution in Middle Eastern populations of the Egyptian fruit bat

Here, we present a study of the population genetic architecture and microevolution of the Egyptian fruit bat (Rousettus aegyptiacus) at the environmental margins in the Middle East using mitochondrial sequences and nuclear microsatellites. In contrast to the rather homogenous population structure typical of cave‐dwelling bats in climax tropical ecosystems, a relatively pronounced isolation by distance and population diversification was observed. The evolution of this pattern could be ascribed to the complicated demographic history at higher latitudes related to the range margin fragmentation and complex geomorphology of the studied area. Lineages from East Africa and Arabia show divergent positions. Within the northwestern unit, the most marked pattern of the microsatellite data set is connected with insularity, as demonstrated by the separate status of populations from Saharan oases and Cyprus. These demes also exhibit a reduction in genetic variability, which is presumably connected with founder effects, drift and other potential factors related to island evolution as site‐specific selection. Genetic clustering indicates a semipermeability of the desert barriers in the Sahara and Arabian Peninsula and a corridor role of the Nile Valley. The results emphasize the role of the island environment in restricting the gene flow in megabats, which is also corroborated by biogeographic patterns within the family, and suggests the possibility of nascent island speciation on Cyprus. Demographic analyses suggest that the colonization of the region was connected to the spread of agricultural plants; therefore, the peripatric processes described above might be because of or strengthened by anthropogenic changes in the environment.