土埋深度影响物种水平的种子质量-种子出苗关系

种子出苗对种间关系和群落组成具有重要影响。种内研究表明种子质量与种子出苗之间存在正相关关系, 但这种关系很少在物种水平进行检验, 尤其是在不同土壤埋藏深度条件下。为此, 该文开展了一个因子实验(10种植物和5种土埋深度(0、1、2、4和8 cm))以检验是否在不同土层中“种子质量-种子出苗之间的正相关关系”始终存在。该文在不同土埋深度播种50粒种子(重复5次), 连续30天观测种子出苗, 并提出了一个耐土埋性指标。结果表明: (1) 10种植物的最适出苗深度为0-2 cm土层; 6种植物的最大出苗率发生在1 cm土埋深度。(2)种子质量与耐土埋性之间存在显著的正相关关系, 种子质量越大耐土埋性越强, 适宜出苗的土层越深。(3)当土层较深(4或8 cm)时, 种子出苗率和持续出苗时间随种子质量增加而增大, 种子出苗率与持续出苗时间之间存在正相关关系; 这些关系在较浅土层(0、1或2 cm)并不存在。这些结果有助于进一步理解种子大小与出苗之间的关系, 以及种子出苗过程中的策略。     

Parallel pathways coordinate crawling in the medicinal leech,Hirudo medicinalis

Changes in the behavior of crawling leeches were investigated after various kinds of manipulations, including selective transection or inactivation of body parts, as well as partial or complete transection of the central nerve cord, using a frame-by-frame analysis of video tapes of the crawling animals. From these studies, we found that: 1. Leeches made rhythmic crawling cycles even after their suckers were prevented from contacting the substrate by covering them over with glue. Hence, engagement and disengagement of the suckers are not necessary links in the crawling cycle. 2. Cutting the small, medial connective (Faivre's nerve) had no influence on crawling, but contraction during the whole-body shortening reflex was interrupted. Thus two behaviors which use the same motor output (i.e., whole-body shortening and the contraction phase of crawling) are mediated by two different pathways. 3. Cutting all the connectives between two ganglia in the middle of the leech resulted in a loss of coordination between the parts of the animal on either side of the cut. Therefore, temporally coordinated sucker activity must be mediated through these connectives. 4. Pieces of leech bodies produced by complete transection produced rhythmic crawling cycles as long as the pieces included the head or tail plus 2–4 adjacent midbody segments. In all cases, the crawling movements progressed without delays as the movements reached the cut ends. Pieces of animals that included only midbody segments did not produce crawling movements. 5. These results can be explained by a model composed of intersegmental pathways for both elongation and contraction, circuits in the head and tail brains that switch between elongation and contraction, and both ascending and descending inhibitory influences that determine when the cycle switches from elongation to contraction and back again.Abbreviations C1-C7 caudal segments 1 through 7 (comprise the tail sucker) - Circ. circular muscle(s) - CD circular element driver - CPG central pattern generator - ED elongation element driver - El elongation - El _init initiation of elongation - FN Faivre's nerve - fs + front sucker attachment - s— front sucker release - Long longitudinal muscle(s) - M1-M21 midbody segments 1 through 21 - R1-R4 rostral segments 1 through 4 (comprise the head) - rs + rear sucker attachment - rs rear sucker release - Sens sensory input - SR stretch receptors(s) - ti tonic inhibition     

Feeding strategies of Japanese monkeys against deterioration of habitat quality

Field observations of the feeding behaviour of Japanese monkeys were carried out from autumn to winter on Kinkazan Island which is covered with cool temperate forest. As a result, the following two points became clear: (1) the available food items were fixed for a long time; and (2) the habitat quality deteriorated monotonously because the monkeys themselves or their competitors, such as wild mice, utilized the food resources. Against the decrease in food intake caused by this deterioration of the habitat quality, the monkeys controlled the decrease in food intake by employing the following strategies: (1) they recovered their feeding speed by exploiting new food patches (patch-increase strategy); (2) they extended the time spent on feeding (time-extension strategy); and (3) they changed their food (food-change strategy). The former two strategies operated earlier than the third one.     

Is the scaling of swim speed in sharks driven by metabolism?

The movement rates of sharks are intrinsically linked to foraging ecology, predator–prey dynamics and wider ecosystem functioning in marine systems. During ram ventilation, however, shark movement rates are linked not only to ecological parameters, but also to physiology, as minimum speeds are required to provide sufficient water flow across the gills to maintain metabolism. We develop a geometric model predicting a positive scaling relationship between swim speeds in relation to body size and ultimately shark metabolism, taking into account estimates for the scaling of gill dimensions. Empirical data from 64 studies (26 species) were compiled to test our model while controlling for the influence of phylogenetic similarity between related species. Our model predictions were found to closely resemble the observed relationships from tracked sharks, providing a means to infer mobility in particularly intractable species.     

The annual cycle of a trans-equatorial Eurasian-African passerine migrant: different spatio-temporal strategies for autumn and spring migration

The small size of the billions of migrating songbirds commuting between temperate breeding sites and the tropics has long prevented the study of the largest part of their annual cycle outside the breeding grounds. Using light-level loggers (geolocators), we recorded the entire annual migratory cycle of the red-backed shrike Lanius collurio, a trans-equatorial Eurasian-African passerine migrant. We tested differences between autumn and spring migration for nine individuals. Duration of migration between breeding and winter sites was significantly longer in autumn (average 96 days) when compared with spring (63 days). This difference was explained by much longer staging periods during autumn (71 days) than spring (9 days). Between staging periods, the birds travelled faster during autumn (356 km d(-1)) than during spring (233 km d(-1)). All birds made a protracted stop (53 days) in Sahelian sub-Sahara on southbound migration. The birds performed a distinct loop migration (22 000 km) where spring distance, including a detour across the Arabian Peninsula, exceeded the autumn distance by 22 per cent. Geographical scatter between routes was particularly narrow in spring, with navigational convergence towards the crossing point from Africa to the Arabian Peninsula. Temporal variation between individuals was relatively constant, while different individuals tended to be consistently early or late at different departure/arrival occasions during the annual cycle. These results demonstrate the existence of fundamentally different spatio-temporal migration strategies used by the birds during autumn and spring migration, and that songbirds may rely on distinct staging areas for completion of their annual cycle, suggesting more sophisticated endogenous control mechanisms than merely clock-and-compass guidance among terrestrial solitary migrants. After a century with metal-ringing, year-round tracking of long-distance migratory songbirds promises further insights into bird migration.     

Terminal speed and size sorting of insect eggs

Engineering data for improving the design of applicators for beneficial insect's eggs and facilitating egg cleaning at mass-rearing plants are presented. A vertical air column was developed to measure terminal speed of beneficial insect eggs. Raw material was sorted into fractions according to terminal speed and photos were taken for measuring dimensions of particles. Particle distribution was evaluated for two beneficial insect eggs used in biological control (Chrysoperla rufilabris and Ephestia kuehniella eggs parasitized by Trichogramma brassicae) and for one unparasitized host eggs (E. kuehniella). Density measurements were performed as these data were required for calculating terminal speeds using the theory of free falling bodies. Unparasitized E. kuehniella and C. rufilabris eggs stored at 5°C showed constant terminal speed (1.9 and 1.34 m/s, respectively) and density (1.05 g/cm³, for both). Terminal speed of parasitized E. kuehniella eggs decreased from 1.32 to 1.06 m/s with increasing storage time (4-8 days). Photos of subsamples suggested that aerodynamic cleaning could be used for improving the quality of raw eggs. Density evaluations showed that parasitized eggs can be separated by flotation in water. Calculated terminal speeds were accurate for unparasitized eggs but were 10-20% overestimated for parasitized eggs.     

Tail variation of the folding primer affects the SmartAmp2 process differently

Folding primer (FP), together with turn-back primer (TP) and boost primer (BP), is one of the major components of SmartAmp2, a rapid amplification-based method for SNP detection. FP has a unique design where the annealing region is combined with a tail that can fold back. FP tails can be classified as either “strong” or “weak”, depending on the melting temperature and free energy of the hairpin structure. We report that FP tails affect the amplification process differently; by changing the FP concentration, we can increase the amplification reaction speed with “strong tails”. Unlike “strong tails”, concentration change of FP with “weak tails” did not show significant impact on the amplification speed. The comparative analyses using gel electrophoresis demonstrate that the FP type and FP ratio in the reaction change the amplification pattern. The above observations can be used to optimize the reaction and manipulate the reaction speed of SmartAmp2.     

The association between meteorological variables and the abundance of Aedes taeniorhynchus in the Florida Keys

The black salt marsh mosquito, Aedes taeniorhynchus, is a serious nuisance pest and a potential vector of a number of arboviruses. This study examined the effect of wind direction, wind speed, temperature, and time of year on the abundance of Ae. taeniorhynchus collected in CO₂‐baited light traps at 12 sites in the Florida Keys during 2004. The dependent variable analyzed was the natural log of weekly mosquito abundance. The previous week's wind speed and wind direction, and the current week's temperature were used as independent variables. Simple and multiple linear regression models were used to assess the significance and nature of association between the meteorological variables and the natural log of mosquito abundance, and to determine whether the meteorological variables had significant associations with mosquito abundance after also controlling for time of year. Week of year was treated as a circular independent variable in the regression models, using the sine and cosine of week in radians to model the periodic seasonal fluctuation in mosquito abundance. Mosquito abundance was significantly associated with all meteorological variables and with week of year. Individually, previous week's wind speed and wind direction, and current week's temperature were able to explain respectively 24.5%, 24.5%, and 52.1% of the variation in mosquito abundance observed over the year. Week of year had the strongest individual association with mosquito abundance, explaining 65.7% of the variation in mosquito abundance. The meteorological variables were still significantly associated with mosquito abundance, after controlling for week of year. Week and the meteorological variables together explained 79.2% of the variation in mosquito abundance. The regression models fit to the data from this study suggest a strong periodic seasonal variation in mosquito abundance, with meteorological conditions explaining a significant portion of the variation beyond the seasonal trend.