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- KOREAN
- P-ISSN2287-8327
- E-ISSN2288-1220
- SCOPUS, KCI
ISSN : 2287-8327
Vol.31 No.2
Abstract
Sensing the approach of a predator is critical to the survival of prey, especially when the preyhas no choice but to escape at a precisely timed moment. Escape behavior has been approached from both proximate and ultimate perspectives. On the proximate level, empirical research about electrophysiological me-chanisms for detecting predators has focused on vision, an important modality that helps prey to sense approa-ching danger. Studies of looming-sensitive neurons in locusts are a good example of how the selective sensitivity of nervous systems towards specific targets, especially approaching objects, has been understood and realis-tically modeled in software and robotic systems. On the ultimate level, general optimality models have provided an evolutionary framework by considering costs and benefits of visually elicited escape responses. A recent pa-per showed how neural network models can be used to understand the evolution of visually mediated antipre-datory behaviors. We discuss this new trend towards integration of these relatively disparate approaches, the proximate and the ultimate perspectives, for understanding of the evolution of behavior of predators and prey. Focusing on one of the best-studied escape pathway models, the Orthopteran LGMD/DCMD pathway, we discus how ultimate-level optimality modeling can be integrated with proximate-level studies of escape behaviors in animals.
Abstract
Subsocial behavior of the genus Cryptocercus cockroaches has been believed as primitive traits of termite eusociality. Thus, it has been believed that understanding Cryptocercus subsociality is a pre-requisite stage to infer evolutionary route of the eusociality in termites. Woodroaches of Cryptocercus are also well known because of its peculiar characteristics including adults living monogamously in pairs, semelparous reproduction, xylophagy, obligatory association between adults and their offspring, slow development, and anal trophallaxis by adults. Based on the previously accumulated data, we try to understand two major components of Cryptocercus life history, development and reproduction. We hypothesize that harsh winter and length of winter might be one of the main causes driving the appearance of the delayed development and semelparous reproduction in Cryptocercus life history.
Abstract
We measured a set of 37 morphological characteristics in 97 specimens of adult Korean chub, Zacco koreanus, trapped in the Milyang River, Korea, in May and October of 2005. Twelve out of thirty-seven morphometric measurements were significantly different between the sexes. In particular, both the pectoral fin length and the direct distance between the insertion of the dorsal fin and the insertion of the anal fin were highly significant (p < 0.001). This sexual dimorphism may reflect the outcome of sexual selection in this species.
Abstract
We describe plant biomass in the grasslands of the Mongolian steppe obtained using a quadrat sampling technique. Four sites were studied in the northeastern Mongolia located between 47°12'N and 47°40'N and 102°22'E and 112°24'E, which were typical grasslands of the steppe. Biomass, carbon and nitrogen content were determined for the plants collected from the grazed and ungarazed stands. With the measurements above, we expect to obtain information on grazing effects on the grasslands and carbon sequestration of the grassland from the air. In order to estimate the biomass without destroying the stands, we derived an equation to describe the relationship between plant biomass and v-value using plant height and species coverage within the stand. Estimated plant biomass in the ungrazed and grazed stands ranged between 108.0 g m-2 and 13.4 g m-2 and between 97.5 g m-2 and 14.1 g m-2 in late June 2005, respectively. Litter in the ungrazed and grazed stands ranged from 330.3 g m-2 to 78.4 g m-2 and from 188.0 g m-2 to 20.3 g m-2, similarly. Average carbon and nitrogen contents in plants and in litter were 43.0% and 1.9% and 33.7% and 1.4%, respectively. In study sites at Baganuur, the carbon and nitrogen content of plant materials (plant plus litter) was 118.4 g m-2 and 4.7 g m-2 on 30 June 2005.
Abstract
To predict Daphnia secondary productivity along a trophic gradient indexed as total phosphorus(TP) concentration, we estimated energy transfer efficiencies from food quality for Daphnia such as eicosa-Daphnia magna growth experiments were conducted with seston from 9 lakes, ponds and river waters. Primary productivities were estimated from food supply rates in the flow-through experiments, producing energy transfer efficiencies from seston to D. magna. We found DHA content was the best predictor of energy transfer efficiencies among the essential fatty acids. An asymptotic saturation model explained 79.6% of the variability in energy transfer effi-ciencies. Based on empirical data in this study and empirical models from literature, we predict that Daphnia productivity would peak in mesotrophic systems by decreasing food quality and increasing food quantity along trophic gradient.
Abstract
This study investigated the population densities and diversity of heterotrophic bacteria, and the rhizosphere-to-soil ratios (R/S) in the rhizosphere soil of halophyte Phragmites communis at the western coastal mudflats of Korea. The population densities of aerobic heterotrophic bacteria on the rhizosphere soil of P. communis were in the range of 3.3 ± 0.9 × 107~1.2 ± 0.5 × 108 cfu g-1 dry weight (d. wt.). Population densities of amylolytic bacteria ranged from 1.1 ± 0.2 × 106 to 3.0 ± 1.2 × 106 cfu g-1 d. wt., while those of cellulolytic bacteria and proteolytic bacteria ranged from 5.6 ± 2.3 × 106 to 1.5 ± 0.3 × 107 cfu g-1 d. wt. and from 1.4 ± 0.3 × 106 to 3.5 ± 2.3 × 107 cfu g-1 d. wt., respectively. The R/S ratios ranged from 2.26 to 6.89. Genetic (16S DNA) analysis of fifty-one isolates from the roots of P. communis suggested that the dominant species were closely related to the γ-proteobacteria group (18 clones) and the α-proteobacteria group (14 clones). We found that halophyte species and mudflat environment both affected the rhizosphere bacterial communities.
Abstract
To clarify the relationship between the timing and the duration of flowering among populations, plants, and individual flowers, the dates of flower budding, flowering and deflowering were monitored for ten woody species from March 1 to June 30, in 2005, 2006 and 2007, in temperate deciduous forests at three sites of Namsan, and individual plants from seven woody species were monitored from March 1 to May 31, in 2006. Total durations of flower budding, flowering, and deflowering varied among the plant species. Three durations of these phenological stages of Stephanandra incisa were the longest (74 days, 109 days, and 101 days, respectively), and those of Prunus serrulata var. spontanea were the shortest (7 days, 7 days, and 4 days, respectively). For each species, phenological durations varied among years but were similar among the study sites in the same year. There was no relationship between flowering time and flowering duration on the population level. On the plant level, the duration of flower budding was over 11 days in all specie; S. incisa had the longest duration (73.3 days), and that of Styrax japonica was long as well (29.0 days), while that of Prunus leveilleana was the shortest (11.3 days). The longer the mean flower budding duration, the greater the difference among the plants within a species. The flowering duration of for S. incisa was 92.2 days, while that of Forsythia koreana was 27.2 days. The flowering durations of all other species were 10～20 days. The deflowering duration was 92.0 days in S. incisa and <15 days in all other species. Differences among the plants in deflowering duration were smaller than those of the other phenological stages. In the species that flowered in April, the correlation coefficient between the flowering duration and the first flowering date was negative and significant. However, in the species that flowered in May, the correlation between flowering duration and the first flowering date was not significant. For individual plants of all species except for S. alnifolia, the earlier the flowering time, the longer the flowering duration. Differences between flowering time and flowering duration across years were significant in six species.
Abstract
Feding methods of five species of herons and egrets were studied in an agricultural landscapein Asan city, Chungcheongnam-do, Korea in 2006. Grey herons primarily hunted while standing, whereas great egrets fed while walking slowly. Two smaller species, little and cattle egrets, were active foragers, feeding both while walking quickly and walking slowly. Little egrets were the only species using the foot stirring method. The medium-sized heron, intermediate egrets, foraged mainly while walking slowly or leaning. For grey herons, great egrets and little egrets, the frequency of use of different feeding methods was different between habitats: these species used the leaning method more frequently in rice fields than in reservoirs and ditches. Also, most herons (all species other than great egrets) showed seasonal changes in their feeding methods that are related to changes in habitat condition.
Abstract
The timing of the canopy phenology onset (CPO hereafter) indicates the initiation of the growing season, with rapid increases in exchange rates of carbon dioxide and water vapor between vegetation and atmosphere. The CPO is regarded as a potential indicator of ecosystem responses to global warming, but the CPO shows considerable spatial variation depending on the species composition and local temperature regime at a given geographic location. In this study, we evaluated the utility of satellite observation data for detection of the timing of the CPO. Leaf area indices (LAI) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) were utilized to detect and map the onset dates from 2001 to 2006. The reliability of MODISbased onset dates was evaluated with ground measured cherry blossom flowering data from national weather stations. The MODIS onset dates preceded the observed flowering dates by 8 days and were linearly related with a correlation coefficient of 0.58 (p < 0.05). In spite of the coarse spatial (1 km) and temporal (8 days) resolutions of MODIS LAI, the MODIS-based onset dates showed reasonable ability to predict flowering dates.
Abstract
This study was performed for the purpose of monitoring monthly levels of two pathogenic microorganisms, Cryptosporidium and Giardia, from November 2005 to August 2007 in Sangsa Lake. Water temperatures, pH and DO fluctuated seasonally at the study site. Annual mean values of BOD, COD and SS were 0.8 mg L-¹, 2.3 mg L-¹ and 1.9 mg L-¹, respectively. Although there was distinct seasonal variation in water chemistry and chlorophyll a concentration, the lake generally contains low concentrations of nutrients and chlorophyll a. The relative abundance of coliform bacteria was always greater than that of fecal coliform. The fecal coliform bacteria comprised 8.5~22.1% of total coliform bacteria. Seasonal analysis of Cryptosporidium and Giardia levels in the study site showed that in winter (November through February), Cryptosporidium oocysts and Giardia cysts were most abundant (1.1~1.8 × 10 cells L-¹ and 3.8~5.1 × 10 cells L-¹, respectively), while in summer (July through September) the abundance was lowest (0.0~0.3 × 10 cells L-¹ and 0.9~2.9 × 10 cells L-¹, respectively). Molecular identification revealed two subtypes of Cyrptosporidium parvum in Sangsa Lake.