bluuebunny/crossref_metadata_2025 huggingface dataset:
A high molecular weight glycoprotein in seminal plasma is a sperm immobilizing factor in the teleost Nile tilapia, Oreochromis niloticus
Authors: Mochida Kazuhiko , Kondo Tomoko , Matsubara Takahiro , Adachi Shinji , Yamauchi Kohei
Published: March 2003

Sperm that have acquired potential for motility are kept immotile in seminal plasma in the teleost, Nile tilapia. In order to investigate the mechanism of immobilization, several experiments were performed using a previously characterized monoclonal antibody (TAT‐30) against a molecular weight (Mr) = 120 000 protein that is secreted by Sertoli cells and epithelial cells of the sperm duct, and is also bound to the head of the spermatozoon. First, we assessed sperm motility in the seminal plasma protein fraction (SPP), and demonstrated that the sperm motility is inhibited by SPP in a concentration‐dependent manner. Furthermore, sperm motility was recovered if SPP was pretreated with TAT‐30, suggesting that the TAT‐30 antigen is one of the components of the sperm immobilizing factor. Calibration by gel filtration followed by sodium dodecylsulfate‐ polyacrylamide gel electrophoresis (SDS‐PAGE) and western blotting with TAT‐30 demonstrated that the sperm immobilizing factor was more than Mr = 1 000 000 in seminal plasma, suggesting that it is a homopolymer of the Mr = 120 000 – TAT‐30 positive protein. Additionally, lectin blot analysis showed that the TAT‐30 antigen was reactive with Lens culinarin agglutinin (LCA) and Conavalia ensiformis agglutinin (ConA), indicating that it is a glycoprotein. Immunohistochemical studies showed that the TAT‐30 antigen was localized specifically on the heads of spermatozoa and on the apical surface, lysosomes and rough endoplasmic reticulum of Sertoli cells.
Germline‐specific expression of the Oct‐4/green fluorescent protein (GFP) transgene in mice
Authors: Yoshimizu Tomomi , Sugiyama Noriyuki , De Felice Mario , Yeom Young Ii , Ohbo Kazuyuki , Masuko Kazue , Obinata Masuo , Abe Kuniya , Schöler Hans R. , Matsui Yasuhisa
Published: March 2003

The Pic‐1, Oct‐1,2, Unc‐86 (POU) transcription factor Oct‐4 is specifically expressed in the germ cell line, and a previous study has indicated that the expression of the lacZ gene inserted into an 18 kb genomic fragment encompassing the Oct‐4 gene can come close to mimicking the endogenous embryonic expression pattern of Oct‐4 in transgenic mice. In the present study transgenic mice expressing green fluorescent protein (GFP) in the germ cell line were generated using the same Oct‐4 genomic fragments and the expression pattern was analyzed in detail through all stages of germ cell development. The GFP expressing primordial germ cells were first detected as early as 8.0 days post‐coitum (d.p.c.; early head fold stage) at the base of the allantois in living embryos. The GFP expression was thereafter found in both male and female germ cells at all developmental stages except in male germ cells after differentiating into type A spermatogonia in the postnatal testis. There was also a lower level of expression in female germ cells in the prophase of the first meiotic division. These transgenic mice therefore proved to be powerful tools for isolating living germ cells at various developmental stages to study their nature and to isolate new genes.
Distinct expression of midkine and pleiotrophin in the spinal cord and placental tissues during early mouse development
Authors: Fan Qi‐Wen , Muramatsu Takashi , Kadomatsu Kenji
Published: March 2003

Midkine and pleiotrophin comprise a family of heparin‐binding growth factors, and are expressed in overlapping tissues during the mid‐ to late‐gestation periods of mouse development. Their distinct expression during early mouse development, as revealed by in situ hybridization, was reported. Midkine was expressed in the embryonic ectoderm from as early as embryonic day (E5.5). In the neural tube midkine was expressed specifically in the neuroepithelium, that is, in the whole area of the neural tube at E9.5, and in the ventricular zone from E10.5–13.5. At E15.5, when the neuroepithelium disappeared, midkine concomitantly became undetectable. In contrast, pleiotrophin expression started exclusively in the neural plate at E8.5, and in the lateral plate of the neural tube at E9.5. It then became restricted to a dorsal ventricular zone from E11.5–13.5, and finally to the central gray neurons at E15.5. Moreover, pleiotrophin was expressed in the ventral horns. Among placental tissues, midkine was detected in the chorion, the fetal component of the placenta, whereas pleiotrophin was found in the decidua basalis, the maternal component of the placenta. The distinct expression of midkine and pleiotrophin suggests their differential role in early development.
Analysis of cartilage maturation using micromass cultures of primary chondrocytes
Authors: Kameda Takashi , Koike Chika , Saitoh Kanako , Kuroiwa Atsushi , Iba Hideo
Published: March 2003

A micromass culture (MM‐C) system of primary immature chondrocytes for functional analysis of soluble factors involved in the maturation step of cartilage was previously developed. Ectopically expressed BMP‐2 was shown to induce the expression of the Ihh and Noggin genes. Here it is demonstrated that, upon longer culture, secreted bone morphogenetic protein‐2 (BMP‐2) further promotes the maturation step as judged by the induction of type X collagen and BMP‐6 expression, which are known to be detectable in the later phase of cartilage maturation. Induction of all of these genes by secreted BMP‐2 was not inhibited by ectopic expression of parathyroid hormone‐related peptide (PTHrP) induced by retrovirus vector infection, although the same virus vector showed strong inhibitory effects on the expression of type X collagen gene or alkaline phosphatase activity in mature chondrocytes. These results suggest that the maturation‐promoting activity exhibited by BMP‐2 is dominant over the suppressive effect of PTHrP in immature chondrocytes. When the BMP‐6 gene was introduced into the same virus vector as that used for BMP‐2, it induced the same sets of genes (Ihh, Noggin, type X collagen and endogenous BMP‐6) as BMP‐2 did. These results also suggest that BMP‐6 would autonomously maintain and/or promote a later stage of chondrocytic maturation.
Egg envelope glycoprotein gp37 as a Xenopus homolog of mammalian ZP1, based on cDNA cloning
Authors: Kubo Hideo , Kawano Takehiro , Tsubuki Satoshi , Kotani Masaharu , Kawasaki Hiroshi , Kawashima Seiichi
Published: March 2003

The egg envelope is a kind of extracellular matrix, which surrounds growing oocytes, ovulated eggs and early embryos. Among the glycoprotein components of the Xenopus laevis egg envelope, gp43/gp41 and gp69/64 have already been shown to be frog homologs of the mammalian zona pellucida components ZP3 and ZP2, respectively. To determine the structure of another major component of egg envelope, gp37, the peptides isolated from the lysyl endopeptidase digests of gp37 were sequenced for amino acids to design degenerate primers for polymerase chain reaction. By reverse transcription–polymerase chain reaction with a poly(A)+ RNA from the ovary of a postovulated female Xenopus, a specifically amplified band was obtained and sequenced. The upstream and downstream sequences of the sequenced region were completed by 5′‐ and 3′‐rapid amplification of cDNA ends, respectively. The gp37 cDNA comprises 1674 bp and contains one open reading frame encoding a polypeptide with 543 amino acids. The predicted amino acid sequence of the gp37 cDNA has a close similarity to that of mammalian ZP1. Northern blot and in situ hybridization studies indicated that the transcript (1.8 kb) is exclusively expressed in the oocytes, particularly in the previtellogenic young oocytes, just like the expression pattern of gp43 mRNA, suggesting a coordinate transcription of the gp43 and gp37 genes in Xenopus.
Development and fine structure of the yolk nucleus of previtellogenic oocytes in the medaka Oryzias latipes
Authors: Kobayashi Hirokuni , Iwamatsu Takashi
Published: March 2003

The development and fine structure of yolk nuclei in the cytoplasm of previtellogenic oocytes were examined by electron microscopy during several stages of oogenesis in the medaka, Oryzias latipes. Shortly after oogenesis starts, oocytes 20–30 μm in diameter have much electron‐dense (basophilic) cytoplasm, within which a continuous or discontinuous, irregular ring‐shaped lower electron‐dense area of flocculent appearance (LF) begins to emerge around the nucleus. The yolk nucleus is first recognized within an LF area as a few fragments of dense granular thread measuring 20–25 nm in width. The threads consist of two rows of very dense granules resembling ribosomes or ribonucleoprotein (RNP)‐like particles in size and electron density. These thread‐like fragments gradually increase in number and length until they assemble into a compact, spherical mass of complicated networks. Analysis of serial sections suggests that the yolk nucleus is a complicated mass of numerous, small deformed vacuoles composed of a single lamella with double layers of ribosomes or RNP‐like granules, rather than a mass of granular threads. When oocytes develop to greater than 100 μm in diameter, the yolk nucleus begins to fragment before dispersing throughout the surrounding cytoplasm, concomitantly with the disappearance of LF areas. At this stage of oogenesis, a restricted region of the granulosa cell layer adjacent to the yolk nucleus becomes somewhat columnar in morphology, fixing the vegetal pole region of the oocyte.
Planarian fibroblast growth factor receptor homologs expressed in stem cells and cephalic ganglions
Authors: Ogawa Kazuya , Kobayashi Chiyoko , Hayashi Tetsutaro , Orii Hidefumi , Watanabe Kenji , Agata Kiyokazu
Published: March 2003

The strong regenerative capacity of planarians is considered to reside in the totipotent somatic stem cell called the ‘neoblast’. However, the signal systems regulating the differentiation/growth/migration of stem cells remain unclear. The fibroblast growth factor (FGF)/FGF receptor (FGFR) system is thought to mediate various developmental events in both vertebrates and invertebrates. We examined the molecular structures and expression of DjFGFR1 and DjFGFR2, two planarian genes closely related to other animal FGFR genes. DjFGFR1 and DjFGFR2 proteins contain three and two immunoglobulin‐like domains, respectively, in the extracellular region and a split tyrosine kinase domain in the intracellular region. Expression of DjFGFR1 and DjFGFR2 was observed in the cephalic ganglion and mesenchymal space in intact planarians. In regenerating planarians, accumulation of DjFGFR1‐expressing cells was observed in the blastema and in fragments regenerating either a pharynx or a brain. In X‐ray‐irradiated planarians, which had lost regenerative capacity, the number of DjFGFR1‐expressing cells in the mesenchymal space decreased markedly. These results suggest that the DjFGFR1 protein may be involved in the signal systems controlling such aspects of planarian regeneration as differentiation/growth/migration of stem cells.
Involvement of the signal transduction pathway mediated by epidermal growth factor receptor in the differentiation of chicken glandular stomach
Authors: Takeda Jun , Tabata Hidenori , Fukuda Kimiko , Yasugi Sadao
Published: March 2003

During the development of the chicken proventriculus (glandular stomach), the initially undifferentiated epithelium differentiates into two distinct cell populations: the glandular epithelium, cells of which secrete embryonic chicken pepsinogen (ECPg), and luminal epithelial cells, which express the chicken spasmolytic polypeptide gene (cSP). Based on knowledge of the adult mouse stomach, the ligands of epidermal growth factor (EGF) receptor (EGFR) were expected to affect differentiation of the proventricular epithelium. When EGF was added to the medium in which proventriculi were culturedin vitro, gland formation was suppressed in a dose‐dependent manner and the amount ofECPgmRNA decreased, whereas morphological differentiation of luminal epithelium was stimulated. Simultaneous treatment of the proventriculus with EGF and tyrphostin 47 resulted in the attenuation of the effect of EGF, suggesting that EGF, or other ligands of EGFR, may actually be involved in the normal course of development of the proventricular epithelium.
Distribution and turnover of a mosquito (Tripteroides bambusa) metapopulation among bamboo groves
Authors: Sunahara Toshihiko , Mogi Motoyoshi
Published: March 2003

We surveyed the distribution of a mosquito, Tripteroides bambusa (Yamada), among patchily distributed bamboo groves from 1994 to 1997 in an area of 4 km × 4 km in Saga, south‐western Japan. In the study area, this mosquito uses mainly water‐filled bamboo stumps as its larval habitat. In 1994, a year with little rainfall in the summer, T. bambusa larvae were found in 30 of the 60 groves that contained water‐filled bamboo stumps. By 1997, the number of occupied groves increased to 64, and the number of groves with water‐filled stumps increased to 109. Tripteroides bambusa was found frequently in the area covered by an orange orchard where bamboo groves were dense, and rarely in the open land where bamboo groves were sparse. Colonization of T. bambusa occurred in groves in the orchard and the open land which were less than 0.57 km away from the nearest occupied grove. Large groves were more likely to be occupied, and extinction occurred only in small groves (≤ 0.104 ha). Groves without water‐filled stumps in 1994 were less likely to be occupied in the following period than those with water‐filled stumps in 1994. These findings suggest that the T. bambusa metapopulation will not extend its distribution into all of the bamboo groves in the study area, but will not become extinct because of some highly persistent populations.
Costs and benefits for water strider (Aquarius paludum) females of carrying guarding, reproductive males
Authors: Amano Hideki , Hayashi Kooji
Published: March 2003

We describe the mating system of Aquarius paludum insularis based on field observations and test hypotheses about the effects of body size, hunger level and post‐copulatory guarding on reproductive performance. The mating sequence of this species was typical for temperate water striders, except that most oviposition was carried out by tandem pairs, most of which were submerged. Mate guarding continued until the end of oviposition, lasting up to 18.2 h, which was much longer than that recorded for other species of water striders. Pair partners changed after oviposition. Extended contact guarding reduced female mobility. In the case of females that carried long‐winged males, there was a significant reduction in speed and stride between tandem as opposed to single females. However, when short‐winged males were carried, there was not a significant difference. Short‐term foraging efficiency did not differ significantly between tandem and single females, and thus did not reflect the difference in mobility. Hunger level did not significantly affect female mating receptivity. Although the number of harassment bouts by unpaired males did not differ between single and tandem females, single females suffered significantly more harassment. Females were able to lay fertilized eggs for about 15 days after a single copulation, but they accepted long guarding and multiple mating during this period as well. The cost of resisting male mating attempts appears to be greater than the cost of carrying males.
Species dynamics and colonization patterns in an abandoned forest in an urban landscape
Authors: Bhuju Dinesh , Ohsawa Masahiko
Published: March 2003

Species dynamics in an abandoned urban forest of Central Japan is described in this paper. The dominant species in the urban plantation were Cryptomeria japonica and Chamaecyparis obtusa. A variety of eight patches of the canopy was produced by previous forest management practices. Progressive and retrogressive species dynamics within these eight patches are investigated in this paper. The study elucidates the deterministic role of patchiness in the nature of species colonization and the maintenance of species diversity in an urban forest. Altogether 139 native and/or naturalized species, including 23 shrub and 35 tree species, were recorded in the study area of 3.2 ha. The performance of species varied according to their successional attributes indicating a selective canopy influence. Twenty percent of the tree species were shade‐intolerant pioneers (e.g. Cornus spp., Rhus javanica var. roxburghii) re‐established under selective tree‐felling. Thirty percent were shade‐tolerant climax species (e.g. Neolitsea sericea, Persea thunbergii) dominant in remnant closed patches. The remaining 50% belonged to various seral types with aggressive deciduous species (e.g. Aphananthe aspera, Celtis sinensis) in most of the patches. Some ruderal herbaceous species dominated heavily disturbed clear‐felled patches. This study suggests that canopy modification influences the subsequent colonization pattern. Furthermore, heterogeneous patches contribute to greater species diversity and dynamics in isolated woodlands.
Insect feeding on spores of a bracket fungus, Elfvingia applanata (Pers.) Karst. (Ganodermataceae, Aphyllophorales)
Authors: Tuno Nobuko
Published: March 2003

Insects visiting sporocarps of Elfvingia applanata, a wood‐rotting bracket fungus, were examined in Kyoto, central Japan. Mycodrosophila flies (Drosophilidae: Diptera) were predominant and visited the spore‐producing sporocarps exclusively. They were observed feeding on the spores, and a number of spores seemed to be alive even after having passed through insects’ digestive tracts. In addition, the insects attached a number of spores on their body surfaces. In a rearing experiment with insects caught from E. applanata sporocarps, Mycodrosophila flies excreted 7700–469 000 and dropped 10 000–329 000 of viable spores during 48 h after collection. They were supposed to migrate among the sporocarps of other bracket fungi growing on different logs or stumps, suggesting that Mycodrosophila flies may act as spore‐dispersal agents for E. applanata.
Lichens as bioindicators of temporal variations in air quality around Thessaloniki, northern Greece
Authors: Vokou Despina , Pirintsos Stergios ArG. , Loppi Stefano
Published: March 2003

The epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia, northern Greece) surveyed in 1987 was sampled again in 1997 to monitor any changes in lichen communities and consequently in air quality. A general impoverishment in lichen communities was recorded in the 10‐year period, presumably chiefly due to changes in the air pollution status. A small increase in lichen species diversity was recorded in some stations, probably as a result of the buffering capacity of airborne dust.
Habitat selection by wintering tufted ducks with special reference to their digestive organ and to possible segregation between neighboring populations
Authors: Oka Nariko , Yamamuro Masumi , Hiratsuka Junichi , Satoh Hitoshi
Published: March 2003

Habitat selection by tufted ducks (Aythya fuligula), a diving duck which swallows benthic prey organisms, was studied during winter at two neighboring lagoons (Lakes Nakaumi and Shinji, Honshu, Japan) which differ strongly in their benthic fauna and in their diving duck densities. The ducks fed overwhelmingly on the dominant bivalve found in each of the two lagoons, the mussel Musculista senhousia in L. Nakaumi and the clam Corbicula japonica in L. Shinji. In general, however, the ducks probably preferred the mussels to the clams because of: (i) their high (2.9 times) calorific content for their weight; (ii) their high digestibility; (iii) their greater accessibility; and (iv) their shorter handling time. An average tufted duck (850 g) was estimated to require 1.3 kg of mussels or 3.8 kg of clams to meet their daily energy requirements. As a result, the two wintering populations were estimated to consume 4970 t mussels and 4770 t clams during a single wintering season, amounting to some 20% of the standing clam crop. Throughout the winter the average gizzard weight (37 g), and gizzard–body mass ratio (4.2%) of the Lake Nakaumi population were half those of the Lake Shinji population (73 g, 8.1%, respectively), despite their significantly similar nutritive body condition (% body lipid > 12%). The need to maintain a specialized gizzard mass in order to be able to cope with the different prey species results in little opportunity for ‘sampling’ movements of birds between lakes/prey types and as a result two subpopulations of ducks are indicated to be segregated.
Indirect interactions between two aphid species in relation to ant attendance
Authors: Sakata Hiroshi
Published: March 2003

The influence of foraging by the ant,Lasius niger, on the population growth of two aphid species,Lachnus tropicalisandMyzocallis kuricola, on chestnut trees,Castanea crenata, was examined. The ant‐tending effect was divergent depending on the aphid density per ant: it was positive when there were few aphids per ant, but negative when there were many aphids per ant. In addition, the density of one aphid species also influenced the ant‐tending effect on the other aphid. Furthermore, the influences were asymmetrical: an increase inL. tropicalisdensity per ant reversed the ant’s effect on this species and onM. kuricola, while an increase inM. kuricolaper ant did not significantly influence the ant’s effect onL. tropicalis. Thus, the ant seems to stabilize theL. tropicalispopulation density and keep this species from extinction, while the ant’s effect onM. kuricoladepends on the density ofL. tropicalisand may leadM. kuricolato extermination. This change in the ant‐tending effect corresponds to the previously detected density‐dependent change in predation activity of the ants on aphids. In contrast, the density‐dependent change in the protection effect of the ants against natural enemies does not explain the results.
Selective foraging on terrestrial invertebrates by rainbow trout in a forested headwater stream in northern Japan
Authors: Nakano Shigeru , Kawaguchi Yoichi , Taniguchi Yoshinori , Miyasaka Hitoshi , Shibata Yukiyoshi , Urabe Hirokazu , Kuhara Naotoshi
Published: March 2003

The important contribution of terrestrial invertebrates to the energy budget of drift‐foraging fishes has been well documented in many forested headwater streams. However, relatively little attention has been focused on the behavioral mechanisms behind such intensive exploitation. We tested for the hypothesis that active prey selection by fishes would be an important determinant of terrestrial invertebrates contribution to fish diets in a forested headwater stream in northern Japan. Rainbow trout,Oncorhynchus mykiss, were estimated to consume 57.12 mg m−2day−1(dry mass) terrestrial invertebrates, 77% of their total input (73.89 mg m−2day−1), there being high selectivity for the former from stream drift. Both the falling input and drift of terrestrial invertebrates peaked at around dusk, decreasing dramatically toward midnight. In contrast, both aquatic insect adults and benthic invertebrates showed pronounced nocturnal drift. Because the prey consumption rates of rainbow trout were high at dawn and dusk, decreasing around midnight, the greater contribution of terrestrial invertebrates to trout diet was regarded as being partly influenced by the difference in diel periodicity of availability among prey categories. In addition, selectivity also depended upon differences in individual prey size among aquatic insect adults, and benthic and terrestrial invertebrates, the last category being largest in both the stream drift and the trout diets. We concluded that differences in both the timing of supplies and prey size among the three prey categories were the primary factors behind the selective foraging on terrestrial invertebrates by rainbow trout.
A possible relationship between outbreaks of the oriental migratory locust (Locusta migratoria manilensis Meyen) in China and the El NiÃ±o episodes
Authors: Zhang Zhibin , Li Dianmo
Published: March 2003

We investigated the statistical relationship between outbreaks of the oriental migratory locust (Locusta migratoria manilensis Meyen) in the Huang Ho and Huai Ho regions of China and El NiÃ±o episodes during 1905–1959, and discussed how El NiÃ±o affects locust outbreaks. The outbreaks of the locust mostly occurred 1–2 years after the El NiÃ±o episodes. El NiÃ±o was suggested to affect the locust outbreaks by changing the precipitation and air temperature in Northern China.
Phenology of a common roadside fig in Sarawak
Authors: Harrison Rhett D. , Yamamura Norio , Inoue Tamiji
Published: March 2003

The phenology of a dioecious fig (Ficus fulva, Reinw. ex Bl.; 25 female, 26 male trees) was studied at Lambir Hills National Park, Sarawak. Dioecious fig phenology provides an excellent opportunity to investigate the influence of climate and sexual specialization on the obligate fig–fig pollinator/ovule parasite interaction. Leaf phenology was strongly correlated between sexes. Trees dropped leaves during drought and initiated new leaf growth after the renewal of rain. Before the production of large crops of syconia, trees shed their leaves and then new leaves and syconia were initiated together. Syconia were produced in synchronous crops with asynchrony between trees maintaining a relatively even production of syconia within the tree group. Syconia abortion on male but not female trees, was negatively correlated with the proportion of trees with male phase syconia. A severe drought in early 1998 significantly disrupted the phenology thereafter. The duration of crop development was approximately twice as long on female trees as on males, and total syconia production was much higher on male trees. Plots of syconia diameter versus dry weight suggest sexual specialization in the investment profile during crop development. Male trees also sometimes produced a small crop of syconia immediately before a large crop, probably to supply wasps for the main crop. Sexes had different growth strategies with male trees growing more as small individuals and slightly delaying reproduction. Diameter at breast height was significantly correlated with total syconia production in male trees but not in females. Syconia production was best predicted by canopy width.
Bird community composition patterns in urban parks of Madrid: The role of age, size and isolation
Authors: Fernández‐Juricic Esteban
Published: March 2003

This study intends to assess the influence of fragment age, size and isolation (from the regional species pool) on bird community composition patterns in urban parks in Madrid, and the role of local and regional factors on community structure. Park age was a good indicator of habitat complexity. Park age and area accounted for 62% of the variability in species richness, but two measures of isolation from the regional species pool were not included as significant factors. Species composition in urban parks showed a high degree of nestedness, which was associated with park age and area, but not with two measures of isolation from the regional species pool. The degree of nestedness increased with park age; the distribution of species varying from nested in old and mature parks to random in young parks. The incidence (% of species occurrence in parks) in young parks was correlated with regional densities, whereas in mature and old parks the incidence was correlated with local densities. In this urban landscape, species composition appears to be regulated by local factors (particularly in mature and old parks), such that species accumulate in an orderly (not random) fashion in relation to park age and area. Regional influences seem to be more pronounced only in young parks, which are mainly colonized by species from the regional species pool.
Some effects of inclement weather conditions on the survival and condition of bull‐headed shrike nestlings
Authors: Takagi Masaoki
Published: March 2003

Inclement weather struck Japan in 1993, permitting a natural experiment for examining the effect of weather conditions on nesting success and nestling growth of the bull‐headed shrike, Lanius bucephalus. Aspects of the breeding biology of bull‐headed shrikes in relation to weather conditions and timing of breeding in 1992 and 1993 were examined. The two breeding seasons were divided into two periods, early and late, in each year. While the probability of nest survival in nestling stages during both periods was almost equal, the probability of nest survival in the egg stage during the early period was significantly lower than that during the late period. In 1993, the probability of nestling survival during the late period was significantly lower than during the early period; the late period had larger fluctuations of precipitation and was colder than the same period in 1992. The number of ‘disappeared’ nestlings positively correlated with mean precipitation per day. The greater part of the disappeared nestlings was the lightest in each brood. Late breeders fledged lighter young than the early breeders. Although shrikes adopted hatching asynchrony, the late breeders could not surmount the unpredictable inclement weather in 1993.
Experimentally increased insectivorous bird density results in a reduction of caterpillar density and leaf damage to Pyrenean oak
Authors: Sanz Juan José
Published: March 2003

The indirect effect of insectivorous breeding‐bird density on Pyrenean oak (Quercus pyrenaica) through consumption of leaf‐damaging caterpillars in a temperate deciduous forest was examined. Caterpillar abundance, caterpillar body mass and the resultant leaf damage were compared between a plot with nest‐boxes and a plot without nest‐boxes within the same forest. First, the installation of nest‐boxes led to an increase in the breeding population of insectivorous birds. Second, the present study reports experimental evidence, under natural conditions, that a high breeding‐bird density depresses the numbers of free‐living defoliating caterpillars. Third, caterpillars reached significantly lower body masses in the nest‐box plot than in the control plot. Finally, caterpillar damage to oak leaves was significantly less in the nest‐box plot compared with the control plot. Therefore, the installation of nest‐boxes is an effective means of decreasing insect damage to oak leaves. These results suggest that breeding‐bird predation (the third trophic level) can be important in the regulation of interactions between oak and caterpillars (the first and second trophic levels, respectively).
Patterns of bird abundance and habitat use in rice fields of the Kanto Plain, central Japan
Authors: Maeda Taku
Published: March 2003

Rice fields, the most widespread cropland in Japan, provide important habitat for birds, but few studies have examined bird communities that are influenced by agriculture in rice fields. I studied the seasonal pattern of bird abundance and their habitat preferences in terms of agricultural habitats in the rice fields of the central Kanto Plain, central Japan. In total, 19 waterbird species and 31 landbird species were recorded over the study year. Waterbird occurrence was largely restricted to the cultivation season (i.e. the flooded season, May–August), with maximum abundance in August. Rice fields dried up during winter and supported few waterbirds except for irregular occurrences of little egrets (Egretta garzetta) and common snipes (Gallinago gallinago), which selectively used ditches with shallow water. Landbird abundance increased after the start of cultivation (May) to August, but more birds were attracted to the rice fields in midwinter (around January). For both waterbirds and landbirds, most species preferred levees and fallow grass fields, but avoided fields with rice vegetation. Unplowed fields after harvest were preferred by several species including skylarks (Alauda arvensis), while plowed fields were less attractive to most species. These results suggest the need for advanced agricultural practices to include improvement in habitat quality for birds.
Nutrient compositions of acorns and horse chestnuts in relation to seed‐hoarding
Authors: Shimada Takuya
Published: March 2003

Nutritional compositions of acorns (Quercus serrata Thunb. and Quercus mongolica Fisch. var. grosseserrata Rehd. et Wils.) and horse chestnuts (Aesculus turbinata Blume) were analyzed. Major nutrients of acorns and horse chestnuts were carbohydrate, protein and fat. They proved to contain considerable amounts of tannins (7.28–11.72% dry mass−1) and saponins (6.20%), respectively. The nutrients and the secondary metabolites of seeds buried for either 1 month or 3 months were analyzed to evaluate effects of seed‐caching by animals. Noticeable changes were not observed, which suggested that caching may not bring any advantages to the seed‐hoarders with respect to nutrition.
Community diversity and invasion resistance: An experimental test in a grassland ecosystem and a review of comparable studies
Authors: Hector Andy , Dobson Kim , Minns Asher , Bazeley‐White Ellen , Hartley Lawton John
Published: March 2003

The relationship between community diversity and invasion resistance in a grassland was examined using experimental plant assemblages that varied in species richness and composition. The assemblages were weeded for three seasons to remove unsown species and we used the number of weeded seedlings, their total biomass and the number of species removed as indicators of community resistance and susceptibility to invasion. In general, we found a positive relationship between invasion resistance and increasing community diversity. Similar patterns of establishment were observed at the end of the fourth field season after several months without weeding. Increased invasion resistance with higher diversity appears to come through reduced levels of several above‐ and belowground resources, although these did not fully explain the effects of species richness in the study’s analyses. Experimental increases and reductions of litter biomass within the study’s experimental plant assemblages did not modify these patterns significantly. A review of comparable studies of invasion across directly manipulated diversity gradients revealed similar patterns. Positive effects of species diversity on invasion resistance were found in experimental manipulations of plant diversity conducted in the field and in the glasshouse, from studies with aquatic microcosms and in a marine system. Although some exceptions to this pattern were found in both terrestrial plant systems and aquatic microcosms, it was concluded that in biodiversity manipulation experiments more diverse communities are generally more resistant to invasion.
What makes a species vulnerable to extinction? Comparative life‐history traits of two sympatric snakes
Authors: Webb Jonathan K. , Brook Barry W. , Shine Richard
Published: March 2003

Although it is well known that species vary in their vulnerability to extinction, the reasons are poorly understood. Theory predicts that long‐lived species with ‘slow’ life histories (small litters, slow growth, late maturation) should be at greater risk than short‐lived species with high potential rates of increase. This hypothesis was tested by comparing life‐history traits of two species of sympatric, elapid snakes: the endangered broad‐headed snake, Hoplocephalus bungaroides, and common small‐eyed

snake, Cryptophis nigrescens. From 1992 to 2000 a mark–recapture study

of both species was undertaken in Morton National Park, south‐eastern Australia,

and this information was used to construct transition matrices for each species.

The endangered H. bungaroides was found to mature late (6 years of age), had

a high juvenile (54.7%) and adult (81.6%) survival rate, and a long

generation length (10.4 years). In striking contrast, the common C. nigrescens

matured early (within 3 years), had a lower juvenile (30.4%) and adult (74.4%)

survival rate (but higher recruitment rate), and a substantially shorter generation

length (5.9 years). Elasticity analyses revealed that H. bungaroides was considerably

more sensitive to survival past the age of 2 years (68.6%) than C. nigrescens (37.4%). These results provide support for the hypothesis that species with slow life histories are more vulnerable to extinction.
Food webs in space: On the interplay of dynamic instability and spatial processes
Authors: Holt Robert D.
Published: March 2003

Ecologists increasingly recognize that a consideration of spatial dynamics is essential for resolving many classical problems in community ecology. In the present paper, I argue that understanding how trophic interactions influence population stability can have important implications for the expression of spatial processes. I use two examples to illustrate this point. The first example has to do with spatial determinants of food chain length. Prior theoretical and empirical work has suggested that colonization–extinction dynamics can influence food chain length, at least for specialist consumers. I briefly review evidence and prior theory that food chain length is sensitive to area. A metacommunity scenario, in which each of various patches can have a food chain varying in length (but in which a consumer is not present on a patch unless its required resource is also present), shows that alternative landscape states are possible. This possibility arises if top predators moderate unstable interactions between intermediate predators and basal resources. The second example has to do with the impact of recurrent immigration on the stability of persistent populations. Immigration can either stabilize or destabilize local population dynamics. Moreover, an increase in immigration can decrease average population size for unstable populations with direct density‐dependence, or in predator–prey systems with saturating functional responses. These theoretical models suggest that the interplay of temporal variation and spatial fluxes can lead to novel qualitative phenomena.
Effects of rainfall events on soil CO2 flux in a cool temperate deciduous broad‐leaved forest
Authors: Lee Mi‐sun , Nakane Kaneyuki , Nakatsubo Takayuki , Mo Wen‐hong , Koizumi Hiroshi
Published: March 2003

The effects of rainfall events on soil CO2 fluxes were examined in a cool temperate Quercus/Betula forest in Japan. The soil CO2 fluxes were measured using an open‐flow gas exchange system with an infrared gas analyzer in the snow‐free season from August 1999 to November 2000. Soil CO2 flux showed no significant diurnal trend on days without rain. In contrast, rainfall events caused a significant increase in soil CO2 flux. To determine the effect of rainfall events and to evaluate more precisely the daily and annual soil carbon flux, we constructed a multiple polynomial regression model that included two variables, soil temperature and soil water content, using the soil CO2 flux data recorded on sunny days. Daily soil carbon fluxes on sunny days calculated by the model were almost the same as those determined by the field measurements. On the contrary, the fluxes measured on rainy days were significantly higher than those calculated daily from the soil carbon fluxes by the model. Annual soil carbon fluxes in 1999 and 2000 were estimated using models that both do and do not take rainfall effects into consideration. The result indicates that post‐rainfall increases in soil CO2 flux represent approximately 16–21% of the annual soil carbon flux in this cool temperate deciduous forest.
Effects of partitioning allochthonous and autochthonous resources on food web stability
Authors: Huxel Gary R. , McCann Kevin , Polis Gary A.
Published: March 2003

The flux of energetic and nutrient resources across habitat boundaries can exert major impacts on the dynamics of the recipient food web. Competition for these resources can be a key factor structuring many ecological communities. Competition theory suggests that competing species should exhibit some partitioning to minimize competitive interactions. Species should partition both in situ (autochthonous) resources and (allochthonous) resources that enter the food web from outside sources. Allochthonous resources are important sources of energy and nutrients in many low productivity systems and can significantly influence community structure. The focus of this paper is on: (i) the influence of resource partitioning on food web stability, but concurrently we examine the compound effects of; (ii) the trophic level(s) that has access to allochthonous resources; (iii) the amount of allochthonous resource input; and (iv) the strength of the consumer–resource interactions. We start with a three trophic level food chain model (resource–consumer–predator) and separate the higher two trophic levels into two trophospecies. In the model, allochthonous resources are either one type available to both consumers and predators or two distinct types, one for consumers and one for predators. The feeding preferences of the consumer and predator trophospecies were varied so that they could either be generalists or specialists on allochthonous and/or autochthonous resources. The degree of specialization influenced system persistence by altering the structure and, therefore, the indirect effects of the food web. With regard to the trophic level(s) that has access to allochthonous resources, we found that a single allochthonous resource available to both consumers and predators is more unstable than two allochthonous resources. The results demonstrate that species populating food webs that experience low to moderate allochthonous resources are more persistent. The results also support the notion that strong links destabilize food web dynamics, but that weak to moderate strength links stabilize food web dynamics. These results are consistent with the idea that the particular structure, resource availability, and relative strength of links of food webs (such as degree of specialization) can influence the stability of communities. Given that allochthonous resources are important resources in many ecosystems, we argue that the influence of such resources on species’ and community persistence needs to be examined more thoroughly to provide a clearer understanding of food web dynamics.
Food webs in river networks
Authors: Power Mary Eleanor , Dietrich William Eric
Published: March 2003

Food webs and river drainages are both hierarchical networks and complex adaptive systems. How does living within the second affect the first? Longitudinal gradients in productivity, disturbance regimes and habitat structure down rivers have long interested ecologists, but their effects on food web structure and dynamics are just beginning to be explored. Even less is known about how network structure per se influences river and riparian food webs and their members. We offer some preliminary observations and hypotheses about these interactions, emphasizing observations on upstream–downstream changes in food web structure and controls, and introducing some ideas and predictions about the unexplored question of food web responses to some of the network properties of river drainages.
Structure and dynamics of a Castanopsis cuspidata var. sieboldii population in an old‐growth, evergreen, broad‐leaved forest: The importance of sprout regeneration
Authors: MIURA MASAHIRO , YAMAMOTO SHIN‐ICHI
Published: March 2003

The population structure and dynamics of Castanopsis cuspidata var. sieboldii were studied to evaluate vegetative and sapling regeneration in an old‐growth, evergreen broad‐leaved forest exposed to low‐severity typhoon disturbances by annual typhoons on the Tsushima Islands in Japan. The density of individuals ≥5 cm d.b.h. was 38.0 ha−1 in 1990; 7.9% were multiple‐stemmed individuals. Over the 7‐year study period (1990–1997), the number of individuals decreased, although the number of stems increased. Over 30% of apparently dead individuals were reconstituted by sprouting stems. Compared with sprout regeneration, sapling regeneration rarely occurred and was only observed in canopy gaps. Most individuals had at least one sprout shoot (H ≥30 cm, d.b.h. <5 cm), and the number and size of sprout shoots increased as the size of the individuals increased. During the study period, larger individuals with stem breakage tended to produce sprout stems. The density of saplings was 1074 ha−1 and they were more abundant in canopy gaps than under closed canopies, but large saplings were very rare even in canopy gaps. The population of C. cuspidata var. sieboldii consisted primarily of single‐stemmed individuals with a few multiple‐stemmed individuals providing a sprout bank. Larger individuals responded to the low severity typhoon disturbances and formed sprout stems. Although many saplings were observed, regeneration occurred more often by sprout formation than by growth of saplings. Thus, sprout regeneration is an important mode of regeneration, which allows this pioneer‐like species to maintain its population in this forest.
Evaluation of antidotes for poisoning by organophosphorus pesticides
Authors: Johnson Martin K , Jacobsen Dag , Meredith Tim J , Eyer Peter , Heath Andrew J , Ligtenstein David A , Marrs Tim C , Szinicz Ladislaus , Vale J Allister , Haines John A
Published: March 2003

Poisoning by organophosphorus pesticides results from inhibition of acetylcholinesterase. The outcome and optimum treatment depend on properties which differ among individual compounds. Treatment consists of supportive care, especially aimed at respiratory complications, and specific antidotal treatment. Treatment with atropine and diazepam is well established, but there is controversy concerning treatment with oximes capable of forcing reactivation of inhibited acetylcholinesterase. Although all parameters have not been fully established, initial bolus doses followed by continuous intravenous infusion to achieve plasma concentrations of 85–170 μmol/L of pralidoxime or 10–20 μmol/L of obidoxime have been recommended. These are well above concentrations that were likely to have been achieved by many of the ineffective regimens reported in the literature. Several independent reasons for failure of attempts at oxime therapy are discussed in this overview. If nothing else, it is likely that maintenance of adequate levels of oxime will shorten the period that a patient requires assisted ventilation with its associated risks. Topics for further laboratory and clinical research are listed. It is important to seek further understanding and the introduction of better practice because death rates from this type of poisoning remain significant.
Using the Toomey syringe as an oesophagal detector device
Authors: Marillier Eleanor , Bailey Paul , Rogers Ian R
Published: March 2003

In this report we describe the negative‐pressure or ‘Wee’ test for detection of inadvertent oesophageal intubation with reference to the published data on its reliability and potential problems. We also raise the possibility of using the readily available, low‐cost 50 mL catheter‐tipped (Toomey) syringe as an oesophageal‐detector device and present the results of a pilot study into the feasibility of this variation. Given the high sensitivity and specificity of these techniques, their widespread use is encouraged.