Distribution of echinoderms and their larvae in the southwestern Peter the Great Bay, Sea of Japan

Based on results of processing planktonic and benthic samples collected in 1996 and 1997, a spatial distribution of echinoderms in the bottom and of their larvae in the plankton were collated for the water area of the Southern region of the Far Eastern State Biosphere Marine Reserve. Some correlation between distributions of the adult and larval sea star Asterias amurensis in July was revealed. At the same time, there was no correlation between distributions of larvae and adult individuals of the brittle star Ophiura sarsi and sea urchin Echinocardium cordatum, which are most abundant in the area. The size structure of bottom populations of the brittle stars O. sarsi and Amphiodia fissa in the studied area was assessed. The correlation coefficient between the distribution of young-of-the-year and the population density was 0.47 in O. sarsi and 0.74 in A. fissa respectively, which implied a selective settling of larvae of those species in areas inhabited by adult brittle stars. Recruitment of bottom populations from 1996 spawning was 5% in O. sarsi and 3.3% in A. fissa.     

Ecological Distribution of Polychaetous Annelids from the New England Outer Continental Shelf,Georges Bank

Four hundred and eight quantitative grab samples collected during the winter and spring of 1977 from the New England Continental Shelf (Georges Bank) yielded 333 species of polychaetes. Polychaetes comprised 53.8% of the number of all infaunal species, 53% of the density, and 60.5% of the wet weight biomass for all soft-bodied organisms, at least for the winter. Mean number of species and mean density was significantly higher in the spring than in the winter. Mean values of number of species, H', SDN, density, and biomass were associated with various environmental factors. Based on numerical classification (normal and inverse) five polychaete site groups were identified. To a great extent these site groups were molded by major physical, geologic and biologic processes which influence the productivity of this ecologically and economically important area.     

Larval Chironomidae (Diptera) of the Big Thicket streams

Eighty-seven species of chironomid larvae were collected from streams in the Big Thicket area of southeast Texas. Samples of leaf debris, wood debris, and sand were taken from the streams and the larvae occupying the substrates were analyzed. Four subfamilies were represented including Tanypodinae (12 species), Diamesinae (2 species), Orthocladiinae (30 species), and Chironominae (43 species). Dominant species included Lopescladius sp., Polypedilum ? convictum, Polypedilum ? halterale, Cladotanytarsus sp. group A, Rheotanytarsus sp., and Tanytarsus sp. 2. A brief account of the habitat and the distribution of each species encountered during this study is given.     

Food and feeding habits of pearly razorfish, <Emphasis Type="Italic">Xyrichtys novacula </Emphasis>(Linnaeus, 1758), in the southern Tyrrhenian Sea: variation by sex and size

We collected pearly razorfish, Xyrichtys novacula (Labridae), from a sandy bottom of Capo dOrlando (Tyrrhenian Sea) to study their feeding habits. We caught fish by hand-lines and seine nets and identified, counted and weighed food items in their stomachs. We evaluated the importance of the different prey types by calculating the frequency of occurrence, abundance and mass. We used these values to calculate the index of relative importance (IRI) for each taxonomic category and a modified index (MI) which did not incorporate %N into the formula. Gammarideans were dominant food items in terms of %F but showed a very low MI value; the bivalve Acanthocardia tubercolata was the dominant species in terms of %W and MI value. The prey items were mostly benthic organisms belonging to the assemblage of fine, well-sorted sands showing that X. novacula is a benthic feeder. Despite the large number of prey taxa found, few species accounted for most of the prey consumed, indicating specialist feeding, as confirmed by the low value of the Levins standardised index. We found significant differences in prey distribution among size classes, with the highest prey diversity recorded in 120–140 mm TL size classes. Correspondence analysis showed a trend of increasing predator size classes among prey items, with small prey, such as copepods and amphipods, in the smallest predator size classes and bigger prey in the larger ones. Prey caught by larger predators differed significantly in weight from those taken by smaller specimens. There was a significant positive correlation of fish length with bivalves, decapods and echinoids, and a negative one with copepods, ostracods, caprellids, gammarideans. There were no significant differences between males and females of overlapping sizes. Juveniles are able to exploit only small, vulnerable prey, while adults take few, large prey, thereby avoiding competition with juveniles.     

Habitat ecology of chironomid larvae of the Big Thicket streams

Chironomid larvae were collected from streams in the Big Thicket area of East Texas from November, 1981 to October, 1982. Primary stations were sampled monthly and secondary stations bi-annually. Samples of leaf debris, wood debris, and sand were taken from each station and the chironomid larvae occupying the substrates were analyzed.A total of 15 112 individuals including 87 species were collected. Four subfamilies of Chironomidae were represented: Tanypodinae (12 species), Diamesinae (2 species), Orthocladiinae (30 species), and Chironominae (43 species). The collections yielded a larger number of individuals and species than previous environmental studies in the Big Thicket. Twenty-two species are reported for the first time from Texas.The lowest number of individuals occupied the leaf debris with Rheotanytarsus sp. and Tanytarsus sp. 2 being dominant. The wood debris, probably the most stable of the substrates, contained the highest number of species with Tanytarsus sp. 2 being dominant. Most individuals occurred in the sandy bottom where Lopescladius sp. was dominant. Tanytarsus sp. 1 occurred in over 65 percent of the samples.The populations were generally higher during the autumn. This was probably a result of the life cycle and the effects of environmental factors. More younger instars occurred during the late summer and autumn. Also, water flow during the summer and autumn was low, providing a more stable environment, promoting chironomid population growth.     

Detritivores in Kenyan highland streams: more evidence for the paucity of shredders in the tropics?

1. The relationship between coarse particulate organic matter (CPOM) standing stock and benthic macroinvertebrate assemblages in Kenyan highland streams was determined by sampling seven sites on three rivers (2000–2700 m a.s.l.). Taxa recorded were allocated to functional feeding groups using published literature, mouthpart analysis and examination of gut contents. Patterns were compared with five structurally similar streams in three areas of Europe (south-west France, south-east England, north-east England).
2. Number of individuals and proportion of detritivores in Kenyan streams were equivalent to, or greater than, those in European sites. Shredders were, however, almost completely absent from Kenyan sites, despite high standing stocks of CPOM. Shredders were abundant in all European sites.
3. The phenomenon of low shredder abundance has been observed in other tropical streams in south-east Asia and Central and South America but, in contrast to these regions, the African rivers studied were devoid of shrimps or fish which may occupy the shredding niche elsewhere.
4. These preliminary data suggest that shredder-mediated detritus processing, which is a key functional component of streams in the North Temperate Zone, does not operate in East African streams. There are three possible reasons for this. The first is that tropical African rivers are functionally different to those in temperate regions. This could be because of enhanced microbial activity replacing shredder activity at high temperatures. Alternatively, it could be a result of low palatability of detrital inputs from dominant riparian trees in the region. The second and third are methodological: that our allocation to functional feeding groups is incorrect, and that our sampling methods missed a potentially key shredding taxon – the freshwater crab Potamonautes sp.     

生态学研究的新领域--分子生态学

分子生态是生态学的一个新的研究领域。它采用分子生物学的技术与方法来研究生态活动规律的分子机理。本文简要介绍了分子生态学的定义、研究内容、研究方法和研究热点等,以期描述出分子生态学的概貌。     

江淮稻区稻象虫生物学、生态学的研究

在扬州地区,稻象虫一年发生1代。以老熟幼虫越冬,其越冬存活率免耕田>少耕田>常规耕田,肾发育的高低温临界点为38．16℃和9．84℃,最适发育温度26.52℃,有效积温117.8日度,每头稻虫产卵卵3-29粒,平均18．8粒;成虫羽化后17-31天为产卵盛期;产卵孔平均高度为4.1±1.5cm,水象下卵孔占28．6％：产卵孔与取食孔特征不同．卵期7±1．8天．成,幼虫的各群空间格局基本属密集颁布（仅x^-≤3时的成虫种群为随机分布)．单季稻的为害重于双季稻;沙质土壤的发生量多于粘壤土,稻—麦（油菜）两熟制田的为害显重于稻-稻麦(油菜）三熟制田。     

青新园蛛的生物生态学研究

为调查青新园蛛的生物生态学特征,分别在田间和实验室条件下对其进行观察.如预期所示,幼蛛、亚成熟蛛和成蛛一起群居越冬.在湖南,青新园蛛每年可以繁殖3-4代,其中第4代寿命最长,第2-3代寿命最短.青新园蛛有织网的习性,雌蛛和雄蛛多次交配,一只雌蛛最多可产12个卵袋,每个卵袋平均含82.2颗卵粒.在群居模式中,刚孵化的蛛幼会安全的生活在雌蛛的背部.青新园蛛幼蛛的生长历期为40-120天,成蛛为33-176天.除第二代外,青新园蛛雌雄蛛的性别比率均小于1.该文详细描述了青新园蛛幼龄期和亚成熟期的生物学特征.在实验室条件下,青新园蛛的饥饿耐受力要强于抗旱力.     

An analysis of changes in the invertebrate community along a southern New Zealand montane stream

Changes in benthic community structure at four sites along a flood-prone montane stream continuum in the South Island of New Zealand were analysed using rank correlation (Kendall's Tau and Spearman's r_s) and a community similarity index (S_c) developed initially for stream pollution assessment. Species richness was highest in a forested headwater stream, which is attributed to its relatively greater physical stability and habitat heterogeneity. Community similarity decreased with distance apart, and pairs of open and forested sites showed the greatest similarity. Species composition and relative abundance along the continuum changed least in the numerically dominant Ephemeroptera and Plecoptera, groups in which several species had broad habitat requirements. In contrast, a number of dipteran and trichopteran species had more restricted distributions. The more specialised niche requirements of some species in these orders are attributed to their generally small size, their ability to spin silk, and their holometabolous development. Physical rather than biological factors appeared to limit the distributions of most invertebrates, and there was little evidence of ecological segregation by either food resource partitioning or differences in life history patterns amongst many closely related species. Theories that stream communities are well ordered entities maximising the efficiency of energy utilisation cannot realistically be applied to such unstable stream systems.     

缓步动物门(Tardigrada)研究进展

本文简要概述了20世纪以来缓步动物在分类学、生物学和生态学的研究进展和成就.按照缓步动物前沿研究的发展趋势,结合我国的研究现状,作者提出了几点建议.     

Hierarchical competition models with the Allee effect II: the case of immigration

ABSTRACT

This is part II of an earlier paper that dealt with hierarchical models with the Allee effect but with no immigration. In this paper, we greatly simplify the proofs in part I and provide a proof of the global dynamics of the non-hyperbolic cases that were previously conjectured. Then, we show how immigration to one of the species or to both would, drastically, change the dynamics of the system. It is shown that if the level of immigration to one or to both species is above a specified level, then there will be no extinction region where both species go to extinction.