Ammonia beccarii and Ammonia tepida (Foraminifera): morphofunctional arguments for their distinction

New observations from Yeu Island and the Bay of Bourgneuf on the Atlantic coast of France show that Ammonia beccarii s.s. and Ammonia tepida have different morphofunctional adaptations to their habitats and environments. Adult A. beccarii s.s. may be epiphytic, living on the calcareous alga Corallina officinalis or on the red alga Gigartina acicularis along rocky shores, while A. tepida is endopelic, living in sediments of brackish environments. Rapid 3-D emission of pseudopodia from interlocular spaces on both umbilical and spiral sides of adult A. beccarii s.s. can support its test within the seaweed framework. This behaviour is characteristic of phytal species. Thus, it appears that the major difference between A. beccarii s.s. and A. tepida is the presence of large interlocular spaces on spiral side of the former, corresponding to a potential morphofunctional adaptation to the epiphytic mode of life. We believe that these observations could help to solve the long-lasting A. beccarii problems of specific distinction.     

Population dynamics and production of Acanthocyclops robustus (Sars) and Mesocyclops leuckarti (Claus) in Tjeukemeer

The population dynamics and production ecology of the two dominant copepod species, Acanthocyclops robustus and Mesocyclops leuckarti, in Tjeukemeer (The Netherlands) were studied for three successive years. Since copepods in Tjeukemeer show continuous recruitment, a population dynamics model INSTAR was developed and used to integrate field data on population density, population structure and fecundity and laboratory data on development rates and length-weight relationships. The pattern of size specific mortality indicated that both invertebrate and vertebrate predation were important in the regulation of population numbers.     

Population dynamics of the parasitic stages of Ostertagia spp. in sheep

Callinan A. P. L. and Arundel J. H. 1982. Population dynamics of the parasitic stages of Ostertagia spp. in sheep. International Journal for Parasitology12: 531–535. The development and survival of continuing infections of Ostertagia spp. in weaner sheep were studied in order to develop a general model of the parasitic stages of the life cycle of these sheep nematodes. After 10 days, 13.8% of infective larvae (L₃) given at the rate of 1 dose of 1000 L₃ twice per week (group 1) and 20.8% of L₃ given at the rate of 10,000 L₃ twice per week (group 2) were recovered in the first of the serial nematode counts. In the final counts at 137 days, 7.7 and 0.7% were recovered in these groups. The build up and maintenance of nematode populations was regulated and related to the level of infection. A model in which the death rate of the parasitic stages was a function of the time of exposure to infection and rate of infection was used to describe the serial total nematode counts. During the experiment there was no noticeable trend in numbers of fourth stage larvae (L₄) in nematode counts, the size of adult nematodes, nematode egg counts (EPG) and egg output per female nematode (EPF). After 112 days, liveweight gains were significantly reduced in group 2 only, but increases in wool lengths were significantly reduced in both groups.     

Population dynamics of hypolimnetic rotifers in the Pluss-see (North Germany)

The hypolimnetic rotifer populations of the Pluss-see (Keratella hiemalis, Filinia terminalis, Filinia hofmanni) show similar patterns of changing population parameters indicating that they respond to particular environmental signals in the same way.     

Population dynamics and energy budget of Marionina southerni (Cernosvitov) (Enchytraeidae,Oligochaeta) in the shallow littoral of Lake Esrom,Denmark

Marionina southerni (Cernosvitov) was numerically the dominant oligochaete in a shallow, strongly exposed surf zone locality (0–1 m depth) in the mesotrophic Lake Esrom. It comprised 21,500 ind m^–2 or nearly 50% of the total oligochaete community, which otherwise was dominated by Nais spp. and the lumbriculid Stylodrilus heringianus Claparède. M. southerni appears to have a 1-y life cycle. Individual biomass ranged from 3 to 48 µg ash free dry weight. Annual net production at the site was 5.1 kcal m^–2 (size-frequency method) with a P/B ratio of 2.5. This is about 0.5% of the estimated mean zoobenthic production in the littoral zone from 0 to 2 m depth in Lake Esrom. At 5° C M. southerni showed a constant oxygen uptake down to 25% oxygen saturation, but practically no regulatory respiration was found at 20 °C. In the field M. southerni was never found in sediment with less than 60% oxygen saturation. The annual community respiration of M. southerni was 14.2 kcal m^–2, and annual assimilation thus made up 19.3 kcal m^–2 with a net production efficiency of 26.5%.     

鼎湖山南亚热带常绿阔叶林荷木种群动态变化

荷木(Schima superba)是鼎湖山南亚热带常绿阔叶林群落中的优势种,为了解南亚热带常绿阔叶林的群落构建机制,该研究分析了鼎湖山南亚热带常绿阔叶林20 hm2样地中荷木种群在2005—2017年间的动态变化,并从径级和生境两个方面分析了其死亡率的分布特征。结果表明:(1)荷木种群个体数量从2005—2017年呈现出减少的态势。(2)在径级方面,荷木的死亡率和相对生长率的变化在不同径级区间呈现出不同的变化规律。径级在1～10 cm范围的荷木相对生长率大并迅速下降,死亡率上升且维持在较高水平;径级在10～50 cm范围的荷木随着径级增大,相对生长率减缓,然后下降,而死亡率不断下降;在50 cm以上的径级范围内,荷木相对生长率小、死亡率大。(3)不同生境中,2010年各个生境死亡率相差不大,2015年高海拔生境(高坡、山脊、高谷)死亡率大于低海拔生境(低坡、低谷),2017年则为低海拔生境大于高海拔生境。(4)荷木的死亡率与土壤中酸碱度呈正相关关系,而与土壤有机质、总氮、总磷、有效钾、有效氮含量呈负相关关系。     

Population dynamics of Tubificoides amplivasatus (Oligochaeta,Tubificidae) in the Oresund,Denmark

A two year fortnightly collection of data from the 27 m station in the Oresund on the tubificid species Tubificoides amplivasatus was analyzed for population trends and life stages. Recruitment patterns from year to year were consistent in timing but very irratic in magnitude, being similar to patterns seen in other estuarine and marine annelids. Sexually mature T. amplivasatus were found throughout the study period, but mature mated specimens were more abundant during late summer and autumn. It is estimated that from 120 to 150 days is spent, by this species, in the cocoon and individuals may reach maturity in less than one year. There was some indication of individuals with regressed genital organs indicating that they may live longer than one year. At the 27 m station T. amplivasatus is part of a complex and well developed benthic community. Temporal variation in this species was highly correlated to that of other major taxa (bivalves, ophiuroids).     

Population dynamics of Microtus arvalis in a weed strip

A population of Microtus arvalis Pallas, 1779, living in a weed strip was studied by capture–recapture method over a 2-year period. Weed strips are characterized by their linear shape and high vegetation cover, and are not comparable to the habitats examined in most previous studies on M. arvalis.Abundance of voles was found to be high in the strip with a maximum of 410 voles/ha known to be alive in the first year and 641 voles/ha in the successive year. Abundance was minimal in spring and increased until July. A decrease in population size at the beginning of August was followed by a new increase in both years. One difference between the 2 years was a pronounced peak abundance at the end of June in the second year. The peak may be related to a shift in sex ratio in favour of females in this year (ratio of males:females of 1:8). Also the time of residency of females was significantly longer in the second year than in the year before, and the survival rate of females was greater than in males.The turnover was generally very high and reached maximum values of 80% renewal of population every 2 weeks.     

Planktonic foraminifera from the eastern Indian Ocean: distribution and ecology in relation to the Western Pacific Warm Pool (WPWP)

Faunal assemblages, principal component (PCA), canonical correspondence (CCA), and factor analysis are applied to planktonic foraminifera from 57 core-top samples from the eastern Indian Ocean. The foraminiferal lysocline occurs at 2400 m north of 15°S where carbonate dissolution is induced by the Java upwelling system, and occurs deeper south of 15°S where carbonate dissolution is characteristic of the oligotrophic regions in the Indian Ocean. Dissolution effects, the February standing stock at the time of collection of the plankton-tow material, and different production rates explain the different foraminiferal assemblages found between plankton-tow and core-top samples. Core-top samples are differentiated by PCA into four groups — Upwelling, Western Pacific Warm Pool (WPWP), Transitional, and Southern — that are related to environmental variables (temperature, salinity and nutrients); all environmental variables follow a strong latitudinal component as indicated by the CCA analysis. Similarly, three assemblages are recognized by factor analysis: Factor 1 (dominated by Globigerinoides sacculifer, G. ruber, Globigerinita glutinata and Globorotalia cultrata), factor 2 (dominated by Globigerina bulloides and Globorotalia inflata) and factor 3 (dominated by Neogloboquadrina dutertrei) explain more than 92% of the variance, and are related to sea-surface temperature, thermocline depth and nutrient levels. The seasonal influence of the Java upwelling system supplies nutrients, phyto- and zooplankton to the oligotrophic eastern Indian Ocean (factor 1). South of 24°S, a deep chlorophyll maximum, a deep euphotic zone, a deep thermocline, SSTs below 22°C, and brief upwelling pulses seem to explain factors 2 and 3. The ratio of G. sacculifer and N. dutertrei, two mutually excluding species, appears to indicate the southern boundary of the WPWP. This ratio is applied to core Fr10/95-11 to demonstrate past shifts of the southern boundary of the WPWP.     

穴蚁蛉的自然种群动态

本文主要报道了穴蚁蛉 Myrmeleon(Morter) sagax(Walker)幼虫的野外自然种群数量动态。穴蚁蛉 1年发生 1代 ,在自然界其幼虫 3～ 5月份数量平稳略有下降 ,5、6月间数量迅速下降 ,6月初数量最少 ;7～ 9月份数量迅速上升 ,而后下降 ;新一代穴蚁蛉幼虫 (蚁狮 )在 6月份出现。其种群 ,秋季以 1龄幼虫数量为多 ,冬季主要以 2龄幼虫为主越冬 ,春季以 3龄蚁狮占优势。春季野外采集来的蚁狮 ,在每日光照 14小时、每周两饲 (每次饲 1头米蛾 Corcyra cephalonica成虫 )的条件下饲养 ,结果发现 ,采集回时处于 3龄期的蚁狮比自然界大约提前 1个月结茧化蛹和羽化 ;而采集回时处于 2龄期的蚁狮则和自然界中的情况基本一致。     

Population dynamics and production of cladoceran zooplankton in the highly eutrophic Lake Kasumigaura

The growth rate, birth rate, death rate and production of the cladocera of Lake Kasumigaura were studied. Standing crop of zooplankton seemed to be governed by predation rather than food. Maximum productivity of cladocerans was observed in late August and early September. There were differences in production between sampling stations. The highest production was recorded in the most eutrophic basin, where heavy water blooms of Microcystis aeruginosa occurred. Maximum secondary production coincided with maximum primary production, which was mainly due to M. aeruginosa. Cladocerans probably utilize decomposed or decomposing Microcystis cells and bacteria in summer. Estimates of annual production of cladocerans varied from 4.2 to 13.1 g dry wt · m^–3, and annual P:B ratios ranged from 36 to 108. The production of cladocerans in Takahamairi Bay was 2.7% of gross primary production.     

Population dynamics of Bosmina longirostris (Crustacea: Cladocera) in Lake Kariba,Zimbabwe

The population dynamics of Bosmina longirostris in a large tropical reservoir, Lake Kariba, Zimbabwe, are described. Population density showed two peaks associated with periods of high nutrient fluxes. Fecundity was always low. Two eggs per female was the maximum ever recorded. Instantaneous rates of birth, death and population growth calculated from field data using the egg ratio method are discussed. The rate of biomass change fluctuated in a regular pattern, probably linked to food availability or predation by a clupeid, Limnothrissa miodon.     

Population dynamics of the citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae) in Japanese pear orchards

In spring a population of the citrus red mite (Panonychus citri),a non-diapausing species, migrated to a Japanese pear orchard, mainly from nearby Japanese holly trees, but in autumn most of the mites starved to death while the rest returned to the holly trees. In the Japanese holly trees, the population of mites reached their maximum density in late May1993 and in mid-June 1994 on overwintered leaves and moved to newly opened leaves in mid-June 1993 and late June 1994. The mites tended to disperse abruptly in early June or mid-June and again towards the end of June. The mites inhabiting the holly trees appeared to migrate to the Japanese pear trees in June but their densities on pear leaves remained low until mid-August. In the pear orchard, the mites initially tended to increase on pear leaves near the holly trees and then gradually spread to other leaves farther away from the holly trees. Their highest density in the pear orchard occurred in mid-October. When pear leaves were inoculated with two or five female adults at different times from May to September, the leaves inoculated before mid-August showed no increase in the number of mites. A possible cause for the suppression of the population increase on pear leaves from June to mid-August is discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Population dynamics, growth and production of the neozoon Marenzelleria cf. viridis (Verrill, 1873) (Polychaeta: Spionidae) in a coastal water of the southern Baltic Sea

The propagation of an immigrant from North America, viz. the spionid Marenzelleria cf. viridis in the Darss-Zingst Bodden (DZB) (southern Baltic Sea), was studied at three stations from March 1992 to December 1995. Highest mean abundances (over 28 000 ind. m^-2) and wet weights (400 g m^-2) were recorded at station 2 in 1994. The spionid also reached its highest dominances in terms of biomass (40 to 90%) at this station, which was selected for the population dynamics, growth and secondary production studies. The spionid has a life span of about 3 years, and many individuals achieved sexual maturity after one year. Their growth curve is steepest during the first year of life, during which the animals grow to a length of about 180 segments. However, growth depression was observed during the ripening of the gametes in April, May and June. Secondary production was in the region of 55 to 85 g AFDW m^-2 y^-1. Productivity (P/B) varied considerably from generation to generation, ranging between 0 and 4.8 with an average between 1.2 and 1.6.     

湘北地区三化螟种群消长的原因探讨

本文根据湘北 4 9年水稻三化螟 Tryporyza incertulas( Walker)种群密度消长的历史资料 ,着重分析了 1996～ 1998年连续 3年三化螟在湘北猖獗为害的原因 ,即中稻、一季晚稻面积增加 ,杂交中、晚稻“双两大”的推广 ,晚稻的大面积早插都便于三化螟辗转繁殖为害 ;稻田春收作物——油菜的大面积种植 ,增加了三化螟的有效越冬虫源 ;水稻播期拉长及品种的多元化和栽培方式的多样化 ,使水稻危险生育期与蚁螟盛孵期吻合度加大 ;三化螟对农药的抗性增强和主害代发生期变得不整齐 ,增加了防治的难度     

Population dynamics of Mus minutoides and Steatomys pratensis (Muridae: Rodentia) in a subtropical grasslandin Swaziland

The population dynamics of Mus minutoides and Steatomys pratensis are virtually unknown. These two species were live-trapped over a 12-month period in a subtropical grassland in Swaziland. Numbers of M. minutoides were relatively high in winter, declined in spring and the population disappeared in summer and autumn. By contrast, numbers of S. pratensis increased gradually from winter to summer and reached a peak in autumn. There were no differences between the mean weights of male and female M. minutoides and S. pratensis. There were, however, seasonal differences in the mean weight of male S. pratensis, with highest weights recorded in summer. Individuals of both species came into breeding condition in spring (October–November). Reproduction had ceased by the end of autumn (April–May). Monthly survival rates of M. minutoides were highest in winter, but did not vary seasonally in S. pratensis. Burning had a pronounced effect on the distribution of S. pratensis. Steatomys pratensis individuals selected recently burnt but revegetated areas over unburnt areas. The effect of burning on the M. minutoides population is difficult to assess, as this species disappeared shortly after the fire.     

Population dynamics of the oriental fruit fly, Bactrocera dorsalis （Diptera： Tephritidae） in the Kunming area,southwestern China

Population dynamics of Bactrocera dorsalis Hendel （Diptera： Tephritidae） were studied through pheromone trapping over 4 years （1997, 1999, 2000, 2003） in the Kunming region, a high plateau area in southwestern China. B. dorsalis immigrates from southern Yunnan to Kunming each year, and occurs during early May through November. Annual trap captures recorded an increase in the B. dorsalis populations from May to July, when they peaked in abundance, and a decline until November. No flies were detected from November to April. The fruit flies had two generations. There was considerable overlapping due to the continuous arrival of immigrating flies during the summer months. Annual capture rates were significantly related to numbers of flies caught in July when peak captures were recorded; whereas the peak captures, in turn, positively depended on numbers of flies recorded in May, the first month of fly appearance in the current year. It suggested that the annual population abundance was mainly dependent on the size of the initial emigrating population. A daily average temperature of 18℃ was probably the threshold temperature required for the flies to undertake long-range dispersal, which partially explained the start of the fly in May each year on this high plateau. Under field conditions, the fruit flies can withstand 13℃ as a daily average temperature. No flies were recorded in any of the study years at a daily temperature colder than 10 ℃.