Comparative bioenergetics of permanent and temporary pond populations of the freshwater clam,Musculium partumeium (Say)

The population energetics of a temporary and a permanent pond population of Musculium partumeium in Southwest Ohio were studied. In the permanent pond (surface area = 396 m², maximum depth = 0.7 m) the population was bivoltine and iteroparous whereas in the temporary pond (surface area = 1042 m², maximum depth = 0.9 m) the population was usually univoltine and semelparous.Growth and biomass were assessed as total organic carbon and total nitrogen to provide estimates of productivity and seasonal changes in C:N for each generation. Productivity (non-respired assimilation = growth + reproduction; N-R.A. = G + R) was 6939 mgC·m^–2·a^–1 (3858 and 3353 mgC·m^–2·a^–1 for each generation) and 1661 mgC·m^–2·a^–1 for the permanent and temporary pond populations respectively. The average standing crop biomass (B) was 606.8 mgC·m^–2 (357.5 and 249.3 mgC·m^–2 for each generation) and 231.9 mgC·m^–2 with overall productivity: biomass ratios of 11.4 and 7.2 for the permanent pond and temporary pond populations respectively.Respiration rates were converted to carbon equivalents (respired assimilation = R.A.) and used to evaluate the components of total assimilation (T.A. = R.A. + N-R.A.) and the efficiency of partitioning this energy to N-R.A. for G and R. When expressed as a percentage, the production efficiencies (100 × N-R.A.:T.A.) were 50.4 and 62%, and the reproductive efficiencies (100 × R:N-R.A.) were 26.4 and 18% for the permanent and temporary pond populations respectively. The reproductive efficiencies for populations of these viviparous clams are greater than those for most oviparous molluscs.The comparative information on the energetics of these populations does not completely fit any theoretical consideration of reproductive effort or life-history strategy. These data are discussed in relation to selection for population success in temporary ponds.Funded in part by grants to Albert J. Burky from the Ohio Biological Survey and the University of Dayton Research CouncilFunded in part by grants to Albert J. Burky from the Ohio Biological Survey and the University of Dayton Research Council     

Population Dynamics of Heterodera glycines Life Stages on Soybean

Population fluctuations of Heterodera glycines differ in fields with high and low initial population densities. In a field with low initial numbers of nematodes, the numbers of cysts and eggs in soil remained low through 100 days from planting then increased during the remainder of the growing season. In a field with high initial nematode populations, numbers increased at 30 days, decreased to low numbers at 100 days, and then resurged to maximum populations at harvest. Numbers of juveniles were greatest at 100 days in the low initial population density field and at planting in the high initial population density field. The initial numbers of eggs in the soil gave the best correlation to soil and root nematode populations 15 and 30 days later. Juveniles in the soil at planting gave the largest correlation coefficients with nematode populations in the roots at 15 days in the field with the low initial population density. Eggs and juveniles in the soil at harvest were poorly related to numbers that overwintered.     

Seasonal Fluctuations of Globodera tabacum solanacearum as Estimated by Two Soil Extraction Techniques

Two soil extraction methods were compared to determine their efficiency in recovering cysts and juveniles of a tobacco cyst nematode, Globodera tabacum solanacearum. The methods were equally efficient when extracting nematodes from soil samples seeded in the laboratory; however, there was a significant extraction method × month interaction when the methods were used to estimate field soil populations over 2 years. The centrifugal sugar flotation method recovered greater numbers of cysts when densities were near 400 cysts/100 cm³ soil and greater numbers of juveniles in all samples. The sugar flotation method recovered greater numbers of cysts during months when densities were less than 400 cysts/100 cm³ soil. Numbers of cysts and juveniles were lowest in June and July following land tillage in May. A soil freeze in January 1982 may have been responsible for unusually high numbers of recovered cysts in February and March 1982, a pattern that did not occur in 1983.     

Propagation in vitro of the apple rootstock M4: effect of phytohormones on shoot quality

The quality of shoots in cultures of the apple rootstock, M4, was used as a criterion for the selection of an optimum medium. The frequency of shoots in defined shoot clases was monitored for each of five media, which differed in the type and concentration of phytohormone. Media containing BA (1.15 mg l^-1) and IBA (either 0.15 or 0.20 mg l^-1) produced the maximum number of shoots that were desirable for transplantation and acclimatization.     

云南兔Lepus comus G.Allen的分类订正——包括两个新亚种的描记

云南兔Lepus comus G.Allen是云贵高原和滇西山地目前发现的唯一的一种野兔,初由G.M.Allen（1927）根据采自云南西部腾冲的标本命名。其后,国内外学者（包括G.M.Allen本人在内）对云南兔究竟是一独立种或为高原兔Lepus oiostulus（Hodgson）的一个地理亚种意见纷纭（罗泽珣,1981;高耀亭等,1964;Allen,1938;Ellerman et al.,1951;Angermann,1967;Corbet,1978。我们曾对国内有关单位所收藏的这两个类群的100余号标本进行较详细的对比研究。发现云南兔在形态上与高原兔确有明显区别,在分布上又有同域现象,因而主张仍应将云南兔保持其原定种的种级地位;同时,又查对了采于各地的云南兔所有标本,发现云南北部（丽江）至中部（景东、景谷）标本以及云南东部、南部和贵州西部标本都有异于滇西地模标本,且占有不同的地理分布区。经研究,应属两个新的亚种。其中,云南东部,南部和贵州西部的新亚种,为纪念先师彭鸿绶先生毕生献身于云、贵、川的科学考察事业和他的指导与培养,特以彭先生之姓氏命名,以资纪念。     

白纹伊蚊实验种群动态的研究

在实验室条件下观察白纹伊蚊种群发育、存活和繁殖的动态,得出年龄特征存活率、繁殖率等数据,编制成生命表,计算出有关种群各项参数,包括内禀增长能力(r_m=0.1333),净增殖率(R₀=45.3017),增殖有限速率(λ=1.1426),平均世代周期长(T=33.3299天),瞬时出生率和死亡率(b=0.5562,d=0.4229),稳定年龄组配,成虫前期占90.66%,成虫期占9.34%。该蚊种群大约每隔5.2天增加一倍。根据结果对该蚊种群传播登革热的关系和防制加以讨论。     

Observations on the seasonal and yearly occurrence and the distribution ofAtyaephyra desmaresti (Millet, 1831) (Crustacea,Decapoda, Natantia) in The Netherlands

Summary The seasonal occurrence ofAtyaephyra desmaresti in The Netherlands has been studied by sampling the cooling-water filtering screens of power stations situated along the rivers Rhine and Meuse. The shrimps were only found in large numbers at the two power stations with vegetation in the cooling-water intake areas. Fluctuations in the seasonal occurrence showed great similarity for these two localities. Highest numbers of shrimps were impinged in November. High numbers also occurred in September, while a lower peak in numbers was found in May.Changes in the numbers of records during the last 30 years in The Netherlands were compared with climatological fluctuations (severe or mild winters), indicating that this mainly southern-European species is living here at the limits of its ecological and geographical range.The distribution in The Netherlands reveals thatAtyaephyra desmaresti mainly occurs in freshwater habitats, although it tolerates higher chlorinities.     

Oxygen demand and long term changes of profundal zoobenthos

The paper attempts to combine the low oxygen content of the hypolimnion during stratification and the oxygen uptake of zoobenthos. Data of declining oxygen content in the hypolimnion and critical limits of respiration are combined for Chironomus anthracinus, Potamothrix hammoniensis and three species of Pisidium, P. casertanum, P. subtruncatum and P. henslowanum. The respiratory adaptation to low oxygen content influences both growth and population dynamics of the different species. The results have important bearing on eutrophication of the Lake Esrom ecosystem and temperate eutrophic lakes in general as well as the composition of profundal zoobenthos and its population dynamics.Publication No. 389 from Freshwater-Biological Laboratory, University of Copenhagen.     

Genetic structure of natural populations of the red-spotted newt,Notophthalmus viridescens

Genetic variation is described at 15 loci in 2 neotenic and 12 nonneotenic populations of red-spotted newts. Though high levels of genetic similarity (I=0.990) were found among all populations, allele frequencies at six of the eight most polymorphic loci show significant heterogeneity across populations. Change in allele frequencies at two of these loci (Pep-2 and Ldh-1) is significantly correlated with latitude. Interspecific homologies are established for newt peptidases based on substrate specificities and lactate dehydrogenases based on tissue distribution, thermal stability, and kinetic properties. Nonneotenic populations are highly variable (H=0.157) and neotenic populations are only slightly, but significantly, less variable (H=0.120). The high levels of heterozygosity detected in nonneotenic populations may result from large effective population size and/or environmental heterogeneity. The unexpectedly high heterozygosity values obtained for the neotenic populations may indicate adult dispersal or the presence of some previously undetected red efts at these localities. In any case, a major change in life history has apparently had little effect on the genetic structure of these populations.This research was supported by grants from the Blakeslee Fund of Smith College.     

Evolution of nesting strategies of ants: genetic evidence from different population types of Formica ants

Genetic population structure was studied in two types of populations in the ants Formica exsecta and F. pressilabris: populations consisting of single-nest colonies (monodomy) and populations consisting of multi-nest colonies (polydomy). These characteristics seem to be associated with the number of egg-laying females (gynes) in a nest, mating structure of the population, sex ratio and male size variation. The monodomous populations are characterized by single-gyne nests, the population sex ratio is either I:1 or female-biased, males are mainly large-sized, and there is slight inbreeding in the population. The polydomous populations have multi-gyne nests with gynes related to each other, sex ratio is strongly male-biased, most males are small-sized, and there is slight genetic microdifferentiation within the populations. Diploid males found in a polydomous F. pressilabris population suggest that the population is inbred and isolated. Habitat localization is presented as a plausible explanation for the evolution of the polygynous and polydomous population structure.