七种啮齿动物视觉器官形态结构的比较研究

用光镜和扫描电镜观察褐家鼠,黑线姬鼠、大仓鼠、棕色田鼠、甘肃Ｆｅｎ鼠、达乌尔黄鼠和岩松鼠的视沉器官形态与构造,对其视网膜的厚度、各核层胸核的层数及大小进行了比较,在扫描电镜下统计了褐家鼠和达乌尔黄鼠和视细胞密度,结果表明,鼠类视觉器官的形态结构与其生活习性相关,即生活习性相似的种类,视器的形态结构也相似;即生活习性差异较大的种类,视器的形态结构差异也较大,同时还发现夜行性鼠视网膜上的核层局部增厚,     

NO EFFECT OF ENVIRONMENTAL HETEROGENEITY ON THE MAINTENANCE OF GENETIC VARIATION IN WING SHAPE IN DROSOPHILA MELANOGASTER

Theory suggests that heterogeneous environments should maintain more genetic variation within populations than homogeneous environments, yet experimental evidence for this effect in quantitative traits has been inconsistent. To examine the effect of heterogeneity on quantitative genetic variation, we maintained replicate populations of Drosophila melanogaster under treatments with constant temperatures, temporally variable temperature, or spatially variable temperature with either panmictic or limited migration. Despite observing differences in fitness and divergence in several wing traits between the environments, we did not find any differences in the additive genetic variance for any wing traits among any of the treatments. Although we found an effect of gene flow constraining adaptive divergence between cages in the limited migration treatment, it did not tend to increase within‐population genetic variance relative to any of the other treatments. The lack of any clear and repeatable patterns of response to heterogeneous versus homogeneous environments across several empirical studies suggests that a single general mechanism for the maintenance of standing genetic variation is unlikely; rather, the relative importance of putative mechanisms likely varies considerably from one trait and ecological context to another.     

THE MAINTENANCE OF GYNODIOECY AND ANDRODIOECY IN A METAPOPULATION

Males and females are at a selective disadvantage relative to hermaphrodites (cosexuals) in species with a colonizing habit, as only cosexuals are able to establish new colonies on their own. The implications of this disadvantage are assessed by means of a computer model of metapopulation dynamics, in which individual colonies are established through different rates of immigration and suffer different rates of local extinction. Results are given for simulations of an island model, a stepping-stone model, and for a partial analysis of the island model with simplifying assumptions. It is shown that: (1) unisexual frequencies in a metapopulation can be reasonably approximated by a linear function of the logarithm of the ratio of the immigration rate to the colony extinction rate; (2) metapopulation dynamics favor the maintenance of females (gynodioecy) over males (androdioecy) with cosexuals when they would otherwise be equally likely in a panmictic situation; (3) the way in which extinction and immigration rates affect unisexual frequencies at metapopulation equilibrium interacts with whether sterility is determined by a dominant or a recessive allele; and (4) unisexual frequencies are affected in a qualitatively similar way by the dynamics of a metapopulation when cosexuals are self-incompatible to when they are self-compatible, although only in the former case are high frequencies of unisexuals maintained when extinction and colonization rates approach the threshold at which the metapopulation goes extinct. These results are discussed with reference to existing data from species with nuclear male or female sterility.     

三峡水库底栖动物群落结构特征及其与蓄水前资料的比较

为了解三峡水库在蓄水后底栖动物的群落结构特征, 探索水文情势改变对底栖动物群落结构的影响,于2012 年8 月、11 月及2013 年4 月对三峡水库的秭归、巫山、云阳、忠县和木洞五个断面底栖动物的群落结构进行了调查分析。结果表明: (1)共记录底栖动物43 个属种, 木洞种类最多(29 种), 秭归最少(12 种)。优势种为多足摇蚊(Polypedilum sp.)、前突摇蚊(Procladius sp.)、肥满仙女虫(Nais inflata)、霍甫水丝蚓(Limnodrilus hoffmeisteri)和一种钩虾(Gammaridae);(2)在空间分布上, 密度以木洞最高(81802740) ind./m2,忠县最低(11642) ind./m2;生物量以木洞最高(8.663.65) g/m2, 云阳最低(0.170.06) g/m2;(3)在季节动态上,密度以秋季最高(31401450) ind./m2, 夏季最低(11537) ind./m2;生物量则以春季最高(3.832.11) g/m2, 夏季最低(0.650.46) g/m2;(4)底栖动物密度和生物量随着水深的增加呈下降趋势, 在水深小于20 m 的浅水区递减率最大;(5)丰度/生物量比较曲线(ABC 曲线)分析显示, 巫山属于中等干扰条件下的群落结构(W=-0.003), 而木洞属于严重干扰条件下的群落结构(W=-0.101);(6)与建坝前相比, 三峡水库底栖动物密度和生物量趋于减少。流速减缓、水深增加、水位波幅加大和沉积物中营养盐的升高可能是造成三峡水库底栖动物群落结构改变的主要因素。       

三峡库区甘井河水域牧场浮游植物群落结构及水质评价

为了解三峡库区的忠县甘井河段水域牧场生态渔业对水环境的影响, 于2013 年3、6、9 及12 月按季度对该河段4 个站点进行了浮游植物群落结构及水体理化因子的监测, 并采用生物多样性指数法和综合营养状态指数法对水体营养状况进行了评价。结果表明, 该河段浮游植物有7 门93 个属种, 其中绿藻门的物种数最多, 有37 种, 占浮游植物群落总数的39.79%, 其次为硅藻门和蓝藻门, 物种数分别为26 种和13 种,分别占浮游植物群落总数的27.96%和13.98%;浮游植物的年均丰度为757.67104 ind./L, 变化范围(3.065743.99)104 ind./L, 年均生物量为4.40 mg/L, 变化范围0.0317.67 mg/L;水体的年平均透明度为1.18 m, 叶绿素a、总磷、总氮含量分别为8.54 g/L、0.13 mg/L、1.95 mg/L;浮游植物香农多样性指数(H')、均匀度指数(J)年均值分别为2.90 和0.88, 全年综合营养状态指数值为37.5971.86, 由此推断, 甘井河水质属于中污染轻污染状态、中营养型富营养型。在鱼类生长旺季的6 月, 甘井河段养殖区内的水质优于非养殖区, 这可能与养殖区内放养滤食性鱼类有关, 证实了水域牧场没有带来水环境的污染, 反而能提高生物多样性, 在一定程度上改善了水体。       

CLADISTIC AND BIOGEOGRAPHIC ANALYSIS OF THE "BLUE ASH' EUCALYPTS

Abstract— A cladistic analysis of the "blue ash" eucalypts ( Eucalyptus , Myrtaceae) is presented. Five equally parsimonious trees were found, and a strict consensus tree constructed. A revised informal classification, recognizing five series ( Planchonianinae, Sphaerocarpinae, Piperitinae, Fraxininae and Haemastominae , informal subgenus Monocalyptus ) is based on the consensus cladogram. A biogeographic analysis applies a new implementation of Assumptions 0 and 1, coding data in the form of three-area statements and using parsimony analysis. These results are used to evaluate hand resolution of Assumption 2. In comparison, Brooks parsimony analysis did not produce area cladograms that best fit the data. Series and subseries were analysed separately for area relationships, which showed a repeated pattern across the blue ash clade; combining all the data in one analysis was seen as equivalent to confounding paralogy and orthology in molecular studies. A resolved area cladogram is presented for southeastern Australia.     

STRUCTURE OF TRACHEIDS IN THREE SPECIES OF LYCOPODIUM

The structure of tracheids in Lycopodium lucidulum, L. clavatum, and L. tristachyum was studied with the light microscope. Protoxylem development is at least sometimes and possibly always mesarch in indeterminate axes of all three species. Centrifugally formed protoxylem elements are reticulate and discontinuities in the secondary walls of these elements are sometimes conspicuously bordered. Wall thickenings of first formed protoxylem elements consist mainly of indirectly connected rings. Late centripetally formed protoxylem elements and transitional elements have a reticulate secondary wall pattern. The narrowest metaxylem elements have circular bordered pits while in wider metaxylem elements pits are bordered and may vary from circular to scalariform. Pitting is uniseriate to triseriate in tracheids of all three species, and intermittent tetraseriate pitting was occasionally observed in L. lucidulum. Crassulae occur in tracheids of the three species, and in L. clavatum an additional framework, probably representing thickened compound middle lamella, is also present. Pits often appear helically arranged, and in all three species pits are connected by thin areas in the secondary wall. Macrofibrils approximately 0.5 μ wide were observed in tracheids of the three species. In L. clavatum the arrangement of macro-fibrils was predominantly bidirectional.     

三峡水库坝前水域浮游植物群落时空动态研究

于20122013 年对三峡水库坝前水域浮游植物组成、优势种、密度、生物量及多样性进行了周年季度调查, 共鉴定浮游植物151 种属, 其中绿藻门71 种, 硅藻门47 种, 蓝藻门20 种, 隐藻门和甲藻门各4 种,裸藻门和金藻门各2 种, 黄藻门1 种。浮游植物优势种的季节更替明显, 夏季和秋季优势种类为硅藻和绿藻,冬季为硅藻、蓝藻和绿藻, 春季为绿藻、硅藻和隐藻。浮游植物年均密度和生物量分别为3.95106 ind./L 和4.078 mg/L, 空间差异表现为支流和库湾远高于干流, 季节动态表现为夏季最高, 春季和冬季次之, 秋季最低。三峡水库坝前水域浮游植物多样性指数偏低, 水体污染类型属于-中污染。研究为客观了解三峡水库坝前水域浮游植物群落的空间分布与季节变化特征提供一定的参考依据。       

SHORT-TERM EVOLUTION IN THE SIZE AND SHAPE OF PEA APHIDS

Phenotypic evolution in contemporary populations can generally be witnessed only when novel selective forces produce rapid evolution. Examples of conditions that have led to rapid evolution include drastic environmental change, invasion of a new predator, or a host-range expansion. In cyclical parthenogens, however, yearly cycles of phenotypic evolution may occur due to the loss of adaptation during recombination in the sexual phase (genetic slippage), permitting an opportunity to observe adaptive evolutionary change in contemporary populations that are not necessarily subject to new patterns of natural selection. In insect herbivores, comparative studies suggest that morphological features that aid individuals in remaining on the plant or exploiting it as a food source are likely targets for selection. Here, we estimated the genetic variability of morphological traits in a cyclical parthenogen, the pea aphid (Acyrthosiphon pisum), to determine the potential for their evolution and we tested the hypothesis that size and/or shape evolves by clonal selection during one season of parthenogenetic reproduction. Genetic variation in a set of morphological traits was estimated using laboratory-reared descendents of clones collected from a single alfalfa field in May 1988 and April 1989 (henceforth, the “early” collections). In both years, there was significant clonal heritability early in the season both for overall morphology and for several individual aspects of size and shape. Because the course of short-term evolutionary change in the multivariate phenotype is a function of patterns of genetic covariance among characters, genetic correlations between size and 12 shape variables were also estimated for these early collections. A comparison between the mean phenotype of each early collection and that of a corresponding “late” collection made from the same field seven to eight clonal generations later in the same years revealed qualitatively similar changes in the average multivariate morphological phenotypes between the time periods in both years, although the difference was only significant for the 1989 samples. The pattern of genetic correlations that we estimated early in the 1989 season between overall size and various shape variables suggests that the observed short-term evolutionary changes in shape could have been due to natural selection acting only to increase overall size. We tested this hypothesis by estimating selection on size using a separate data set in which both demographic and morphological variables were measured on individuals reared under field conditions. Highly significant regressions of individual relative fitness on size were found for two major fitness components. Thus, it is likely that the evolutionary change in morphology that we observed is attributable to natural selection, possibly acting primarily through body size. A shift back to smaller size between the late 1988 and early 1989 collections from the same field suggests that either a cost of recombination or opposing selective forces during overwintering may produce persistent yearly cycles of morphological evolution in this cyclically parthenogenetic species.     

INTEGRIN EXPRESSION AND COLLAGEN TYPE II IMPLICATED IN MAINTENANCE OF CHONDROCYTE SHAPE IN MONOLAYER CULTURE: AN IMMUNOMORPHOLOGICAL STUDY

Chondrocytes grown in monolayer culture at low density, with serum added, either dedifferentiate after several days whereby their cell shape changes or they are overgrown by fibroblast-like cells. The aim of this study was to optimize the cultivation of chondrocytes in monolayer culture and to slow down their transformation or their overgrowth by fibroblast-like cells. For this purpose freshly isolated chondrocytes of cartilage anlagen from 17-day-old mouse embryos were grown on plastic or collagen type II-coated substrates. With this model: (a) chondrocytes grown on plastic substrates had almost completely changed to fibroblast-like cells after 5 days in culture. (b) When grown on collagen type II, the chondrocytes maintained their round phenotype for more than 2 weeks in culture. (c) Immunomorphological investigations showed that chondrocytes produce collagen type II and fibronectin and express specific surface receptors (integrins of the β1-group) on the membrane from day 1 until the end of the culture period when grown on collagen type II. (d) Treatment with β1-integrin antibodies clearly reduces chondrocyte adhesion on collagen type II by about 70%. Hence, these data indicate that the most probable influence of collagen type II on cellular behaviour depends on the integrins participating in a chondrocyte—collagen type II interaction, and this model represents a pure chondrocyte culture which allows cell growth for an extended period.