长江口中肋骨条藻赤潮发生全过程调查报告

于1990年6月在长江口赤潮多发区定点观测到一次中肋骨条藻赤潮发生的全过程，对中肋骨条藻赤潮发生过程中浮游植物群落结构的变动及细胞形态的变化进行研究。结果表明，（1）中肋骨条藻赤潮发生前，水体中甲藻数量多于硅藻；赤潮发生后，中肋骨条藻增殖，逐渐成为主要优势种，硅藻在数量上超过了甲藻；浮游植物种类丰度指数的大小能较好地反映赤潮发生的各个阶段。（2）赤潮发生过程中，中肋骨条藻细胞增殖率次序为：发展阶段＞维持阶段＞起始阶段。（3）在赤潮发生的维持阶段后期和消亡阶段，有5％-7．8％的中肋骨条藻形成休眠孢子，一个中肋骨条藻细胞仅形成一个休眠孢子，且同一个中肋骨条藻群体链上的所有细胞形成休眠孢子是同步的。     

生活史(休眠孢囊)作为甲藻有害藻华年际频发和地理扩散的一种关键机制的研究进展

过去几十年,中国近海有害藻华的发生频率、规模和面积不断增大, 对我国水产养殖业、渔业和近岸生态系统造成了重大损失和威胁。 在引起有害藻华的众多原因中,藻华甲藻的特殊生活史策略,尤其是形成休眠孢囊,提供了一种关键的机理,因为孢囊的形成过程常伴随着基因重组从而增加了藻华藻的生态适应性;孢囊厚的囊壁增加了其对不利环境条件的耐受性;厚的囊壁使其免于病原体感染和捕食攻击;孢囊的适时萌发为藻华提供了“种源”;孢囊可通过自然或人为原因如船舶压舱水传播从而扩大了其地理分布。我们综述并讨论了甲藻生活史和孢囊研究的如下几个重要方面：１）甲藻生活史的复杂性和有关甲藻孢囊概念及归类的争议;２）沉积物中孢囊“作图（cyst mapping）”在藻华模型和预测（报）中的重要性以及孢囊分布/丰度与藻华规模耦合关系的复杂性和条件依赖性;３）孢囊形成和萌发的若干影响因子及其复杂性和可变性;和４）最近些年来分子生物学技术和各种组学手段在甲藻生活史和孢囊研究中的部分应用,特别是植物激素在孢囊形成、萌发过程中的可能作用。在简要评述了国际、国内有关研究历史中的路标性成果后,最后强调了四个值得重视的研究方向。     

http://www.sciencedirect.com/science/article/pii/S1674987114000887

The increasing number of fossil pterosaur eggs sheds light on nesting environments and breeding be- haviors of these extinct flying reptiles. Here we report the first partial three-dimensional egg of the pterosaur, Pteroduustro guinazui, from central Argentina. The specimen was discovered from the same Albian deposits as the exceptional R guinazui embryo described in 2004. Microscopic characterizations indicate a pristine preservation of the 50 Bm thick calcium carbonate, which differs significantly from the soft shell of Chinese pterosaur eggs. Estimate of the eggshell conductance implies that the nest had a minimum moisture content of 75%. This moisture estimate, combined with geological and taphonomical data, suggests that P. guinazui may have adopted a nesting strategy similar to those of grebes and flamingos rather than being buried on land, as previously hypothesized. Moreover, our results demon- strate that the nesting paleoenvironment of this pterosaur species was closely linked to a mesohaline lacustrine ecosystem in a basin governed by regional tectonic subsidence, a setting characteristic for the feeding and reproduction of modern flamingos.     

Knoblochia cretacea,Late Cretaceous insect eggs from Central Europe

The genus Knoblochia is established for fossil insect eggs. The fossils are small, longitudinally ridged, ovoid to round with projections on both ends. Their thin perforated wall is covered by minute papillae, inner surface of the wall is smooth or covered by rectangular files of cells. Fossils assigned here to Knoblochia cretacea were earlier assigned to the genus Spirellea, which encompass a heterogenous complex of small fossils being or resembling angiosperm seeds from the Late Cretaceous. The majority of species of the genus Spirellea clearly represents remains of angiosperms. However, fossils described by Knobloch and Mai (1986) as Spirellea kvacekii are distinct, particularly in having external walls perforated, neither apex nor basal projection showing any absition scar or micropyle in the botanical sense. Attribution of these fossils to insects led us to designate the new name Knoblochia cretacea with a new holotype for fossils of this kind. Comparison of Knoblochia with insect eggs of species of Phasmatodea and Lepidoptera, and seeds of Stemonaceae showed clear affinity to insects. Due to the high amount of extinction among insects since the Cretaceous, the systematic affinity of Knoblochia remains open.     

Modulation of longevity in Daphnia magna by food quality and simultaneous exposure to dissolved humic substances

Various abiotic and biotic factors determine the natural fluctuations of Daphnia spec. populations; food quality and dissolved humic substances (HSs) being among these factors. In this contribution, we try to disentangle the relative impact of food quality and simultaneous HSs exposure on the fertility and longevity of D. magna. It is understood that HS-mediated stress leads to reduced fecundity in well-fed D. magna females; hence, it was expected that poor food, as a second stressor, would aggravate the HS-mediated effects. Three diets were tested: the green algae Pseudokirchneriella subcapitata, baker’s yeast alone, and baker’s yeast plus dissolved ascorbic acid, and exposed D. magna to a HS preparation which has been shown effective in previous bioassays. It was hypothesized that the lifespan and fertility of D. magna would be best when fed green algae, and worst when fed only baker’s yeast. However, contrary to these expectations, any addition of HSs reduced the stress caused by poor food quality and increased lifespan and fecundity. In the yeast series, asexually produced diapausing eggs occurred via a so far unknown pathway. With yeast diet, the expanded lifespans were slightly above, whereas the increased offspring numbers lay below, the corresponding data of the algae-fed individuals. The potential of HSs as an additional food source and as a means to extend the lifespan is discussed. These findings open the innovative perspective that under low quality food conditions, additional stressors at certain intensities may even be beneficial to individuals and populations.     

Eggs and larvae of the trevally caranx georgianus (Teleostei: Carangidae)

The development and distinctive features of the eggs and larvae of Caranx georgianus Cuvier, 1833 are described. Diameters of the egg and oil globule range between 0.76 mm and 0.86 mm, and 0.20 mm and 0.25 mm respectively. At 21 °c, the eggs hatched approximately 28 h after fertilisation.     

Sediments of lakes Rotoroa and Rotoiti,South Island,New Zealand

The chemistry and mineralogy of the sediments of Lakes Rotoroa and Rotoiti, South Island, New Zealand (41° 51 S, 172° 38 E and 41° 50 S, 172° 50 E respectively) , were studied. In general, the cation exchange properties, element concentrations, and mineral compositions of the sediments show little variation between samples from each lake. However, some nutrient concentrations, notably exchangeable calcium, magnesium, and potassium, and total nitrogen and sulphur, are higher in sediments from weed beds than in sediments underlying deeper water; iron and manganese concentrations tend to show the opposite trend. Concentrations of exchangeable calcium and total nitrogen, sulphur, manganese, and iron generally decrease down the sediment profiles from the sediment/water interface. Differences between lakes, notably higher concentrations of illite and of the elements potassium, aluminium, titanium, and zirconium, and lower concentrations of calcium in the sediments of Lake Rotoiti than in those from Lake Rotoroa, are probably due mainly to the different geological settings rather than to differences in the diagenetic processes operating within the lakes. Mineralogical analyses indicate that the lake sediments are derived mainly from the valleys of the major inflow rivers rather than from the slopes at the sides of each lake.     

Rates of coastal erosion and accretion in New Zealand

Abstract

Rates of coastal erosion and accretion for New Zealand are calculated for the period since early European colonisation. Methods used for calculating rates from cadastral plans, vertical aerial photographs and field measurements are described, evaluated, and illustrated with examples. The most natural reference line for measurements of shoreline changes and for defining the seaward boundary of land is the seaward limit of land vegetation. Measurements made from air photographs and plans at scales larger than 1:4000 have errors less than ± 1 m. As scales become small, errors increase proportionately. Along depositional shorelines, erosion and accretion generally occur at 0.5–4.0 m.y^?1. Maximum erosion and accretion rates are 25.4 m.y^?1 at North Kaipara Head and 68.9 m.y^?1 at Farewell Spit respectively. Cliff recession generally occurs at 0.25 ‐ 1.0 m.y^?1 with maximum rates of 2.25 m.y^?1 for mudstone cliffs at Cape Tumagain and 3.46 m.y^?1 for conglomerate cliffs at Ngapotiki.     

Possible functions of surface structure and size in some planktonic eggs of marine fishes

Chorionic surface sculpturing on the eggs of 7 marine fish species was examined under a scanning electron microscope. The effect of sculpturing on descent rates of 3 of these eggs was experimentally compared with 10 non‐sculptured egg types of different sizes. It is suggested that although in some species sculpturing represents vestigial tendrils, in others sculpturing and increased egg size may relate to ascent rates between the spawning site and the sea surface.     

Thermoregulatory and osmoregulatory responses to dehydration in the bushy-tailed gerbil Sekeetamys calurus

Desert rodents are occasionally exposed to long spells of drought. We aimed to examine how such dehydrating conditions affect resting metabolic rate (RMR), non-shivering thermogenesis (NST) and osmoregulatory capabilities in the desert inhabiting species Sekeetamys calurus. Dehydration was imposed by gradually increasing salinity of drinking water and by feeding the animals a high-protein diet. S. calurus responded to osmotic stress by reducing RMR, increasing NST capacity, reducing urine volume and increasing urine concentration. It is suggested that the reduction in RMR is an adaptation for conserving water, while the increase in NST capacity compensates for the reduction in RMR.