A field test for competitive effects of<Emphasis Type="Italic"> Aedes albopictus</Emphasis> on<Emphasis Type="Italic"> A. aegypti</Emphasis> in South Florida: differences between sites of coexistence and exclusion?

We tested whether interspecific competition from Aedes albopictus had measurable effects on A. aegypti at the typical numbers of larval mosquitoes found in cemetery vases in south Florida. We also tested whether the effect of interspecific competition from A. albopictus on A. aegypti differed between sites where A. aegypti either persists or went extinct following invasion by A. albopictus. Similar experiments manipulating numbers of A. albopictus in cemetery vases were conducted at three sites of A. aegypti persistence and three sites where A. aegypti was apparently extinct. The experiments were done using numbers of larvae that were determined by observed numbers of larvae for each site, and with resources (leaf detritus) that accumulated in experimental vases placed into each field site. In both the early rainy season (when number of mosquito larvae was low) and the late rainy season (when number of mosquito larvae was high), there was a significant effect of treatment on developmental progress of experimental A. aegypti. In the late rainy season, when numbers of larvae were high, there was also a significant effect of treatment on survivorship of A. aegypti. However, the competition treatment × site type (A. aegypti persists vs extinct) interaction was never significant, indicating that the competitive effect of A. albopictus on A. aegypti did not differ systematically between persistence versus extinction sites. Thus, although competition from A. albopictus is strong under field conditions at all sites, we find no evidence that variation in the impact of interspecific competition is associated with coexistence or exclusion. Interspecific competition among larvae is thus a viable explanation for exclusion or reduction of A. aegypti in south Florida, but variation in the persistence of A. aegypti following invasion does not seem to be primarily a product of variation in the conditions in the aquatic environments of cemetery vases.     

胰岛素样生长因子IGF系统与鱼类性腺的研究进展

IGFs系统包含3个配体(IGF-1、IGF-2、IGF-3)、2个受体(IGF-1R、IGF-2R)和6个IGF结合蛋白(IGFBP).生殖和生长是生物体最基本的特征,两者既密切相关又相互区别,胰岛素样生长因子(IGFs)是生长轴和生殖轴相交联的关键因子.最近研究表明:鱼类性腺的发育及成熟伴随着细胞分化和组织生长,传统的生长因子IGF-1、IGF-2和最近发现的IGF-3,对鱼类性腺发挥着重要作用.本文重点介绍鱼类特有的配体IGF-3的结构,鱼类IGFs系统的信号通路及其与鱼类性腺的相关性研究进展.     

L－赖氨酸盐酸盐精制与研究

利用Ｄ型—大孔吸附树脂处理工业品Ｌ－赖氨酸盐酸盐,其精制品含量高,收得率高,适用于工业化生产。精制品可以用于氨基酸输液或其它氨基酸制剂中,也可做食品添加剂使用。     

Sexual differentiation,gonad development,and spawning seasonality of the Hawaiian butterflyfish,Chaetodon multicinctus

Synopsis The reproductive biology of the coral reef butterflyfish,Chaetodon multicinctus, was investigated by histological examination of gonads sampled over an 18 month period from a shallow inshore population on Oahu, Hawaii. Most gonads developed directly from previously undifferentiated tissue. Ovarian development (the structural formation of lamellae and primary oocytes) was observed in fish ≥44 mm and testicular development (the formation of spermatogenic crypts) in fish ≥62 mm standard length (SL). In addition, testis formation was identified within the ovarian lamellae of several differentiated but immature fish. It is hypothesized that prematurational sex change may facilitate monogamy within the highly competitive social structure of this site attached species. Oocyte development in mature females was marked by distinct phases of primary growth, the formation of yolk vesicles, and vitellogenesis. Spawning activity was histologically identified by the maturation and hydration of fully yolked oocytes, and presence of postovulatory follicles. Recently spawned females from field collections and experimental gonadotropin-treatments exhibited postovulatory follicles that were estimated to persist at least 24 h after ovulation. Atresia of yolked oocytes was classified into four stages of cell degeneration and resorption. Monthly analyses of oocyte development and atresia within the sample population show thatC. multicinctus has a protracted annual spawning season with a major peak during the early spring and evidence of spawning activity among some individuals in the fall. Histological analyses of spawning activity provide more accurate and unambiguous information than do traditional gonadosomatic assays in this and probably other coral reef fishes.     

Seasonal variation and the immune response: a fish perspective

The environment in which an animal lives affects the physiology and psychology of that animal. The greater the distance from the equator the more profound this influence becomes, as the environment becomes more variable over the years. Temperature, photoperiod, precipitation and other environmental conditions, which are directly or indirectly controlled by the season, can affect an animal. It is becoming apparent that these conditions may impact on the immune system, and this can affect animal health. This review looks at the known mechanisms for transducing environmental cues and how these can affect immune parameters and function. The main focus is fish, especially in relation to aquaculture and the associated disease risks. Work on other animal classes is included for comparison.     

Freshwater fish biodiversity in the Yangtze River basin of China: patterns, threats and conservation

We synthesized information on freshwater fish biodiversity in the Yangtze River basin. We documented 361 species and subspecies that had been recorded and described from the basin. Of these, 177 species are endemic. The basin is usually divided into three parts, i.e. the upper reaches, the middle reaches and the lower reaches. This study indicated that the three reaches approach was not supported by fish distribution patterns. Hydrological alterations are perhaps the largest threat to fish biodiversity in the basin. Fishes in the upper reaches will be seriously affected by the construction of the Three Gorges Dam and other dams, and action should be taken for priority conservation. The most immediate restoration need is reconnection of the Yangtze River with its lakes. The cluster of lakes in the Central Yangtze should be protected to maintain habitats for spawning, feeding and migration of migratory fishes. Our study indicates a need to identify areas of high fish biodiversity and to select nature reserves to mitigate the loss of fish biodiversity in the Yangtze River basin.     

A multi-level approach using Gambusia affinis as a bioindicator of environmental pollution in the middle-lower basin of Suquía River

The Suquía River middle-lower basin (Córdoba, Argentina) is subjected to a strong anthropogenic impact because it receives pollutants from different sources. The main goal of this study was to evaluate the introduced fish species Gambusia affinis as a bioindicator of environmental pollution in the middle-lower basin of the Suquía River. The assessment was performed by measuring biomarkers at different levels of biological organization, at two sampling sites (before and after Córdoba city), and at dry and wet seasons. Water quality evaluation was made through a water-quality index (based on physico-chemical parameters), heavy-metals and pesticides concentrations in water. The water quality varied between sampling sites, showing the most degraded conditions downstream Córdoba city. The same pattern of variation was detected in the biomarkers studied, mainly in: gill and liver histopathological indexes, copulatory organ (gonopodium) morphology and vitellogenin expression in males and females. The present study characterized the environmental conditions in the middle-lower basin of the Suquía River and revealed the low freshwater quality at the most polluted site. Although G. affinis is an introduced species, it could be considered a good sentinel of water resource quality of invaded Neotropical basins. Our results demonstrated the importance of addressing the environmental quality monitoring through an integrated analysis of water quality parameters together with histological, morphological and molecular parameters. Thus, our study provides a good model for application in other basins of South America.     

Resistance of an invasive gastropod to an indigenous trematode parasite in Lake Malawi

Successful establishment and spread of biological invaders may be promoted by the absence of population-regulating enemies such as pathogens, parasites or predators. This may come about when introduced taxa are missing enemies from their native habitats, or through immunity to enemies within invaded habitats. Here we provide field evidence that trematode parasites are absent in a highly invasive morph of the gastropod Melanoides tuberculata in Lake Malawi, and that the invasive morph is resistant to indigenous trematodes that castrate and induce gigantism in native M. tuberculata. Since helminth infections can strongly influence host population abundances in other host-parasite systems, this enemy release may have provided an advantage to the invasive morph in terms of reproductive capacity and survivorship.     

A preliminary study on quantitative relations among growth,reproduction and mortality in fishes

As a quantitative approach to the life histories of fishes, the present paper attempted to predict a relation among reproduction, growth and mortality numerically with a technique of control theory, the discrete maximum principle. A method for predicting the relation was derived on the postulate that natural selection maximized the net reproductive rate subject to a few constraints. The derived method was applied to Atlantic cod and Atlantic herring populations in the Southern Gulf of St. Lawrence as numerical examples. The examples demonstrated that the theoretical reproductive effort and body weight were well consistent with the observed ones every age but the theoretical survival rates were slightly different from the observed ones. For the reasons mentioned below, however, it should be interpreted that the examples rather support the adopted postulate to a certain degree. First, in general, it is very difficult to obtain good estimates of the rates with traditional methods. Second, intense fishing pressure possibly changes the life history parameters to some extent in fish populations. Moreover, the examples also suggested that, to examine the postulate in further detail, similar analyses had to be made with the data of many fish populations on which intense fishing pressure had not been exerted.     

娘子关泉胶串珠藻生长和分布的季节动态

1992年9月至199年6月间,对分布于山西娘子关泉的胶串珠藻(Batrachospermum gelatinosum)生长和分布的季节动态进行了研究.定期测定水温、pH值、流速、藻体出现频度、平均盖度和藻体的一些形态特征.结果表明,娘子关泉域水体温度、水体的pH值和流速季节变化幅度都不大;藻体出现频度和盖度有明显的季节性变化,从秋季到次年的春季逐渐增加,生长最旺盛的时期在5月;藻体生长发育有明显的季节性变化规律,在晚秋到早夏生长良好,在春末夏初生长达到高峰,而且藻体各部分的生长和发育基本上同步.     

淡水鱼类寄生粘孢子虫两新种的记述

在整理1982年从湖北省宜都市和1984年从湖北省黄岗市团风镇采集的长江鱼类粘孢子虫标本的过程中,作者发现寄生于鳜[Siniperca chuats(Basilewsky)]和蛇(Saurogobio dabrui Bleeker)的两种粘孢子虫,经鉴定是文献中没有报道的新物种[1]。模式标本保存在中国科学院水生生物研究所鱼病病原标本室。     

Exotic species of freshwater decapod crustaceans in the state of São Paulo,Brazil: records and possible causes of their introduction

Based on recent surveys of the freshwater decapod fauna, distributional data of five exotic species of freshwater decapod crustaceans for the hydrographic basins of the state of São Paulo are presented, as part of a large initiative for a comprehensive survey of the state’s biodiversity (BIOTA-FAPESP Program). These species are the North American crayfish Procambarus clarkii (Girard) (Cambaridae), the crab Dilocarcinus pagei Stimpson (Trichodactylidae) from the Amazon and Paraguay/lower Paraná River Basins, and the palaemonid shrimps Macrobrachium rosenbergii (De Man), from the Indo-Pacific region, Macrobrachium amazonicum (Heller) and Macrobrachium jelskii (Miers), both from the Orinoco, Amazon and the Paraguay/lower Paraná River Basins. Possible modes by which their introduction might have occurred are commented upon and potential consequences are discussed.