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1.
    
Harbours are important sites for the containment and dispersal of invasive species throughout the world, so the study of life history traits of species is important to understand the success of their invasion and their potential effects on the habitat. In recent years several invasive species have been reported in Argentinian harbours; however, studies of the ecology and life history of these species are scarce. We studied the population dynamics and reproductive biology of Monocorophium acherusicum and Ericthonius punctatus, in order to update the published information on the introduced amphipods in Mar del Plata harbour. Both species showed a seasonal pattern characterized by high densities in warmer months, related to the highest reproductive activity and the increase of recruitment in summer and early autumn, and lower densities in the cold season. The sex ratio was always female-biased and the number of eggs carried by females was positively correlated to the size. The present study suggests that both species have colonized Mar del Plata harbour successfully, showing viable populations (cohorts of juveniles, males, females and ovigerous females). This work provides the basis for monitoring the impact generated by introduced amphipods over the existing fauna.  相似文献   

2.
    
Since the first discovery along the Italian coasts in 2004 of the polychaete Branchiomma bairdi, it has spread very quickly, reaching some localities in very high densities. In order to monitor its colonization, recruitment was investigated by means of PVC panels immersed in the Mar Grande of Taranto (Ionian Sea). Panels were monitored every three months from April 2013 to January 2015. The species showed the ability to settle on bare panels as well as on panels with a developed fouling community. Two years of monitoring identified two different cohorts, with recruits appearing in both years on panels submersed from July to October. Based on these observations B. bairdi is a short-lived species (no more than one year), reproducing at a temperature ranging from 20 to 29°C and reaching sexual maturity three months after recruitment. Oocytes were found in the coelom only in the warmest months and oogenesis was not synchronous either within each individual or within the population. Total annual secondary production was estimated at 43.42?g?m?2?year?1. Annual mean biomass was 20.03?g?m?2. The corresponding P/B ratio was 2.1678. This study may explain the invasiveness of B. bairdi; indeed, a rapid generation turnover coupled with a short lifespan, rapid growth and early maturity are common traits in most invasive species.  相似文献   

3.
Different studies on the position of the non-indigenous species Neogobius melanostomus within the coastal food web of the Pomeranian Bay (western Baltic) were performed, resulting in a quantitative and qualitative species list of prey organisms found in the stomachs of the invader and an estimation concerning the importance of round goby as prey for different resident predators. It seems that the colonization process is not fully completed yet, but the results reveal that the species is already established in the food web 16 years after the first observation within the study area. The results show that N. melanostomus feed upon a wide range of different resident organisms. While a direct predation effect on native fish species appears rather unlikely, indirect effects such as competition cannot yet be excluded. In addition, our results reveal an ontogenetic diet shift and that the round goby itself already serves as an important prey for piscivorous fish and seabirds. Finally, we formulate different hypotheses based on our results which will require further research.  相似文献   

4.
The non-native seagrass species Halophila stipulacea has spread throughout the Eastern Caribbean since 2002, and could potentially impact the functioning of local seagrass ecosystems. Important characteristics for invasiveness, such as dispersal, recruitment and expansion of H. stipulacea at a local scale, are unknown. We assessed H. stipulacea expansion rates within Lac Bay, Bonaire, Dutch Caribbean (7?km2), since its establishment in 2010 and tested the settlement potential of uprooted vegetative fragments of H. stipulacea. Using 49 fixed locations, we observed that between 2011 and 2015 the occurrence of H. stipulacea in the bay increased significantly from 6% to 20% while native Thalassia testudinum occurrence decreased significantly from 53% to 33%. Free-floating H. stipulacea fragments that were collected and tethered above the sediment rooted within 10 days with a settlement success rate of 100%. The growth of settled fragments was on average 0.91 shoots d?1. The ongoing shift from native T. testudinum to introduced H. stipulacea dominated meadows may have important consequences for multiple Caribbean seagrass ecosystem functions. Given the large difference in size between the two seagrass species, functions such as coastal protection, habitat structure, food availability, and the stability and resilience of these systems can be altered. The next steps towards modelling future expansion of H. stipulacea throughout the Caribbean and beyond should include the assessment of fragment viability and dispersal distance, and the impacts of natural and anthropogenic disturbance on vegetative fragment density, dispersion and settlement by this species.  相似文献   

5.
The common scoter Melanitta nigra, velvet scoter M. fusca and long-tailed duck Clangula hyemalis (Aves: Anatidae) are among the more abundant sea ducks on the southern coast of the Baltic in winter, but their parasitic trematode fauna (Platyhelminthes, Digenea) in this region is little known. The aim of this study, conducted in 2007–2009, was a general comparison of the trematode fauna of these ducks in NW Poland. The prevalence and intensity of trematode infection were 68.3% and 119.9 in common scoter (101 examined), 77.6% and 13.1 in velvet scoter (58 examined) and 70.6% and 23.7 in long-tailed duck (68 examined). The following trematodes were found: Diplostomum pungitii, Apatemon gracilis, Australapatemon minor, Typhlocoelum sisowi, Echinochasmus spinulosus, Echinoparyphium recurvatum, Psilostomum brevicolle, Psilotrema simillimum, Catatropis verrucosa, Notocotylus attenuatus, N. gibbus, Paramonostomum alveatum, Prosthogonimus ovatus, Levinseniella propinqua, Gymnophallus bursicola and Cryptocotyle concava. The common scoter differs from the velvet scoter and long-tailed duck in its statistically significantly higher prevalence of G. bursicola; from long-tailed duck in its higher prevalence and greater intensity of infection with P. alveatum; and from velvet scoter in its greater intensity of infection with C. concava. The velvet scoter is distinguished from the long-tailed duck by its greater intensity of infection with P. brevicolle, lower prevalence of L. propinqua and lower intensity of infection with C. concava. Links between the differences found and the biology and ecology of the hosts, as well as the means of transmission of the parasites, are also discussed.  相似文献   

6.
As invasions become increasingly prevalent, it is important to understand how spread may be moderated by environmental conditions. This study considered the effect of location and changing substratum temperature on the early life-history processes of the alien barnacle Balanus glandula and its native comparator, Chthamalus dentatus, along the South African coast. Using settlement plates of different colours, temperature was manipulated to assess settlement, mortality, recruitment and growth of the two species. These variables were tracked over 10 weeks using repeat photography. Unexpectedly, there was no evidence of an effect of temperature on early life-history processes of either species. Settlement by the two barnacles was spatially segregated, with B. glandula occurring only on the West Coast where it is the dominant intertidal barnacle, while C. dentatus settled only on the South Coast, which has only recently been invaded by the alien. Despite this, it was notable that the relative settlement of B. glandula on rock was higher than that of C. dentatus. However, the lack of mortality of the native resulted in comparable levels of recruitment among the species. Nonetheless, the propensity of B. glandula to settle sporadically, coupled with fast growth, suggests that the invader may still possess the ability to become dominant along the newly invaded South Coast. This study highlights that measurements of early life-history parameters may not adequately predict the future range and impacts of alien species unless interpreted within the broader context of the nature of the recipient region and species-specific traits of the invader.  相似文献   

7.
This study documents the monsoonal and lunar effects on species composition and abundance of microzooplankton in a tropical estuary. We investigated microzooplankton abundance in relation to the various environmental and biotic parameters, sampled in the Matang mangrove (Malaysia) from April 2013 to February 2014. A total of 39 microzooplankton taxa comprising four major groups, i.e. loricate ciliates (37.72%), aloricate ciliates (29.46%), dinoflagellates (24.33%) and meroplanktonic nauplii (8.49%) were identified. The loricate ciliates were the most diverse group with 31 taxa recorded. Four major species of loricate ciliates were identified, i.e. Tintinnopsis beroidea, Tintinnopsis rotundata, Stenosemella avellana and Tintinnidium primitivum, while Strombidiidae and Strobilidiidae dominated the aloricate ciliates. Although small loricate ciliates were ubiquitous, redundancy analysis shows marked shifts in microzooplankton community structure, from one that was dominated by loricate ciliates during the drier SW monsoon, to aloricate ciliates at the onset of the wet NE monsoon, and then to dinoflagellates towards the end of the drier NE monsoon period. These shifts were associated with rainfall, dissolved inorganic nutrients, salinity, temperature and microbial food abundance. There was no clear lunar effect on abundance of microzooplankton except for Favella ehrenbergii and copepod nauplii, which were more abundant during neap than spring tides.  相似文献   

8.
9.
Kelly Bulkeley 《Dreaming》2003,13(1):49-60
This essay explores the influence of dreams and dreaming on the filmmaking of DavidLynch. Focusing particular attention on Mulholland Drive (2001), Lost Highway (1997), Blue Velvet (1986), and the television series Twin Peaks (1990–91), the essay will discuss the multiple dream elements in Lynch's work and how they have contributed to the broad cultural influence of his films. Lynch's filmmaking offers an excellent case study of the powerful connection between dreaming and movies in contemporary American society.  相似文献   

10.
One of the principal difficulties in assessing Science as aProcess (Hull 1988) is determining the relationship between the various elements of Hull's theory. In particular, it is hard to understand precisely how conceptual selection is related to Hull's account of the social dynamics of science. This essay aims to clarify the relation between these aspects of his theory by examining his discussion of the``demic structure' of science. I conclude that the social account cando significant explanatory work independently of the selectionistaccount. Further, I maintain that Hull's treatment of the demicstructure of science points us toward an important set of issues insocial epistemology. If my reading of Science as a Process iscorrect, then most of Hull's critics (e.g., those who focus solelyon his account of conceptual selection) have ignored promisingaspects of his theory.  相似文献   

11.
本研究在室内环境条件下进行,研究了不同饥饿程度和再投喂后中国林蛙的生长变化,并对中国林蛙饥饿后的补偿生长及其机制进行了分析。结果表明:中国林蛙经饥饿后再投喂,各处理组的体重已经赶上对照组的体重,其体重逐渐增加,经单因素方差分析,对比变化不显著,呈现出完全补偿生长。体重恢复过程中,各饥饿处理组的特殊生长率(SGR)、摄食率(FR)及饵料转化率(CE)均存在不同程度的差异。  相似文献   

12.
Lymphocytes derived from Lewis (LE), Brown-Norway (BN), or the F1 hybrid (LBNF1) rats respond in vitro to the mitogens phytohemagglutinin, concanavalin A, and pokeweed mitogen. The magnitude of the response, as determined by incorporation of 3H-thymidine, 14C-adenine, and 3H-leucine, was highest for LE and lowest for BN animals. These proliferation response differences were observed for lymph node lymphocytes and peripheral blood lymphocytes. The response to antigen, as measured by lymphocyte transformation, reflected the mitogen responsiveness of the strains tested, i.e., LE animals responded to a higher level than did BN animals. Equivalent levels of antibody were found in all animals immunized with antigen. In addition, BN rats are suppressed to a greater magnitude than are LE rats when both strains are primed, rechallenged, and assayed via lymphocyte transformation to the test antigen.  相似文献   

13.
Responses to concanavalin A or antigen by allogeneic combinations of Lewis (LE) and Brown-Norway (BN) rat derived lymphocytes and macrophages were of comparable magnitude to responses by the syngeneic combinations. But at increased concentrations of macrophages to lymphocytes, suppression of lymphocyte reactivity, as assayed by incorporation of tritiated thymidine, was evident. Suppression associated with BN derived macrophages alone, or in combination with LE or Buffalo derived macrophages, was consistently of a greater magnitude. Possible explanations of the macrophage associated suppression are discussed.  相似文献   

14.
Lewis (LE) and Brown-Norway (BN) rats treated in vivo with rabbit anti rat thymocyte serum demonstrate a reversal in relative responsiveness when assayed to mitogens and antigens via lymphocyte transformation, i.e., the BN rat now responds to a greater magnitude than the LE rats. Spleen cells, from both strains, that have been eluted from glass wool columns, demonstrate elevated responses to mitogens and antigens when compared to unfractionated spleen cells. The responses by these unfractionated and nonadherent populations can 1) be further enhanced subsequent to the treatment with anti-thymocyte serum and 2) suppressed after addition of macrophages from either strain, but especially by BN derived macrophages. The adherent cells from LE spleens respond to the above treatments in a similar fashion as the other populations. The responsiveness of adherent BN cells is only partially restored following treatment with anti-thymocyte serum, and is not further suppressed upon the addition of macrophages. These data are indicative of a lymphocyte-macrophage cooperation in this mechanism of suppression.  相似文献   

15.
在室内环境条件下研究了不同饥饿程度和再投喂后中国林蛙肝脏中蛋白质、糖原和脂肪含量的变化,并对中国林蛙在补偿生长过程中能量来源的变化进行了分析.结果 表明,饥饿状态下,中国林蛙的能量消耗主要来源于肝糖原,其次是蛋白质,即饥饿时中国林蛙首先动用糖原和蛋白质提供能量.  相似文献   

16.
温度变化对中国林蛙胚胎发育的影响   总被引:10,自引:1,他引:10  
开展中国林蛙南移和人工养殖是一项很有意义的工作,而南方多变的气温是否影响其胚胎发育是一个尚未研究的课题。本文利用受精卵在不同温度的恒温培养箱间移换,研究了温度变化对中国林蛙早期胚胎发育的影响,结果表明:(1)快速升温对中国林蛙胚胎孵化率、正常率均有影响,且温差越大影响越大;缓慢升温对胚胎的影响与温差大小和升温起点有关,高起点的升温对胚胎的影响比低起点的升温更大,生产中快速升温以不超过2℃,慢速升温以不超过4℃为宜。(2)慢速降温幅度为4℃时,对胚胎发育无影响,为8℃时,有影响;快速降温幅度为4℃时,对胚胎孵化率和正常率均有影响,生产中慢速降温以不超过8℃,快速降温以不超过4℃为宜。(3)变温幅度相同时,变温速度越大,对胚胎的影响越大。(4)原肠期是中国林蛙胚胎发育的升温敏感期,神经管期为升温非敏感期,中国林蛙胚胎发育中对升温变化较降温敏感。(5)中国林蛙的胚胎发育不会因南方天气的异常而遭到严重的影响。  相似文献   

17.
In 1988, David Hull presented an evolutionary account of science. This was a direct analogy to evolutionary accounts of biological adaptation, and part of a generalized view of Darwinian selection accounts that he based upon the Universal Darwinism of Richard Dawkins. Criticisms of this view were made by, among others, Kim Sterelny, which led to it gaining only limited acceptance. Some of these criticisms are, I will argue, no longer valid in the light of developments in the formal modeling of evolution, in particular that of Sergey Gavrilets’ work on adaptive landscapes. If we can usefully recast the Hullian view of science as being driven by selection in terms of Gavrilets’ and Kaufmann’s view of there being “giant components” of high-fitness networks through any realistic adaptive landscape, we may now find it useful to ask what the adaptive pressures on science are, and to extend the metaphor into a full analogy. This is in effect to reconcile the Fisherianism of the Dawkins–Hull approach to selection and replicators, with a Wrightean drift account of social constructionist views of science, preserving, it is to be hoped, the valuable aspects of both.
John S. WilkinsEmail:
  相似文献   

18.
    
Galvão P 《Bioethics》2007,21(6):324-328
I argue that David Boonin has failed in his attempt to undermine Donald Marquis's future-like-ours argument against abortion. I show that the ethical principle advanced by Boonin in his critique to that argument is unable, contrary to what he claims, to account for the wrongness of infanticide. Then I argue that Boonin's critique misrepresents Marquis's argument. Although there is a way to restate his critique in order to avoid the misrepresentation, the success of such restatement is precluded by the wrongness of infanticide.  相似文献   

19.
柑桔新害虫——高氏瘤粉虱研究   总被引:2,自引:1,他引:2  
高氏瘤粉虱AleurotubercutustakahashiDavidetSubramaniam是福建福州郊区桔园新发现的一种小型刺吸性害虫。国外在印度最早发现,并于1976年被鉴定命名。本文通过该虫在替换寄主茉莉花上的田间调查和室内饲养观察,对该虫的形态特征、生物学特性及防治对策作了初步探讨。高氏瘤粉虱在福州年发生约8-9代,主要以成虫、若虫刺吸为害柑桔和茉莉叶片,在28±1℃条件下,世代历期为26-31天。以高龄若虫或拟蛹越冬。其寄生性天敌有桨角蚜小蜂(Eretmocerussp.)、恩蚜小蜂(Encarsiasp.)等,寄生率为7.07-17.84%。  相似文献   

20.
应用日立835—50型氨基酸自动分析仪,对哈士蟆十种干样品进行了氨基酸成分的比较分析,结果表明:①必需氨基酸含量由高至低依次为雄蛙腿肉,雌蛙腿肉、卵、整只雄蛙、整只雌蛙、雄蛙皮、哈士蟆油、雌蛙皮、雌蛙腿骨、雄蛙腿骨。②氨基酸总量由高至低依次为雄蛙腿肉、雌蛙腿肉、雄蛙皮、雌蛙皮、卵、整只雄蛙、整只雌蛙、哈士蟆油、雌蛙腿骨、雄蛙腿骨。③雄蛙腿肉和雌蛙腿肉中各种氨基酸含量由大到小的排列顺序基本一致。  相似文献   

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