This paper challenges two paradigms long held in relation to the ecology of parasites in freshwater systems: (1) autogenic species are poorer colonisers than allogenic ones; and (2) parasites with direct life cycles are more successful colonisers than those with complex life cycles. Using new and existing data for Acanthocephala in freshwater fish from the British Isles, it is suggested that all six species present have been able to colonise and persist successfully, in spite of the supposed limitations of their autogenic life-style. It is proposed that these parasites have overcome these limitations by a variety of means, which apply equally to all species considered. Foremost among these is the utilisation of a migratory fish host as either a preferred or a suitable host in their life cycle, allowing colonisation of new areas and rescue effects in established areas, whilst equally important is the use of a common and widespread crustacean as the intermediate host. In addition, all six species appear to exhibit resource partitioning by host at either or both the larval and adult stages, thus reducing the potential for competition and further facilitating colonisation and survival. This hypothesis is supported by data from previous studies both on acanthocephalans from Europe and North America and on other autogenic parasites. It also provides an explanation for the apparently atypical host utilisation patterns of some acanthocephalan species in areas on the edge of their distributions, notably in Ireland.
Over the decades, islands have provided a useful background for the evaluation of the consequences of isolation upon populations. Epigenetic and morphometric divergence among black rat (Rattus rattus) populations from Western European island (São Miguel, Terceira, Flores, Porto Santo, Berlenga, Corsica) were analysed and compared with mainland reference populations (Portugal, France, Morocco). Neither of the two approaches showed insular samples to have greater distinctiveness than those from the mainland. The overall pictures of epigenetic and morphometric similarity among populations were concordant, apparently in agreement with their probable origin from founder individuals brought by former maritime traffic. Mainland populations were more variable, but only according to morphometric characters. The adaptive and evolutionary significance of the patterns found may be related to both the period of population isolation and island area.
In natural European waters, the congeneric monogeneans Gyrodactylus derjavini Mikailov, 1975 and G. salaris Malmberg, 1957 are primarily found on brown trout Salmo trutta L. and Atlantic salmon Salmo salar L., respectively. Interestingly, rainbow trout, Oncorhynchus mykiss (Walbaum), originating from North America, is as susceptible as brown trout to G. derjavini. However, the mechanisms involved in this host specificity are poorly understood but may include behavioural, mechanical and chemical factors affecting parasite attraction, attachment, feeding, reproduction and host responses. In the present laboratory work, this question has been studied. Detached parasites (either G. derjavini or G. salaris) were offered a choice in small aquaria between fry of rainbow trout, Atlantic salmon and carp Cyprinus carpio L. Within 48 hours more than 90% of G. derjavini colonised rainbow trout and left salmon almost uninfected. Some parasites were found on carp. During the same time span, more than 60% of G. salaris attached to salmon, the rest infected rainbow trout and none were found on carp. Following attachment, the parasites need appropriate stimuli to initiate feeding and reproduction but even such a successful specific colonisation can be followed by a host response. Both humoral and cellular elements have been suggested to participate in these reactions but in the present work it was demonstrated by immunoblotting and immunocytochemistry that no antibodies in host mucus and host plasma bound to any parasite structures or epitopes.
Článek se zabývá otázkou hospodářských a politických podmínek, které se promítly do sídelní výstavby trutnovského městského regionu ve 13.–14. století. Vznik manských sídel v rámci trutnovského lenního obvodu, podmíněný strategickými zájmy českých panovníků na pomezí Čech a Slezska, předpokládal nejprve kolonizaci podhorského kraje a vytvoření prvotních hospodářských struktur. Ty spojujeme se zavedením ekonomicko- správních institucí na německém právu (vikbilda) ve 2. polovině 13. století. Vznik manských vesnic a opevněných sídel, datovatelný na základě písemných i hmotných pramenů do 1. pol. 14. stol., resp. do doby kolem královského záboru konstituujícího se města Trutnova na přelomu 13. a 14. stol., znamenal nejen zahušťování sídelní sítě, ale také dotváření spádové tržní oblasti. Efektivní kolonizace, právní výhody, využívání přírodních zdrojů, tranzitní poloha a hospodářský rozvoj kraje poskytovaly v ekologicky náročných podmínkách záruky stability sídel a plnění jejich ekonomických a politicko-vojenských funkcí. and This article considers the question of the economic and political conditions projected onto the settlement build-up around Trutnov town in the 13th–14th centuries. The colonisation of the unoccupied foothills and the creation of the initial economic structures foreshadowed the appearance of vassal settlements in the Trutnov feudal lien, conditioned by the strategic interests of the Bohemian sovereigns in the Czech/Silesian borderlands. These are linked to the established economic/administrative institutions of German law (the weichbild) in the second half of the 13th century. The appearance of vassal villages and fortified seats, dated on the basis of written and material sources to the first half of the 14th century, i.e. to the period around the royal annexation constituting Trutnov at the turn of the 14th century, not only meant an increase in the density of the settlement network, but also the completion of a market catchment area. Effective colonisation, legal advantages, the use of natural resources, a transit location and the economic development of the region provided settlements a guarantee of stability in environmentally challenging conditions and of the fulfilment of their economic and politico-military functions.
Various population indices are widely used to monitor relative population size of many pest and game species to aid their management. However, information on the level of uncertainty associated with their estimates is rarely available. Here we explore sampling and systematic error associated with the index of re-opened burrow entrances which is used extensively in central Europe for surveying common vole populations. We found that relative sampling errors were enormous for low-density populations, attaining almost 400%. However, in high-density populations and for large sample sizes, the relative error dropped below 10% and the estimate is quite reliable. The dispersion of burrow entrances became more clumped at low population densities enhancing further the sampling variation. We demonstrated that the index is related to population size in a non-linear fashion, overestimating the population change at high densities. Consequently, population dynamics of the common vole described by the untransformed burrow index appear more variable than they are in reality.
Large migratory movements that followed after Sutamarský peace (1711) in Hungary significantly changed the ethnic structure of its population. They included also migration of Slovaks to present-day Romania Bihor area. This colonization process took place in several waves since the late 18th to 19th century, supported by the Hungarian aristocracy. In contrast to the settlement of fertile lowlands in "Dolná zem" (Lower Country) the motivation of migration were land use of mountain Plopis, located in Bihor in northwestern Romania. Article deals with the problem of the origin of the Slovak population in Romania Bihor in the context of the work of Romanian linguist and Slovakist - Grigore Benedek, with respect to the language.