Salinity dependence of parasite infestation in the European eel Anguilla anguilla in northern Germany

The aim of the study was to examine metazoan parasite communities of European eels (Anguilla anguilla) in fresh-water, brackish water and marine localities in northern Germany. In all, 29 parasite species/taxa were found in 170 eels: eight digeneans, one monogenean, five cestodes, ten nematodes, two acanthocephalans, and three crustaceans. Measures of diversity characteristics of the helminth communities included species richness, Shannon's diversity index and its evenness, and the Berger–Parker dominance index. The highest species diversity and lowest dominance values were calculated for the helminth communities of eels from the two Baltic Sea localities. Parasite communities of European eels clearly exhibit the habitat preferences of their hosts, salinity-dependent specificities, and a clustering into fresh-water, brackish, and marine groups. The highly pathogenic parasite species Anguillicola crassus and Pseudodactylogyrus spp. were found at all sampling sites in fresh water and brackish water, with high prevalence. Basic information is provided on the risks of restocking programmes solely focusing on fresh-water sites

Population structure of anisakis simplex (nematoda) in harbor porpoises phocoena phocoena off Denmark

The population structure and habitat selection of Anisakis simplex in 35 harbor porpoises off Denmark are described. The nematodes were collected from the stomach and duodenal ampulla and were categorized as third-stage larvae, fourth-stage larvae, subadults, and adults. The porpoises harbored 8,043 specimens of A. simplex. The proportion of adults and subadults increased with infrapopulation size. The number of development stages across infrapopulations covaried significantly (Kendall's test of concordance). Concordance was higher in hosts with the highest intensities than in those with low and medium intensities. All stages occurred mainly in the forestomach, but this trend was stronger for the adults. Adult and subadult sex ratios did not depart significantly from 1:1. Our data suggested that recruitment and duration of each stage were the main factors accounting for infrapopulation structure. The preference of A. simplex for the forestomach conformed with previous studies, but the narrower distribution of adults relative to other stages might indicate a strategy to enhance mating opportunities. Information on sex ratios of A. simplex is scarce and contradictory. We suggest that the discrepancies might partly reflect differences in categorization criteria and statistical methods.Herreras Belled, Maria Victoria, [email protected] ; Balbuena Diaz-Pines, Juan Antonio, [email protected] ; Aznar Avendaño, Francisco Javier, [email protected] ; Raga Esteve, Juan Antonio, [email protected]

The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms

Many parasitic infections, including those of humans, are caused by complex lifecycle parasites (CLPs): parasites that sequentially infect different hosts over the course of their lifecycle. CLPs come from a wide range of taxonomic groups-from single-celled bacteria to multicellular flatworms-yet share many common features in their life histories. Theory tells us when CLPs should be favoured by selection, but more empirical studies are required in order to quantify the costs and benefits of having a complex lifecycle, especially in parasites that facultatively vary their lifecycle complexity. In this article, we identify ecological conditions that favour CLPs over their simple lifecycle counterparts and highlight how a complex lifecycle can alter transmission rate and trade-offs between growth and reproduction. We show that CLPs participate in dynamic host-parasite coevolution, as more mobile hosts can fuel CLP adaptation to less mobile hosts. Then, we argue that a more general understanding of the evolutionary ecology of CLPs is essential for the development of effective frameworks to manage the many diseases they cause. More research is needed identifying the genetics of infection mechanisms used by CLPs, particularly into the role of gene duplication and neofunctionalisation in lifecycle evolution. We propose that testing for signatures of selection in infection genes will reveal much about how and when complex lifecycles evolved, and will help quantify complex patterns of coevolution between CLPs and their various hosts. Finally, we emphasise four key areas where new research approaches will provide fertile opportunities to advance this field

Massovaja invazija metacerkarijj Bucephalus polymorphus Baer 1827, v glazu leshha - Abramis brama (L.)

The mass incidence of the parasite was detected in Abramis brama (L) from the dam reservoir of the Gródek-Żur electricity works on the Wda river (Bydgoszcz voivodeship). Seven breams weighing 530-1530 g, measuring 29/35-41/49 cm in lenght (longitudo corporis, longitudo totalis). In all fishes there was a strong protrusion of the cornea that showed small white spots, visible with naked eye (Phot. 1). Post-mortem examinations revealed considerable enlargement of the anterior chamber of the eye with small amount of the vitreus and sticky, hazy fluid in the bulbus. The cornea contained numerous metacercariae (Phot. 2); a mass incidence of the latter was also found under the skin, on the head, anterior part of the body, on pectoral fins and on gills. The most charactcristic changes appeared in the cornea, where metacercariae were present in extremely high numbers; they were either single and disseminated of formed large accumulations. Occasionally, the cornea showed canals burrowed by migrating larvae prior to incystation (Phot. 3). On the transversal sections of the cornea there are holes containing encysted metacercariae; laceration of the corneal surface and separation of the tissue layers are visible (Phot. 4). At autopsy, the cornea was friable, which could be seen distinctly from the presence of transversal fissures in the microtome sections (Phot. 5)