Heavy Metals — Soil Communities at Ecological Risk

This article outlines an effect of the different kinds of environmental pollution on the soil nematode communities at two industrial regions (Krompachy and Jelšava) of eastern Slovakia. At the locality Krompachy, soil nematode communities were significantly affected by increased concentrations of As, Cd, Cu, and Zn. At the other location Jelšava, despite low concentrations of heavy metals, long-term emissions of magnesium dust had indirect impact on soil environment through altered soil conditions, mainly by alkaline pH. Pollution effects at the community structure (trophic and c-p groups) of soil nematodes were found to be the highest near the pollution sources, where communities with low population densities consisted mainly of disturbance-tolerant taxa from c-p 1 and c-p 2 groups. With an increasing distance from the pollution sources, the nematode communities were more structured and complex, with higher proportions of sensitive c-p 4 and 5 nematodes, composed mainly of predators and omnivores. Ecological indices (H´, MI2-5, SI) also clearly showed deteriorating environmental conditions towards the pollution sources. The greatest difference in the nematode community structure between the two localities was found in the proportion of c-p 1 and c-p 2 bacteriovorous nematodes. At the locality Krompachy characterised by critical heavy metal load, c-p 2 nematodes dominated, while c-p 1 nematode group prevailed at under extremely alkaline soil conditions in Jelšava. Results also showed that the free-living nematodes are useful tools for bioindication of industrial contamination and could be used as an additional source of information to the common approaches based on chemical methods

Ecological Risk and Distribution of Polychlorinated Biphenyls in Fish

The distribution and concentrations of polychrolinated biphenyls (PCBs) were determined in nine freshwater fish species and the parasite Acanthocephalus lucii in Zemplínska šírava, a heavily polluted water reservoir in Slovakia. The study performed at two different time points five years apart (2004 and 2009) revealed excessive PCB contamination of the fish muscle tissue and significant interspecies as well as tissue-specific differences in PCB uptake by fish. Total PCBs broadly correlated with the trophic position of individual fish species within a food chain (P adipose tissue > muscles > hard roe > bones > brain. Maximum concentrations of PCBs were recorded in the liver of northern pike (214.0 mg.kg-1 lipid wt) and the hepatopancreas of freshwater bream (163.0 mg.kg-1 lipid wt). Individual congeners were not distributed homogeneously within the investigated organs and the adipose tissue. PCB 153 was present in the higher concentrations than other congeners in all fish organs as well as the adipose tissue. Acanthocephalans absorbed significantly higher concentrations of PCBs (P<0.001) than the muscles, liver, kidney, brain and adipose tissue of their host. About 20-fold lower PCB levels was detected in the liver and almost three times in the muscles of infected perch. Data on PCB accumulation in perch infected with acanthocephalans demonstrated a decline of PCB values in all organs as well as the adipose tissue compared to uninfected fish. The study has shown that the fish species, its feeding habit and specific conditions of the habitat are mutually interrelated factors that are responsible for significant variations in fish body burdens

What are the evolutionary constraints on larval growth in a trophically transmitted parasite?

For organisms with a complex life cycle, a large larval size is generally beneficial, but it may come at the expense of prolonged development. Individuals that grow fast may avoid this tradeoff and switch habitats at both a larger size and younger age. A fast growth rate itself can be costly, however, as it requires greater resource intake. For parasites, fast larval growth is assumed to increase the likelihood of host death before transmission to the next host occurs. Using the tapeworm Schistocephalus solidus in its copepod first intermediate host, I investigated potential constraints in the parasite’s larval life history. Fast-growing parasites developed infectivity earlier, indicating there is no functional tradeoff between size and developmental time. There was significant growth variation among full-sib worm families, but fast-growing sibships were not characterized by lower host survival or more predation-risky host behavior. Parental investment also had little effect on larval growth rates. The commonly assumed constraints on larval growth and development were not observed in this system, so it remains unclear what prevents worms from exploiting their intermediate hosts more aggressively

The taxonomic status of

The taxonomic status of the fish cestode Proteocephalus dubius La Rue, 1911, a rare parasite of perch (Perca fluviatilis), is discussed on the basis of morphological and isoenzyme analyses. The results reveal that P. dubius represents only an infrequent morphological form of P. percae characterized by a small, rounded and shallow apical organ, elongate and/or rectangular proglottides and relatively long cirrus-sac reaching to the mid-line of the proglottis

On the host specificity of fish tapeworm

Host-parasite interactions established between Proteocephalus exiguus and its fish hosts have been analysed in two localities in Slovakia. P. exiguus occurred and sexually matured in three salmonid hosts - rainbow trout(Oncorhynchus mykiss), brown trout(Salmo trutta m. fario), brook trout (Salvelinus fontinalis) — and in perch (Perca fluviatilis), first recorded as a final host of this parasite. The parasite usually strictly prefered its principal, most suitable host (rainbow trout) or some other salmonid hosts. The new fish host species (perch) harboured P. exiguus rather frequently, but only in altered ecosystem, if salmonids were not available in sufficient number in the environment. Large adaptive ability of P. exiguus manifested in its survival in four fish hosts of two distant families (Salmonidae, Percidae) and modified seasonality in unusual fish host indicate broader host specificity (stenoxenous in sense used by Euzet & Combes, 1980) than generally attributed to this species. The host specificity in some other Proteocephalus tapeworms is briefly discussed