Plumatella trasimenica and Plumatella timwoodi, two new species belonging to the 'repens group' from central Italy (Bryozoa : Phylactolaemata : Plumatellidae)

Two new species – Plumatella trasimenica, from Lake Trasimeno and from an external sedimentation pond of a tropical fish farm, and Plumatella timwoodi, from Lake Piediluco – are described. These species belong to the ‘repens group’ (P. bushnelli Wood, 2001; P. geimermassardi Wood & Okamura, 2004; P. nitens Wood, 1996; P. repens (Linné, 1758); P. rugosa Wood, Geimer & Massard, 1998; P. similirepens Wood, 2001; P. viganoi Taticchi, 2010), because the annulus-chamber pores of the floatoblast are always characterised by the presence of long spines regularly distributed around the pores. Here, further morphological features, which distinguish them from the other species of the repens group, are described for both new species. The coexistence in the same sampling sites of species of the repens-group indicates that the new species are not ecomorphs of similar species.

Heavy metal contamination and antioxidant response of a freshwater bryozoan (Lophopus crystallinus Pall., Phylactolaemata)

Monthly variations of total glutathione, glutathione-S-transferases, glutathione peroxidase, glutathione reductase, glyoxalase I, glyoxalase II, and catalase were studied in Lophopus crystallinus, a freshwater bryozoan, collected from Lake Piediluco. Specimens were sampled during the vegetative period from November to April for two different cycles: cycle I from 1996 to 1997 and cycle II from 1999 to 2000. Simultaneously, analyses of heavy metal content such as lead, cadmium, chromium, nickel, copper, iron, and zinc were determined in the samples of L. crystallinus. Specimens of cycle II displayed highest chromium and iron accumulation and elevated levels of biochemical parameters. Total glutathione content, catalase, and glutathione peroxidase activities, were related with the highest metal concentrations in L. crystallinus from Lake Piediluco.

The strategy of ecosystem development: specific dissipation as an indicator of ecosystem maturity

The ratio of entropy generation rate to entropy embodied in structures relatively to the surroundings can be considered as an indicator of the ability of a self-organizing dissipative system to maintain itself far from equilibrium by pumping out entropy. The higher the ratio (which may be called the specific entropy production or the specific dissipation of a system), the lower the capacity of a system to convert the incoming low-entropy energy into internal organization. It appears that the ratio attains special significance for interpreting the evolution of biological systems, as the maximum expression of self-organizing systems, from the sub-cellular to the ecosystem scale. This paper proposes specific dissipation, written as the ratio of biological entropy production to exergy stored in the living biomass, as a thermodynamic orientor as well as an indicator of the development state of ecological systems. After having presented a method for estimating the specific dissipation in lakes, the adequacy of the proposed indicator is discussed and also tested by comparing its response to those of some classical ecological attributes (successional sequences of species, biodiversity, individual body size, structural organization and generation time of organisms) throughout the seasonal progression of the plankton community in Lake Trasimeno (Umbria, Italy). The results support the hypothesis that the minimization of specific dissipation is a primary criterion of evolution of ecological systems and also sustain the use of specific dissipation as an indicator of ecological maturity.

Antioxidant responses and bioaccumulation in Ictalurus melas under mercury exposure

Laboratory experiment was carried out to determine mercury accumulation in tissues (gills, kidneys, liver, and muscle) and biochemical responses in the liver of freshwater teleost Ictalurus melas. Catfish were subjected to different concentrations of Hg(2+) (35, 70, and 140 microg/L) for 10 days. The chemical analyses showed higher mercury concentrations for all treatments in gills and kidneys followed by liver and muscle. At the lowest mercury concentration a decrease in glutathione (GSH) content and an increase of GSH peroxidase Se-dependent and glyoxalase II enzymes were observed. An increasing trend was observed also for GSH-S-transferase and glyoxalase I, while GSH peroxidase Se-independent enzyme and GSH reductase showed no significant variation in activities. The increase in the enzymes activities of catfish, involved in the inactivation of reactive molecules formed during oxidative stress, could provide an additional protection against the oxidative damage induced by mercury.