Lake Vela is a shallow lake facing eutrophication, like many other freshwater reservoirs. A reduction in biodiversity has been observed and cyanobacterial blooms are frequent, occasionally leading to large fish kills. An annual sampling cycle was carried out in the present study, with the aim of understanding the present seasonal variation of Lake Vela’s physico-chemistry and cladoceran assemblage. The present results were compared with those obtained in previous studies. Presently, Lake Vela is facing higher nutrient and Chl a levels than in past years. The cladoceran assemblage is now dominated by small-bodied forms, such as Chydoridae and Bosmina longirostris, except in the spring peak of Daphnia longispina. Still, the seasonal pattern of the cladoceran community is more or less coherent with the general model observed in other temperate lakes. The results also suggest that this was a rather unusual year, with a Daphnia summer peak, probably because of a large fish kill that occurred in late spring.

Six species of the sub-family Cyclocypridinae were found in the Upper Miocene of the Turiec Basin, 4 of which are new Cypria isosceles, C. lenticulata, C. polyphema, C. bodergatiae. The differences in arrangement of the zone of the fusion on ventral margin were used to distinguish the species. The genus Cypria is represented in whole area of the Turiec Basin but the species are restricted to the ecologically well determined biotopes. Valve shape is compared with ecological stability of the paleobiotopes.

Tetrazolium reduction and enzyme kinetics were examined to estimate the ETS activity of decomposing reed (Phragmites australis /Cav./ Trin. ex Steud.) rhizome to collect information on the activity of microbial decomposers. Optimal incubation time was determined at 22 °C. For complete enzyme extraction, 4-6 min. of homogenization was necessary. The main substrates of the enzymatic reaction were NADH and NADPH. The reaction was fastest when 2-(-p-iodophenyl)-3-(-p-nitrophenyl)-5-phenyl tetrazolium chloride (INT ; 0.8 mM), NADPH (0.25 mM) and NADH (1.7 mM) were applied simultaneously. The optimal incubation time should be less than 20 minutes. The pH optimum of the enzyme reaction is 8.0-8.4. ETS activity of decomposing reed rhizome can be used to estimate potentially the oxygen consumption of microorganisms involved in decomposition and, indirectly, the rate of decomposition.

A new species of the genus Allocyclops Kiefer, 1932 (Cyclopidae, Cyclopinae) is described from the subterranean waters of Barrow Island, Western Australia. It belongs to the subgenus Psammocyclops Kiefer, 1955, but has not any close relatives among the recent known species. With the addition of the new representative the genus Allocyclops now includes thirteen species on all continents, except Asia and Antarctica. A key to aid in their identification is provided.

The larval morphology of 20 water mite species from Alpine springs is described, with that of Protzia distincta, Tartarothyas romanica, Sperchon mutilus, S. resupinus, S. violaceus, Bandakia concreta, Lebertia cuneifera, L. lativentris, L. sefvei, Atractides adnatus, A. panniculatus, A. macrolaminatus and A. walteri being presented for the first time. For the other 7 species (Panisus michaeli, Panisopsis curvifrons, Thyas palustris, Partnunia steinmanni, Sperchon thienemanni, Lebertia zschokkei and Hygrobates norvegicus), old descriptions exist but, in most cases are not accurate enough to be usable in taxonomy. These species have therefore been re-described. Some general observations on larval morphology and taxonomy are discussed. A short survey of the larval descriptions of West-Palaearctic water mites in general and of spring-living taxa in particular is given, together with a perspective for future research into larval morphology in this geographical area.

A revised diagnosis of Mixobates Thor, 1905, is given, including the proposal to rank this taxon as a separate genus. The species so far published from the palaearctic region are revised. Adults of M. caucasicus Tuzovskij, 1990 are described for the first time and the following synonyms are established : M. uncatus Sokolow, 1930 = M. processifer Thor, 1905 ; M. lundbladi Schwoerbel, 1957 = M. incurvatus Láska, 1954. The latter species is for the first time recorded from the Mediterranean area. Four new species are described : M. acutidentatus, M. brachypalpus and M. uncatellus from Russia, and M. maghrebinus from Morocco. A dichotomic key for the determination of the palaearctic species is presented.

From an ecological viewpoint, diel vertical migration (DVM) of zooplankton is an adapted response to environmental factors. DVM coincides with changes in light intensity, but persists also under constant illumination conditions. This fact suggests the existence of an internal clock. In Daphnia longispina, it could be located in the eye. Indeed, the spatial distribution of the pigments containing in the eye ommatidia exhibits significant changes over time when Daphnia are kept under light/dark (LD) conditions. These variations coincide with displacements of the organisms. Furthermore, it is observed that the blue/dark conditions, which inhibit DVM, also stop changes in the distribution of pigments in the ommatidia. The modifications of the eye observed under LD white light represent either the internal clock or its manifestation.

This paper focuses on relationships between the North Atlantic Oscillation Index (NAO) and the ice conditions in coastal lakes (Jamno, Bukowo, Gardno and Lebsko) of the southern Baltic Sea. The data on ice conditions included : date of first ice appearance (F), date of last ice disappearance (D), number of days with ice (N), length of the ice season (in days ; S) and maximum ice thickness (H) during the given winter. The period examined covers the winters from 1960/61 to 1999/2000. The monthly values of the NAO index for the same period were applied in accordance with Jones et al. (1997). Correlation and regression analysis methods were applied to determine and study the relationships between NAO (independent variable) and the parameters of ice conditions (dependent variables). The strongest relationships, with a linear correlation coefficient exceeding - 0.80, were obtained for the date of the last ice disappearance (D) in Lebsko Lake (- 0.853) and Gardno Lake (- 0.828) for the January March period. In contrast, the relationships between the NAO index and the date of first ice appearance (F) are much weaker. They are statistically significant only in November and early winter (Nov.-Dec., Nov.-Jan.). The correlation coefficients in the coastal lakes of the Southern Baltic Sea coasts generally increase eastwards, a phenomenon related to the severity of winters and to the increasing continuity of ice phenomena during a given winter in this direction.

Pourriotia carcharodonta gen. et sp. nov. is described from freshwater plankton collected at the subantarctic Kerguelen islands. The new taxon is provisionally placed in the Notommatidae. Main diagnostic characters separating the new taxon and the other genera of the family are provided by the morphology of the trophi. Apical rami chambers with toothed inner margin and blunt projection on outer margin. Apical rami teeth and subuncinal teeth with accessory spines. Proximal margin of major uncinal teeth firmly connected to distal margin of apical chambers, forming grasping unit. Fulcrum dumb-bell-shaped. Information is presented on the trophi structure of the genus Pleurata (Notommatidae).