Lethal and mutagenic effects of elevated temperature on haploid yeast

Summary The lethal and cytoplasmic mutagenic effects of 52°C incubation during the cell cycle of a haploid strain of Saccharomyces cerevisiae were examined. Both effects varied periodically in a rather parallel pattern: the maximum thermosensitivity was seen at budding time, corresponding to the S period (Williamson, 1965). The 52°C induction of a nuclear forward mutation was also examined: canavanine-resistant mutants were induced by this treatment. Exponentially growing cells were much more sensitive than resting cells to the different effects of heating which were studied. On the other hand, on comparing asynchronous cultures of 6 different radiosensitive mutants only one (xrs₅) showed a greater thermosensitivity than the corresponding wild type.     

Vertical distribution of vendace Coregonus albula L. and other pelagic fish species in some Polish lakes

Studies on the vertical distribution of vendace Coregonus albula (L.), smelt Osmerus eper-tanus (L.) and bleak Alburnus alburnus (L.) in lakes have been carried out with the application of an echo sounder and then compared with control catches of fish and plankton, Methods and results have been discussed. Some remarks have been made on taking these species of fish.     

Lake connectivity and fish species richness in southern Brazilian coastal lakes

Connectivity is a key factor in metacommunity ecology, because it influences dispersal and colonization rates. However, it has received less attention in aquatic than in terrestrial ecology research. We investigated whether connectivity is a good predictor of species richness in functional fish communities (freshwater, FS; estuarine, ES and estuarine-freshwater, EFS) from 31 coastal lakes in southern Brazil. We used a model selection approach, including lake area and distance from the ocean as additional predictors of species richness and two connectivity metrics: primary connectivity (C _P) and estuarine connectivity (C _E), which measure connectivity to neighboring lakes and system-wide connectivity, respectively. Both metrics estimate functional connectivity and were calculated on habitat-based cost distances. Connectivity was more important for predicting richness of functional communities than for total richness, particularly C _E, which was distinctively related to each functional fish community richness (directly related to ES and EFS, and inversely related to FS; C _P was related only to ES). Remarkably, connectivity was more important than area for predicting ES and EFS richness. These results add support to dispersal limitation as an important mechanism influencing fish communities. We suggest that incorporating environmental filters (habitat type) to quantify connectivity is useful for accessing the patterns of species richness.     

Production of some oligochaete species in large Estonian lakes

The production of Potamothrix hammoniensis, Lamprodrilus isoporus, and Uncinais uncinata was estimated in the eutrophic lakes Peipsi-Pihkva and Vôrtsjärv. Growth characteristics of these species are briefly described. Calculated production values were 6–32 (P. hammoniensis), 19–79 (L. isoporus), and 1–4 kJ m² (U. uncinata), respectively. The annual P/B ratios for the same species were, 0.8–1.7, 2.5–4.8, and 4.4–5.4, respectively.     

Seasonal and artificially elevated temperatures influence bioenergetic allocation patterns in the common pond snail, Physella virgata

Allocation of organic carbon (OC) to primary energetic pathways was estimated under seasonal and artificially elevated ambient temperatures for a field population of a freshwater pulmonate snail, Physella virgata. Allocation to respiration increased with temperature. Snails allocated most assimilated OC to reproduction within their natural temperature range (15 degrees -35 degrees C), where assimilation efficiencies remained relatively stable at 25%-35%. However, in artificially heated waters exceeding 35 degrees C, declining assimilation rates and increasing respiratory demands inhibited allocation to reproduction and growth. At the species' 40 degrees C upper thermal limit, assimilation efficiencies fell below 10%, while average consumption levels more than doubled relative to snails unaffected by the thermal effluent. Ambient temperature substantially influenced OC allocation over P. virgata's natural temperature range and negatively affected growth and reproduction at temperatures approaching or exceeding maximum natural levels.     

Studies on chrysophyceae from some ponds and lakes in Alaska vi occurrence of synura species

Summary The Synura species found in samples from a variety of freshwater habitats in Alaska are identified by electron microscope studies of their scales. Synura petersenii f. macracantha Petersen & Hansen and Synura spinosa f. curtispina Petersen & Hansen are raised to specific rank. Synura petersenii f. praefracta n. f., Synura curtispina f. reticulata n. f., and Synura echinulata f. leptorrhabda n. f. are described. Electron micrographs of some scales belonging to undesignated formae are given.Some remarks on the ecology of the Synura species are given.

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Zusammenfassung Synura Arten, die in Proben aus verschiedenen Süßwasser-Lokali-täten in Alaska gefunden werden sind, werden durch elektronenmikroskopische Untersuchungen ihrer Schuppen beschrieben. Zwei Formen, Synura petersenii f. macracantha Petersen & Hansen und Synura petersenii f. curtispina Petersen & Hansen, werden zur Rangstufe der Arten erhoben. Zwei neue Formen, Synura petersenii f. praefracta and Synura curtispina f. reticulata, werden beschrieben.Elektronen-mikroscopische Abbildungen einiger Schuppen, die von unbeschriebenen Formen herrühren, werden gegeben.Einige Anmerkungen über die Ökologie der Synura-Arten werden gemacht.

     

Lethal temperatures of a Neotropical fish relic in Patagonia, the scale-less characinid Gymnocharacinus bergi

Southern South America has a rather low fish species diversity. Gymnocharacinus bergi, the southernmost characid fish of the world, is the only member of Characoidei in the Argentine Patagonia. The isolation of this species in an endorheic stream has been linked to the thermal conditions of its habitat, the head-waters of the Valcheta Stream, which is the only site where this species occurs. We provide information on the distribution and thermal habitat of this species and other fishes in the Valcheta Stream. The responses of G. bergi to high and low temperatures were assessed in the laboratory under different temperatures and heating and cooling rates. Our results suggest that G. bergi is unable to extend its distribution to the colder waters nearby, as well as to waters with greater temperature fluctuations. We discuss the implications of our experimental data, the habitat of G. bergi, and the known responses of a few other paranensean fishes to temperature, within the framework of the thermal ecology of freshwater fishes.     

Larval anisakid infections of some tropical fish species from north-west Australia

Despite the commercial and zoonotic importance of larval anisakid infestations of teleosts, their distribution among Australia's diverse marine fish fauna is poorly understood. A preliminary survey of Australia's tropical north-west revealed a generally high prevalence of larval anisakids representing four genera (Anisakis, Terranova, Thynnascaris and Raphidascaris) among only seven fish species. The potential impact of high larval anisakid infections on both the health of recreational fishermen and aquaculture environments is discussed.     

Assessing lake typologies and indicator fish species for Italian natural lakes using past fish richness and assemblages

In order to establish a fish-based typology of Italian lakes and identify possible reference and indicator fish species for each lake type, we analysed historical data on fish assemblages of all Italian natural lakes >0.5 km² from the period prior to the major decline in water quality in the 1950s. General linear regression models showed the ecoregion and lake altitude being the best predictors of fish species richness. The number of species was significantly higher in the Alpine than in the Mediterranean ecoregion. Among Alpine lakes, the number of fish species increased significantly with lake volume whilst decreased with altitude. In the Mediterranean lakes, none of the selected parameters was significant. Cluster analysis of fish assemblages (presence/absence) divided the lakes of the Alpine and Mediterranean ecoregions into four and two types, respectively. Pike (Esox lucius), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were the main indicator species for the small and mostly shallow lakes in both the Alpine (Type 1) and Mediterranean (Type 6) ecoregions, minnow (Phoxinus phoxinus) for the alpine high altitude lakes (Type 2) and landlocked shad (Alosa fallax lacustris), European whitefish (Coregonus lavaretus) and burbot (Lota lota) for the large and very deep alpine lakes (Type 4). The European whitefish was the only indicator species for the deep Mediterranean lakes (Type 5). These species and associated fish assemblages may be useful indicators in future assessments of the ecological status of Italian lakes according to the European Directives (2000/60/EC and 2008/105/EC).     

Trace elements as fingerprint of lake of provenance and of species of some native and exotic fish of northern Patagonian lakes

A survey of trace element contents in fish muscle and liver was performed in different lakes of two northern Patagonian national parks: Nahuel Huapi and Los Alerces national parks. The aim of the work was to obtain the first set of reference data on elements that are not liable to be disturbed by human activities and to identify compositional patterns related to the species and site of collection. The species studied are native creole perch and velvet catfish and exotic brown trout, rainbow trout, and brook trout. The elements analyzed are Br, Cs, Fe, Rb, Se, Na, and Zn. Trace elements in muscle of brown trout, rainbow trout, and creole perch showed statistical patterns that allow one to identify the national park of origin, as well as which of the lakes (Traful, Espejo Chico, or the Nahuel Huapi-Moreno system) of the Nahuel Huapi National Park from which they come. Contents in the liver provide similar but less clear patterns than contents in muscle; however, in some particular cases, they provide additional information. Trace element contents in muscle are also good indicators of the species collected within a lake.     

Ectoparasite infection of some fish species in lake Pleshcheev

Ectoparasites have been investigated on gills of the ruff, perch, white bream, roach, bream, ide, and European cisco from the Pleshcheevo lake. 13 parasite species were found: Dactylogyrus falcatus, D. distinguendus, D. cornoides, D. cornu, D. sphyrna, D. robustus, D. amphibothrium, Ancyrocephalus paradoxus, Argulus foliaceus, Ergasilus sieboldi, Achtheres percarum, Ancyrocephalus percae, and Rhipidocotyle companula. A reliable negative correlation between the number of monogeneans An. paradoxus and the copepods Ac. percarum on the perch. D. falcatus, the specific monogenean of the bream, was found on the roach. The comparison of the obtained data with those of 1939 has shown the decrease of oxyphilic copepods E. seiboldi, that prove the increasing eutrophication.     

The growth of young pike in small Finnish lakes with different acidity-related water properties and fish species composition

Pike growth was generally slower in small Finnish lakes than has been reported from large lakes or brackish coastal waters. Growth was unrelated to pH, alkalinity, COD, or conductivity of the water, but length of 1–2-year-old pike correlated positively with water colour (i.e. humic content), nitrogen content, and phosphorus content. These water properties also correlated with each other. Growth of 1–2-year-old pike was negatively correlated with lake area in lakes smaller than 20 ha.
In lakes with a strong roach population or without ruffe the 0 group pike grew faster than in lakes without roach or with ruffe. The growth of pike aged 1–4 years in two very acid and practically fishless lakes did not differ clearly from the rest of the lakes, although the pike were forced to forage for abundant acid resistant invertebrates like dragonfly nymphs (Odonata) or Asellus aquatlcus .
The results of this work support earlier studies where the growth rate above all depends on water temperature and food availability. Acidity was not shown to affect the growth rate of pike.     

Fatty acid content of some freshwater fish of commercial importance from tropical lakes in the Ethiopian Rift Valley

Fifty samples of freshwater fish, representing eight tropical species, were collected from Ethiopian Rift Valley lakes in order to study the variation of lipids and fatty acids (FA) both within and between species. Most specimens (36 samples) were low in fat, ≥5% of dry weight (dw). Medium- (nine samples) and high-fat fish (five samples) contained ≤6% and >10% dw, respectively. The extent of variation was more pronounced in the herbivore Oreochromis niloticus than in the omnivorous (e.g. Barbus sp.) or carnivorous–piscivorous ( Clarias gariepinus ) fishes. Twenty-eight FA of various chain lengths and saturation levels were identified. Most FA were unsaturated and long-chained. The major individual FA were palmitic acid (16:0), stearic acid (18 : 0), oleic acid (18 : 1ω9) and docosahexaenoic acid (DHA) (22 : 6ω3). The ω3/ω6 ratio varied considerably (1·1–7·6) and O. niloticus from Lake Haiq was found to be superior in lipid quality to all the tropical fish species considered in this study. The data show that tropical freshwater fish are comparable to temperate freshwater fish as sources of polyunsaturated FA.     

Studies on Chrysophyceae from some ponds and lakes in Alaska

Summary A new variety, Mallomonopsis elliptica var. salina, of M. elliptica var. elliptica Matwienko is described as seen in the living state in the light microscope, and in the electron microscope. The locality in which it was found is described.

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Zusammenfassung Eine neue Varietät, Mallomonopsis elliptica var. salina, von M. elliptica var. elliptica Matwienko wird beschrieben. Sie wurde in lebendiger Gestalt in dem Lichtmikroskop and in dem Elektronenmikroskop beobachtet. Der Fundort wird beschrieben.