Effect of hydrophyte thickets density on zooplankton

An experimental study on the zooplankton community in the thickets of elodea Elodea canadensis Michx. of different densities (2, 4, and 8 g/L, wet weight/L) has been conducted. It is revealed that specific cationic composition and pH and sharp daily fluctuation of oxygen concentrations is a characteristic of the water in dense thickets of plants. Changes in water chemistry and in spatial organization of the environment influence zooplankton diversity and population dynamics of some species. With an increase in density of thickets, the number of Daphnia longispina O.F. Müller decreases, while the share of predators (Cyclopidae and Polyphemus pediculus O.F. Müller) increases. The abundance of Ceriodaphnia quadrangula (O.F. Müller) increases in the presence of plants, but does not depend on the density of the thickets. The correlation between the development of Simocephalus vetulus (O.F. Müller) and Diaphanosoma brachyurum (Liévin) and water cationic composition, changing in the process of growth and senescence of plants, is revealed.     

Pelagic cladocera in upper volga water reservoirs

The results of cladoceran crustaceans studies in the pelagial of the Ivankovo and Uglich water reservoirs were generalized. In the period of 1973–1995, both waterbodies were similar in terms of Cladocera species composition and the dominating complex. The list of species composition of pelagic cladocerans has increased since the 1950s. The highest abundance of cladocerans was observed in the Ivankovo water reservoir. Daphnia cucullata G. Sars has been stably dominant in zooplankton summary biomass, while Chydorus sphaericus (O.F. Müller) and Bosmina longirostris (O.F. Müller) prevailed in terms of abundance. Changes in the pelagic cladoceran complex composition is evidence of the waterbodies’ eutrophication. The share of Cladocera in the zooplankton’s total summer biomass was 68 and 53% in the Ivankovski and Shoshinski stretches of the Ivankovo water reservoir, correspondingly, and 60% in the Uglich water reservoir (on average for 1970s–1990s).     

Mitochondrial morphogenesis and ultrastructure of basidiomycetes from genera Agaricus and Pleurotus

Supravital study of rhodamine-stained mitochondria in cells of aerial and submerged micelium of 31 strains from 9 species from genus Agaricus (A. arvensis Schaeff., A. bisporus (Lange) Imbach, A. bitorquis (Quel.) Sacc., A. campestris L., A. excellens, (F.H. Müller) F.H. Müller, A. macrocarpus (F.H. Müller) F.H. Müller, A. silvaticus Schaeff., A. silvicola (Vittad.) Peck, A. xanthodermus Genev) and of 2 strains from 2 species from genus Pleurotus (P. ostreatus (Jacg.) P. Kumm., P. pulmonarius (Fr.) Quel.) was carried out. Mitochondrial morphogenesis in micelial cells of species from Agaricus and Pleurotus genera has many common features in distribution of mitochondria in micelial cells both under the favorable growth conditions and during chondriom reorganization (fission and fragmentation of mitochondria to small subunits) under unfarovable growth conditions and during aging. During the balanced growth of mycelium of heterokaryotic strains from genera Agaricus and Pleurotus for 7–14 days on agar media as well as during cultivation of mycelium of oyster mushroom and several strains of field mushroom in submerged culture, distribution of mitochondria by the type 1 (small granular mitochondria in the apical zone—1, long rod-like mitochondria in the subapical zone—2 and short rod-like and granular mitochondria formed as a result of fragmentation of rod-like mitochondria in mature mycelium cells—3) was observed. Under unfarovable growth conditions (starvation), in mycelium cells of homokaryotic strains of champignon, during long cultivation of all strains and species from the studied genera and during cultivation on liquid wort, for majority of champignon, distribution of mitochondria by the type 2 was observed (sphere-like mitochondria in all cells of the studied mycelium zones). Mitochondrial profiles at ultrastructural level had specific features, such as associations of the outer mitochondrial membrane with cytoplasmic ribosomes and changes in cristae structure. The preliminary test for apoptosis-like phenotype of the submerged mycelium cells of Bs94 champignon that hardly grows in the submerged culture gave positive result. Thus, mitochondrial morphogenesis in mycelium cells of Agaricus and Pleurotus species under different conditions and terms of cultivation occurs similarly and is determined by a complex of physiological and biochemical processes reflecting the state of mycelium cells.     

Eudiaptomus anatolicus n.sp. (Copepoda: Calanoida) from Turkey

Eudiaptomus anatolicus n.sp. displays similarity to E. transylvanicus (Daday, 1890) by possessing an outer marginal spine located proximally on the second exopodite segment of the male right P₅, but it differs from this closest species in the presence of a chitinous projection on the second exopodite segment of the male right P₅, and in the typical shape of the female's thoracic wings. E. transylvanicus (Daday, 1890) has three chitinous processes located on the basipodite segment of the male right P₅, whereas Eudiaptomus anatolicus n.sp. has only one small process on this part. This new species is living in lake Poyraz, which is small and shallow. Some cladoceran species, namely, Pleuroxus truncatus (O.F. Müller, 1785), Pleuroxus laevis (Sars, 1862), Pleuroxus trigonellus (O.F. Müller, 1785), Simocephalus exspinosus (Koch, 1841), Eurycercus lamellatus (O.F. Müller, 1785), Alonella excisa (Fischer, 1854), Lathonura rectirostris (O.F. Müller, 1785), Pseudochydorus globosus (Baird, 1843) and two cyclopoid copepods, Megacyclops viridis (Jurine, 1820) and Eucyclops serrulatus (Fischer, 1851) share the same habitat. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of individual variability on the outcome of competition between cladoceran species

Simulation modeling was performed to study the impact of individual variability on the population dynamics of particular cladoceran populations and the outcome of interspecific competition at low and high temperatures. The study was performed on one species of small size (Ceriodaphnia quadrangula O.F. Müller) and one species of large size (Simocephalus vetulus O.F. Müller). Laboratory experiments were performed to estimate the average values of principal demographic parameters of these species and their coefficients of variability at two temperatures, 18 and 27°C. Population dynamics of the two species in mono- and mixed cultures was simulated with and without accounting for individual variability using available published data and our own data on demographic parameters. Individual variability was shown to help populations survive unfavorable trophic conditions and to give competitive advantage over populations in which all individuals of the same age are identical. Individual variability decreased with rising temperatures due to probable acceleration of physiological processes.     

The dynamics of abundance of <Emphasis Type="Italic">Simocephalus vetulus</Emphasis> (O.F. Müller, 1776) (Crustacea,Cladocera) under acyclic stepwise changes in temperature

This experimental study examines the influence that acyclic stepwise temperature regimes with 4.4 and 8.8°C increments in a range of 14.8 to 25.5°C have on the dynamics of the number of Simocephalus vetulus (O.F. Müller). It is revealed that an increase in the number of this dominant species of littoral zooplankton may be stimulated by differently directed acyclic stepwise changes in temperature. However, the maximal development of the population is registered after a decrease in water temperature from 24.3 ± 0.7 to 20.4 ± 0.5°C and from 19.9 ± 0.8 to 15.5 ± 0.4°C. Under the same temperature conditions, a prolonged stimulating effect is observed. Our results confirm the assumption put forward earlier that, in order to define the real ecological optimum for a species by a specific environmental factor, it is necessary to consider not only the limits of the optimal values of the factor, but also the dynamics of their changes and the possibility of after-effects of the factor (prolonged and delayed effects).     

The freshwater fauna of Macquarie Island, including a redescription of the endemic water-flea Daphnia gelida (Brady) (Anomopoda: Crustacea)

The freshwater invertebrate fauna (excluding the Protozoa) of Macquarie Island is collated. This includes two Platyhelminthes, two Gastrotricha, three Tardigrada, 41 rotifera, at least eight Nematoda, nine Annelida, and 21 Arthropoda. The latter comprises six species of Anomopoda, two Copepoda, two Ostracoda, an Isopoda, five Acarina, and at least five species of Insecta with aquatic or semi-aquatic larvae. The freshwater Anomopoda (Cladocera) of Macquarie Island are re-evaluated, six species are now recognized and the largest, identified as Daphnia gelida (Brady), is redescribed. The records of both Alona weinecki Studer and Pleuroxus macquariensis Frey are confirmed, while that of Macrothrix hirsuticornis Norman and Brady is accepted with some reservations. Alona quadrangularis (O.F. Müller) is re-instated and records of Chydorus sphaericus O.F. Müller ascribed to C. patagonicus Ekman.     

Chydorus arcticus n.sp., a new cladoceran crustacean (Chydoridae: Chydorinae) from the North Atlantic arctic and Subarctic areas

Chydorus arcticus n.sp. (Cladocera: Chydoridae: Chydorinae) is described, figured, and differentiated from the closely relatedC. sphaericus (O.F. Müller, 1785). The known distribution of the species is given, and some aspects of speciation of arctic crustaceans are pointed out.     

Length–weight relationship of Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) off Brazil,southwestern Atlantic Ocean

This study reports the length–weight relationships (LWRs) for two elasmobranch species, Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) collected from the southwestern Atlantic, off Brazil. Both are considered endangered species. The LWR data can be taken into consideration for further management and conservation plans.     

Comparing the low‐salinity tolerance of Ulva species distributed in different environments

The green macroalgal genus Ulva (Ulvales, Ulvophyceae, Chlorophyta) is distributed worldwide from marine to freshwater environments. Comparative analyses of hyposalinity tolerance among marine, brackish, and freshwater Ulva species were performed by fluorescein diacetate viability counts. The subtidal marine species Ulva sp., collected from a depth of 30 m, showed the poorest tolerance to low salinity. This species died in 5 practical salinity units (PSU) artificial seawater or freshwater within 1 day. Its closely related species U. linza L. (an intertidal species) and U. prolifera Müller (a brackish species) showed varying tolerances to low salinity. After 7 days of freshwater exposure, the viability of U. linza L. decreased to approximately 20%, while U. prolifera Müller showed nearly 100% viability. The freshwater species U. limnetica Ichihara et Shimada, not yet found in coastal areas, was highly viable in seawater.     

Effects of tissue extract of adults on metamorphosis in Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller)

Unhatched, but fully developed larvae of two solitary ascidians Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller) were incubated in a variety of adult tissue extracts, which an earlier study had shown to accelerate metamorphosis. Our study confirmed this observation and showed, furthermore, that tissue extracts induce tail resorption in unhatched larvae of Ascidiella. For both species, the most active induction of metamorphosis was obtained with tunic tissue extracts. The results indicate that chemical stimulation without the presence of tactile cues may initiate metamorphosis. We suggest that the ability of tunic extracts to induce metamorphosis may explain juvenile establishment on adult ascidians and their aggregated distribution found in nature.     

Distribution Patterns and Habitat Characterization of Elmidae and Hydraenidae (Insecta: Coleoptera) in the Weidlingbach Near Vienna,Austria

A total of 870 adult and 831 larval Elmidae and Hydraenidae were caught from September 1995 to September 1996 at the Weidlingbach, a fourth order tributary of the Danube near Vienna, Austria, using a Heß sampler at 14 sampling stations from source to mouth. Elmis maugetii (Latreille ) and Riolus subviolaceus (Müller ) accounted for 66.3% of the total, whereas Hydraena gracilis (Germar ) was the most abundant Hydraenidae species. Based on head width, instars 1–6 were collected in E. maugetii, instars 2–6 in R. subviolaceus and instars 3–6 in Limnius volckmari (Panzer ) and Riolus cupreus (Müller ); from the remaining species, only instars 4–6 were sampled. E. maugetii was most abundant on coarse, moss-covered substrates (median = 22.2 mm) exposed to high water velocity (median = 69.4 cm/s; range = 6.0–117.6 cm/s); the latter was also true for R. subviolaceus although it favoured smaller sediment grain sizes (median = 10.7 mm). Sites exposed to only moderate flow and with abundant filiform algae were preferred by Esolus parallelepipedus (Müller ) and L. volckmari, whereas the Hydraenidae species, Esolus angustatus (Müller ), R. cupreus and Oulimnius tuberculatus (Müller ) were collected mostly at sites with moderate current speed and abundant moss-covered pebbles of various size. Species richness and population density increased from source to mouth. At the spring sampling site Elmidae and Hydraenidae were completely lacking.     

Changes in the chlorophyll content of grape leaves could provide a physiological index for responses and adaptation to UV‐C radiation

Stilbenes are a group of phytoalexins that play an important role in grapevine (Vitis) basal immunity and can be induced by biotic and abiotic stresses. The levels of chlorophylls, the main pigments in plant cells, can also indicate the tolerance of plants to various stresses. Here, the response of different grapevine genotypes to UV‐C radiation treatment was tested and the abundance of chlorophyll in the Hoe29 and Ke53 genotypes was observed to increase significantly within 6 h of UV‐C treatment. Conversely, chlorophyll levels decreased markedly in the Augster Weiss and Müller–Thurgau genotypes. Furthermore, stilbene abundance increased substantially in the Hoe29, Ke53, Ke83 and Pinot Blanc genotypes, but increased only slightly in Augster Weiss and Müller–Thurgau. The expression of resveratrol synthase, which encodes a key enzyme in the stilbene synthesis pathway, increased in Hoe29, Ke53, Ke83 and Pinot Blanc following UV‐C treatment, in a manner consistent with stilbene accumulation. In addition, we observed that reactive oxygen species (ROS) provide a key trigger in physiological responses and changes in secondary metabolite contents. In summary, the results from this study support a link between ROS, chlorophyll levels and genetic diversity for stilbene abundance in different grape genotypes, providing insights into mechanisms for plant physiological and biochemical responses and adaptations to stress.     

The turbellaria fauna of a small water reservoir in Central Russia

The Turbellaria fauna has been studied in the Uvod’ Reservoir. A total of 18 species have been found representing three orders: Catenulida, Macrostoimida, and Neorhabdocoela. The patterns of Turbellaria distribution in the reservoir have been analyzed. The most abundant species have been determined: Stenostomum leucops Duges, 1828, Microstomum lineare (O.F. Müller, 1774), Bothromesostoma essenii M. Braun, 1885, and Mesostoma lingua (Abildgaard, 1789).     

Some considerations on the geographical distribution of rotifers

In the course of investigations on the systematics and zoogeography of rotifers, the author found that 48% of all taxa treated showed a limited distribution (most were periphytic or benthic periphytic species from shallow waters). The following species were limited to the Palaearctic Region: Marine: Synchaeta triophtalma Lauterborn, S. vorax Rousselet, and S. curvata Lie-Pettersen. Brackish water: Colurella dicentra (Gosse), C. halophila Wulfert, and C. unicauda Eriksen. Among Holarctic species, Notholca psammarina Buchholz & Rühmann and the two semi-species N.(striata) bipalium (O. F. Müller) and N(striata) striata (O. F. Müller) are discussed. A series of warm-stenothermic species were found to be pantropical: Lecane leontina Turner, L. monostyla (Daday), L. harringi (Ahlstrom), Lepadella latusinus (Hilgendorf), Trichocerca chattoni (de Beauchamp), and Platyias leloupi Gillard, while Lecane plesia Myers and L. punctata (Murray) seemed to be confined to the Neotropical Region. The data collected also suggest that:

1. i) Keratella wirketissi Kutikova, K. kamtchatica Kutikova, K. cruciformis (Thompson), and K. eichwaldi (Levander) might be good species.
2. ii) Brachionus forficula Wierzejski, an Old World species, is a geographical vicariant of both B. havanaensis Rousselet and B. trahea Murray from the New World.
3. iii) Cases of ecological vicariance are found in Testidinella elliptica (Ehrb.) and T. clypeata (O. F. Müller) from fresh and brackish water respectively; Keratella cruciformis (Thompson) and K. eichwaldi (Levander) from the sea and brackish water respectively; Keratella quadrata (O. F. Müller), K. valga (Ehrb.), and K. tropica (Apstein), dominant in arctic to cold-moderate, in warm-temperate, and in subtropical-tropical climates respectively.

Some rotifer species are presently in expansion: the cases of K. tropica and of Brachionus falcatus Zacharias in Europe are analysed. A related case is that of man-made faunas: the presence of Brachionus havanaensis in Sangchrist Lake, Ill., USA, and the Rotifer fauna of the River Loire (France) are discussed.     

A chromosomal investigation of some British Cantharidae (Coleoptera)

The karyotypes of 20 species of Cantharidae occurring in the British Isles are described and illustrated, 19 of which are hitherto unrecorded. These are Cantharis cryptica Ashe, Cantharis fusca Linnaeus, Cantharis lateralis Linnaeus, Cantharis livida Linnaeus, Cantharis nigra (Degeer), Cantharis nigricans (O. F. Müller), Cantharis pallida Goeze, Cantharis pellucida Fabricius, Cantharis rufa Linnaeus, Cantharis rustica Fallén, Cantharis thoracica (Olivier), Rhagonycha fulva (Scopoli), Rhagonycha lignosa (O. F. Müller), Rhagonycha limbata Thomson, Rhagonycha lutea (O. F. Müller), Rhagonycha testacea (Linnaeus), Silis ruficollis (Fabricius), Malthinus seriepunctatus Kiesenwetter, Malthodes dispar (Germar) and Malthodes minimus (Linnaeus). The main findings were as follows: (1) Cantharis, Rhagonycha and Silis have karyotypes of six pairs of autosomes plus sex chromosomes, which are X0 (male), XX (female). (2) Malthinus and Malthodes differ from the other genera in having only five pairs of autosomes. (3) The chromosome complement of Silis differs from those of the other genera studied in having a variable number of B-chromosomes in individuals from the same population. (4) The karyotypes of the Rhagonycha species show a degree of uniformity in the relative chromosome lengths, centromere positions and C-banding patterns. (5) The karyotypes of the Cantharis species are much more distinct from each other where these characteristics are concerned. (6) Maturation of the gonads takes place in the late larval stage. (7) The segregation of the X chromosome of Cantharis rufa during meiosis is pre-reductional.     

Environment of planktic crustaceans as changed by hornwort: Effect on abundance of Daphnia

The effect of submersed hydrophyte Ceratophyllum demersum L. on the abundance of Daphnia longispina O.F. Müller has been studied. The experiments demonstrated that the hydrochemical characteristics in overgrowths of Ceratophyllum are within the limits of tolerance for D. longispina. The concentrations of waterborne phosphates, chlorophyll a, and bacterial biomass increase in the presence of hornwort. In plant overgrowths, Daphnia is suppressed due to the restriction of its movement. In a medium containing only metabolites of Ceratophyllum, the abundance of Daphnia longispina increases due to the enrichment of food resources.     

Contributions of climate and Brassica oleracea cultivar to gastropod abundance and assemblage in southeastern Brazil

1. Terrestrial gastropods (slugs and snails, Mollusca: Eupulmonata) are destructive pests of brassica crops. These organisms defoliate plants and contaminate the harvest, leading to reduced crop yield and marketability. Losses caused by molluscs have escalated in recent years in Brazil.
2. We aimed to determine the seasonal activity of gastropods in brassica fields and unravel the environmental variables associated with these dynamics. Gastropod abundance, assemblage and within-plant distribution were also compared among Brassica oleracea cultivars (broccoli, cabbage and cauliflower).
3. Mild temperatures and rainy periods were found to coincide with gastropod peaks. Regression analyses confirmed a positive association of rainfall and humidity with gastropod abundance, whereas gastropod abundance increased with decreasing temperature. Deroceras laeve (Müller) (Agriolimacidae) and Bradybaena similaris (Férussac) (Bradybaenidae) were the most constant species. Mollusc abundance and assemblage differed amid B. oleracea cultivar; cabbage had the highest abundance and its species composition differed from broccoli and cauliflower. Slugs and snails were more concentrated on lower plant portions, regardless of the cultivar.
4. Management efforts should be reinforced in mild-temperature and rainy periods to reduce damage by gastropods, and cabbage should be monitored more closely than other cultivars.

     

Spatial patterns and population dynamics of plant-associated microcrustacea (Cladocera) in an English shallow lake (Little Mere, Cheshire)

Little Mere (Cheshire) is a small (2.7 ha) and shallow (average depth 0.7 m) fertile lake in Cheshire, UK. Nymphaeids cover almost 40 % of its entire surface during the growing season (April to October) and practically all the rest is covered by a mixed community of submerged plants. The lake was intensively sampled for plant-associated Cladocera and zooplankters from April 1998-April 2000. Samples were collected at five sites across the lake, three of them located within lily beds, the other two over submerged plant beds of mixed composition. Specific sampling techniques were developed for floating lily leaves, petioles, submerged plants and water. Significant horizontal differences were identified for most cladoceran species, both open-water and plant-associated, for chydorid periphyton scrapers and for filter-feeders. Daphnia hyalina (L.) and Ceriodaphnia sp were significantly more abundant in lily beds than in more open water in both growing seasons, suggesting lily beds are an effective refuge against fish predation. Size-structure and egg-ratio data support this contention. Egg-ratio models were examined for Daphnia hyalina and Simocephalus vetulus (O.F. Müller), a plant-associated cladoceran. The fertility of S. vetulus in lily beds was generally high throughout growing seasons. The construction of egg-ratio models for this species was hampered by their generally very patchy distributions.     

Ciliate grazing on <Emphasis Type="Italic">Nitrosomonas europaea</Emphasis> and <Emphasis Type="Italic">Nitrospira</Emphasis><Emphasis Type="Italic">moscoviensis</Emphasis>: Is selectivity a factor for the nitrogen cycle in natural aquatic systems?

Ciliated protists are important predators of bacteria in many aquatic habitats, including sediments. Since, many biochemical transformations within the nitrogen cycle are performed by bacteria, ciliates could have an indirect impact on the nitrogen cycle through selective grazing on nitrogen-transforming bacteria. As a case study, we examined ciliate grazing on nitrifying bacteria of the genera Nitrosomonas and Nitrospira. All experiments were designed as in vitro-experiments with cultures of different bacteria and ciliate species. The nitrifying bacteria used in our experiments were Nitrosomonas europaea [Winogradsky 1892] and Nitrospira moscoviensis [Ehrich 2001]. The ciliates comprised of four species that are known as efficient bacterivores and common members of the protist community in aquatic systems: Paramecium aurelia [Müller 1773], Euplotes octocarinatus [Carter 1972], Tetrahymena pyriformis [Ehrenberg 1830] and Cyclidium glaucoma [Müller 1786]. Our experimental approach, using a combination of DAPI and FISH staining, was successful in allowing the observation of ingestion of specific bacteria and their detection within ciliate food vacuoles. However, the ciliates in this study showed no significant selective grazing. No food preferences for a any bacterial taxon or any size class or morphotype were detected. Correlation with time between ciliate abundance and bacterial abundance or biovolume, using log transformed growth rates of ciliates and bacteria, showed no significant results. On the bacterial side, neither an active defence mechanism of the nitrifying bacteria against ciliate grazing, such as changes in morphology, nor competition for resources were observed. These results suggest that in our in vitro-experiments grazing by ciliates has no influence on abundance and growth of nitrifying bacteria and nitrification.