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.     

The general biology of Verruca stroemia (O. F. Müller). IV. Effect of salinity and temperature on survival,behaviour, and osmotic relations

The effect of changes in salinity and temperatures on the survival and osmotic behaviour of Verruca stroemia (O.F. Müller) have been investigated. The species is an ‘osmoconformer’ over a wide range of salinities, but the haemolymph is maintained slightly hypertonic to the medium. The species survives over a wide range of salinities. The ecological implications of the observations are discussed.     

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 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.     

Identification of the Daphnia species (Crustacea: Cladocera) in the lakes of the Ob and Yenisei River basins: morphological and molecular phylogenetic approaches

The morphological and genetic variability of Daphnia species from 16 lakes in the upper watersheds of the Ob and Yenisei Rivers were investigated. Four species, namely D. galeata Sars 1863, D. cristata Sars 1862, D. curvirostris Eylmann, 1887 and D. longispina O.F. Müller, 1776 inhabit these lakes. In addition, longispina-like individuals in Lake Borzu-Khol (the Bolshoi Yenisei River basin) were found which were, however, clearly distinguishable from the other species by morphometric and mitochondrial DNA analyses and could belong to D. umbra based on the 12S sequences.     

Development of a zooplankton community including <Emphasis Type="Italic">Heterocope saliens</Emphasis> Lillijeborg in an experiment with hydrophytes

The influence of the submerged plants Ceratophyllum demersum L. and Elodea canadensis Michx. and the floating plant Hydrocharis morsus-ranae L. on the species composition and quantitative parameters of a zooplankton community was studied experimentally. Among submerged vegetation, the development of the predaceous calanid Heterocope saliens Lilljeborg was suppressed. An increase in the number of zooplankter species was observed in all experimental ecosystems with hydrophytes. The species similarity of zooplankton was higher between communities with plants of the same ecological group than with plants of different groups. The highest average zooplankton biomass, as determined by the abundance of Daphnia longispina O.F. Müller and Simocephalus vetulus (O.F. Müller), was observed in experiments with Elodea. The highest average abundance over the experimental period was recorded among Ceratophyllum, where the abundance of Rotifera, chydorids, and copepods common in hydrophyte beds was higher than in other versions of the experiment.     

Comparative study of glial fibrillary acidic protein (GFAP)-like immunoreactivity in the retina of some representative vertebrates.

A polyclonal glial fibrillary acidic protein (GFAP) antiserum was used to study the distribution of GFAP-like immunoreactivity in the retina of adult vertebrates (teleosts, amphibians, reptiles, birds and mammals). GFAP-positive Müller cells were demonstrated in all the species studied, although with different degrees and patterns of immunoreactivity. In nonmammalian vertebrates, Müller cells were the only immunoreactive retinal elements. The staining was located throughout the retina of the species examined, with the exception of the rabbit, which exhibited regional variability in the expression of GFAP. The data indicate that GFAP expression in retinal Müller cells is a common feature of a wide variety of adult vertebrate species.     

Evidence for High Variability in Temporal Features of the Male Coda in Müller’s Bornean Gibbons (<Emphasis Type="Italic">Hylobates muelleri</Emphasis>)

Most pair-living primate species engage in duets, wherein males and females produce coordinated vocalizations. Previous analyses of male gibbon contributions to the duet have shown that calls are individually distinct. Here we investigate variation in the temporal and spectral parameters in the male contribution to the duet, also known as the coda, of wild, nonhabituated male Müller’s Bornean gibbons (Hylobates muelleri), recorded both opportunistically and as a response to playbacks at the Stability of Altered Forest Ecosystems site in Sabah, Malaysia. We used linear discriminant function analysis to estimate the intra- and interindividual variation in 13 spectral and temporal parameters of the vocalizations (N?=?337) of 31 male gibbons. To further understand how call features vary within and between individuals we used a multivariate, variance components model to investigate how variance in features was partitioned at these two levels. We could identify males with a 66% accuracy using leave-one-out cross-validation, a relatively low score compared to female Müller’s Bornean gibbons and males of other species. We found that for some features (such as maximum frequency of the notes) most of the variance occurred between males, but for others (specifically total duration of the call and duration of rest in between notes) most of the variance occurred within a single male. Overall, male Müller’s Bornean gibbon coda vocalizations showed greater variability relative to their female counterparts, raising questions about potential differences in the function of the male and female contributions to the duet in Müller’s Bornean gibbons and the gibbon taxon as a whole.     

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.     

An experimental study of the use of arm regeneration in estimating rates of sublethal injury on brittle-stars

The ophiuroids Ophiomyxa flaccida (Say), Ophionereis reticulata (Say), Ophiocoma wendtii Müller & Troschel, O. echinata (Lamarck), O. pumila Lütken, Ophioderma appressum (Say), O. cinereum Müller & Troschel, and Ophiolepis impressa (Lütken) in back-reef populations in Jamaica were found to differ significantly in the number of arms regenerating. The proportion of arms regenerating varied from 74.4% for Ophionereis reticulata to 28.3% for Ophiolepis impressa. Regeneration rates, hitherto unknown except for Ophiocoma pumila, were determined for all the species for a single arm over a 3-month period. O. wendtii had the highest rate, regenerating 55% of its mean maximum arm length in 3 months, and O. impressa the slowest, regenerating only 23% of its mean maximum arm length in the same time.Injury rates, i.e., the number of arms broken and the total percent loss estimated to have occurred in the month prior to collection, were determined by dating wounds with reference to regeneration rates over 1 month. The species differed significantly in injury rates. O. pumila and O. reticulata suffered the highest levels of injury and O. impressa the least. Injury rates were not simply related to either the palatability to predators or the behaviour of the brittle-stars.     

Temperature effects of interspecies competition between cladoceran species in experimental conditions

In experiments with mono- and polycultures the hypothesis that small-size cladoceran species (Diaphanosoma brachyurum Lievin and Ceriodaphnia reticulata Jurine) are more successful at higher temperatures whereas large-size species (Daphnia magna Straus and Simocephalus vetulus O.F. Müller) under low temperatures was tested. The biomass of Simocephalus vetulus exceeded the biomass of the other species both in mono- and polycultures. An increase of temperature from 18 up to 25°C led to reduction of the biomass of all species. The largest species, D. magna, responded to higher temperature by increased mortality. We assume that the reduction of the biomass of the large species allowed the small C. reticulata to develop successfully in mixed cultures at higher temperature; however it was completely eliminated at lower temperature. Apparently, the survival strategy of large cladocerans involves delayed juvenile development at lower temperatures. However, at higher temperatures, juvenile development of large species accelerates, and their mortality increases. Individual strategies of the studied species to survive at different temperatures are analyzed. On the whole the increase of temperature can result in decrease of the biomass of cladocerans and prevailence of small-size species over large-size ones.     

Isoenzyme differences between three closely related species of Lineus (Heteronemertea)

Starch-gel electrophoresis was employed to compare six enzymes in three closely related species of nemertean worms, Lineus ruber (Müller, 1774), Lineus sanguineus (Rathke, 1799), and Linens viridis (Müller, 1774). Differences in mobility recorded for most of the enzyme loci examined support the hypothesis that these nemerteans are distinct taxa.     

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).     

The general biology of Verruca stroemia (O. F. Müller). V. Effect of feeding,temperature, and light regime on breeding and moulting cycles

That the absence of breeding in natural populations of Verruca stroemia (O. F. Müller) during the autumn and early winter is due to the absence of food has been confirmed; animals brought into the laboratory and held under ambient light and temperature conditions produce viable egg masses throughout this period when liberally fed. Breeding is not inhibited in either constant light or dark. A temperature of 20°C is lethal even over moderate periods. There is no increase of moulting frequency between 10° and 15°C.     

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.     

Population dynamics and estimation of production in Bosmina longirostris (O. F. Müller) in the River Danube (Danubialia Hungarica,CVIII)

Analysis of the population dynamics of Bosmina longirostris (O. F. Müller) was carried out in the River Danube in the years 1981 and 1982. An estimation method of secondary production elaborated far standing waters was adapted to river conditions. In the River Danube, compared to lakes, standing crop and production values were smaller, while fecundity, P/B values were larger and turnover time was shorter. Possible reasons for this are discussed.     

Variability of reproduction examined in the laboratory between natural populations of Helix aspersa Müller from the Brittany region]

Laboratory experiments were conducted to investigate the effects of geographical localization of natural populations and sampling dates on the reproduction of the garden snail Helix aspersa Müller. In Brittany, reproductive variability between populations shows the adaptive flexibility of characters describing reproductive activity and the relative stability of reproductive ability.     

New and little-known ostracode species from the Middle Neopleistocene to Holocene of the southeastern West Siberian Plain

New data are provided on the ostracode fauna of the Middle Neopleistocene to Holocene of the southeastern West Siberian Plain. Several species are recorded for the first time in the West Siberian Plain: Fabaeformiscandona aff. hyalina (Brady et Robertson), F. harmsworthi Scott, F. holzkampfi Hartwig, Pseudocandona insculpta Müller, Candona weltneri Hartwig, C. inaequivalvis Sars, and C. muelleri jacutica Pietrzeniuk. New evidence is presented on the distribution of the species Pseudocandona stagnalis Sars, Eucypris pigra (Fischer), Dolerocypris fasciata Fischer, Cyclocypris ovum Müller, and C. triangula Negadaev. New species, Candona kazminae sp. nov. and Ilyocypris pustulata sp. nov., are described. The study resulted in establishing the Late Karginian ostracode association.     

Molecular genetic identification and phylogeny of Daphnia species (Crustacea, Cladocera) from water bodies of the Lake Chany basin

The data on the molecular genetic identification of Daphnia species from the water bodies of the Lake Chany basin are presented. Phylogenetic relationships between these species have been established. The fragments of the mitochondrial DNA genes were used as genetic markers. According to the data obtained, the water bodies examined were inhabited by five Daphnia species, including Daphnia (Daphnia) galeata Sars, D. (D.) longispina O. F. Müller, D. (D.) curvirostris Eylmann, D. (D.) pulex Leydig, and D. (Ctenodaphnia) magna Straus. In addition, longispina a-like individuals that form a separate phylogenetic lineage was identified.     

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.