Methods for obtaining an Axenic culture of Habrotrocha Rosa Donner 1949

A culture of the bacterivorous rotifer H. rosa was separated from other Eucaryota in activated sludge and then purified by passages from most representatives of the bacterial microflora. A fully axenic culture was finally obtained by use of a lysing buffer and certain antibiotics.     

Wetlands and mosquitoes: a review

This review brings together information on mosquitoes, the diseases they transmit and the wetlands that provide habitats for the immature stages (eggs and larvae). Wetland values are mentioned, though the main literature on this does not generally overlap the mosquito issue. Mosquito management is overviewed to include: the use of larvicides, source reduction in intertidal wetlands and management in freshwater systems. There is not a great deal of information on mosquitoes and freshwater systems, except for constructed wetlands and they are considered separately. We then consider restoration mainly in the context of wetlands that have been the subject of habitat modification for mosquito control. Land use and climate change, as they affect mosquitoes and the diseases they transmit, are also reviewed, as this will affect wetlands via management activities. Finally the review addresses the critical issue of balancing health, both human and environmental, in an adaptive framework. It concludes that there is a need to ensure that both mosquito and wetland management communicate and integrate to sustain wetland and human health.     

Effects of temperature and stocking density on intensive culture of Pacific white shrimp in freshwater

In aquaculture, the application of predictive techniques based on statistical-mathematical modeling allows not only to project and study individual growth trajectories, but also to evaluate the probable effect of external factors that would explain their behavior over time. This is the case of this work, which takes the above as a principle to demonstrate the effect of water temperature on the growth of the Pacific white shrimp Litopenaeus vannamei cultured in fresh water (0 mg L⁻¹), using densities of 90, 120, 180, 230, 280 and 330 shrimp m⁻². Shrimp were exposed to water temperature between 11.5 °C and 31.6 °C. Temperature effect was determined using a parameterized Gompertz growth model with experimental data from each initial culture density. The best shrimp productivity yield was obtained above 26 °C, and the least efficient was below 22 °C. Densities of 90–180 shrimp m⁻² and 230–330 shrimp m⁻² generated a maximum average size of 12.6 g and 8.8 g in 30 weeks, respectively. Here we present the implications of the effect of water temperature on the intensive culture of white shrimp with zero salinity (0 mg L⁻¹) using these techniques from a predictive analytical approach.     

Current knowledge of Chytridiomycota diversity in Northern Europe and future research needs

Chytridiomycota is the most species-rich phylum of basal lineage fungi involved in vital processes in both terrestrial and aquatic ecosystems. Still, the diversity and richness of this group remains cryptic. In Northern Europe, few species have been recorded despite the numerous intact lake systems covering this region. Recent classifications of early diverging fungal lineages differ considerably on the diversity of chytrid species and their taxonomic placement. Here, we present the current knowledge of the Chytridiomycota diversity within Northern Europe by using the Global Biodiversity Information Facility (GBIF) data and compare how this diversity distributes across two recently proposed classification systems. Furthermore, we illustrate how various sampling types are influencing the recorded classification levels. Lastly, we discuss how metabarcoding has contributed to the overall understanding of the Chytridiomycota diversity in revealing the “dark matter fungi”, and we point out future research needs in the field of aquatic mycology in the Nordic region.     

DISTRIBUTION AND DIVERSITY OF MKUZE SWAMP FISHES DURING A SUMMER FLOOD

SUMMARY

Very little information is available on the fishes of the Mkuze swamps and this paper presents the results of an ichthyofaunal survey conducted in March 1988. The study, which coincided with a major river flood, determined that the fish fauna was considerably more diverse than expected and 25 species were collected from 31 localities. Several distinct communities are recognized including a river channel/floodplain community, lagoonal community, feeder stream community and lower swamp community. The subtraction of tropical freshwater fish species in the region is documented and a complete checklist for the Mkuze River system, including several new records from this survey, is presented.     

Physiological responses to variable environments: storage and respiration in starving rotifers

1. Zooplankton exist in environments where food availability varies greatly over time, and success depends in part on the ability to store resources when food is abundant and to conserve them when food is scarce. This paper reports on interspecific differences in the size of stored reserves, and in respiration rate during food deprivation, of four species of planktonic rotifers.
2. The size of reserves varied from 42 to 71% of initial (well-fed) body mass. Interspecific differences in reserve size explained some of the previously observed differences in starvation time.
3. The initial response of respiration rate to food deprivation was quite variable between species. Brachionus calyciflorus was the only species to conserve energy by decreasing respiration rate in response to food deprivation. In contrast, the respiration rate of starved Asplanchna priodonta increased, while that of A. silvestrii and Synchaeta pectinata did not change, during food deprivation.
4. Theory predicts that temporal variation in resource level may facilitate the coexistence of competing species. This theory depends upon trade-offs between traits that confer competitive success in different environments. Although rotifers show a trade-off between competitive ability and maximum population growth rate, we found no evidence for trade-offs between either of those two traits and the size of reserves.     

Dramatic decline of two freshwater killifishes,main anthropogenic drivers and appropriate conservation actions

Freshwater fish biodiversity loss in the Mediterranean Basin is regarded as among the highest globally, with long-term population data sets required to discern long-term population trends of threatened species, in order to design appropriate conservation interventions. In this study, we assessed the population trends of two threatened freshwater fishes, Valencia letourneuxi and Valencia robertae, employing the most recent and largest compiled database to date (16 populations over 14 years). We applied the innovative methodology of the Living Planet Index (LPI) to assess the average rate of change over time across a set of V. letourneuxi and V. robertae populations in Greece. The LPI application revealed a dramatic decline of both species, with V. letourneuxi declining by 97.7% and V. robertae by 91.0%. Beta regression showed that water pollution, eutrophication and alien Eastern mosquitofish Gambusia holbrooki’ presence were the three best fitting predictors of the decline of V. letourneuxi and V. robertae populations. Based on the above, we outline the conservation measures urgently required to revert the near collapse of the populations of the two species. Conservation actions include the strict protection of the their lowland spring habitats, habitat improvement through changes in water management and agricultural practices, mosquitofish invasion prevention and mosquitofish impact mitigation measures, as well as translocation actions and captive breeding. Lastly, the association patterns of the proposed conservation actions with anthropogenic pressures and their expected outcomes were analysed through an alluvial diagram, providing insights on the scale of pressures mitigated by conservation actions and on their conservation benefits.     

Impairment of nucleoid segregation and cell division at high osmolarity in a strain of Escherichia coli overproducing the chaperone DnaK

Abstract Fourteen species of ciliates, seven of which are new, were found living in a sample of anoxic water collected from a small lake in Spain. The species belong to all six orders in which anaerobic ciliates have been described and they include the first anaerobic representatives of the order Prostomatida. This surprising diversity is probably sustained because it embraces all ciliate feeding types, and because protozoa are the only important consumers of the diversity of microbes in anoxic habitats. Six of the anaerobic ciliate species have aerobic congeners; this strengthens the contention that anaerobic ciliates evolved independently from aerobes belonging to several taxonomic groups.     

Dispersal-limited zooplankton distribution and community composition in new ponds

Twelve new experimental ponds were constructed identically, filled simultaneously, had similar physical and chemical properties, and were maintained with minimal manipulation. Colonizing zooplankton communities were sampled bi-weekly for one year. Rotifers dominated zooplankton communities in densities, biomass, and species number (47 of 61 observed species were rotifers). Only 14 species were observed in all 12 ponds; 9 were rotifers. Twenty-nine species (26 rotifers) were recorded in <-6 ponds. Species with high vagility exhibited greater viability. Ponds differed in zooplankton community composition throughout the year, due to differences in both vagility and viability among colonizing species.