Cannibalism and Coprophagy Are Modes of Transmission of Blastocrithidia triatomae (Trypanosomatidae) between Triatomines

Transovarial transmission was not detectable among Blastocrithidia triatomae- infected Triatoma infestans . Rather, B. triatomae was transmitted directiy between triatomines by cannibalism and coprophagy. Cannibalism conditions that excluded coprophagy always resulted in an infection of Dipetalogaster maxima . The efficiency of transmission was not influenced by the blood source—mice or chickens—fed to the infected donor bugs although chicken blood lyses the epimastigotes of the stomach population. Triatoma infestans was infected by coprophagy only if fed, not if unfed. Blastocrithidia triatomae in dry feces was taken up only if the feces were redissolved in fresh feces. Infections also appeared in groups of bugs fed on chickens previously used for feeding infected bugs.     

Seasonal shifts in genotype frequencies in the invasive cladoceran Daphnia lumholtzi in Lake Texoma,U.S.A.

1. We examined the ecological genetics of the invasive cladoceran Daphnia lumholtzi in a reservoir (Lake Texoma) in the southern USA. This species originates from the Old World subtropics and has spread across North America since the late 1980s after its inadvertent introduction to a reservoir in northeastern Texas. 2. The population genetic structure of D. lumholtzi was examined seasonally on 22 dates over a 3‐year period along a natural temperature and salinity gradient. 3. A two‐allele polymorphism at the phosphoglucose isomerase (PGI) locus was detected, while other loci tested showed no variation. Significant temporal heterogeneity existed in genotype frequencies with a major shift between summer and autumn. 4. Results of a multiple linear regression analysis revealed that a significant amount of variation was explained by day length, temperature and conductivity. Additionally, significant spatial heterogeneity of genotype frequencies between lake stations was observed, but was restricted to the summer. 5. Clonal isolates were used in controlled laboratory temperature and salinity tolerance experiments. Results suggest that salinity and temperature tolerance differed between PGI genotypes. 6. Genotype × environment interactions may play a significant role in the micro‐evolutionary dynamics of this invasive species and may have facilitated its rapid expansion across the North American continent.     

Flood-mediated dispersal versus hatching: early recolonisation strategies of copepods in floodplain ponds

1. We explored the quantitative contribution of two alternative recolonisation strategies by a combination of experimental and field data from the Little Tallahatchie floodplain (Mississippi, U.S.A.). In this area, several floods of short duration occur in winter and spring. During floods, lentic and lotic waterbodies of different size are connected for a limited period. 2. Shortly before the onset of the flood season we collected sediment samples from six temporary ponds. The emergence of seven cyclopoid species was recorded from the experimentally flooded sediments and was quantified over a 4‐week period. Water samples were taken in the same ponds after flooding, from which eight further species were recorded and quantified. 3. The contribution of flood‐dispersed individuals was variable among flooded ponds (between 38 and 94%), but numbers of flood‐dispersed colonists did not differ significantly from those of hatching individuals in flooded ponds. Our results demonstrate the equal importance of both hydrological connections and hatching from dormant stages as pathways for recolonisation by copepods if ponds are hydrologically connected. 4. The significance of recolonisation by hatching individuals in disconnected waterbodies was apparent in an isolated temporary pond that was exclusively recolonised by cyclopoid copepods emerging from the sediment.     

Inhibitors acting on Nucleic Acid Synthesis in an Oncogenic RNA Virus

IN infection with an oncogenic RNA virus, synthesis of viral RNA seems to be catalysed by an RNA dependent DNA polymerase in the host cell^1–4. Several specific inhibitors of viral DNA polymerases have been found^5–7 and Spiegelman⁸ has shown that the activity of viral enzymes depends strongly on the chemical composition of the template. We report here first a new highly specific poison of the Rauscher murine leukaemia virus (RMLV) DNA polymerases; second, several inactivators of the RNA and DNA template involved in the RMLV enzyme systems; and third, the action of actinomycin D on viral DNA polymerases and on host DNA/RNA polymerase. The results are discussed with respect to the influence of actinomycin D on virus multiplication.     

Voltinism flexibility of a riverine dragonfly along thermal gradients

Potential effects of future warming should be reflected in life history patterns of aquatic organisms observed in warmer climates or in habitats that are different in ambient temperature. In the special case of the dragonfly Gomphus vulgatissimus (L.) (Odonata: Gomphidae) previous research suggests that voltinism decreases from south to north. We analysed data on voltinism from 11 sample sites along a latitudinal gradient from about 44°N to 53°N, comprising small streams to medium-sized rivers. Furthermore, to simulate different conditions and to allow projections for future climate change scenarios, we developed a population dynamic model based on a projection matrix approach. The parameters of the model are dependent on temperature and day length. Our field results indicate a decrease in voltinism along the latitudinal gradient from southern to northern Europe and a corresponding increase of voltinism with higher temperatures. An increase in voltinism with width of the running water implies an effect of varying habitat temperature. Under the impact of global warming, our model predicts an increased development speed, particularly in the northern part of the latitudinal gradient, an extension of the northern range limit and changes in phenology of G. vulgatissimus , leading to an extension of the flight season in certain regions along the gradient.