Parasitoid–host relationships when host size varies: the case of Pseudacteon flies and Solenopsis fire ants

Abstract. 1. Phorid flies in the genus Pseudacteon are parasitoids of ants. Variation in host size preferences of four South American and two North American Pseudacteon species on monogyne and polygyne forms of their host Solenopsis species [ S. invicta Buren and S. geminata (F.), respectively] was documented.
2. Monogyne Solenopsis workers were, on average, significantly larger than polygyne workers, and the average size monogyne worker attacked was significantly larger than the average size polygyne worker attacked in four of the six Pseudacteon species.
3. Three South American Pseudacteon species attacked larger than average size workers, whereas one attacked smaller than average size workers, in both monogyne and polygyne forms. Both North American Pseudacteon species attacked larger than average size polygyne workers and smaller than average size monogyne workers.
4. Three Pseudacteon species were reared from eggs to adults in infected ants in the laboratory. The size of the emergent phorid fly was related positively to the size of the host worker ant, with females emerging from larger hosts. Similar patterns were documented for both monogyne and polygyne forms.
5. The mean size of worker host from which phorids emerged did not differ significantly between the monogyne and polygyne forms in the subsample of phorids reared to adults.
6. The observed patterns elucidate factors that may cause variation in Pseudacteon sex ratios, and have implications for biological control efforts of pest Solenopsis species.     

Probiotic (symbiotic) bacterial languages

Symbiotic gut microorganisms release of various soluble low molecular weight (LMW)molecules of different chemical nature (surface and exogenous proteins, nucleases, serpins, sirtuines, other enzymes, lectins, peptides, amines, bacteriocines, fatty and amino acids, lactones, furanons, miRNA, NO, etc). These LMW molecules are able to sense environment, interact with corresponding cell surface, membrane, cytoplasm and nucleic acid receptors, to reply quickly and coordinately by induction of special sets of genes, to support stability of host genome and microbiome, to modulate epigenomic regulation of gene phenotypic expression, to ensure the information exchange in numerous bacterial and bacteria-host systems playing an important role in the control for many genetic and physiological functions, biochemical and behaviour reactions, in supporting host health in general. Various symbiotic (probiotic) strains produce different spectrum of such LMW molecules. There is chemical and functional similarity between LMW molecules synthesized by host eukaryotic cells, indigenous and probiotic microorganisms and some micronutrients. It means many LMW compounds of different origin may be the universal regulators contributing to the transmission of information, quorum sensing effects, metagenome stability and epigenomic control for cell growth and development as well as phenotypic expression of different genes. Knowledge accumulated concerning molecular languages of symbiotic microorganisms allows us to better understand the mode of action of known probiotics and to design in principle novel probiotics (metabiotics) with increased health effectiveness. Now we are only at the beginning of a new era of molecular personal biotherapy and nutrition. Soon we can successfully manipulate both the host and its microbiota through interfering in their cross talk, stability and epigenomic regulation of expression of genes using various types of eukaryotic, prokaryotic and nutrition origin LMW molecules are capable to modulate genetic, metabolic and physiological activities.     

Difference in response by two cyprinid species to predatory threat from the nocturnal catfish Silurus asotus

Response to predators may not be identical between different prey species with different life histories and body sizes, particularly when the threat of predation is not great. To clarify this hypothesis, we introduced two prey species (10 Japanese dace, Tribolodon hakonensis, and 10 pale chub, Zacco platypus) into each experimental pond (in total, 8 ponds×4 trials) in which benthic algae had been allowed to grow. The presence or absence of Far Eastern catfish, Silurus asotus, and a refuge for prey fish was used to produce four treatments. The presence of catfish and/or a refuge did not affect either the feeding behavior or growth rate of Japanese dace. In contrast, when catfish were present and no refuge was available, the incidence of bottom feeding for pale chub greatly decreased. Pale chub growth rate was low when catfish were present and a refuge was available, indicating that pale chub spent more of their time in the refuge and lost opportunities of acquiring food. Japanese dace can reach a threshold size at which the prey are safe from predation, but pale chub cannot, and this may explain the differences in response to predators of the two species.     

Costs and benefits of pre‐feeding for possum control

Abstract

Four control operations, each with paired pre‐feed and no‐pre‐feed treatments, and comprising two baited with carrot and two with cereal, provided strong support for the hypothesis that pre‐feeding produces higher possum kills than no pre‐feeding. In these replicates, even where high kills were achieved, the modelled two‐ to three‐fold extension of the period of population depression given by pre‐feeding was sufficient to warrant the expense of the additional bait sown. The benefits of pre‐feeding were clear‐cut, and were greatest where poorest kills were achieved, irrespective of bait type. Pre‐feeding is thus likely to reduce the probability of failure and should be considered a form of operational insurance.     

Arundo micrantha,a new reed species for Italy,threatened in the freshwater habitat by the congeneric invasive A. donax

Arundo micrantha Lam., a reed species from southern Mediterranean area, has found in Sardinia. Its presence represents the first record for Italy and the third one for western Europe. Investigations on distribution and ecology of the Sardinian population have been carried out, with special focusing on synecology of the species. A. micrantha has found in 40 localities mainly distributed along temporary streams and permanent rivers in the central and southern part of the island. Most of Sardinian populations occurs on alluvial soils in Thermomediterranean bioclimatic context. The autonomy of Sardinian phytocoenoses was characterized with the definition of exclusive floristic taxa, biological and chorological elements, and syndinamic relationships with other assemblages. Comparing the community with other reed beds from the Mediterranean basin, a marked floristic differentiation arose between the phytocoenoses characterized by autochthonous Arundo species and those dominated by the invasive Arundo donax. Finally, management activities are proposed to ensure the conservation of this threatened autochthonous plant community in freshwater habitat.