Optimisation of a semiochemical slow-release alginate formulation attractive towards Aphidius ervi Haliday parasitoids

BACKGROUND: Optimisation of alginate formulations is described in order to develop semiochemical (E-β-farnesene and E-β-caryophyllene) slow-release devices in biological control approaches by attracting predators and parasitoids of aphids. Various formulation criteria were optimised with respect to semiochemical encapsulation capacity. Moreover, the optimised formulation was characterised by texturometry and confocal microscopy. The slow-release rates of semiochemicals were calculated in laboratory controlled conditions. The attractiveness of semiochemical formulations towards Aphidius ervi was demonstrated by olfactometry. RESULTS: Two major parameters were highlighted in encapsulation optimisation: the type of alginate (Sigma L) and the type of crosslinker ion (Ca²⁺). Other formulation parameters were optimised: ionic strength (0.5 M), Ca²⁺ (0.2 M) and alginate (1.5%) concentrations and the maturation time of beads in CaCl₂ solution (48 h). After physical characterisation of beads, semiochemical slow-release measurements showed that alginate formulations were efficient sesquiterpene releasers, with 503 µg of E-β-farnesene and 1791 µg of E-β-caryophyllene totally released in 35 days. The efficiency of semiochemical alginate beads as attractants for female parasitoids was demonstrated, with high percentages of attraction for semiochemical odours (88 and 90% for E-β-farnesene and E-β-caryophyllene respectively) and significant statistical results. CONCLUSION: Semiochemical alginate beads can be considered as efficient slow-release systems in biological control. These formulations could be very useful to attract aphid parasitoids on crop fields. Copyright © 2011 Society of Chemical Industry     

The free-water pond under a trickle source: A field test of existing theories

  The size of the free-water ponds under drippers is an important field characteristic of trickle irrigation. Here we review four existing analytical theories that purport to describe 3-D infiltration. We show how they can be used to predict the extent of the pond from basic soil parameters, and the dripper discharge rate. Via a numerical example it is shown that the different theories give significantly different free-water pond radii, especially for high drip discharge rates when the flow is dominated by gravity. We then describe field experiments that were carried out to permit a comparison of the measured and predicted values using independently-measured soil parameters. This test of the different theories was conducted on a loamy soil. Raats' (1971) solution gave the best estimates of the free-water pond radius, across the range of discharge rates. The free-water pond radius, a determinant of the lateral spread away from the dripper, was found to vary only weakly with drip discharge in the range of practical applications. Consequences for management are discussed. Received: 24 September 1995     

Development and comparison of four real-time polymerase chain reaction systems for specific detection and quantification of Zea mays L

Four real-time polymerase chain reaction systems aiming at the specific detection and quantification of maize DNA are described. They have been developed in four independent laboratories targeting different maize sequences, i.e., alcohol dehydrogenase (Adh1), high mobility group protein (hmga), invertase A (ivr1), and zein, respectively. They were all fully specific, showing a very similar quantification accuracy along a number of distantly related maize cultivars and being either single or low copy number genes. They were highly sensitive and exhibited limits of quantification below 100 maize genomic copies. In consequence, they are considered suitable for use as maize specific endogenous reference genes in DNA analyses, including GMO quantitative tests.     

Temperature sex reversal implies sex gene dosage in a reptile

Sex in reptiles is determined by genes on sex chromosomes or by incubation temperature. Previously these two modes were thought to be distinct, yet we show that high incubation temperatures reverse genotypic males (ZZ) to phenotypic females in a lizard with ZZ and ZW sex chromosomes. Thus, the W chromosome is not necessary for female differentiation. Sex determination is probably via a dosage-sensitive male-determining gene on the Z chromosome that is inactivated by extreme temperatures. Our data invite a novel hypothesis for the evolution of temperature-dependent sex determination (TSD) and suggest that sex chromosomes may exist in many TSD reptiles.     

Negative effect of the arthropod parasite, Sarcoptes scabiei, on testes mass in Iberian ibex, Capra pyrenaica

Testes mass is a key factor in male reproductive success and is potentially exposed to so-called 'parasitic castration'. This is the result of the direct destruction or alteration of reproductive cell lineages (parasitic castration sensu stricto), or the indirect detrimental effects - for example, via body condition - on the ability of progenitors to produce or rear offspring (parasitic castration sensu lato). There are enormous gaps in our knowledge on the effects of parasites on the testes of wild mammals and in an attempt to rectify this dearth of data we examined the relationship between the skin parasite Sarcoptes scabiei and testes mass in Iberian ibex Capra pyrenaica. We considered data from 222 males that were culled in the population from the Sierra Nevada in Spain. Our results provide evidence that sarcoptic mange is associated with reduced size-corrected testes mass in Iberian ibex which supports the hypothesis that parasitism is a determining factor in gonad plasticity in male mammals. We discuss several hypothetical causes of this relationship and highlight the need to deepen the sub-lethal effects of pathogens if we are to accurately understand their modulator effects on host population dynamics.     

Genome sequence of a polydnavirus: insights into symbiotic virus evolution

Little is known of the fate of viruses involved in long-term obligatory associations with eukaryotes. For example, many species of parasitoid wasps have symbiotic viruses to manipulate host defenses and to allow development of parasitoid larvae. The complete nucleotide sequence of the DNA enclosed in the virus particles injected by a parasitoid wasp revealed a complex organization, resembling a eukaryote genomic region more than a viral genome. Although endocellular symbiont genomes have undergone a dramatic loss of genes, the evolution of symbiotic viruses appears to be characterized by extensive duplication of virulence genes coding for truncated versions of cellular proteins.     

Colour measurement, using the CIELCH colour space, of muscle of rainbow trout, Oncorhynchus mykiss (Walbaum), fed astaxanthin: effects of family, ploidy, sex, and location of reading

Thirty two families (representing 397 fish of 900 g average weight) of rainbow trout. Oncorhynchus mykiss (Walbaum) (16 diploid sib-groups and their homologous triploids obtained by heat shock) were fed astaxanthin (96 mg kg^-1 feed) for 39 days, resulting in a red colouring of the muscle. The colour was measured in the CIELCH colour space using a chromameter at three points of fish muscle (head, middle and tail). The effects of ploidy, sex, family and location of measurement on the colour attributes offish muscle (lightness, chroma and hue angle) were analysed. Diploid fish had a higher chroma than triploid ones (P<0.02), but no ploidy effect was found on lightness nor on hue angle. Sex had little influence on colour attributes, except for the hue angle which was slightly higher (P<0.07) in females than in males. Family had a strong effect on chroma (P<0.002), hue angle (P<0.02), and, to a lesser extent, on lightness (P<0.07). However, within families the muscle colour was very variable from one fish to another (highly significant variation [P<0.0001] on every colour attribute). The location effect was highly significant on lightness (P<0.0001), chroma (P<0.0001), and hue angle (P<0.0001). Data from the tail part of the fish muscle were higher than those from the head part. The middle part always exhibited the lowest data.     

Marine mammal stranding response in Mexico: Lessons learned

1. Marine mammals are indicators of ecosystem health, and thus stranding records are an invaluable information source. The response to marine mammal stranding (RMMS) must be comprehensive, taking into account three components: (i) operations, (ii) research, and (iii) information dissemination. Although RMMS had previously been practised in several coastal locations in Mexico, the recent enforcement of a new regulation for RMMS has posed a challenge to actors as they adapt to it.
2. To understand the functioning of RMMS in Mexico, Bahía Todos Santos and Bahía de La Paz, two localities with over 20 years of experience in RMMS, were selected. To achieve this goal, a document review to identify the actors involved and their functions was undertaken together with a social network analysis to identify relevant actors in each locality and semi-structured interviews to identify key topics for RMMS.
3. The composition of the involved actors was similar at both locations. Some actors were found to have mandatory functions (i.e. governmental actors), while others (i.e. civil society organizations) performed functions beyond those established in official documents. Governmental agencies, the academic sector, and civil society organizations were the most connected actors and could help disseminate information, facilitate communication within the network, and influence decision-making.
4. The main topics identified were, in order of relevance: (i) economic constraints; (ii) actors' involvement; (iii) stranding response logistics; and (iv) recognition among actors.
5. In conclusion, several limitations to the RMMS exist at both localities, mainly related to the lack of economic resources, but actors involved in RMMS actions are motivated by their own interests. This study proposes the integration of actors into local networks that take into consideration the biological, physical, and social characteristics of each place.