IAPV, a bee-affecting virus associated with Colony Collapse Disorder can be silenced by dsRNA ingestion.

Colony Collapse Disorder (CCD) has been associated with Israeli acute paralysis virus (IAPV). CCD poses a serious threat to apiculture and agriculture as a whole, due to the consequent inability to provide the necessary amount of bees for pollination of critical crops. Here we report on RNAi-silencing of IAPV infection by feeding bees with double-stranded RNA, as an efficient and feasible way of controlling this viral disease. The association of CCD with IAPV is discussed, as well as the potential of controlling CCD.

Analyses of avocado (Persea americana) nectar properties and their perception by honey bees (Apis mellifera).

Honey bees are important avocado pollinators. However, due to the low attractiveness of flowers, pollination is often inadequate. Previous work has revealed that avocado honey is relatively unattractive to honey bees when compared with honey from competing flowers. We characterized avocado honey and nectar with respect to their odor, color, and composition of sugars, phenolic compounds, and minerals. Furthermore, we tested how honey bees perceive these parameters, using the proboscis extension response bioassay and preference experiments with free-flying bees. Naïve bees were indifferent to odors of avocado and citrus flowers and honey. Experienced bees, which were collected in the field during the blooming season, responded preferentially to odor of citrus flowers. The unique sugar composition of avocado nectar, which contains almost exclusively sucrose and a low concentration of the rare carbohydrate perseitol, and the dark brown color of avocado honey, had no negative effects on its attractiveness to the bees. Phenolic compounds extracted from avocado honey were attractive to bees and adding them to a solution of sucrose increased its attractiveness. Compared with citrus nectar and nonavocado honey, avocado nectar and honey were rich in a wide range of minerals, including potassium, phosphorus, magnesium, sulfur, iron, and copper. Potassium and phosphorus, the two major minerals, both had a repellent effect on the bees. Possible explanations for the presence of repellent components in avocado nectar are discussed.

Determination by near-infrared spectroscopy of perseitol used as a marker for the botanical origin of avocado (Persea americana Mill.) honey.

This paper reports the application of near-infrared (NIR) reflectance spectroscopy to determine the concentration in honey of perseitol, a sugar that is specific to avocado honey. Reference values for perseitol were obtained by high-performance liquid chromatography analysis in 109 honey samples. Although the average concentration of perseitol in honey samples was only 0.48%, accurate prediction equations were successfully developed. The regression model of modified partial least squares was superior to that of principal component regressions. Calibrations based on the first or second derivative of Log(1/R) were equally good (R(2) > 0.95). Using half of the samples for calibration and the second half for validation, the correlation between actual and predicted values of the second half was satisfactory (R(2) = 0.87), the slope did not differ from 1, bias was low (0.005%), and the standard error of prediction was relatively low (0.13%). It was concluded that NIRS analysis may be used to detect to what extent honeybees have harvested avocado nectar but not to authenticate avocado honey as unifloral.

Risk-sensitive foraging: choice behaviour of honeybees in response to variability in volume of reward.

We tested risk sensitivity towards variability in volume of reward with harnessed honeybees, Apis mellifera, in a proboscis-extension conditioning paradigm. We conditioned each subject to turn its head and extend its proboscis towards one of two presented odours; one odour was associated with a constant reward volume and the other with a variable reward volume that was either low or high, with probabilities P=0.75 and (1-P)=0.25, respectively. The volumes of rewards were varied among three experimental conditions. In conditions I and II, the variable reward option included a low reward of zero (i.e. reinforcement was withheld in the low reward value); in condition I, the mean of the variable and of the constant reward options were the same, and in condition II, the variable reward option had a higher mean reward than the constant reward option. The behaviour of subjects did not differ between treatments and the majority of individuals were risk averse. In condition III, the variable reward option did not include a zero reward and the mean reward did not differ between options. Very few of the individuals assigned to condition III developed a preference for either reward option. Thus, honeybees are risk sensitive to variability in volume of reward in some conditions and the degree of risk sensitivity depends on characteristics of the reward distributions. The most salient characteristic may be a relative measure of variability, such as the value of the coefficient of variation of reward. The experimental paradigm that we developed is a powerful tool for studying the mechanism of risk sensitivity in bees, as well as other aspects of learning, decision making, perception and memory. Copyright 1999 The Association for the Study of Animal Behaviour.

Protein, Vitellogenin, and Vitellin Levels in the Hemolymph and Ovaries during Ovarian Development in Penaeus semisulcatus (de Haan).

The concentration of vitellogenin (Vg) in the hemolymph of Penaeus semisulcatus was found to increase from an average of 50 µg ml-1 to 439 µg ml-1 in female shrimp during ovarian development. The most significant increase in Vg occurred concomitant with the increase in the vitellin (Vt) content of oocytes with an average diameter (AOD) ranging between 150 and 250 µm. The amount of Vt in the oocytes was found to increase linearly from a mean of 0.0126 mg to 4.55 mg per gm body weight. However, the percentage of Vt in the total protein was found to decrease, from 67% in ovaries with AOD of 150-250 µm, to 39.7% in ovaries with AOD of 350 µm or larger. The volume of the hemolymph was found to be 0.4 ml per gm body weight and did not change significantly during ovarian development. Assuming that Vg in the hemolymph represents either an extraovarian origin of Vt or an active secretion from the ovary, a turnover rate of two to three times per day was calculated over one full cycle of oocyte development. However, during the most significant increase in Vt in the ovary (in ovaries with AOD of 150-250 µm), the turnover rate in the hemolymph could reach seven to eight times per day. The results lead to the conclusion that the contribution of Vg to the formation of Vt in the ovary is quantitatively insignificant.

In vivo Incorporation of Labeled Methionine into Proteins, Vitellogenin, and Vitellin in Females of the Penaeid Shrimp Penaeus semisulcatus de Haan.

[35S]-Methionine was injected into 11 intact vitellogenic females of the penaeid shrimp Penaeus semisulcatus de Haan. Levels of radiolabeled methionine, total protein and vitellogenin/vitellin (Vg/Vt) were measured in the hemolymph during 24 h following methionine injections. The same parameters were measured 24 h after injection, in the hepatopancreas and ovaries of sacrificed females. Proteins were precipitated by trichloroacetic acid and Vg/Vt was immunoprecipitated by anti-Vt serum. Hemolymphatic protein and Vg/Vt levels were constant throughout the 24 h of the experiment starting from the first sampling of hemolymph, two h after injection. Similar amounts of Vg/Vt were found in the hepatopancreas compared to the ovary 24 h after injection, and 10% of the labeled protein in the ovary and 6.4% in the hepatopancreas were Vg/Vt. Free-labeled methionine was still present in all tissues examined after 24 h. The labeled protein and Vg/Vt in the ovary and the hepatopancreas could not be explained by the hemolymphatic content of the two organs. The hemolymphatic Vg is 24-fold labeled over the ovarian Vt, 24 h after injection. The results indicate more intense involvement of the hepatopancreas in the vitellogenic process than can be deduced from earlier in vitro studies. This study confirms the earlier definition of the oogenic stage of rapid Vt accumulation in the ovary (AOD range of 150-250 {mu}m) and also indicates a role for the hemolymph in transporting Vg between its processing sites.

Is There Extraovarian Synthesis of Vitellogenin in Penaeid Shrimp?

Extraovarian synthesis of vitellogenin (Vg), has been reported for several crustaceans, mainly in the subepidermal adipose tissue (SAT) or the hepatopancreas (HEP). The precise site(s) of Vg synthesis in penaeid shrimp is hitherto unknown and was investigated in a large local species Penaeus semisulcatus de Haan. Protein synthesis was determined in SAT and HEP tissue pieces incubated in vitro. Incubations were at 25{deg}C for eight hours in an oxygen enriched atmosphere, under sterile conditions in a physiological medium, containing 14C-leucine. At the end of the incubation period, tissue homogenates and medium samples were analyzed for de novo protein synthesis. Total protein synthesis was determined by trichloroacetic acid precipitation. Specific vitellin (Vt) synthesis was determined by radioimmunoprecipitation with a polyclonal Vt-specific antiserum. Characterization of other de novo synthesized proteins was carried out by fluorography from polyacrylamide gels. Subepidermal adipose tissues removed from females at all stages of ovarian development did not synthesize Vt-specific proteins, in spite of the fact that total protein synthesis levels were high. The major protein synthesized de novo in the SAT of males and females is a protein with an identical electrophoretic mobility as hemocyanin in polyacrylamide gels. In vitro protein synthesis in HEP tissues was low compared to SAT or ovary systems. Vt-specific de novo synthesized protein was identified in HEP's from early vitellogenic females, but constituted less than 15% of total protein synthesis. We have previously shown that ovarian tissues from vitellogenic females incubated in vitro exhibited high levels of protein synthesis, an average of 38% of which is Vt-specific (Browdy et al., 1990, J. Exp. Zool. 255:205-215). The calculated Vt synthesis rates in ovaries were up to 23 times higher than in HEP. We conclude that the extraovarian contribution to vitellogenesis in P. semisulcatus is low.

Causes and consequences of sea urchin abundance and diversity in Kenyan coral reef lagoons.

Large differences in community structure of sea urchins and finfish have been observed in Kenyan reef lagoons. Differences have been attributed to removal of finfish predators through human fishing activities. This study attempted to determine (i) the major sea urchin finfish predators, (ii) the effect of predation on sea-urchin community structure, and (iii) the possible effect of sea urchin increases and finfish decreases on the lagoonal substrate. Six reefs, two protected and four unprotected, were compared for differences in finfish abundance, sea urchin abundance and diversity and substrate cover, diversity and complexity. Comparisons between protected and unprotected reefs indicated that finfish populations were ca. 4 x denser in protected than unprotected reefs. Sea urchin populations were >100 x denser and predation rates on a sea urchin, Echinometra mathaei, were 4 x lower in unprotected than in protected reefs. The balistidae (triggerfish) was the single sea-urchin finfish predator family which had a higher population density in protected than in unprotected reefs. Balistid density was positively correlated with predation rates on tethered E. mathaei (r=0.88; p<0.025) and negatively correlated with total sea-urchin density (r=-0.89; p<0.025) on the six reefs. We conclude from observations that the balistids Balistaphus undulatus and Rhinecanthus aculeatus are the dominant sea-urchin predators. The sea-urchin assemblage had its greatest diversity and species richness at intermediate predation rates and low to intermediate sea-urchin densities. At low predation rates and high sea-urchin density E. mathaei dominated the assemblage's species composition. Preferential predation on the competitive dominant maintains the assemblage's diversity, supporting the compensatory mortality hypothesis (Connell 1978) of coral reef diversity. Protected reefs had greater cover of hard coral, calcareous and coralline algae, and greater substrate diversity and topographic complexity than unprotected reefs which had greater algal turf and sponge cover. Coral cover and topographic complexity were negatively correlated with total sea urchin density. Although experimentation is lacking, these substrate changes may be due to the switch from finfish to sea-urchins as consumers which results from overfishing of finfish. Removal of top invertebrate-eating carnivores appears to have cascading effects on the entire coral reef ecosystem.