Factors influencing codling moth larval response to α-farnesene

Behavioral responses of newly-emerged codling moth (Cydia pomonella L.) larvae to α-farnesene were compared for a laboratory-reared strain (‘lab’, 160 generations inbred) and a recently collected strain (‘wild’, 3 generations). Video recordings of single larvae placed 20 mm from Bond papers releasing a range of seven α-farnesene concentrations were scored for head turning, head lifting, head direction, and movement across a Petri dish. The laboratory strain was significantly less successful at finding the treated papers than the wild strain. The lab strain was also significantly less active, shown by more random orientation, slower walking speed, less head turning and less head lifting. Both strains showed lower response to α-farnesene concentrations less than 10⁻⁶ (w/v) α-farnesene. Orientation, walking speed, and head turning rate were significantly higher in the presence of α-farnesene concentrations >10⁻⁷ w/v, for both strains. Head lifting did not show any effect from α-farnesene. Head turning was associated with both head lifting and walking speed and this association improved with the presence of α-farnesene. Increased attraction to odour source was correlated with improved direction finding at concentrations above 10⁻⁷ w/v. Activity factors such as head turning and walking speed influenced time to locate odour source more than orientation factors. Odour-guided orientation to α-farnesene in codling moth larvae was composed of both locomotory, and to a lesser extent, orientation responses, which increased in a directed fashion to the stimulus.     

Measurement of pH changes in an inaccessible aqueous phase during biocatalysis in organic media

Summary The pH of the aqueous phase trapped within biocatalyst particles in organic media may be measured using very hydrophobic esters of fluorescein. These remain completely in a pentan-3-one phase, but they ionise there in response to the pH of an equilibrated aqueous phase. They show that the catalyst pH may be significantly shifted from the pre-adjusted value by partitioning of an acidic reactant (N-formyl-tyrosine during chymotrypsin-catalysed esterification) or product (acetic acid during lipase-catalysed ester hydrolysis).     

Effects of cholestyramine on lipoprotein levels and metabolism in Syrian hamsters.

Oral administration of cholestyramine to adult male hamsters not only induced a marked decrease in plasma concentrations of cholesterol and LDL but had a similar lowering effect on plasma triacyglycerol and VLDL concentrations. The hypotriglyceridaemic effects of resin administration were not due to an increase in lipoprotein lipase, as post-heparin plasma lipoprotein lipase activities were unchanged, but rather to a 35% decrease in VLDL synthesis. Measurement of the disappearance rate of apolipoprotein B from VLDL after i.v. injection of 125I-labelled hamster or human VLDL into control and cholestyramine-fed recipient animals showed a 2-times lower T1/2 in the drug-treated animals. The fraction of VLDL apolipoprotein B, recovered at any time after injection in the LDL, was equal or higher in cholestyramine-fed animals as compared to controls. These data indicate that the lowering in plasma LDL by cholestyramine in male hamsters is due not only to LDL receptor up-regulation but also to a lower rate of VLDL synthesis. No indications were found for a decreased efficiency of VLDL to LDL conversion in cholestyramine-fed animals.     

Caterpillar‐induced plant volatiles attract conspecific herbivores and a generalist predator

Plants release volatiles in response to caterpillar feeding that attracts natural enemies of the herbivores, a tritrophic interaction which has been considered to be an indirect plant defence against herbivores. On the other hand, the caterpillar‐induced plant volatiles have been reported to either repel or attract conspecific adult herbivores. This work was undertaken to investigate the response of both herbivores and natural enemies to caterpillar‐induced plant volatiles in apple orchards. We sampled volatile compounds emitted from uninfested apple trees, and apple trees infested with generalist herbivore the pandemis leafroller moth, Pandemis pyrusana (Lepidoptera, Tortricidae) larvae using headspace collection and analysed by gas chromatography/mass spectrometry. Infested apple trees uniquely release six compounds (benzyl alcohol, phenylacetonitrile, phenylacetaldehyde, 2‐phenylethanol, indole and (E)‐nerolidol). These compounds were tested on two species of herbivores and one predator in apple orchards. Binary blends of phenylacetonitrile + acetic acid or 2‐phenylethanol + acetic acid attracted a large number of conspecific male and female adult herbivores. The response of pandemis leafroller to herbivore‐induced plant volatiles (HIPVs) was so pronounced that over one thousand and seven hundred conspecific male and female adult herbivores were caught in traps baited with HIPVs in three‐day trapping period. In addition, significantly higher number of male and female obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera, Tortricidae), was caught in traps baited a binary blend of 2‐phenylethanol + acetic acid, or a ternary blend contains 2‐phenylethanol and phenylacetonitrile + acetic acid. This result challenges the current paradigm hypothesized that HIPVs repel herbivores and question the indirect defensive function proposed for these compounds. On the other hand, a ternary blend of phenylacetonitrile and 2‐phenylethanol + acetic acid attracted the largest numbers of the general predator, the common green lacewing, Chrysoperla plorabunda. To our knowledge, this is the first record of the direct attraction of conspecific adult herbivores as well as a predator to the caterpillar‐induced plant volatiles in the field.     

Hemlock woolly adelgid invasion affects microhabitat characteristics and small mammal communities

Hemlock woolly adelgid (HWA) invasion and preemptive logging practices alter the habitat structure of New England forests and may indirectly affect associated small mammal communities. Microhabitat structure was measured and small mammals were censused in eight large experimental plots to quantify these effects. The Harvard Forest long-term ecological research experiment is a replicated two-block design that includes four ~ 0.81-ha canopy treatments: (1) hemlock control, (2) hardwood control, (3) girdled Treatment, in which hemlock trees were killed by girdling in 2005 and left standing to simulate HWA invasion, and (4) logged treatment, in which trees were removed to simulate preemptive logging management practices. Nine microhabitat characteristics were measured from plot photos revealing differences among ground and canopy microhabitat structure. Small mammals were censused during high (2012) and low (2013) abundant years. Populations of common species were estimated with mark-recapture analysis. Peromyscus spp. were not affected by treatment in either year, but southern red-backed vole populations were greatest in the girdled treatments in 2012 and rarely captured in 2013. Between 6 and 9 mammal species were recorded in all treatments and species composition varied slightly. Estimated species richness was greater in girdled treatments than hemlock controls, but did not differ between girdled and logged treatments, which suggests preemptive logging is as detrimental to some small mammal species as HWA invasion. Overall, there is little evidence of a major shift in small mammal community structure in response to HWA invasion, with only minor changes in relative abundance both years.     

The very hungry amphipod: the invasive <Emphasis Type="Italic">Dikerogammarus villosus</Emphasis> shows high consumption rates for two food sources and independent of predator cues

The invasion of the Ponto–Caspian amphipod Dikerogammarus villosus in European rivers is assumed to reduce macroinvertebrate diversity and to alter ecosystem functions. D. villosus shows an extraordinarily flexible feeding behavior including the ability to use various food sources. On the other hand, its response to predation risk seems to depend on environmental factors. To evaluate the ecological function of D. villosus, we estimated the daily food consumption for different food sources and analyzed potential effects of predator avoidance behavior on feeding. D. villosus consumption of willow leaves or chironomid larvae was quantified in 24-h laboratory experiments with and without kairomones of the European bullhead (Cottus gobio). Consumption rates were estimated based on gut content and gut evacuation rate under semi-natural laboratory conditions enabling the animals to feed over the whole time of the evacuation rate experiment. We observed very high evacuation rates and consequently high consumption rates up to 89% of body weight per day. Consumption rates differed significantly between food sources: D. villosus ingested more leaves than chironomid larvae. In contrast, predator cues did not affect the feeding of D. villosus. This might be explained by its strong refuge affinity and probably benefits its successful invasion. A comparison of the estimated consumption rates with results of an own consumption experiment (and other studies) under more artificial conditions indicated that more natural conditions result in higher consumption rates. Consequently, feeding rates from highly artificial experiments should be used with great caution to assess the ecosystem function of D. villosus.     

Returning home after fire: how fire may help us manage the persistence of scrub-steppe specialist bird populations

Semi-natural open habitats have drastically changed in the last few decades due to agricultural intensification and rural depopulation. Steppe-birds, and especially those adapted to primary stages of vegetation succession, are threatened by an increase in scrub cover, and management actions are being applied to reverse scrub encroachment and restore habitat suitability in semi-natural open habitats. In this paper we evaluated for the first time, the long-term effects of a wildfire on habitat structure, vegetation productivity, and the associated response of an endangered scrub-steppe specialist bird, the Dupont’s Lark Chersophilus duponti. Wildfire occurred in a Mediterranean steppe of central Spain dominated by permanent community of dwarf cushions scrubs. Bird abundance was evaluated by line transects in the burnt and unburnt areas 3 years prior to the fire and 4 and 7 years after the fire. We quantified changes in habitat structure at fine scale level through vegetation sampling points and in vegetation productivity by estimating the Normalized Difference Vegetation Index (NDVI). Fire had strong effects for at least up to 4 years after the fire, when lower NDVI values, less scrub cover and fewer, but not significant, number of males were detected in the burnt area with respect to the pre-fire conditions. Seven years after fire most vegetation variables measured did not differ between areas, number of males detected within the burnt area was recovered and NDVI values in burnt area were slightly recovered but were significantly lower than in control area. Slow regeneration of the scrub cover after fire explained the unsuccessful occupation of the burnt area by the Dupont’s Lark up to several years after fire. The more dispersed and shorter habitat created by fire 7 years after the fire seems to be more suitable for the species than that in control areas. The large number of males around the burnt area may have played a role in the recolonization process. In sum, vegetation recovery and the presence of a low scrub-steppe specialist, as the Dupont’s lark, suggests that fire management could be integrated into conservation plans to effectively manage scrub encroachment processes in Mediterranean scrub-steppes.