Improved insect performance from host-plant defoliation: winter moth on oak and apple

ABSTRACT. 1. We test the hypothesis that defoliation has short-term and long-term negative effects on performance of winter moth Operophtera brumata L. on two species of food plants: Garry oak ( Quercus garryana Dougl.) and apple ( Malus domesticus L.).
2. Pupal weight (and hence potential fecundity of females) decreased with increased defoliation in the current year on both tree species.
3. Pupal weight increased, however, with increased level of defoliation in the previous year.
4. Increased weight of pupae from larvae which had fed on previously defoliated trees may buffer population decline by increasing fecundity of moths in the next generation.     

Proteins in Intercellular Washing Fluids from Leaves of Barley (Hordeum vulgare L.)

Primary leaves of barley were detached, infiltrated with variousbuffers, and centrifuged to yield ‘intercellular washingfluid’ (IWF). Effective pH control of the IWF was obtainedonly with Tris, among all buffers tried. In these liquids, upto 30 proteins were detected by gradient gel electrophoresis.Intracellular protein from injured cells at the cut ends ofleaves was present in IWF but did not contribute significantlyto the total protein recovered in this liquid. The yield ofprotein in the IWF depended on the buffer used for infiltrationand on the concentration of the buffer. Higher concentrationsof buffer yielded more protein. In other experiments leaves were infiltrated with Tris, centrifuged,and then infiltrated a second time with this buffer containingvarious concentrations of the zwitterionic detergent CHAPS,a sulphobetaine derivative of cholate. Gel electrophoresis ofthe IWF obtained after the second centrifugation revealed protein‘bands’ not detected when the detergent had beenomitted from the infiltration buffer. The electrophoretic patternsof protein ‘bands’ in the gels differed dependingon the CHAPS concentration used for infiltration. The effect of CHAPS on plasmalemma integrity was studied byobserving infiltrated tissue with the electron microscope andby treating isolated protoplasts with the detergent. After infiltrationwith CHAPS at 0.6 mM or 2.0 mM no plasmalemma breaks were detectedin leaves, and isolated protoplasts survived exposure to CHAPSat these concentrations for 2 h without bursting. Evidently,CHAPS at these low concentrations did not destroy the integrityof the plasmalemma; the additional protein recovered in theIWF under these conditions probably originated in the cell wall.Infiltration of leaves with 6.0 mM CHAPS resulted in breaksof the plasmalemma, in tissue collapse and leaf tip necrosis.Isolated protoplasts burst within minutes after being exposedto CHAPS at this concentration. Key words: Cell wall permeability, Intercellular space, Detergent, CHAPS, Protoplasts     

Behavioural circadian rhythms measured in real-time by automatic image analysis: applications in parasitoid insects

Abstract. A video analysis system was developed to study behavioural circadian rhythms in insects. Technical innovations were performed in image analysis and in the use of robotics. In image analysis, both the automatic detection of the insect and the calculation of several variables (linear and angular speed, locomotor activity, etc.) are carried out in real-time, which saves time and allows long-term studies without any intervention of the operator. The displacement of the camera by robotics allows the simultaneous study of many individuals (i.e. sixty individuals for the study of locomotor activity of adult insects, more than 400 individuals for the study of the emergence of adult parasitoids from their host). Four applications of this new device are presented. They deal with circadian rhythms in parasitoid insects: locomotor activity and time variation in locomotory parameters, daily distribution of the emergence and onset of the locomotor activity in adults. The adaptability of the system to several experimental materials and situations is discussed and the interest of the study of behavioural rhythms in the approach of host-parasitoid associations is emphasized.     

A Redescription of Rhabdalestes tangensis (Lönnberg) (Pisces, Characidae) from East Africa

Rhabdalestes tangensis (Lönnberg, 1907), a small African characin, is redescribed on the basis of new material from the Pangani River Basin in northern Tanzania. The morphometric and meristic variations described encompass those of R. leleupi Poll, 1967.     

Generalist predation on forest tent caterpillar varies with forest stand composition: an experimental study across multiple life stages

1. Generalist enemies can regulate low‐density forest insect populations, and are widely considered to cause greater mortality in more diverse habitats. Forest tent caterpillars (Malacosoma disstria Hübner; FTC) are a major defoliator of aspen (Populus tremuloides Micheaux) in the boreal forest, a region with a mosaic of forest stand types. This heterogeneity may influence FTC outbreaks if generalist predation or parasitism differs among stands of different tree composition. 2. Using exclusion experiments we estimate predation and parasitism of FTC across multiple life‐history stages in low‐density populations occupying both aspen (low diversity) and mixedwood stands (high diversity). 3. Arthropod and avian generalist predators were responsible for most natural enemy‐caused mortality of immature FTC, but their relative impacts varied among FTC life‐history stages. Contrary to expectation, predation on late instar larvae and pupae was higher in the less diverse aspen stands and early instar mortality did not differ. 4. By considering multiple life‐history stages, our results provide a more comprehensive view of natural enemy‐caused morality of immature FTC. Because generalist predation on FTC was higher in aspen than in mixedwood stands, we suggest that FTC populations may be slower to reach outbreak levels in aspen stands.     

Melanocytes Respond to Mechanical Stretch by Activation of Mitogen‐Activated Protein Kinases (MAPK)

Cells of human epidermis are permanently targeted by mechanical stimuli. Besides mechanical forces from external sources the body itself generates mechanical forces via muscle contractions and growth processes. Recently, it was demonstrated that mechanical stretch is connected to enhanced proliferation in epidermal cells. The underlying biochemical events are still a matter of debate. Here we show that mechanical stretch leads to activation of both ERK1/2 and SAPK/JNK in human melanocytes and keratinocytes. In response to a 5 min single stretch ERK1/2 becomes moderately induced in melanocytes and peaked 30 min after the stimulus. In keratinocytes strong activation of ERK1/2 is present directly after the stimulus. SAPK/JNK shows the same activation pattern in both cell species – a slow but steady activation. The different kinetics of both MAPK suggest that different signalling cascades were activated. Future studies should evaluate the relevance of stretch‐dependent MAPK activation in triggering the cell proliferation.     

The responses of central acoustic and vibratory interneurones in bushcrickets and locusts to ultrasonic stimulation

ABSTRACT. Analysis of the ultrasonic content of the calling songs of two tettigoniids, Decticus verrucivorus L. and Tettigonia cantans Fuessly, showed that the major secondary energy peaks in the ultrasonic range are only about 15–20 dB below the main audible frequency peaks. The song of the acridid, Locusta migratoria L., contains no appreciable secondary peaks at ultrasonic frequencies, Bifunctional acoustic-vibratory interneurones are present in the ventral nerve cord of all three species. They are divided into three categories, according to their response characteristics: VS (vibration and sound), S (sound) and V (vibration) neurones. All the unit-types capable of coding sound signals in the ventral cord (VS and S neurones) are sensitive to frequencies of up to 100 kHz, with one exception (S3). In tettigoniids, three of these unit-types are more sensitive at ultrasonic frequencies than they are at the audible frequencies of their conspecific songs. Among the vibratory neurones (V), one unit-type receives inhibitory inputs from ultrasonic acoustic primary receptors. The possible importance of ultrasonic perception in the natural environment is briefly discussed.     

Pyrgomorphid grasshoppers of the genus Phymateus contain species-specific decapeptides of the AKH/RPCH family regulating lipid-mobilization during flight

Abstract. Using heterologous and conspecific bioassays, two peptides have been isolated from methanolic extracts of corpora cardiaca from the pyrgomorphid grasshopper Phymateus morbillosus L.The structures of both peptides were elucidated by a combination of Edman degradation, after deblocking the N-terminal pyroglutamic acid residue, and mass spectrometric techniques.One peptide is an octapeptide (pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH₂) which also occurs in other insects and is code-named Scg-AKH-II.The second peptide is a novel decapeptide member of the AKH/RPCH family (pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-SerNH₂ code-named here Phm-AKH.It is the first example of a different peptide in the same genus.The analysis of changes of metabolites in the haemolymph, fat body and flight muscles of male P.morbillosus during a 30 min flight and rest after flight reveal an overall picture of flight metabolism similar to that of Locusta migratoria. Carbohydrate-fuelled metabolism is pronounced during the first 15 min of flight, whereas lipid-based metabolism is mainly used thereafter.By analogy with work on L.migratoria , it is concluded that the endogenous peptides of P.morbillosus regulate these metabolic events.