Behavioral analysis of polarization vision in tethered flying locusts

For spatial navigation many insects rely on compass information derived from the polarization pattern of the sky. We demonstrate that tethered flying desert locusts (Schistocerca gregaria) show e-vector-dependent yaw-torque responses to polarized light presented from above. A slowly rotating polarizer (5.3° s^–1) induced periodic changes in yaw torque corresponding to the 180° periodicity of the stimulus. Control experiments with a rotating diffuser, a weak intensity pattern, and a stationary polarizer showed that the response is not induced by intensity gradients in the stimulus. Polarotaxis was abolished after painting the dorsal rim areas of the compound eyes black, but remained unchanged after painting the eyes except the dorsal rim areas. During rotation of the polarizer, two e-vectors (preferred and avoided e-vector) induced no turning responses: they were broadly distributed from 0 to 180° but, for a given animal, were perpendicular to each other. The data demonstrate polarization vision in the desert locust, as shown previously for bees, flies, crickets, and ants. Polarized light is perceived through the dorsal rim area of the compound eye, suggesting that polarization vision plays a role in compass navigation of the locust.     

Adjustment of flight speed of gregarious desert locusts (Orthoptera: Acrididae) flying side by side

In tethered flying locusts, optomotor thrust responses induced by translatory pattern motion within the lateral visual fields were studied under closed-loop conditions. By modulating thrust in a compensatory manner, locusts counteracted a bias motion superposed on the thrust-related motion. This way, pattern speed was kept at 0° s^–1, indicating the set point of the respective optomotor control circuit. Though the quality of bias compensation varied greatly, it was largely independent from pattern characteristics. It might indicate that the gain of behavior not only is controlled by an automatic mechanism but also is affected by spontaneous modulations. Compensation of bias motion was critically dependent on the relation between self- and bias-generated motion: Locusts did not take control over pattern motion if self- and bias-generated motion differed greatly. Instead, locusts adopted a constant, supposingly preferred, thrust value. Therefore, flight speed is assumed to be controlled by two systems: the optomotor and a preferred thrust system. In free flight, an equalization of the flight speed of locusts within a swarm might result from similar behavior. In combination with a presumed coordination of the locusts' course direction, this may explain the continued cohesion of swarms in the field.     

The fine structure of the sense organs of the cephalopod mollusc Nautilus

Summary The structure of the rhinophore, digital tentacles, post-ocular tentacles and the eye of Nautilus macromphalus are described. The rhinophore is composed of mucous cells, ciliated cells, and flask-shaped ciliated cells. The latter are probably olfactory receptors. The digital tentacles are composed of mucous cells and pigmented cells. Motor-end-plates found in the muscle layer below the epithelium of the digital tentacles are similar to those described in other cephalopods. The post-ocular tentacle contains receptor cells that bear macrocilia. These may be mechanoreceptors. The retina is composed of retinula cells and supporting cells. A complex rhabdom is formed at the distal ends of the retinula cells. The supporting cells send processes up between these rhabdoms. Both types of cells contain pigment granules but the retinula cell has a complex membranous structure in its perikaryon. No synapses were found at the bases of the retinula cells. At the side of the retina are mucous cells that are presumed to produce the jelly-like substance that fills the inside of the eye in life. The likely function of the eye is discussed and it is suggested that it is capable of simple discriminations. It is suggested that the sense organs are probably comparatively unchanged from those of fossil nautiloids. Acknowledgements. This paper is dedicated to the late Dr. Yves Merlet who collected the nautiluses used in this study.We would like to thank Prof. J. Z. Young for all his support and encouragement. The Royal Society, The Percy Sladen Memorial Fund, and University College, London, provided the financial support that enabled one of us (V.C.B.) to collect nautiluses. The Science Research Council, U.K., provided the electron microscope used in the major part of the study and a grant to one of us (V.C.B.). We would also like to thank Prof. J. B. Gilpin-Brown who provided Fig. 1, Dr. R. Catala, for aquarium facilities, Mr. M. P. Legand and the Institut Français d'Oceanie, Noumea, New Caledonia, for laboratory facilities, Dr. J.-M. Bassot and Dr. Anna Bidder for advice on catching and preserving nautiluses, Mrs. Judy Parkes and Mr. M. Barker for photographic assistance, and Miss J. Date for secretarial assistance.     

Variability among strains of Trichoderma harzianum in their ability to reduce take-all and to produce pyrones

Antagonism tests on agar-plates and glasshouse screening indicated that three isolates of Trichoderma harzianum varied in their ability to antagonize the take-all fungus (Gaeumannomyces graminis var. tritici). Isolate 71 which was the most effective in suppressing take-all of wheat, produced two pyrones and other undetermined analogues. Isolates of T. koningii and T. hamatum shown to suppress take-all, produced a simple pyrone compound. Although T. harzianum isolates 70 and 73 did not produce any pyrones, they reduced the disease albeit to a much lesser extent than isolate 71; with isolate 73 showing distinct host growth promotion effects. It is proposed that the success of isolate 71 of T. harzianum was related to the pyrones it produces and that the ability of isolates 70 and 73 to reduce take-all may be related to mechanisms other than those involving antibiotics.     

The larval eye of the aeolid nudibranch Trinchesia aurantia (Alder and Hancock)

Summary The larval eye of the aeolid nudibranch Trinchesia aurantia has been investigated at three different stages; in all, the eyes remain closely attached to, and in cellular contact with, the central ganglia. The larval eye is a simplified version of the adult eye in that, the eye and the constituent cells, nuclei, lens, microvilli and pigment granules are all smaller, and the interdigitation between the retinal cells is not developed. The absence of the small cells of the cornea and of the spherical vesicles in the cytoplasm of the sensory cells, is further evidence of the incomplete formation of the eye. The possible origin of the eye of Trinchesia is discussed and compared with that of other gastropods.I am very grateful for the help and guidance of my supervisor Dr. D. A. Dorsett throughout the preparation of this paper. I was sponsored by a grant from the N.E.R.C.     

Separation of translation and rotation by means of eye-region specialization in flying gypsy moths (Lepidoptera: Lymantriidae)

A partial functional specialization of eye regions in the visual control of flight was studied in male gypsy moths, Lymantria dispar,under open-loop conditions. When stimulated by means of a rotating striped drum, surrounding either the moth 's longitudinal or its transverse body axis, the induced torque response was always such as to compensate for a simulated translatory disturbance of flight, if the stimulus was restricted to the ventral visual field. If restricted to the lateral visual field(s), the response was always such as to compensate for a simulated rotatory disturbance. Though the conclusions refer to only a limited subset of visual stimuli the moths experience during free flight, the induced responses give reason to suppose that at least some of the simultaneous control of translation and rotation in free flight is based on a regional specialization of the compound eye.     

Close coupling between extrusion of H+ and uptake of K+ by barley roots

Extrusion of H⁺ by intact barley (Hordeum vulgare L.) roots was automatically titrated. Simultaneously, uptake of K⁺ into the roots, transport of K⁺ through the roots, and (as a residual term) accumulation of K⁺ within the root tissue were determined. When no monovalent cation was present in the medium the steady rate of H⁺ release was close to zero. Addition of K⁺ stimulated H⁺ extrusion within less than 1 min. The stimulation of H⁺ release was apparently limited only by the movement of K⁺ through the apoplast of the roots. The steady rate of H⁺ extrusion depended on the availability of external K⁺ and saturated at a K⁺ concentration of about 100 mol· dm^-3. Half-maximum rates of net K⁺ uptake and H⁺ extrusion were reached at a K⁺ concentration of about 10 mol·dm^-3. With (slowly absorbable) sulfate as the only anion present, the stoichoimetry between H⁺ release and net K⁺ uptake was one. In conclusion, the uptake of K⁺ across the plasmalemma of the cells of the root cortex is electrically coupled to H⁺ extrusion.     

Surgical lesion of the anterior optic tract abolishes polarotaxis in tethered flying locusts, <Emphasis Type="Italic">Schistocerca gregaria</Emphasis>

Many insects can detect the polarization pattern of the blue sky and rely on polarization vision for sky compass orientation. In laboratory experiments, tethered flying locusts perform periodic changes in flight behavior under a slowly rotating polarizer even if one eye is painted black. Anatomical tracing studies and intracellular recordings have suggested that the polarization vision pathway in the locust brain involves the anterior optic tract and tubercle, the lateral accessory lobe, and the central complex of the brain. To investigate whether visual pathways through the anterior optic tract mediate polarotaxis in the desert locust, we transected the tract on one side and tested polarotaxis (1) with both eyes unoccluded and (2) with the eye of the intact hemisphere painted black. In the second group of animals, but not in the first group, polarotaxis was abolished. Sham operations did not impair polarotaxis. The experiments show that the anterior optic tract is an indispensable part of visual pathways mediating polarotaxis in the desert locust.     

How to avoid becoming a prey: Predatory encounters between an orb-weaving spider,Araneus pinguis (Karsch) (Araneae: Araneidae) and flying insects

Insects flying into the web of an orb-weaving spiderAraneus pinguis (Karsch) and their avoidance of (pre-hitting process) and escapes from (post-hitting process) the web were examined by direct observation under natural and semi-natural conditions. In the pre-hitting process, mobile insects such as Brachycera, Lepidoptera and Hymenoptera showed a low hitting ratio (number of insects hitting/number of insects flying within 1 m³ space around the web-site) because of active web avoidance and flying activity in layers lower or higher than those in which the webs are usually laid. In contrast, less mobile insects like Heteroptera, Coleoptera and Homoptera showed a high hitting ratio. In the post-hitting process, Brachycera, Lepidoptera and some Nematocera frequently escaped without being detained by the web. Many Orthoptera and Hymenoptera escaped without any sign of detection by the spider. Coleoptera frequently escaped during the spider's attack. Small insects from the Homoptera, Nematocera and Hymenoptera rarely escaped from the web, but were not immediately attacked. Mean escape time of insects was correlated significantly with capture success of the spider. Overall most of the escapes occurred in the early phases of the predation process. This indicates that escapes are unlikely to result in heavy loss of time and energy expenditure due to unsuccessful predation. Escape patterns of insects seem to be related to their mobility.     

Energy coupling and respiration inNitrosomonas europaea

Intact cells ofNitrosomonas europaea grown in an ammonium salts medium will oxidise ammonium ions, hydroxylamine and ascorbate-TMPD; there is no oxidation of carbon monoxide, methane or methanol. TheK _m value for ammonia oxidation is highly pH dependent with a minimum value of 0.5 mM above pH 8.0. This suggests that free ammonia is the species crossing the cytoplasmic membrane(s). The measurement of respiration driven proton translocation indicates that there is probably only one proton translocating loop (loop 3) association with hydroxylamine oxidation. The oxidation of endogenous substrates is sometimes associated with more than one proton-translocating loop. These results indicate that during growth hydroxylamine oxidation is probably associated with a maximum P/O ratio of 1.Abbreviations H⁺/O ratio g equiv. H⁺ translocated/g atom O consumed     

Changes in dye coupling of stomatal cells of Allium and Commelina demonstrated by microinjection of Lucifer yellow

Lucifer yellow has been microinjected into stomatal cells of Allium cepa L. epidermal slices and Commelina communis L. epidermal peels and the symplastic spread of dye to neighboring cells monitored by fluorescence microscopy. Dye does not move out of injected mature guard cells, nor does it spread into the guard cells when adjacent epidermal or subsidiary cells are injected. Dye does spread from injected subsidiary cells to other subsidiary cells. These results are consistent with the reported absence of plasmodesmata in the walls of mature guard cells. Microinjection was also used to ascertain when dye coupling ceases during stomatal differentiation in Allium. Dye rapidly moves into and out of guard mother cells and young guard cells. Hovewer, dye movement ceases midway through development as the guard cells begin to swell but well before a pore first opens. Since plasmodesmata are still present at this stage, the loss of symplastic transport may result from changes in these structures well in advance of their actual disappearance from the guard cell wall.Abbreviations DIC differential interference contrast - GMC guard mother cell - LY Lucifer yellow - Pd plasmodesmata You can observe a lot by watching Lawrence Berra, as quoted in Sports Illustrated, vol. 60 (No. 14), p. 94, 2 April 1984     

Translational coupling in a penP-lacZ gene fusion in Bacillus subtilis and Escherichia coli: Use of AUA as a restart codon

Summary An out-of-frame fusion between the penicillinase gene (penP) of Bacillus licheniformis and the -galactosidase gene (lacZ) of Escherichia coli was shown to direct the synthesis of an active -galactosidase with the same electrophoretic mobility as the wild-type protein, both in B. subtilis and E. coli. This synthesis was dependent on translation of the truncated penP gene and appeared to result from translational coupling. The fusion point between penP and lacZ contained the sequence AUAG, in which the UAG and AUA codons were in-frame with the penP and lacZ reading units, respectively. N-terminal amino acid sequence analysis of the -galactosidase protein suggested that, both in B. subtilis and E. coli, reinitiation of translation occurred at the AUA codon present at the gene fusion point.     

Calcium binding to the subunit c ofE. coli ATP-synthase and possible functional implications in energy coupling

The 8-kDa subunit c of theE. coli F₀ ATP-synthase proton channel was tested for Ca⁺⁺ binding activity using a⁴⁵Ca⁺⁺ ligand blot assay after transferring the protein from SDS-PAGE gels onto polyvinyl difluoride membranes. The purified subunit c binds⁴⁵Ca⁺⁺ strongly with Ca⁺⁺ binding properties very similar to those of the 8-kDa CF₀ subunit III of choloroplast thylakoid membranes. The N-terminal f-Met carbonyl group seems necessary for Ca⁺⁺ binding capacity, shown by loss of Ca⁺⁺ binding following removal of the formyl group by mild acid treatment. The dicyclohexylcarbodiimide-reactive Asp-61 is not involved in the Ca⁺⁺ binding, shown by Ca⁺⁺ binding being retained in twoE. coli mutants, Asp61Asn and Asp61Gly. The Ca⁺⁺ binding is pH dependent in both theE. coli and thylakoid 8-kDa proteins, being absent at pH 5.0 and rising to a maximum near pH 9.0. A treatment predicted to increase the Ca⁺⁺ binding affinity to its F₀ binding site (chlorpromazine photoaffinity attachment) caused an inhibition of ATP formation driven by a base-to-acid pH jump in whole cells. Inhibition was not observed when the Ca⁺⁺ chelator EGTA was present with the cells during the chlorpromazine photoaffinity treatment. An apparent Ca⁺⁺ binding constant on the site responsible for the UV plus chlorpromazine effect of near 80–100 nM was obtained using an EGTA-Ca⁺⁺ buffer system to control free Ca⁺⁺ concentration during the UV plus chlorpromazine treatment. The data are consistent with the notion that Ca⁺⁺ bound to the periplasimic side of theE. coli F₀ proton channel can block H⁺ entry into the channel. A similar effect occurs in thylakoid membranes, but the Ca⁺⁺ binding site is on the lumen side of the thylakoid, where Ca⁺⁺ binding can modulate acid-base jump ATP formation. The Ca⁺⁺ binding to the F₀ and CF₀ complexes is consistent with a pH-dependent gating mechanism for control of H⁺ ion flux across the opening of the H⁺ channel.This work was supported in part by grants from the Department of Energy and the U.S. Department of Agriculture.On leave from the Institute of Soil Science and Photosynthesis, Russian Academy of Science, Pushchino, Russia.     

Regulation of electrical coupling between Arabidopsis root hairs

Voltage clamp was used to measure the voltage dependence of cell-to-cell coupling via plasmodesmata between higher-plant cells (root hairs of Arabidopsis thaliana (L.) Heynh.). In addition, ionophoresis was used to introduce a variety of ions [Ca²⁺, inositol-trisphosphate, Li⁺, K⁺, Mg²⁺, ethylene glycol-bis(-aminoethyl ether)-N,N,N, N-tetraacetic acid (EGTA), 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid (BAPTA), H⁺, and OH^–] to examine whether they regulate cell-to-cell coupling. Electrical coupling showed high variability in this single cell type at the same developmental stage; the coupling ratio ranged from near 0% to about 90% with a mean value of 32%. It was voltage independent for intracellular voltage gradients (transplasmodesmatal) of -163 to 212 mV. While Ca²⁺ closes the plasmodesmatal connections (at concentrations higher than those causing cessation of cytoplasmic streaming), inositol-trisphosphate and lithium are without effect. Apparently, inositol-trisphosphate may not cause increased cytosolic Ca²⁺ in root hairs. Alkalinization by OH ionophoresis caused a modest decline in cell-to-cell coupling, as did acidification by H⁺ ionophoresis (to an extent causing the cell to become flacid). Increases in cytosolic K⁺, Mg²⁺, and the calcium chelator BAPTA by ionophoresis had no effect on cell-to-cell coupling. The regulation (and lack thereof) reported here for plant plasmodesmata is quite similar to that of gap junctions.Abbreviations BAPTA 1,2-bis(2-aminophenoxy)ethane-N,N,N, N-tetraacetic acid     

Synthesis of peptides employing 9-fluorenylmethyl chloroformate as a coupling agent

The synthesis of peptides employing 9-fluorenylmethyl chloroformate(Fmoc-Cl) as a coupling agent has been described. The method is simple, efficient and rapid. All the peptides have been obtainedin good yield (70–95%). Furthermore, both the ¹H NMR and the HPLC studies on Fmoc-Phg-Phe-OMe and Fmoc-D-Phg-Phe-OMe revealed that the coupling is free from racemization.     

The activation and inactivation of the Dunaliella salina chloroplast coupling factor 1 (CF1) in vivo and in situ

Preillumination of intact cells of the eukaryotic, halotolerant, cell-wall-less green alga Dunaliella salina induces a dark ATPase activity the magnitude of which is about 3–5-fold higher than the ATPase activity observed in dark-adapted cells. The light-induced activity arises from the activation and stabilization in vivo of chloroplast coupling factor 1 (CF₁). This activity, 150–300 μmol ATP hydrolyzed/mg Chl per h, rapidly decays (with a half-time of about 6 min at room temperature) in intact cells but only slowly decays (with a half-time of about 45 min at room temperature) if the cells are lysed by osmotic shock immediately after illumination. The activated form of the ATPase in lysed cells is inhibited if the membranes are treated with ferri- but not ferrocyanide, suggesting that the stabilization of the activated form of CF₁ is due to the reduction of the enzyme in vivo in the light.     

Synthesis of peptides employing 9-fluorenylmethyl chloroformate as a coupling agent

Summary The synthesis of peptides employing 9-fluorenylmethyl chloroformate (Fmoc-Cl) as a coupling agent has been described. The method is simple, efficient and rapid. All the peptides have been obtained in good yield (70–95%). Furthermore, both the¹H NMR and the HPLC studies on Fmoc-Phg-Phe-OMe and Fmoc-D-Phg-Phe-OMe revealed that the coupling is free from racemization.     

Mechanical sensitivity and cell coupling in the ciliated epithelial cells ofMytilus edulis gill

Summary Transmission electron microscopy has not provided strong evidence for gap junctions inMytilus edulis gill tissue, in spite of extensive physiological evidence for coupled ciliary arrest in lateral cells and coupled activation in abfrontal cells. To investigate the kinds and relative distribution of cell junctions and also to determine whether ciliary membrane particle differences exist in these two types of oppositely mechanically sensitive cells, we analyzed the structure of these and two other ciliated cell types (frontal and laterofrontal) by freeze-fracture replication. Gap junctions occur in all four ciliated cell types, but they are relatively small and of variable morphology, often consisting of elongate, winding complexes of membrane particles. Statistically, such structures rarely would be recognized as gap junctions in thin sections. Gap junctions appear to be most abundant between the highly coupled abfrontal cells, minimal between laterofrontal cells, and not evident in the epithelial cells that separate coupled ciliated cell types. The ciliary necklaces of the mechanically activated abfrontal cilia are typically 4- or 5-stranded while those of the remaining three cell types are mainly 3-stranded. In developing gill tips, ciliated cells have abundant gap junctions and newly formed cilia have a full complement of necklace particles. Nascent lateral cilia are not mechanically sensitive, indicating that the acquisition of mechanosensitivity does not correlate with the presence of ciliary necklace or other membrane particles. Lateral and laterofrontal cells become sensitive to neurotransmitters soon after the appearance of the latter during development, but mechanosensitivity of both lateral and abfrontal cells arises substantially later.