Evaluation of sticky light traps for sampling mosquito larvae

Very simply constructed aquatic sticky light traps employing a chemical solution emitting a bright light attracted large numbers of all larval instars, but few pupae of Aedes cantans in trials in England. During April numbers of larvae per trap ranged from 73±14.2 to 163±19.9, whereas dipping with a ladle yielded only 6.9±5.5 to 11.8±7.7 larvae/dip. The traps were also effective in sampling larvae of Culiseta morsitans and in Sierra Leone larvae of Aedes aegypti. It was concluded that sticky light traps could be valuable in sampling relative numbers of mosquito larvae and merited further evaluation.

---

Résumé Des pièges adhésifs lumineux faciles à réaliser sont construits pour les captures des larves de moustiques. Ils sont formés de paires de boîtes de Pétri en plastique contenant une solution émettrice de lumière provenant de bâtons lumineux chimiques Cyalume^®. Chaque piège est recouvert d'une feuille de plastique de 16×16 cm enduite d'une substance qui reste adhésive sous l'eau. Les larves de moustiques attirées vers la source lumineuse viennent se coller à la feuille adhésive.Ces pièges ont été utilisés avec succès en Angleterre pour l'échantillonnage de tous les stades larvaires d'Aedes cantans, mais pas avec le même efficacité pour les nymphes. Des tests plus restreints ont montré que la technique était également utilisable pour les larves de Culiseta morsitans. Les nombres moyens d'A. cantans capturés pendant une piode de 12 h (73±14,2–163±19,9) étaient supérieux à ceux obtenus en plongeant une louche (6,9±5,5–11,8±7,7). En utilisant les pièges adhésifs lumineux, les captures moyennes de C. morsitans étaient également supérieures (12,6±4,7–35,8±8,9) contre (5,7±6,1–8,9±7,8) avec la méthode de la louche.En Sierra Leone, des stades larvaires immatures d'A. aegypti se développant dans des containers de stockage d'eau ont également pu être capturés à l'aide de ces pièges.Bien qu'une évaluation plus poussée soit encore nécessaire, il ne fait aucun doute que ces pièges adhésifs lumineux aient un intérêt considérable pour l'échantillonnage larvaire dans les sites inaccessibles, tels que les trous d'arbres ou les trous de crabes, où les méthodes d'échantillonage classiques sont souvent d'un emploi difficile.

     

Comparison of the killer toxin of several yeasts and the purification of a toxin of type K2

A total of 13 killer toxin producing strains belonging to the genera Saccharomyces, Candida and Pichia were tested against each other and against a sensitive yeast strain. Based on the activity of the toxins 4 different toxins of Saccharomyces cerevisiae, 2 different toxins of Pichia and one toxin of Candida were recognized. The culture filtrate of Pichia and Candida showed a much smaller activity than the strains of Saccharomyces. Extracellular killer toxins of 3 types of Saccharomyces were concentrated and partially purified. The pH optimum and the isoelectric point were determined. The killer toxins of S. cerevisiae strain NCYC 738, strain 399 and strain 28 were glycoproteins and had a molecular weight of M_r=16,000. The amino acid composition of the toxin type K₂ of S. cerevisiae strain 399 was determined and compared with the composition of two other toxins.     

The extracellular space and blood-eye barrier in an insect retina: An ultrastructural study

Summary (1) The distribution of the extracellular space (ECS) in the outer part of the locust compound eye has been mapped with lanthanum and ruthenium red, applied to the retina. (2) In the photoreceptor zone, about 2.4% of the volume is ECS, in agreement with radiotracer and electrical estimates. Of this ECS, about 70% lies in lacunae between ommatidia, but only 1–2% adjacent to the photosensitive rhabdom. The lacunae are filled with material which binds applied tracers, and are thought to be structural spaces. (3) It has been suggested several times that such a small cation pool is insufficient to sustain more than a few large photoresponses, but this is shown to be incorrect. Enough Na⁺ lies within the rhabdomal ECS and within rapid diffusional access to it, to impose no immediate limitation. (4) The palisade vacuoles surrounding the rhabdom are intracellular, and are typical of light as well as dark-adapted eyes. (5) Tracers fail to penetrate more than about 30 m into the axon zone, in agreement with electrical, dye and radiotracer indications of a blood-eye barrier near this point. Septate and gap junctions between glial membranes proliferate at this level, the lacunae disappear, and the axonal clefts narrow, but no tight junctions were seen. Comparison is made with the barrier around the nerve cord. (6) The secondary pigment cells in the retina may function as osmotic/ionic buffers, in conjunction with the blood-eye barrier.     

Extracellular matrix fibrils and cell contacts in the chick embryo

Summary The migration of neural crest and sclerotome cells and the extension of ventral root axons in chick embryos at stages 16–20 were studied by light microscopy as well as scanning and transmission electron microscopy at the leg bud level of fixed specimens. Extensive cellular movements take place in association with an extracellular matrix consisting of microfibrils. The neural crest and sclerotome cells migrate into the large matrix-filled extracellular space surrounding the neural tube and notochord, apparently using microfibril bundles as substratum. The cells exhibit pseudopodia which are closely associated with the matrix fibrils. The fibrils around the notochord show a spatial arrangement indicating that the sclerotome cells are contact-guided to their subsequent positions. Mutual cell contacts, including those established by cell processes, frequently show cytoplasmic electron dense plaques at adjacent membranes. These small plaque contacts might be correlated to contact inhibition of locomotion between the cells and participate in the guidance of cells. The growth cones of extending axons exhibit filopodia contacting both surrounding mesenchyme cells and extracellular fibrils. The orientation of the axons might thus be affected by contacts with cell surfaces as well as with extracellular material.Technical assistance was given by Mrs. Kerstin Ahlfors, Mrs. Charlotte Fällström, Mrs. Annika Kylberg and Mrs. Stine SöderströmSupported by grants from The Swedish Natural Science Research Council     

Interpretation of sedimentation data measured in a former tidal channel Lake Volkerak

In Lake Volkerak, situated in the southwest of the Netherlands, downward settling fluxes are related to external inputs of suspended solids and wind action. The settling fluxes, measured using sediment traps, were 55 g (dw) m ^–2 d ^–1 on average. The ratio of metal concentration to scandium concentration was used to discriminate between external (polluted) suspended solids and internal (relatively clean) suspended solids. Generally, the contribution of the river suspended solids was small compared to that of resuspended material; the river-transported material was mainly deposited in the centre and to the east of the lake. The amount of material trapped increased substantially with increasing wind velocity.A simple model was used to interpretate the data. This model does not have a predictive capacity, but can be used to interpret and assess the significance of material retained in the sediment traps. Erosion was related to the wind velocity, using an empirical relationship between the orbital velocity of the wind-generated waves at the bottom and the wind velocity. The critical wind velocity for erosion to occur was estimated to be 5.5 m s^–1. The extremely high amounts retained in the sediment traps in shallow areas during storms emphasised the importance of these wind conditions for the transport of fine sediments.     

Labelling the blueberry leaftier, Croesia curvalana with foliar sprays of rubidium chloride

The feasibility of labelling blueberry leaftier by rearing the larvae on blueberry plants treated with foliar sprays of rubidium chloride (RbCl) at concentrations of 1000, 5000, 10 000 and 20 000 ppm were assessed. RbCl sprays above 5000 ppm significantly reduced survivorship to adult stage. The adult longevity, fecundity and mating were not affected when the larvae were reared on foliage treated with 5000 ppm RbCl solution. Reciprocal matings of 5000 ppm treated moths with untreated moths revealed transfer of label above the 0.1 µg Rb/insect threshold level from treated males to untreated females (in 8 out of 13 pairs) and vice versa (in 1 out of 9 pairs). Considerable loss of Rb (56–64%) occurred from the leaves over a 15 day period. All of the moths and pupae collected from the RbCl treated plots in 1989 and 1990 respectively, had a Rb content higher than the threshold level. In a preliminary dispersal study, marked male and female moths were found in sweepnet samples collected 20 and 60 m from the centre of the treated field. Labelled male moths were also captured in pheromone traps arranged in a circle, 40 m from the treated plot.     

Monensin inhibits the first cellular movements in early chick embryo

Summary In early chick blastoderm at stage XIII, the interaction of the hypoblast with the epiblast triggers on the epiblast the first extensive cellular migrations, which result in formation of the primitive streak, the source of the axial mesoderm. During this period, extracellular material (ECM) is secreted and assembled into an organized network in the extracellular spaces and is implicated in regulating the behaviour of the cells that contact it. The first cellular migrations and inductions are inhibited when early chick blastoderm is treated with the glycosylation-perturbing ionophore monensin. The difference in amount and in organization of ECM between monensin-treated embryos and control embryos is striking. Even blastoderms at stage X, which are essentially free of ECM, show extensive ECM after monensin treatment. Monensin produces a substantial change in the polypeptide pattern with the induction or marked accentuation of multiple charged species (isoforms) of polypeptides different from those present in the control embryos. The interference of monensin with the migration and induction mechanisms is permanent in embryos before the primitive streak (PS) stage, and it seems that the respective signals or the sensitivity of the epiblast/hypoblast cells to them must be very stage specific. Monensin-treated embryos probably secrete abnormal ECM that does not provide the proper conditions for the hypoblast to interact with the epiblast cells.     

Light-dependent quenching of chlorophyll fluorescence in pea chloroplasts induced by adenosine 5′-triphosphate

Addition of ATP to chloroplasts causes a reversible 25–30% decrease in chlorophyll fluorescence. This quenching is light-dependent, uncoupler insensitive but inhibited by DCMU and electron acceptors and has a half-time of 3 minutes. Electron donors to Photosystem I can not overcome the inhibitory effect of DCMU, suggesting that light activation depends on the reduced state of plastoquinone. Fluorescence emission spectra recorded at ?196°C indicate that ATP treatment increases the amount of excitation energy transferred to Photosystem I. Examination of fluorescence induction curves indicate that ATP treatment decreases both the initial (F_o) and variable (F_v) fluorescence such that the ratio of F_v to the maximum (F_m) yield is unchanged. The initial sigmoidal phase of induction is slowed down by ATP treatment and is quenched 3-fold more than the exponential slow phase, the rate of which is unchanged. A plot of F_v against area above the induction curve was identical plus or minus ATP. Thus ATP treatment can alter quantal distribution between Photosystems II and I without altering Photosystem II-Photosystem II interaction. The effect of ATP strongly resembles in its properties the phosphorylation of the light-harvesting complex by a light activated, ATP-dependent protein kinase found in chloroplast membranes and could be the basis of physiological mechanisms which contribute to slow fluorescence quenching in vivo and regulate excitation energy distribution between Photosystem I and II. It is suggested that the sensor for this regulation is the redox state of plastoquinone.