Ulrich Schlüter

Extraocular photoreceptors in the brain of Epilachna varivestis (Coleoptera, Coccinellidae)

SummaryWithin the optic lobe of adult Mexican bean beetles, Epilachna varivestis, three complex areas were detected that display elements with the morphological appearance of photoreceptors. Each of these complexes contains about eight cells that show fully differentiated rhabdomeres, screening pigments and other features typical of photoreceptors. It was shown that these areas originate from larval stemmata, which move into the depth of the head capsule during metamorphosis and are finally embraced by the outgrowing optic lobes. Although the function of these formations is not yet known, there are some indications that they may play a role in the entrainment of circadian clocks.

Occurrence of weight gain reduction and inhibition of metamorphosis and storage protein formation in last larval instars of the Mexican bean beetle, Epilachna varivestis, after injection of azadirachtin

Injection of the insect growth regulator azadirachtin into 40‐h‐old last larval instars of Epilachna varivestis (Mulsant) inhibited metamorphosis at doses lower than 0.3 μg. Various higher doses (0.3–1.0 μg) caused in addition weight gain reduction, whereas weight gain was almost entirely suppressed after injection of 2.5 μg. Histological and electrophoretical analyses showed that storage protein formation in the fat body, necessary for pupation, did not occur in higher dose treated (1.0 μg) individuals, but it was not affected by low dose (0.1 μg) treatment. It is assumed that azadirachtin causes metabolic defects at higher concentrations.

Ultrastructural evidence for inhibition of chitin synthesis by nikkomycin

SummaryThe nucleoside antibiotic nikkomycin has proved to be an effective inhibitor of chitin synthesis in the Mexican bean beetleEpilachna varivestis. Ultrastructural investigations show defects in the procuticular area after nikkomycin application which suggest the complete absence of chitin. A cuticle like this is inflexible and too brittle to satisfy its normal function as an exoskeleton. The individuals are not able to free themselves from the exuvia and finally die. Therefore nikkomycin seems to be a potential insecticide with high specifity.

Über Die Temperaturabhängigkeit Des Wachstums Und Des Häutungszyklus Von Argulus Foliaceus (L.) (Branchiura)

[The effect of temperature on the postembryonic development of Argulus foliaceus (L.) has been examined. Growth, interval, and frequency of moulting are proportional. The shorter the interval of moulting and the larger the growth with successive moults, the larger is the rate of growth. The growth of A. foliaceus is influenced by temperature. In the examined range (16°-28° C), growth increases with higher temperatures. This relation is not linear. Differences between the sexes do, if at all, only appear after maturity. The relative rate of growth per moult does not depend on temperature an only a little so on sex: the stature of the animal is decisive in this respect. The chronological order of the postembryonic moultings has been determined., The effect of temperature on the postembryonic development of Argulus foliaceus (L.) has been examined. Growth, interval, and frequency of moulting are proportional. The shorter the interval of moulting and the larger the growth with successive moults, the larger is the rate of growth. The growth of A. foliaceus is influenced by temperature. In the examined range (16°-28° C), growth increases with higher temperatures. This relation is not linear. Differences between the sexes do, if at all, only appear after maturity. The relative rate of growth per moult does not depend on temperature an only a little so on sex: the stature of the animal is decisive in this respect. The chronological order of the postembryonic moultings has been determined.]

Plasmalemma-mitochondrial complexes involved in water transport in the hindgut of a milliped, Scaphiostreptus sp.

SummaryPlasmalemma-mitochondrial complexes (PMC) are known to be very active in water transport in different tissues. The PMC in the hindgut cells of the milliped, Scaphiostreptus sp., differ from those found in other transporting epithelia of hindguts; they are closely connected with cisternae of the endoplasmic reticulum. This arrangement is thought to be very efficient in ion and water transport.

Fine structure of the pyloric glands inpolydesmus angustus latzel andglomeris marginata villers (diplopoda)

Summary1.Exocrine glands found in the anterior hindgut of the millipedesPolydesmus angustus andGlomeris marginata should be termed pyloric glands.2.The pyloric glands ofPolydesmus angustus are appropriately differentiated hindgut epithelial cells. Every single cell shows secretory activity.3.InGlomeris marginata the pyloric glands are composed of three types of cells: secretory cells, transitional cells, and canal cells.4.The size and form of the pyloric glands are related to the length of the hindgut.5.The secrete of the pyloric glands is dispersed on the hindgut intima as a thin film.6.This secretion layer seems to influence the permeability of the hindgut and play an essential role in the reabsorption of water and other important compounds.Zusammenfassung1.Die DiplopodenPolydesmus angustus undGlomeris marginata besitzen im vorderen Enddarm exokrine Drüsen, die als Pylorusdrüsen bezeichnet werden.2.Die Pylorusdrüsen vonPolydesmus angustus sind Abkömmlinge von Enddarm-Epithelzellen, die sich in entsprechender Weise differenziert haben. Jede Zelle für sich ist sekretorisch tätig.3.Im Gegensatz dazu sind die Pylorusdrüsen vonGlomeris marginata aus drei unterschiedlichen Zellarten zusammengesetzt: Sekret-, Übergangs- und Kanalzellen.4.Die unterschiedliche Ausbildung und Größe der Pylorusdrüsen korreliert mit der Länge des Enddarms.5.Die Pylorusdrüsen beider Diplopoden sezernieren ein Sekret, das sich auf der Enddarmintima als dünner Film verteilt.6.Die Funktion der Sekretschicht wird darin gesehen, dab sie eine permeabilitfits-beeinflussende Wirkung auf der Enddarmintima ausfibt. Eine solche Schicht dtirfte somit eine wesentliche Rolle bei Rtickresorption wichtiger Stoffe aus dem Enddarmlumen spielen.

Inducing melanotic nodules within the fat body of the last instar larvae of Epilachnà varivestis (Coleoptera) by azadirachtin

Abstract Injection of minute amounts of azadirachtin causes formation of numerous small (20- to 30-μm diameter) nodules in the fat body of last instar larvae of the Mexican bean beetle, Epilachna varivestis. About 1 day after injection, some fat body cells start degenerating by necrosis. The first visible sign is a leakage of the membranes as detected by a tracer substance (colloidal lanthanum nitrate). The remnants of the distributed fat cells are pinocytosed and possibly phagocytosed by other fat cells. Subsequently, such fat cells develop large heterolysosomes. After the degeneration of these cells, the heterolysosomes become free within the intercellular spaces of the fat body and clot with remmants of other cells by forming large aggregations which become black during condensation. During this process, hemocytes form a multilayered coat around the aggregations, which then stop growing. For several reasons it is presumed that the formation of these melanotic nodules is correlated with the interference of azadirachtin with premetamorphic events in the larvae.

The anal glands of Rhapidostreptus virgator (Diplopoda, Spirostreptidae)

SummaryDuring each moult the anal glands in Rhapidostreptus virgator are partly dissolved and subsequently rebuilt and enlarged by embryonic cells within the anal sac epithelium. An embryonic cell undergoes two mitoses thus producing the four cells which are present in a glandular unit. During the genesis of the glandular units each of the latter secretory cells produce a ciliary process, which is believed to serve as a mould for the canal cell, which in turn secretes the cuticular efferent duct.

Chitin synthesis inhibition by Nikkomycin in the integument of Manduca sexta: An ultrastructural and fluorescence microscopic study

Abstract Nikkomycin exerts a dose-dependent chitin synthesis inhibition when injected into pharate fifth instar larvae of the tobacco hornworm, Manduca sexta. This effect can be clearly visualized by electron microscopy and by fluorescence microscopy. Comparison of the results presented here with previous microscopical studies on other arthropod groups suggest that the length of an intermolt cycle and duration of the cuticle deposition phase may be responsible for the molting inhibitory potence of Nikkomycin in different arthropod taxa.