Ommochrome Synthesis Research Articles

Der Tryptophanstoffwechsel und die Ommochromsynthese während der Embryonalentwicklung der Stabheuschrecke Carausius morosus

The synthesis of ommochromes, ommin, and xanthommatin, was studied during the embryonic development of Carausius morosus. Ommochrome synthesis begins in the epidermis of the embryo at the 46th day after egg laying. The ommochrome accumulation is directly related to the continuous increase of pigment spots on the epidermis of the pharate larva. The concentration of free tryptophan increases progressively from the germ band formation (15th day), until the final position of the embryo in the egg, with the head immediately beneath the operculum (44th day). Subsequent decrease in concentration of tryptophan coincides with the appearance of ommochrome in the epidermis of the embryo. The tryptophan levels decrease considerably from 44th day till the 60th day. During the stage of the pharate first instar larva tryptophan levels remain low until hatching. The concentrations of the intermediates, kynurenine and 3-HO-kynurenine, show no accumulation and remain low during the whole of ommochrome synthesis.

Electrophysiological responses in mutant-eyed drones of Apis mellifera to selected wavelengths of light

The neural responses of eyes of wild-type and seven mutant-eyed drones of Apis mellifera to wavelengths of light between 350 and 700 nm was determined. The responses of all types were identical in young drones (1–3 days after emergence), with maximum sensitivity at 440 nm. No change in the wavelength of maximal sensitivity occurred in the wild-type drones, in the brick mutant, or in three permanently white-eyed mutants, as ageing continued. In two mutants a shift of 40 nm toward the longer wavelengths occurred as ommochrome synthesis proceeded during the first 10 to 12 days of adulthood. It is suggested that binding of the ommochrome with the proteins of the pigment cells alters the quality of light reaching the underlying visual pigment. In the third mutant, a shift of similar magnitude occurred with accumulation of ommochrome precursor. A hypothesis that this material filters the entering light, and hence shifts the response maximum agrees well with the observations obtained.

Die Altersabhängigkeit des Ommochromgehalts im Komplexauge der Bienen. Ein quantitativer Vergleich zwischen Wildtyp und der Augenmutante chartreuse

The content of screening pigment in the eyes of the mutant chartreuse of the honey-bee is different from that of the wild type. Composition and concentration of the ommochromes differ very much from those of the wild type in quantity. Ch-bees (investigations were done on worker bees) have xanthommatin as the only ommochrome. The concentration of the ommochrome in collecting bees is reduced by a factor of 10 compared to that of the wild type. Ommochrome synthesis in wild type bees as well as in the mutants is maintained for at least 10 days of adult life. There is no considerable change of the concentration of the pigment in older bees, even after 8 weeks. It is concluded from the results that there exists a negative influence concerning the optic isolation of neighbouring ommatidia and, on the other hand, a change of spectral transmission by the screening pigments.

Quantitative studies on the pigmentation of the eye in the flourmoth ephestia kühniella : III. Pigmentation in the α-strain after injection of high amounts of kynurenine and the attempt of an interpretation

1. In order to interpret the results of experiments involving the injection of the ommochrome-precursor 3-hydroxykynurenine (3-HOK) into pupae of the red eyed strain and measurement of pigment synthesis (MUTH, 1967, 1968), a model is proposed, based on the following assumptions: a) The presence of cytoplasmatic granules containing RNA is a necessary condition for pigment synthesis. b) The granules originate from preformed material, if the amount of 3-HOK rises in the presence of this material or if the amount of this material rises in the presence of the precursor. The amount of the material being transformed into granules depends on the value of the stationary and on the hight of the rise of the changed variable. The dependence on the precursor is such that the originating granules are saturated by the precursor. c) After a fast synthesis the preformed material becomes inactivated, regardless of whether having been transformed into granules or not. Though the amount of 3-HOK decreases, the rate of inactivation provides a lasting saturation of the granules. 2. The model allows the derivation of a function, which describes the dependence of the rate of ommochrome synthesis on the injected amount of the precursor. 3. The composition of the pigment being synthesized depends on the injected dose. The results are consistent with the assumption that the pigment consists of 2 mixtures,A' andB, the ratio of which,B∶:A' rises with the injected dose. 4. The experimentally obtained values of the mixtureA' fit the function, calculated on the basis of the proposed model.

Quantitative studies on the pigmentation of the eye in the flourmothEphestia kühniella : II. Pigmentation in the,a-strain after injection of small amounts 3-hydroxykynurenine

The rate of ommochrome synthesis in the accessory pigment cells has been studied after injecting various amounts of the ommochrome precursor 3-hydroxykynurenine (3-HOK) into pupae of the red-eyed strain. The rate of pigment synthesis is proportional to the injected dose, provided it does not exceed 1μm per pupa. - Injection at 96-99 hours after pupation causes a short but fast rise of the rate, which is followed by an exponential decrease to about one half of its initial value within a 12 hour's period. - The amount of pigment being synthesized until 180-183 hours after pupation decreases with increasing time of injection. Quantitative comparison of this decrease with pigment synthesis after injection at 96-99 hours allows the conclusion that the exponential drop of the rate after supplying the precursor at 96-99 hours is not due to the decrease of precursor concentration within the pupa. It must be brought about exclusively by developmental processes of the pigmentary system itself. - If an injection of 1 μg 3-HOK atti >99 hours succeeds a first one given at 96-99 hours, the amount of pigment being synthesized betweenti and 181.5 hours is 1.73 times the amount being synthesized after a single injection atti. This value is independent ofti. - The discussion of these results calls for a special mechanism which will adjust the activity of the pigmentary system to the total amount of the precursor.

Veränderungen der Hämolymphe vor der Verpuppung von Cerura vinula L.: Der Gehalt an Eiweiß, Aminosäuren, Ommochrom-Vorstufen und Ommochromen

Ommochrome synthesis at the beginning of lepidopteran metamorphosis is correlated to morpholytic and morphogenetic activity. In order to examine the metabolic alterations involved, data on respiration, haemolymph volume and on concentrations of total carbohydrate, soluble protein and non-protein nitrogen have been collected. Free aminoacids were separated by ion exchange chromatography and the levels of tryptophan, 3-hydroxy-kynurenine and of total ommochromes were determined independently at different stages during transformation of the larva towards the pupa. While the levels of non-protein nitrogen and of total free amino acids remain nearly constant, there is a three- and twentyfold increase of tryptophan and 3-hydroxy-kynurenine, respectively. It is proposed, that ommochrome formation serves in the removal of tryptophan liberated by proteolysis.