Search results for "Ecdysis"
showing 10 items of 17 documents
Condition-dependent ecdysis and immunocompetence in the amphipod crustacean, Gammarus pulex.
2010
The exoskeleton of arthropods forms an efficient protection against pathogens, but this first line of defence is periodically weakened during ecdysis, increasing the opportunity for surrounding pathogens to invade the body cavity. Since the richness of pathogens in the environment can be spatially and temporally variable, arthropods may have a fitness advantage in moulting in a place and time of low infection risk. Consistent with this hypothesis, we found that the amphipod crustacean, Gammarus pulex , exhibits temporal adjustment of the moult cycle in response to elevated risks of infection. Interestingly, this phenomenon is variable between two populations and independent of levels of im…
Identification, sequence and mRNA expression pattern during metamorphosis of a cDNA encoding a glycine-rich cuticular protein in Tenebrio molitor
1995
The study of insect cuticular proteins and their sequences is of interest because they are involved in protein-protein and protein-chitin interactions which confer the mechanical properties and fine architecture of the cuticle. Moreover, in the coleopteran Tenebrio molitor there is a dramatic change in cuticular architecture between pre- and postecdysial secretion. We report the isolation, by differential screening, and the sequence characterization of a cDNA clone encoding a cuticular protein of T. molitor, ACP17. After insertion in the expression vector pEX1, the recognition of the fusion protein by an anti-cuticular monoclonal antibody confirmed the cuticular nature of ACP17. Northern hy…
Identification of proteins and developmental expression of RNAs encoded by the 65A cuticle protein gene cluster in Drosophila melanogaster
1998
0965-1748 (Print) Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S.; Proteins of the third instar larval cuticle of Drosophila melanogaster, LCP5-LCP9, were purified and their N-terminal sequences determined. Three of these proteins (LCP5, 6, and 8) were found to be encoded by two multicopy genes previously mapped to the gene cluster at 65A 5-6 on the left arm of the third chromosome. The analysis of the patterns of developmental expression of the 8 distinct genes at this site showed that all but two were expressed during larval life. The patterns fell into three groups: one where expression was all through larval life, one where expression was primar…
Characterization of two male-specific polypeptides in the tergal glands secretions of the cockroach Leucophaea maderae (Dictyoptera, Blaberidae)
1998
0965-1748 (Print) Journal Article Research Support, Non-U.S. Gov't; During the sexual behavior of cockroaches, the female mounts the courting male to feed on the proteinaceous secretion of the tergal glands. Polyacrylamide gel electrophoresis of male and female protein extracts after cuticle wiping revealed three major bands. Two of 18 and 22 kDa, named Lma-P18 and Lma-P22, are specific to the male tergal extracts. Moreover, Lma-P22 is only found in the male second tergite extracts. The third one of 54 kDa, named Lma-P54, is common to male and female extracts and could be considered as an ubiquitous surface protein. Several other minor proteins are also present on the body surface of adults…
Cuticle: Formation, Moulting and Control
1984
The relative rigidity of the arthropod exoskeleton makes it impossible for body size to increase continuously during the postembryonic development of these animals. Once they have hatched from the egg, they grow in steps, passing through a variable number of (larval) stages (Fig. 1 a). Apart from a few exceptions, there are between 3 and 10 such stages in the arachnids, 3–20 in the crustaceans, and 3–10 in the insects. In many cases a metamorphosis stage intervenes (some crustaceans; holometabolous insects) (Fig. 9b, c).
Morphogenesis of mechanoreceptor and epidermal cells of crickets during the last instar, and its relation to molting-hormone level.
1980
(1) The fine structure of the cercal campaniform sensilla and epidermal cells of Gryllus bimaculatus Deg. (Saltatoria, Gryllidae) was examined, and the ecdysteroid level was monitored throughout the last larval instar. (2) The epidermal cells show changes in shape, cytoplasmic inclusions and differentiation of the apical cell membrane, coupled to the phases of buildup and breakdown of the (cercus) cuticle. (3) The imaginal epicuticle of the epidermal cells begins to form later (by about approximately 6h) than that of the campaniform sensilla. (4) The campaniform sensilla were studied with respect to (a) the morphogenesis of the cuticular apparatus, (b) the inclusion of phenol oxidases in th…
Structure and function of prothoracic glands and oenocytes in embryos and last larval instars of Oncopeltus fasciatus Dallas (Insecta, Heteroptera).
1976
1. Active prothoracic glands and oenocytes of last larval stage are both characteristized by well-developed smooth and rough endoplasmic reticulum (ER). Prothoracic glands also show plasma membrane infoldings, but not oenocytes which contain a large number of pleomorphic vesicles. 2. The fine structure of embryonic oenocytes corresponds after blastokinesis with that of active larval and adult cells. Thus, an activity in the late embryo can be assumed. Embryonic prothoracic glands reveal no signs of activity: smooth and rough ER are absent. The subcellular structure resembles that of organ anlagen, i.e. not yet fully differentiated tissue. Hormone synthesis is not likely. 3. Ecdysone titer w…
Morphogenesis of the wing Anlagen in the mealworm beetle tenebrio molitor during the last larval instar.
1990
The wing Anlagen of Tenebrio develop from epidermal cells located on the lateral margins of meso- and metathoraces. Three to four days after larval ecdysis, these cells start to proliferate slowly, continuing to do so until day 13 which corresponds to the period of the pupal commitment of the remaining epidermis. The wing Anlagen cells then proliferate rapidly until day 18.5. Three days before pupal ecdysis, the mitotic index falls suddenly while 40% of the Anlagen cells disappear owing to cell degeneration. The sudden changes observed in the mitotic index are correlated with two hemolymphatic peaks in ecdysteroid levels. Anlagen of the forewings and hindwings show similar development excep…
Evaluation of Triflumuron, a benzoylphenylurea derivative, onTenebrio molitorpupae (Col., Tenebrionidae): effects on cuticle
1996
Triflumuron (TFM), a benzoylphenylurea (BPU) derivative, exhibited insecticidal activity when injected to newly ecdysed pupae of Tenebrio molitor. Mortality occurs by defect in adult ecdysis. Treatment resulted in a significant increase in the duration of pupal stage and caused a reduction in both cuticle thickness and incorporation of ''C-labelled precursor into chitin compared to controls. Moreover, TFM reduced the amount of cuticle chitin without any significant effect on protein level. Thus, TFM acts by preventing the chitin biosynthesis confirming the primary mode of action of the BPU insecticides.
Degeneration of moulting glands in male crickets
1998
The degeneration of the prothoracic glands of the male cricket, Gryllus bimaculatus, was analyzed by using an in vitro assay for ecdysteroid release from the moulting glands in last instar nymphs as well as in adult animals, and correlated with light and transmission electron microscopy. Apoptosis was examined by the TUNEL-reaction. The ability to synthesize ecdysteroids reached a peak at the 8th day of the last larval instar, identified as the moulting peak. After adult ecdysis it decreased to barely measurable values. Prothoracic gland degeneration was initiated at the time of the moulting peak, characterized by TUNEL positive reactions, nuclear and cytoplasmatic condensation, a striking …