Postecdysial Period Research Articles

Characterization of cuticular chitin‐binding proteins of Leptinotarsa decemlineata (Say) and post‐ecdysial transcript levels at different developmental stages

Seven cuticle chitin-binding proteins (Ld-CP1v1 to 7) were deduced from antenna cDNAs of adult Colorado potato beetles, Leptinotarsa decemlineata (Say), based on their consensus sequences. The mature proteins consisted of 87-188 residues. Ld-CP1v1 formed a distinct orthologous protein cluster (OP1) along with four proteins from other insect species in a neighbor-joining phylogenetic tree. These proteins also contained a proline glutamine-rich (PQ-rich) region and a highly conserved C-terminal motif (Phr). Their consensus region lacked the defined aromatic triad. Ld-CP2 to 6 clustered with those bearing RR-1 consensus and Ld-CP7 with RR-2 consensus. Ld-CP1v1 to 4 were expressed at the post-ecdysial period in all the developmental stages whereas Ld-CP5 to 7 were expressed mainly in adults.

Glycosidase activity in the post-ecdysial cuticle of the blue crab, Callinectes sapidus

We have previously demonstrated a marked change in sugar moieties of glycoproteins of the cuticle of the blue crab, Callinectes sapidus, between 0.5 and 3 h post-ecdysis. The present study has identified a glycosidase that appears in the cuticle during the early post-ecdysial hours. The enzyme has affinities for p-nitrophenyl derivatives of both N-acetylglucosamine and N-acetylgalactosamine. Both activities are competitively inhibited by chitobiose, suggesting that the enzyme could be a N-acetylhexosaminidase (EC 3.2.1.52). Atypical of N-acetylhexosaminidases described to date, this enzyme has a pH optimum of 7.0. The enzyme activity is high during the post-ecdysial period coincident with the changes in glycoprotein profiles observed in vivo. Partial purification of the enzyme has been accomplished by Sephacryl size-exclusion chromatography followed by concanavalin A affinity chromatography.

POSTECDYSIAL CHANGES IN THE PROTEIN AND GLYCOPROTEIN COMPOSITION OF THE CUTICLE OF THE BLUE CRAB CALLINECTES SAPID US

ABSTRACT Postecdysial modifications of the cuticle of Callinectes sapidus were evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of soluble protein extracts. Gels stained with Coomassie blue and with silver demonstrated that major changes in protein composition or mobility occurred immediately after ecdysis. Electroblots of SDS-PAGE gels were probed with various biotinylated lectins. The patterns of lectin binding were also markedly different between blots of pre- and postecdysial cuticle extracts, demonstrating a change in glycosylation or glycoprotein mobility in the early postecdysial period. The dramatic alteration in cuticular composition is concurrent with the onset of sclerotization and mineralization of the preexuvially deposited layers of the cuticle.

Correlation of water translocation, cuticle dehydration and post-ecdysial sclerotization by the american cockroach

1. 1. Haemolymph volume decreases during the initial 16 hr post-ecdysial period, increases after water ingestion and subsequently drops until the inter-ecdysial level is reached. 2. 2. Total body water follows a similar pattern, but the changes are not as pronounced. 3. 3. Tissue water is inversely proportional to the total body water. 4. 4. Soluble cuticle protein declines throughout the initial 16 hr period while both β-glucosidase and alkaline phosphatase activity is lost within 6 hr after ecdysis. 5. 5. Dehydration of the cuticle also occurs during the immediate 6 hr post-ecdysial period. 6. 6. These data suggest that the formation of the protein-insoluble matrix is linked with water loss. 7. 7. Water removal may decrease the distance between molecules allowing specific reactions to take place.

Effects of ovarian maturation and insemination on the length of intermoult in Thermobia domestica

ABSTRACT. A study of the individual variability in the length of intermoult periods allows correlations to be established between reproductive and moulting cycles in adult females of Thermobia domestica (Packard) (Thysanura, Lepismatidae). By keeping the females without or with males and by changing the day of insemination, it is shown that the intermoult periods vary with the rate of ovarian maturation from the beginning of each stadium. Females with slow oocyte growth are never inseminated, even in the presence of males; they have short intermoults. Females with rapid oocyte growth can be inseminated and the timing of insemination regulates the length of the intermoults. It appears that the variability in duration of the intermoult only concerns the first part of the stadium (postecdysial period of the reproductive cycle=period of intense vitellogenesis), whereas the second part of the stadium (pre‐ecdysial period=previtellogenesis) has an almost constant length. The endocrine mechanisms involved are considered, taking into account the cyclic changes in hormonal levels already described in other papers.

Antigonadotropic and antiallatal effects of precocene II in the firebrat, Thermobia domestica (Thysanura, Lepismatidae)

The sensitivity of an apterygote insect to precocene II was investigated for the first time in females of Thermobia domestica. Topical applications of this compound, which has been said to possess anti-juvenile hormone activity, were carried out at various times in the postecdysial period of a reproductive cycle, during intense vitellogenesis in the terminal oöcytes. The effects of treatment were observed on mortality, fecundity, insemination and also on the ultrastructure of corpora allata; they depend on the dose used and on the day of treatment. A single application of 10 μg/insect at the beginning of the postecdysial period induces antigonadotropic effects in females reared both with and without males. The effects of precocene add to those of non-insemination, which also elicits inhibition of oöcyte maturation. In addition, the cytotoxic action of precocene, leading to degeneration of the corpora allata, which is most probably irreversible, was demonstrated.

Comparable activities of left and right corpora allata consistent with humoral control of juvenile hormone biosynthesis in the cockroach

The rates of juvenile hormone (JH) biosynthesis have been measured in vitro for individual members of the paired corpora allata (CA) in the cockroach Periplaneta americana during the first two reproductive cycles. A marked similarity of endocrine activity between left and right glands of the majority of animals was observed, even though total JH biosynthesis by the gland pairs can differ up to 200-fold during this period. In a small number of immature females only one gland in the pair had the capacity to synthesize hormone. These results support the use of 'split pairs' of CA from mature, adult female P. americana in short-term in vitro radioassay of potential exogenous and endogenous modulators of JH biosynthesis, such that each sample bioassayed has a valid control. Furthermore, the observations suggest that, after a short postecdysial period (up to 4 days), the CA of this species are controlled by one or more humoral factors.

Tyrosine side-chain metabolism in larval and adult cockroaches, Periplaneta americana: Post-ecdysial patterns

Patterns of tyrosine side-chain metabolism were studied by radiorespirometric techniques in larval and adult cockroaches, Periplaneta americana. Both stages extensively synthesize two-carbon side-chain metabolites during the teneral period for cuticular tanning. Respired 1- 14CO 2 was nearly equal in both larvae and adults with almost no 2- or 3- 14CO 2. After the teneral period, tyrosine decarboxylation decreased and levelled off throughout the remainder of the post-ecdysial period. Larvae metabolized much less tyrosine during this time than did adults. A shift in pathways was indicated a few days after ecdysis by elevation of 2- and 3- 14CO 2 respired, indicating synthesis of one-carbon side-chain and simple ring metabolites, respectively, the latter in greater quantity. Sustained low level production of N- acetyldopamine and other catecholamines was indicated in both stages throughout the post-ecdysial period but particularly in adults. Metabolism of all tyrosine side-chain carbons was very low just prior to ecdysis, demonstrating that the decarboxylase system for tanning substrate production is not activated until after the insect has emerged from the old cuticle.