Relationship between a metabolic rhythm and emergence rhythm in Drosophila melanogaster

Oxygen consumption and lactic acid dehydrogenase (LDH) activity were determined for Drosophila melanogaster pupae and pharate adults exposed to 12 : 12 or 1 : 23 light-dark (LD) regime. Bimodal circadian fluctuations of oxygen consumption were found in pupae and pharate adults exposed to either LD regime and organisms appeared to demonstrate an anticipatory change in oxygen consumption associated with change in illumination. The oxygen-consumption trend for the entire period spent in the puparium showed a high at the time of emergence, but the diurnal rhythm showed a low at the time of emergence suggesting that emergence occurs at a low in the diurnal cycle. Emergence maximum showed a 3 hr lead over the oxygen-consumption maximum. Changing the LD regime produced similar changes in the phasing of both oxygen consumption and emergence rhythms. LDH activity did not demonstrate a detectable circadian rhythm but did show a steady decrease during pupal and pharate adult development.     

Allatotropic and allatostatic activities in extracts of brain and the effects of Manduca sexta allatotropin and Manduca sexta allatostatin on juvenile hormone synthesis in vitro by corpora allata from the Eri silkworm, Samia cynthia ricini

Both allatotropic and allatostatic activities were found in crude extracts of brain from adult and larval Eri silkworm, Samia cynthia ricini, but it seems that allatotropic activity dominates in each stage. There was a high level of allatotropic activity in the crude extract of brain from newly emerged female adults, but allatostatic activity appeared in the bioassay when excessive amounts of crude extracts of brain were added. Crude extracts of brain from premoulting fourth‐instar larvae and from newly ecdysed fifth‐instar larvae exhibited allatotropic activities, whereas extracts of brain from the second and third day of the fifth‐instar larvae inhibited juvenile hormone (JH) release slightly. Allatotropic activity from the brains of adults and larvae stimulated both adult and larval corpora allata (CA) to synthesize JH. Manduca sexta allatotropin (AT) (Mas‐AT) and M. sexta allatostatin (AST) (Mas‐AST) also stimulated and inhibited both adult and larval S. cynthia ricini CA to synthesize JH, respectively. Higher concentrations of Mas‐AT (10^?4 or 10^?3 M) showed an inhibitory effect on adult CA. CA from newly emerged female adults were the most sensitive to inhibition by Mas‐AST, whereas CA from female pharate adults at about 6 h before adult emergence were the most sensitive to stimulation by Mas‐AT and S. cynthia ricini brain allatotropic activity. An extract of brain and Mas‐AT induced some of the non‐active female pharate adult CA at 12 h before emergence to synthesize a small amount of JH.     

Molting hormone titer changes and their significance during development of the colorado beetle, Leptinotarsa decemlineata

Molting hormone (MH) titer in whole animal extracts of Leptinotarsa decemlineata was determined by chemical extraction and the Musca test (1 MU = 3.5 ng ecdysterone) during the developmental span from newly-ecdysed fourth instar larva to an adult 3 days after eclosion. Within the 17-day period, 21 age groups were chosen to estimate the MH titer. Two peaks of MH titer were detected, one in the post-feeding larval stage and the other during the pupal and pharate adult stage. MH activity was first detected in 2-day-old post-feeding larvae, and reached a maximum of 23.5 MU/g tissue on the third day. It began to decline on 3.5 days, and fell to 5.5 MU/g tissue on 4.5 days, the time of larval-pupal ecdysis. In the pupal and pharate adult stage MH rose after the first day and increased to a maximum of 91.5 MU/g tissue on the third day. The titer again declined on the fourth day, and became undetectable one day before adult emergence and in adults 3 days after emergence. MH was demonstrated to be produced by isolated larval abdomens. A peak of 11.5 MU/g tissue was detected in 7-day post-ligation preparations. The titer decreased to 6.9 MU/g tissue in 10-day post-ligation preparations, which was the time of the ecdysis. The finding raises questions concerning the rôle of MH synthesis by other tissues in relation to the function of the prothoracic glands during insect development.     

Life history traits of adults and embryos of the Antarctic midge Belgica antarctica

Although larvae of the Antarctic midge, Belgica antarctica, live for more than 2 years, the adult and embryonic stages are brief and are less well known than the larvae. In this report, we provide additional details of these understudied life stages with laboratory observation on adult emergence, longevity, preoviposition period and embryonic development. Male adults emerged slightly earlier than females, and they also lived longer. More than a half (57 %) of the adults that emerged in the laboratory were males. Females produced only a single egg mass and died within a day after oviposition. Embryonic development required 16 days at 4 °C, and prior to hatching, the pharate larvae perform a distinct sequence of behaviors that include drinking and peristaltic movement. We also discuss points that need to be resolved for laboratory propagation of this species.     

Hormonal basis of adult eclosion in the gypsy moth (Lepidoptera: Lymantriidae)

Eclosion hormone was found to control the stereotypic adult eclosion behaviour of Lymantria dispar, the gypsy moth. A bioassay for hormonal activity was developed utilizing pharate adult females, and comparisons were made with the Manduca wing assay. The distribution of eclosion hormone activity was confined to the central nervous system tissues including the protocerebrum, corpora allata/corpora cardiaca complex, thoracic and the last abdominal ganglion. Haemolymph ecdysteroid titres were determined daily throughout pupal-adult development, and the peak activity period was found in 3–4 day pupae. Eclosion hormone activity in the brain and corpora allata/corpora cardiaca complex started to increase when the ecdysteroid titre dropped to background levels. Eclosion hormone in the brain peaked in the pharate adult stage, was released in the haemolymph 1 h prior to eclosion, which coincides with the depletion of activity in the retrocerebral complex, and fell to undetectable levels after the adult emerged.     

The contribution of the fatbody to RNA and ribosomal changes during development of the blowfly Calliphora erythrocephala (Meig)

The initiation of blowfly metamorphosis is associated with a pronounced decrease in the number of larval ribosomes; this reduced number then remains constant throughout pharate adult development. Ribosomal RNA accounts for most of the total RNA in larvae shortly after the cessation of feeding and growth, but thereafter the amount of rRNA declines disproportionately to total RNA until early pharate adult development; thereafter, the ratio remains constant until adult emergence. Larval fatbody ribosomes, which constitute about half of the total in the entire organism, are destroyed in situ prior to pupariation. The progressive decrease in fatbody rRNA is accompanied by a corresponding increase in a degraded, relatively insoluble 4–7 S nucleic acid which, stored until adult emergence when it is discarded, accounts for the disparity between total RNA and rRNA. The extracellular ribosomes previously observed during pharate adult development are thus derived from dissolution of larval tissues other than fatbody.     

Effects of host stage on the development of the facultative autoparasitoid Encarsia tricolor (Hymenoptera: Aphelinidae)

Encarsia tricolor is a facultative autoparasitoid of the glasshouse whitefly, Trialeurodes vaporariorum, with a potential in biological control. The rate of development, number of mature oocytes at emergence, number of ovarioles and size of the emerged adults were studied. Five nymphal instars (N1, N2, N3, N4, and pharate adult) of T. vaporariorum were used as hosts for the females. Female larvae and pupae of E. tricolor and Encarsia formosa were used as hosts for the males. Females developed faster when the egg was laid on N3 (18.0 days from egg to adult) and slower on N1 (22.3 days). Females were bigger when developing from N1 and N3 than from N4 and pharate adult. On emergence the mean number of mature oocytes was always small (0.8–2.6). Males developed faster and were smaller than females, and developed faster and were larger on larvae of E. formosa.     

Glycogen phosphorylase activity in pharate adults of the stable fly and the effects of a juvenile hormone analogue

Glycogen phosphorylase was assayed in homogenates of pharate adults of the stable fly, Stomoxys calcitrans, by the release of inorganic phosphorous (Pi) from glucose-1-phosphate (G-1-P) in the presence of glycogen. Activity was determined as active and total phosphorylase present by the absence or presence of adenosine-5-monophosphate (AMP) in homogenates. Homogenates of the pharate adults (that were treated topically immediately after larval-pupal apolysis with a synthetic insect juvenile hormone analogue, (E)-4-[(6,7-epoxy-3-ethyl-7-methyl-2-nonenyl)oxy]-1,2-(methylenedioxy)benzene) displayed no inhibition or enhancement of phosphorylase activity when compared to untreated pharate adults.     

Photoperiodic Regulation of the Daily Rhythm of <Emphasis Type="Italic">Trichogramma</Emphasis> Adult Emergence (Hymenoptera,Trichogrammatidae)

Laboratory experiments demonstrate that the adult emergence rhythms of two Trichogramma species (T. telengai Sor. and T. principium Sug. et Sor.) significantly depend on photoperiod. The synchronicity of adult emergence is maximal at day lengths of 12–16 h. Under longer days (18–20 h) adult emergence is extended, whereas under very short days (4–8 h) a substantial proportion of adults emerge before light-on. The pattern of T. telengai emergence under day length of 4 h suggests the possibility of the existence of two fractions (the first that emerges in the dark and the second that waits for light-on) which results in two peaks of emergence. As a whole, these data agree well with the hypothesis of the periods of “potential readiness” and “obligate activity” forwarded by V.B. Chernyshev. The results of the study can be used for optimization of the methods for laboratory and mass rearing of Trichogramma species.     

Ultrastructure of active and inhibited prothoracic glands.

Changes in the cytoplasm of prothoracic gland cells were compared in pharate adults, dauer pupae, and aminophylline inhibited pupae of H. cecropia. For the first 3 to 4 days after transfer from 4 to 22°C, a similar sequence of changes in the cytoplasmic elements was observed. At day 4 the cytoplasm of pharate adults exhibited further differentiation which was consistent with the initiation of secretion, while dauer and inhibited pupae remained at the stage achieved at day 4 and did not advance further even after a substantial lapse of time. These results are interpreted as indicating that the early changes represent a response by the cells to the temperature change, while the initiation of secretion requires the intervention of brain hormone.     

Juvenile hormone induction of pheromone gland PBAN-responsiveness in Helicoverpa armigera females

The maturation of corpora allata (CA) and the competence of pheromone glands in the adult moth Helicoverpa armigera, are both age-related and appear to be correlated. Sex pheromone glands of pharate adults do not produce sex pheromone independently, nor do they respond to exogenous PBAN. Newly emerged moths produce significantly less pheromone than day one moths. JH (juvenile hormone) II was found to be the main JH form produced by CA in vitro. JH II primed pheromone glands of pharate adults to respond to PBAN. In addition, injection or topical application of JH II to newly-emerged females induced pheromone production in the presence of PBAN. Our findings suggest that JH is involved in the initiation of pheromone production of Helicoverpa armigera.     

Electrophoretic protein patterns and esterase zymograms in ovaries and mature eggs of Bombyx mori in relation to diapause

Starch-gel zone electrophoresis was performed on proteins of pharate adult and emerged adult ovaries, and in mature eggs in adults, in order to ascertain the mode of action of the diapause hormone on protein metabolism in the silkworm, Bombyx mori.     

RNA metabolism during metamorphosis of Drosophila hydei

Determinations of total protein and RNA at various times after the beginning of the pharate pupal stage of Drosophila hydei, revealed an increase in both substances during the first 25 hr and a sudden decrease thereafter until 52 hr. From this time on the total amount of both protein and RNA increases slightly until emergence of the flies at 160 hr after the beginning of the pharate pupal stage. A similar pattern of changes was recorded for the total radioactivity as well as the specific activity of RNA labelled with ³H-uridine after the injection of the isotope immediately before the beginning of the pharate pupal stage.The migration profile of RNA labelled with ³H-uridine during larval development, revealed that shortly after the onset of the pharate pupal stage an essentially normal larval pattern consisting of major fractions of 28, 18, 8 to 9, and 4 to 7 S RNA. At 52 hr only the low molecular weight RNA was present. The ‘normal’ pattern was restored at the time of emergence of the flies, indicating re-utilization of degradation products of previously labelled RNA.     

Cyclic AMP phosphodiesterase activity in the midgut of Manduca sexta

Midgut preparations from Manduca sexta larvae exhibit potent cyclic AMP phosphodiesterase activity. The enzyme exhibits a pH optimum at pH 8·8 and the assay reaction is linear for at least 30 min. Enzyme activity is greatest in larvae during the second day of the fourth and fifth instars and decreases at the end of the instar. Midgut cyclic AMP phosphodiesterase activity rises again in the pharate pupa and during pharate adult development. Whether these alterations in emzyme activity reflect humorally controlled morphogenetic changes in the midgut or are involved in the physiological functions of the midgut is as yet not known.     

Cyclic AMP phosphodiesterase activity during the development of the silkworm, Bombyx mori

Cyclic AMP phosphodiesterase activity has been demonstrated in homogenates of the silkworm, Bombyx mori, throughout larval, pupal, and pharate adult life. The enzyme exhibits a pH optimum at pH 8·0, and the enzyme activity was inhibited in the presence of caffeine and theophylline. The enzyme activity increases after hatching, and a relatively higher level of the activity is maintained through the larval stage. The activity, however, falls markedly before pupation and increases sharply once again before emergence.     

Degradation of haemoglobin in Chironomus during metamorphosis

The degradation of haemoglobin (Hb) during the metamorphosis of Chironomus pallidivitatus was studied by means of spectrophotometry, disc electrophoresis, and isotopic tracer methods. Hb concentration was maximal during the late fourth instar larva and exhibited a continual decline throughout the pharate adult periods; in the mature adult Hb is almost entirely absent. Coupled with this reduction in Hb is an increase in the quantity of bile pigment (tentatively identified as bililatrenes) most probably representing products of the Hb degradation. These pigments are found in considerable quantity within the meconium at the time of adult emergence.Larval, ⁵⁹Fe-labelled, Hb injected into late fourth instar larvae was found to be most concentrated in the midgut portion of the early pharate adult. The quantity of ⁵⁹Fe-haemoglobin in the midgut of early pharate adult was at least five times the concentration found in late pharate pupae. Spectrophotometric and electrophoretic analysis of the midgut contents of untreated larvae showed that Hb was one of the major soluble proteins in the midgut at the time of pupation. This rapid intestinal uptake of Hb suggests that the intestine is involved in the mechanism for the degradation and removal of the Hb, no longer required in the adult stage, a seemingly important step in the metamorphosis of this insect.     

Gene-controlled incorporation of haemolymph protein into the ovaries of Bombyx mori

The haemolymph protein concentration in Bombyx mori decreases normally by about one-fourth during pharate adult development. In females homozygous for the small egg gene, the concentration of haemolymph protein remained constant throughout the pupal and pharate adult stages. The sm gene does not influence the synthesis of vitellogenic female protein of pupal and pharate adult haemolymph (FP). Normal ovaries transferred to the haemocoele of sm females undergo normal vitellogenesis. In the absence of normal alleles of sm, the ovaries encounter difficulties in the incorporation of FP into their oöcytes from pharate adult haemolymph. These results suggest that an active translocation mechanism is involved in the transfer of haemolymph protein into the ovaries.     

A developmental study of the cuticular hydrocarbons of Sarcophaga bullata.

The accumulation of cuticular hydrocarbon was measured throughout the life of Sarcophaga bullata. Less than 5 μg hydrocarbon per insect are present until the third larval instar when synthesis increases the quantity present to 10 to 20 μg by pupariation. The rate of synthesis increases at this time to 5 to 8 μg/day and continues until 40 to 45 μg are present per insect. This amount remains constant until several days before the pupal-adult ecdysis when synthesis again occurs. The rate of synthesis by these pharate adults is >20 μg/day. When the adult emerges it contains between 90 and 100 μg which increases slightly during the adult stadium. Two periods of rapid accumulation of cuticular hydrocarbon are observed: (1) during pupariation and the 3 day period following pupariation, and (2) during the 4 day period preceding the pupal-adult ecdysis. When pupariation is inhibited by contact with water, the rate of hydrocarbon biosynthesis also fails to increase.     

Characterization of the DNA of Hyalophora cecropia

DNA was isolated from the pupae and various tissues of pharate adults of the silkmoth Hyalophora cecropia. CsCl equilibrium density analysis showed the presence of one major band at 1.693 and two minor satellites, 1.705 and 1.709, comprising 3 and 6% respectively of the total DNA. We could detect no difference in the renaturation kinetics of DNA prepared from pupal or pharate adult tissues. The genome appears to be composed of 30% redundant and 70% unique sequences. The haploid information content of the unique sequences is 11.4 × 10¹⁰ daltons.     

Ecdysone titers and prothoracic gland activity during the larval-pupal development of Manduca sexta

The titer of ecdysone in whole animal extracts of Manduca sexta was determined by radioimmunoassay during the fifth (last) larval instar, pharate pupal development and pupation. A subtle peak in ecdysone concentration was noted at day 4 (just prior to the onset of the wandering stage) and a second and greater peak at day 8.5 (coincident with pharate pupal development). The titer fluctuations during development were a result of changes in tissue ecdysone and not of alterations in the ecdysone content of the gut. When prothoracic gland secretory activity was analyzed in vitro at the same stages, the most rapid rate of α-ecdysone secretion was shown to occur on day 7 (one day prior to the peak in whole-animal ecdysone concentration). An earlier peak in prothoracic gland activity may occur at day 4–5. Thin layer and gas-liquid chromatographic analyses revealed developmental changes in the ratio of β:α-ecdysone in hemolymph and whole-animal extracts. It is suggested that the steroid-hydroxylating capacity of the insect increases during the instar.