Pupal Time Research Articles

Cellular immune reactions of larvae of Drosophila algonquin.

The haemocytic reactions of larvae of Drosophila algonquin leading to encapsulation and melanization of eggs of the hymenopterous parasite Pseudeucoila bochei are characterized in part by the premature mass differentiation of plasmatocytes to lamellocytes. Normally this transformation of blood cells occurs at the time of pupation. The data suggest the haemocytes are stimulated to differentiate by chemotactic means. In susceptible host larvae the parasite appears activately to inhibit the immune reactions by blocking cellular differentiation.

Entrainment of the pupation and adult activity rhythms during development in the mosquito Anopheles gambiae

PREVIOUS work on the initiation of the pupation and flight activity rhythms in mosquitoes1–3, has been interpreted4 as showing that there is an ontogenetic distinction between the ‘clocks’ controlling development and adult behaviour. Results with Aedes taeniorhynchus1,2 suggest that the developmental clock stops after controlling the time of pupation and that the adult behavioural clock does not start until some time after emergence. In Culex pipiens pallens3 the adult clock seems to start just before adult emergence. By contrast, the results reported here indicate that in the mosquito Anopheles (Cellia) gambiae Giles, the flight activity rhythm can be entrained during development at least as early as the second larval stage. The same Zeitgeber also sets the phase of the pupation rhythm.

Ultrastructural studies of development and light-dark adaptation of the eye of Coccinella septempunctata L., with particular reference to ciliary structures

On dark-adaptation of the 11-day adult eye, the rhabdomeres move towards the cuticle. Each c-c-r array (of tandem centrioles and ciliary root) maintains its position relative to the rhabdomere, and the length of the root is apparently unchanged. The close association of the array with the rhabdomere is not established until after the first day of adult life. The array is already present at the time of pupation. The distal centriole subsequently becomes the basal body of a transitory ciliary bud, whose formation apparently precedes the onset of rhabdomere differentiation.

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.

The development of the imaginal abdomen of Drosophila melanogaster

The development of the imaginal Drosophila melanogaster was investigated by an analysis of clones of cells marked by somatic crossing-over. The results showed that each abdominal half tergite is initiated by about 11 cells which fail to divide during late embryonic and larval stages. Cell division commences only at the time of pupariation, and continues for the next 32 hr. The spatial pattern of marked clones indicated that each tergite consists of a left and right side—marked cells do not cross the midline. Twin spots were examined and indicated that two daughter cells are aligned preferentially in the transverse orientation. These results are contrasted to data obtained for other imaginal anlage, particularly with regard to the time of cessation of cell division.

"Geographic" Variation in Sensitivity to X-Irradiation in Tribolium: I. Differences in Adult Emergence Due to Species, Strain, and Age at Pupation

Populations of Tribolium castaneum and T. confusum with different geographic background were examined in regard to their sensitivity to ionizing radiation as measured by percent of adult emergence after single exposure: 10 kR of x-rays at 33°C and 70% relative humidity. Second day pupae only were irradiated. T. castaneum exhibited a marked population difference in sensitivity to x-irradiation with a range from 6.80% (Canada) to 47.53% (Kenya) of adult emergence after irradiation. In this respect, T. confusum ranged from 1.69% (Chicago) to 11.74% (Kansas). In general, T. confusum was more radiosensitive than T. castaneum (the overall percent of emergence was 5.35 and 28.48, respectively). Within populations, increasing pupation time is associated with decreasing sensitivity to ionizing radiation. Physiological and genetical factors that might be the cause of intra- and interspecies differences are discussed.

FIFTY PER CENT TIME TO PUPATION AS A MEASURE OF DEVELOPMENTAL TIME INTRIBOLIUM

A technique for measuring developmental time in insects is proposed. The method is similar to the widely used 50% lethal dose (LD50). The major advantage for this technique, TP50for pupation time and TE50for adult emergence time, is the complete avoidance of introducing environmental correlations to the relationship among traits by handling. Standard deviations for TP50and TE50are obtained from the slope fitted to the data without resorting to individual observations.

Simultaneous selection for two correlated traits inTribolium

SUMMARYSimultaneous selection byindependent culling levelsof two correlated traits in all four combinations of directions was investigated withTriboliumin a replicated experiment extending over nine generations. In addition to the two primary traits, 13-day larval weight and pupal weight, four secondary traits (pupation time, adult emergence time, adult weight and larval number) were observed.The observed responses for both selected and unselected traits agreed with theoretical expectations after the latter were adjusted for changes which occurred in genetic and phenotypic parameters. Phenotypio variances for the selected traits were correlated positively with population means, yet genetic variances and heritabilities declined in all selected populations. No change was detected in the genetic correlation between selected traits even though the divergent two-trait selection was designed especially to ‘break’ the positive correlation of + 0·55 ± 0·12 present in the base population.Striking changes in growth and developmental patterns resulting from the divergent selection were discussed in terms of metamorphic limits and ‘stabilizing’ genetic correlations.

Interspecific Hybridization of Heliothis virescens and H. subflexa1

A study was conducted to study development of Heliothis virescens (F.), Heliothis subflexa (Guenee), and their hybrid progeny. H. virescens completed the larval stage in 18.2 days and H. subflexa in 16.7 days. No differences were observed between sexes in rate of larval development in either species. In attempts to hybridize the 2 species, H. subflexa females mated readily with H. virescens males. Eggs were fertile and larvae emerged. Males from this mating required 15.1 days, as contrasted with 17.7 days for females, to complete the larval stage. F1 males were sterile; females were completely fertile. These sterile males may be separated either on the basis of time of pupation or the basis of weight for a sterile release program to control H. virescens . Progeny were not obtained from the reciprocal matings H. virescens females with H. subflexa males. Progeny from F1 females mated with H. virescens males did not show a differential development rate for males or females.

Distribution of haemocytes in larvae of Musca domestica and Musca autumnalis and possible chemotaxis during parasitization

In each of the three larval instars of Musca domestica and M. autumnalis most of the haemocytes were accumulated in the haemocoele in the last two segments of the body. Very few circulating haemocytes were found, and only in second- and third-stage larvae. During development the posterior haemocytic masses increased in size. At the time of pupation the haemocytes were completely dispersed throughout the haemocoele. Experiments with ligated larvae and larvae fixed in liquid nitrogen indicated that the posterior haemocytic masses were not artifacts of fixation. It remains to be determined whether these posterior masses represent haemocytopoietic tissue. The possibility that the haemocytes exhibit chemotaxis during pupation and in response to parasitization is discussed.

A POSSIBLE ROLE OF POSTERIOR HALF OF LARVAL BODY ON THE PUPATION OF THE FLESHFLY, SARCOPHAGA PEREGRINA

In mature larvae of the fleshfly ligatured tightly at the middle of the body, both anterior and posterior halves failed to pupate in dry condition, where intact larvae usually pupate in 17 hr. When the ligatures were loosened after a certain period, the paralized larvae began to pupate in 16-18 hr.Single injection of ecdysterone of 10μg per g body weight induced full pupariation of the isolated anterior and posterior parts, showing that the blocked pupation in both parts of ligatured larvae is due to prevention of synthesis and secretion of ecdysone in the ring gland. Severance of the peripheral nerves just behind the ganglionic mass or of the recurrent nerves just in front of the proventricle did not show any influence upon the pupation time. Artificial shrinking of the crops did not accerelate pupation in wet condition, nor continuous supply of oxygen reduced the duration till pupation of the anterior parts.When ligations were applied at the level behind the 10th segment larger anterior parts pupated mostly within 40 hr.These results suggest that some humoral factor derived from a certain region in posterior segments, probably located in 11th to the last segments, may play an important role in synthesis of ecdysone at the ring gland.

Pleiotropism of wh and el locus in Habrobracon juglandis

The two autonomously manifesting mutations, eyeless (el) and white eyes (wh), of Habrobracon juglandis were compared phenotypically with the wild-type. Eyeless reduces the compound eyes in size. The penetrance is 100%, while expressivity ranges from point-shaped ommochrome crumbs over individual facets to a small eye with abundant facets. There is no correlation between the sizes of left and right eyes. The head capsule is more deformed when the eye is smaller. The homozygote ♀♀ of wild-type have smaller eyes than the hemizygote ♂♂. This gene dose effect is still stronger in el. wh causes white eye colour which remains throughout lifetime. With regard to the amount of eye pigment the three stocks can be arranged in the following sequence: wild type >el>wh. The concentrations of ommochrome precursors, however, do not agree with this sequence. The amount of 3-hydroxykynurenine in el is the same as in wild-type; although in pupal stage the peak in the former appears earlier. The kynurenine concentration in el increases at the time of pupation and induces the beginning of pigmentation earlier than in wild-type; further this process is terminated in el earlier. In wh and in wild-type the amount of kynurenine is also the same. However, there is much less 3-hydroxykynurenine in wh than in wild-type. This is presumably due to a lower kynurenine hydroxylase activity. During the entire postembryonal development there is more xanthurenic and kynurenic acid in wh; in pupal stage, even, there is a second peak. Pupae and adults of wh have a higher kynurenine and presumably also a higher 3-hydroxykynurenine transaminase activity than wild-type. The influence of the mutation wh on the differential rates of hydroxylation and transamination is discussed in relation to the results obtained with mutants of the white locus in Drosophila.

Overcrowding factors of mosquito larvae. 2. Growth-retarding and bacteriostatic effects of the overcrowding factors of mosquito larvae.

LT50, values of the overcrowding factors based on continuous exposure of 1st-stage larvae of Culex pipiens quinquefasciatus Say were 1.4, 5.6, and 6.4 days for 1, ½, and ¼ unit of the factors, respectively, while LD50 was 0.31 unit. The overcrowding factors also retarded larval growth; 1 unit of these factors facilitated only 0.6% of the 1st instars to pupate on the 16th day from the start of the exposure, whereas 68.2% of the untreated larvae pupated, and the median pupation time was reached on the 10th day. First and 2nd instars were more vulnerable in terms of growth delay as well as mortality. Reduction in sizes of the egg rafts laid by females resulting from treated larvae also was noticed. Bacteriostatic or bactericidal activity of the overcrowding factors was shown by determining the number of bacteria in the treated waters and by testing the factors against Bacillus thuringiensis Berliner on nutrient agar. The rate of heartbeat was depressed markedly in larvae treated with these factors as compared with untreated larvae. Reduction in bacterial numbers in the treated water and reduced rates of heartbeat of mosquito larvae are partly responsible for high mortality and growth retardation.

Some Developmental Consequences of Handling, Egg‐eating, and Population Density for Flour Beetle Larvae

Unhandled larvae of Tribolium castaneum (genetic strain cIV—a) were reared in a whole—wheat flour medium (Fortified with dried powdered brewer's yeast, 5% by weight) in a climate of 29°C and 70% RH at three levels of crowding: 100, 200, and 400 per 8 g of flour. At all three densities the median time for pupation was about 18.15 days. Mortality of the developing stages was 3—4% at the 2 lowest densities and about 8% for 400 larvae. Larvae which were subjected to daily handling and reared at the same densities developed more slowly, the prolongation of the larval stage being greatest at density 400. Handling also induced increased mortality at this density but not at lower densities. Handled larvae which were fed eggs of their own kind grew more rapidly than those not fed eggs, and, at the highest egg—feeding rates, the effects of handling and density were almost completely compensated. Evidence is presented that egg—eating would also accelerate the development of unhandled larvae. This is one of the most convincing demonstrations of a nutritional gain on the part of Tribolium cannibals as opposed to noncannibals. We suggest that cannibalism, which is capable of regulating Tribolium populations, is a form of social parasitism which may be favored by natural selection.

THE EVALUATION OF THE "CALLIPHORA TEST" AS AN ASSAY FOR ECDYSONE.

1. The effect of ligation on pupariation in the front or hind parts of larvae of four species of flies, Calliphora erythrocephala, Phormia regina, Sarcophaga bullata, and S. argyrostoma was investigated. Ligation causes effects of delay or inhibition of pupariation which are very differently expressed in the four species. A large proportion of pre- or postcritically ligated specimens of P. regina and S. bullata altogether fail to pupariate in the anterior part. This makes these species unsuitable test subjects for the pupariation test for ecdysone. 2. Test abdomens of C. erythrocephala required significantly less ecdysone for a given pupariation effect when also injected with a CNS-extract. Tanning was also considerably accelerated in this case. 3. The value of the pupariation unit of ecdysone is influenced by a number of factors, such as age at the time of ligation, the waiting period between ligation and injection, the dilution effect of the solvent, and the simultaneous action of a neurohormone. The requirements for natural ecdysone in normal larvae at the time of pupariation are probably substantially lower than the values which have been determined by others with test abdomens and the use of synthetic ecdysones. 4. In confirmation of older data, and contrary to recent claims, tanning was induced in test abdomens of the larvae of C. erythrocephala, P. regina, and S. argyrostoma by the injection of hemolymph from pupariating larvae. Calliphora blood induced tanning in specimens of S. argyrostoma, and vice versa. The conclusions are drawn that differences between the different species in the action of ecdysone are of a quantitative rather than qualitative nature.

On the origin and metabolic fate of α-ecdysone in insects

Injected or ingested 3H-α-ecdysone in Bombyx larvae during the last (fifth) larval instar is rapidly distributed throughout the body and is converted to β-ecdysone and three polar metabolites (designated compounds A, B, and C) separated by liquid chromatography. Compound A, which may be an acidic sidechain-cleavage fragment of α-ecdysone containing C-23 and C-24, is excreted into the gut. Compound C can be hydrolyzed to β-ecdysone and may be an ester conjugate with a polar acid. Nothing is known about the structure of compound B. The conversion of α- to β-ecdysone occurs throughout the fifth instar of Bombyx; the rate of conversion increases, and the rate of further metabolism of the formed β-ecdysone decreases markedly towards the time of pupation. The conversion of α- to β-ecdysone occurs efficiently in isolated abdomens of Calliphora and Bombyx, thus indicating that the ecdysial gland may not be the site of this conversion, and that the observed hormonal effect of α-ecdysone may be due in part to its prior metabolism to β-ecdysone.

Components of growth in genetically diverse populations of Tribolium castaneum.

The growth and developmental patterns of 19 genetically diverse populations of Tribolium castaneum were examined. Measurements were obtained on three primary traits (13-day larval weight, pupation time and pupal weight) and three secondary traits (number of larval molts, adult emergence time and adult weight). The populations were chosen on the basis of their previous selection histories. Selection for different primary traits produced profound effects upon the total growth and development complex.Genetic and environmental relationships between primary traits were estimated within each population, and a consistent asymmetry of correlated responses was observed to be determined by the direction of selection.Possible effects upon the disruption of an intricate balance of the three metamorphosis hormones (activation, molting and juvenile) through selection were postulated.

The timing of adult eclosion in blackflies (Dipt., Simuliidae) in West Cameroon

A description is given of an artificial stream for studying pupation times and pupal periods of Simulium spp., of emergence traps for studying emergence times in rivers, and of a convenient arrangement for rearing batches of pupae in the laboratory.S. damnosum Theo., S. kenyae De Meillon and S. unicornutum Pomeroy pupate mainly by day, each species having a characteristic period of peak pupation.In S. damnosum and S. kenyae the time of pupation influences the pupal period, and for these and other species the pupal period is prolonged by lower temperatures. The pupal period is partly independent of these influences in so far as emergence by night is normally avoided.The timing of adult eclosion is influenced by the temperature on the day of eclosion. On warm days (midday temperature of the river 24·1–28°C) S. damnosum and other forest zone species show a peak of emergence between 06.00 and 09.00 h, while on cool days (midday temperature of the river 20·1–24°C) the peak is delayed until 09.00 to 12.00 h. On artificially cold days (refrigerator temperature 16–20°C), the peak is shifted to the late afternoon.The study of the timing of adult eclosion from pupae brought into the laboratory is complicated by the fact that the normal pattern of emergence is liable to disturbance.In the laboratory a seasonal fluctuation in the sex ratio of emerging flies occurred in S. damnosum.

Cell lineage, growth, and determination in the imaginal leg discs of Drosophila melanogaster

The pattern of cell lineage in the leg discs of Drosophila melanogaster was analyzed by means of X-ray-induced somatic crossing-over. The system is used to demonstrate that cell lineage data can yield important information regarding various developmental problems. Clonally related cells become arranged in longitudinal stripes on the leg, and the data indicate that part of the reason for this is that mitotic division products in the third larval instar become oriented in a radial fashion in the disc. The size of clones induced at specific times was used to estimate the cell number in the leg disc at these times. The presumptive leg disc appears to contain about 20 cells even in the 3-hour embryo, and to be mitotically inactive throughout the remainder of the embryonic period and the first half of the first larval instar. Thereafter it grows continuously with a doubling time of about 15 hours, until about the time of pupation. Observation of gynandromorphs, in which the male tissue was genetically marked, indicated also that the leg disc consists of about 20 cells when it is first delineated from the rest of the embryo. The results show that determination of the leg disc into regions does not occur until after the early third instar. This determinative event, as well as the initial determination of the leg disc, occurs in populations of cells rather than single cells. The results are incompatible with a previous theory of determination in imaginal discs.

Influence of a cytoplasmic polyhedrosis on various developmental stages of the cabbage looper

When the relationship of infections with a cytoplasmic-polyhedrosis virus and the larval, pupal, and adult stages of the cabbage looper, Trichoplusia ni, were studied, the mortality of first-instar larvae was comparatively high and that of fourth-instar larvae was comparatively low. Also, infected larvae pupated as much as 5 days later than healthy larvae, and the pupal weight was lower. This decrease in weight was related to the time of pupation, the number of white fecal pellets excreted by a larva before pupation, the decreased rate of emergence, and the moth deformities. The importance of these effects in regards to prophylactic measures for rearing large numbers of insects is discussed.