First Days Of Adult Life Research Articles

Suppression of Adult Neurogenesis Impairs Olfactory Learning and Memory in an Adult Insect

Although adult neurogenesis has now been demonstrated in many different species, the functional role of newborn neurons still remains unclear. In the house cricket, a cluster of neuroblasts, located in the main associative center of the insect brain, keeps producing new interneurons throughout the animal's life. Here we address the functional significance of adult neurogenesis by specific suppression of neuroblast proliferation using gamma irradiation of the insect's head and by examining the impact on the insect's learning ability. Forty gray irradiation performed on the first day of adult life massively suppressed neuroblasts and their progeny without inducing any noticeable side effect. We developed a new operant conditioning paradigm especially designed for crickets: the "escape paradigm." Using olfactory cues, visual cues, or both, crickets had to choose between two holes, one allowing them to escape and the other leading to a trap. Crickets lacking adult neurogenesis exhibited delayed learning when olfactory cues alone were used. Furthermore, retention 24 hr after conditioning was strongly impaired in irradiated crickets. By contrast, when visual cues instead of olfactory ones were provided, performance of irradiated insects was only slightly affected; when both olfactory and visual cues were present, their performance was not different from that of controls. From these results, it can be postulated that newborn neurons participate in the processing of olfactory information required for complex operant conditioning.

Structural and functional changes in the olfactory pathway of adult Drosophila take place at a critical age.

The olfactory system of several holometabolous insect species undergoes anatomical changes after eclosion of the imago, following those occurring during metamorphosis. In parallel, odor experience and learning performance also evolve with age. Here, we analyze the case of adult Drosophila females. Synaptogenesis in the antennal lobe (AL) starts in late pupa and continues during the first days of adult life, at the same time as the behavioral response to odors matures. Individual olfactory glomeruli (DM6, DM2, and V) display specific growth patterns between days 1 and 12 of adult life. Experience can modify the olfactory pathway both structurally and functionally as shown by adaptation experiments. The modifications associated with this form of nonassociative learning seem to take place at a critical age. Exposure to benzaldehyde at days 2-5 of adult life, but not at 8-11, causes behavioral adaptation as well as structural changes in DM2 and V glomeruli. Altered levels in intracellular cAMP, caused by dunce and rutabaga mutants, do not affect the normal changes in glomerular size, at least at day 6 of development, but they prevent those elicited by experience, establishing a molecular difference between glomerular changes of intrinsic versus environmental origin. Taken together, these data demonstrate an imprinting-like phenomenon in the olfactory pathway of young Drosophila adults, and illustrate its glomerulus-specific dynamics.

Age Dependence of Pheromone Production by the Boll Weevil (Coleoptera: Curculionidae)

Factors influencing pheromone production by the boll weevil, Anthonomus grandis Boheman, have been extensively studied, yet recent research using new methods suggests much remains unknown in this regard. The studies reported herein examined age-related changes in production and composition of pheromone at ages from 0 to 6 d, and at 3, 6, 9, and 12 d, respectively, and evaluated the association between accessory gland condition and pheromone production. Estimates of pheromone from extracted feces were near the upper values previously reported. However, ≈95% of the total pheromone was obtained from headspace collections. Based on feces extractions, pheromone production increased with age until the sixth day, while headspace collections indicated an increase in production until the ninth day of adulthood. The boll weevil pheromone is composed of two alcohols (components I and II) and two aldehydes (components III and IV), and ratios of these components changed with age. Component I was dominant for the first days of adult life, but the composition subsequently stabilized at ≈42.5:42.5:5:10 (I:II:III:IV). Also, high levels of pheromone production were associated with well-developed accessory glands, while weevils with small, transparent glands produced little or no pheromone. These results demonstrate production of pheromone in greater quantities, and at earlier ages, than was previously recognized. Additional study using the methods reported herein should provide improved understanding of the dynamics of boll weevil pheromone production that will facilitate ecological interpretation of field data and improvements in trapping systems.

Phenotypic plasticity of body size at different temperatures in a planktonic rotifer: mechanisms and adaptive significance

Summary Larger body size at low temperatures is a commonly observed phenomenon in ectothermic organisms. The mechanisms that lead to this pattern and its possible adaptive significance were studied in laboratory experiments using the parthenogenetically reproducing rotifer Synchaeta pectinata. At low temperatures of 4 °C mean body volume was 46% larger than in individuals cultured at 12 °C. Egg volume was 35% larger in low vs high temperatures. Larger body size at low temperatures was caused by two mechanisms. First, when exposed to low temperatures, mothers laid larger eggs and the hatchlings of these eggs developed into larger adults (irrespective of temperature). Second, individuals cultured at low temperatures grew to a larger body size during their juvenile phase. The former mechanism had a greater influence on adult size than the latter. The production of larger eggs at low temperatures seemed to be due to a higher reproductive investment into individual offspring as it occurred independently of differences in maternal size. Life table experiments showed that offspring from small eggs (produced at high temperatures) had a significantly higher population growth rate than offspring from large eggs, when cultured at high temperatures. This was mainly due to an increase in fertility during the first days of adult life.

Phenotypic plasticity of adult size and pigmentation in Drosophila: thermosensitive periods during development in two sibling species

Variation of size-related traits and of abdomen pigmentation was investigated in D. melanogaster and D. simulans by transferring cultures from 25°C to 17°C at regular daily intervals. In most cases regular sigmoid curves were obtained, which were adjusted to a logistic model. For wing length, the thermosensitive period (TSP) extended during the last larval instar and most of the pupal stage, with an inflection point (IP) at 5.24±0.24 days. Pigmentation of the last abdomen segments (5–7) in females exhibited a shorter and later TSP (IP at 7.21±0.13 days) extending in the first day of adult life. In anterior segments (2–4) variations were less regular and our data suggest that TSP might extend during the first two days of adult life, at least in males. Significant differences among species were observed for size and pigmentation, but not for TSPs.

Structural and functional changes of the Dufour gland in gynes of the amazon ant Polyergus rufescens (Hymenoptera, Formicidae)

Colony foundation by the slave-making amazon ant Polyergus rufescens requires penetration of the young gyne soon after mating into a colony of the slave species. During this process, she uses decyl butyrate from her large Dufour gland as an effective appeasement allomone. The structural appearance and development of this gland shows a clear age-dependent evolution that is in line with its behavioural function. At the moment of eclosion, young females have a gland with an empty lumen but thick lining epithelium, of which the active secretory cells are characterised by a well-developed Golgi apparatus, abundant mitochondria and smooth endoplasmic reticulum. The basal plasmalemma shows deep invaginations that facilitate the uptake of precursors from the haemolymph, while intercellular contacts display conspicuous interdigitations in the apical cell part. During the first days of adult life, secretion starts to accumulate in the lumen. At the age of 3 weeks, the gland displays a large lumen filled with secretion and a thin epithelium that no longer displays secretory activity. By this time, the gynes are ready for penetration into a slave colony, being loaded with large quantities of the appeasement allomone that are necessary at this initial stage of the usurpation process.

Chemical mimicry between parasitic ants of the genus Formicoxenus and their host Myrmica (hymenoptera, Formicidae)

Ants of the genus Formicoxenus are called xenobiotic ants because they live in close association with their Myrmica host; they cannot live independently of the host but they keep their brood apart. They forage in the host's galleries and obtain food from it through trophallaxies. They also very frequently lick the Myrmica workers and for that reason are called “shampoo ants”. The chemical basis of the integration of the parasite into the host society is studied. In the two host-parasite pairs F. provancheri/M. incompleta and F. quebecensis/M. alaskensis, chemical mimicry in the cuticular hydrocarbons was found. With adoption experiments it is shown that this mimicry was not innate but is acquired during the first days of adult life.

The relationship between level of pollen in the diet, vitellogenin and juvenile hormone titres in AfricanizedApis melliferaworkers

SUMMARYThe relationship between the amount of pollen consumed and vitellogenin (Vg) and juvenile hormone (JH) titres in the haemolymph of Africanized honey bee workers (Apis mellifera) was studied. Analysis of haemolymph from young workers fed on diets differing in pollen content revealed that Vg, but not JH titre, is dependent on pollen consumption. Workers fed on a 50% pollen diet had higher Vg levels than workers fed on a 15% pollen diet. A 0% pollen diet severely impaired the increase in Vg titre normally observed during the first days of adult life. However, the quantity of pollen in the diet was not reflected in the measured JH titre, which was not significantly different in bees fed on the various diets. The results are discussed in terms of regulation of Vg synthesis.

The influence of adult diet and age on lipid reserves in the tropical fruit fly Anastrepha serpentina (Diptera: Tephritidae)

We investigated the effect of diet [dry sucrose (S); dry sucrose + protein (S+P); dry sucrose + open fruit (S+OF); dry sucrose + intact fruit (S+IF); open fruit (OF); and intact fruit(IF)] upon the lipid reserves, onset of oviposition, lifetime egg production and longevity of adult female and male Anastrepha serpentina (Diptera: Tephritidae). Starved flies died at a high rate after the third day of adult life. Lipid reserves in starved flies dropped drastically during the first days of adult life. Egg production and survival were highest in flies maintained on a diet of S+P, followed by flies maintained on diets of OF and S+OF. Longevity and egg production were lower in flies kept on diets of S and S+IF than on the other diets. Flies kept on IF did not produce eggs, and longevity was similar to that of starved flies. Lipid reserves were similar in both sexes fed the same diet. Lipid reserves of flies kept on S+P decreased during the first days of adult life but afterwards were replenished. Lipid reserves in flies kept on diets of S+OF, OF and S+IF oscillated: short periods of utilization were followed by periods of reloading. Flies kept on S and IF alone showed a continuous utilization of reserves without replenishment. Rate of utilization was faster for flies on IF than on S. The link between the variation in nutrient requirements and metabolic processes with possible consequent variations in foraging activity is discussed.

Changes in the mechanics of the cricket ear during the early days of adult life

From behavioural experiments it is known that the thresholds for both positive and the negative phonotaxis in crickets (Gryllus bimaculatus) decrease during the first days of adult life. Neuronal recordings have shown that a part of the changes in threshold has its origin in the ears. In this study we investigate some changes of the mechanics of the ears in the days after the imaginal moult.

Influence of an Erynia neoaphidis Infection on the Relative Rate of Increase of the Cereal Aphid Sitobion Avenae

Experiments were conducted in an attempt to model the action of Erynia neoaphidis on populations of the cereal aphid Sitobion avenae. The rates of increase of healthy and infected S. avenae inoculated as adults on the day of the final molt were compared at four temperatures (10, 15, 20, 25°C). The same parameters were measured for those inoculated at each nymphal instar and at intervals in adult life at 20°C. At 20°C, the duration of the first three nymphal instars was the same for healthy aphids and those infected during the corresponding instar. For nymphs inoculated during each of the four instars, the incubation period of the mycosis was longer than the duration of that instar and no infected nymph which matured to adult produced progeny. Depending on the incubation and infection temperature, the reproductive rate of increase of aphids infected on the first day of adult life was 1.5 to 2.5 times less than for the healthy ones. As expected, at 20°C, the later in life the adults were infected the less was the effect on the number of offspring produced relative to that of healthy ones. A simulation of the effect of time-limited infection on the number of offspring of infected aphids confirms the importance of this parameter in a model of the epidemiology of entomophthorosis on aphids.

Diuresis in newly emerged, unfed mosquitoes. II. The basic pattern in relation to escape from the water, preparation for mature flight, mating and the first blood meal.

A study of 2000 newly emerged adult mosquitoes (Aedes aegypti) shows that the rate of excretion is high at the time of eclosion but falls rapidly over the next few minutes. In both sexes, however, the high rate of excretion is regained during a second peak in the middle of day 1. It remains high for about 6 h and then falls in a remarkably steady manner to reach a low level plain, which persists at least till the end of day 3. In females this plain is not reached till some 8 h after the onset in males. This steady low level of activity, which is higher in females than in males, is here regarded as the basic rate of excretion. The rapid loss of fluid in the newly emerged adult enables the insect to make its first teneral flight, escaping from the surface of the water within minutes of eclosion. The second peak of excretion occurs within the period of rest during the first day of adult life when muscles needed for swimming are being replaced by those needed for flight. The low rate of excretion which follows on day 2 and is continued on day 3 signals the establishment of full flight activity covering mating and, in the female, the first blood meal. During the blood meal and immediately afterwards the rate of excretion is already known to increase significantly; for a truer measure of this increase the amounts should now have the female basic rate, as here defined, deducted from it.

A study of hormonal levels of the locust Locusta migratoria cinerascens artificially changed to the solitary state by a chronic CO 2 treatment of one minute per day

1. 1. The hormonal levels of the three JH (JH 1, 2 and 3) and of ecdysteroids are measured by RIA in the 5th larval age and the 15 first days of adult life in both sexes of the migratory locust Locusta migratoria cinerascens artificially solitarized by means of a chronic one minute daily treatment with CO 2. Comparisons are made with both gregarious form and true solitary form resulting from isolation. 2. 2. The CO 2 treated locusts are characterized by an important level of JH 3 when compared with all other forms, which leads to the conclusion that JH levels may not be a direct determinant factor in the phase differentiation. 3. 3. This JH 3 is absent when the animals are treated by the anti-allatin precocene: thus it is well synthesized by the Corpora allata. 4. 4. JH 1 and JH 2 may also be present in all forms of insects at irregular low levels and different times.

Diuresis and its hormonal control in butterflies

The sudden weight loss after eclosion in the butterflies Acraea horta, Danaus chrysippus and Papilio demodocus is largely due to diuresis. The potassium concentration of the haemolymph is approximately halved as a result, and extensive diuresis leads to increases in sodium concentration and total osmolarity. The isolated Malpighian tubules of all three species are stimulated to fast rates of fluid secretion by cyclic AMP and by homogenates of the brains and corpora cardiaca. The tubules of Papilio lose their sensitivity to stimulation after the first day of adult life, and ingestion of a large volume of artificial nectar by this butterfly does not cause diuresis.

Studies on the regulation of the juvenile hormone titre in bumblebee workers, Bombus terrestris

The synthesis of juvenile hormone (JH) by corpora allata (CA) in vitro was studied in queenright and queenless workers during the first 5 days after emergence. In queenless workers the activity of the CA is strikingly higher than in queenright workers, the first differences were observed on the very first day of adult life. The synthetic activities of the CA correspond fairly well with the JH titre obtained by Galleria bioassay. Since the excretory rate was not found to be lower in queenless workers, it is postulated that the increased JH titre is caused mainly by higher activities of CA. The activity of the CA for its part depends upon the presence or absence of a queen. It is shown by HPLC determination as well as by Galleria bioassay that only JH III is produced in vitro.

Natural selection for covariation in growth components in Tribolium castaneum

The relationships between various components of growth were studied, both at the intra- and inter-populational levels, in twelve laboratory populations of Tribolium castaneum with widely different geographic backgrounds. The components of growth related to body weight — at the 13th day of larval life, Lw, at the first day of pupal life, Pw, at the first day of adult life, Aw, — and to developmental time — at pupation, Pt, at emergence of the adults, At. The relationships between those traits, presumably brought about by natural selection, were compared with similar relationships as disclosed in a study using lines artificially selected for some growth components. The correlations between Pw and Aw and between Pt and At are positive in both naturally and artificially selected populations. This is due to the fact that the rate of decrease in weight between Pw and Aw depends on Pw and to the fact that the developmental time between Pt and At is constant. The consistent significant correlation between growth rate, Lw, and both Pt and At contrasts with the absence of association between Lw and either Pw or Aw. This indicates that the rate of growth relates to developmental time and not to the final body weight. This is confirmed by the lack of consistent correlations, both at the intra- and inter-populational level, between weight, Pw and Aw, and developmental time, Pt and At. The balance achieved between those components of growth are discussed in terms of natural versus artificial selection and their bearing on various triats related to fitness are analyzed.

Reproductive behaviour and physiology of Tenebrio molitor (Coleoptera: Tenebrionidae). III. Histogenetic changes in the internal genitalia, mesenteron, and cuticle during sexual maturation

The histogenic changes in the internal genitalia and mesenteron and the hardening and darkening of the cuticle during the first days of adult life in Tenebrio molitor L. are described. At emergence, the testes contain mature spermatozoa and the ovaries possess small oocytes. During the first 3 days, the shape, size, appearance, and staining characteristics of the secretory cells of the lateral oviducts, female accessory gland, tube accessory glands, bean-shaped accessory glands, and glandular region of the vasa deferentia change. Similar changes were not seen in the seminal vesicles and spermatheca. All of the secondary sex glands are filled with secretion by day 4. In the midgut, changes occur in the size, shape, and appearance of the epithelial cells by the 3rd day, and a peritrophic membrane is secreted during days 2 and 3. Most adults do not begin to feed until after the 3rd day. By day 3, the hardening and darkening of the cuticle are completed. All of these changes clearly are associated with adult maturation, especially sexual maturation, and most or all of the them must take place before the adults are able to copulate and oviposit.

MALE INSEMINATIVE POTENTIAL IN APHYTIS LINGNANENSIS (HYMENOPTERA: APHELINIDAE)

AbstractExperiments were conducted to determine the number of females a single male Aphytis lingnanensis Compere (Hymenoptera: Chalcidoidea) would inseminate during the course of a lifetime and the number of female progenies stemming from these copulations. Comparisons between a 25-year-old laboratory culture and a newly collected field culture of the same species indicated that reproductive effort on the part of males was similar for the two cultures. The mean total number of females copulated by an individual male during this lifetime (about 6 days) was 27.6 for the laboratory culture and 25.6 for the field culture. The mean total number of female progeny per individual male resulting from these copulations was 169.5 for the laboratory culture and 149.1 for the field culture. Males inseminated the most females on the first day of adult life. Number of copulations and inseminative ability decreased rapidly through day 4. Very few occurred during days 5 to 9, the ultimate day any occurred. Females inseminated by a male that had experienced coitus with several females earlier tended to produce more males, thus suggesting that fewer spermatozoa were transferred during later copulations.

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.

Terminal differentiation of the adipose tissue in relation to vitellogenesis in the cricket

Changes in fat body cell ultrastructure were followed in the female cricket during the first days of adult life (at the onset of vitellogenesis). Cytological evidence was obtained for the depletion of stored lipids, and correlative accumulation of glycogen, in connection with lipidic vitellogenesis. The production of glycoproteic yolk precursors is achieved by the adipose cells following a process of terminal differentiation which transforms into secretory cells. The whole process occurs within the four first days of adult life.