Week Of Adult Life Research Articles

Allatostatin-C receptors in mosquitoes

In the present work we describe the functional and molecular characterization of two Aedes aegypti allatostatin-C receptor paralogs (AeAS-CrA and AeAS-CrB) and provide a detailed quantitative study of the expression of the AS-C receptor genes in an adult insect. The tissue distribution of the two AS-C receptors differed significantly; the mRNA levels of AeAS-CrB in the Malpighian tubules were the highest detected, while transcripts for AeAS-CrA were relatively low in this tissue. In addition, the transcript levels of both receptors were different in the thoracic and abdominal ganglia, corpora allata (CA) and the testis of the male. In the CA, the AeAS-CrB mRNA levels were constant from 0 to 72 h after female emergence, while the AeAS-CrA levels increased at 72 h. To complement the receptor expression studies, we analyzed the tissue specificity for allatostatin-C mRNA in female mosquitoes. Expression was high in abdominal ganglia and brain. Transcript levels of allatostatin-C in the head of females were elevated at eclosion and there were no major changes during the first week of adult life or after blood feeding. Fluorometric Imaging Plate Reader (FLIPR) recordings of calcium transients in HEK293T cells transiently expressing both putative receptors showed that they both responded selectively to allatostatin-C stimulation in the nanomolar concentration range. However, the peptide showed slightly greater affinity for AeAS-CrB than AeAS-CrA. Our studies suggest that some of the pleiotropic effects of allatostatin-C in mosquitoes could be mediated by the different receptor paralogs. Transcriptional regulation of the AS-C receptors may not have a critical role in the changes of CA responsiveness to the peptide that we previously described.

Nymph developmental time and survivorship, adult longevity, reproduction and body weight of Dichelops melacanthus (Dallas) feeding on natural and artificial diets

The biology of nymphs and adults of the neotropical pentatomid, Dichelops melacanthus (Dallas), feeding on the natural foods, soybean, Glycine max (L.) Merrill immature pods, and corn, Zea mays L. immature seeds, and on an artificial dry diet, was studied in the laboratory. Nymph developmental time was shorter on the natural foods (ca. 21-22 days) than on the artificial diet (28 days), and most nymphs reached adulthood on the food plants (55% on soybean and 73% on corn) than on the artificial diet (40%). Fresh body weight at adult emergence was similar and higher for females raised as nymphs on the natural foods, compared to females from nymphs raised on the artificial diet; for males, weights were similar on all foods. Mean (female and male) survivorship up to day 20, decreased from 55% on soybean to 40% on corn, down to 0% on the artificial diet. Total longevity for females was higher on soybean, while for males was similar on all foods. About three times more females oviposited on soybean than on corn, but fecundity/female was similar on both foods. On the artificial diet, only one out of 30 females oviposited. Fresh body weight of adults increased significantly during the first week of adult life, and at the end of the 3rd week, weight gain was similar on all foods.

Adult honeybees (Apis mellifera L.) abandon hemocytic, but not phenoloxidase-based immunity

Hemocytes and the (prophenol-) phenoloxidase system constitute the immediate innate immune system in insects. These components of insect immunity are present at any post-embryonic life stage without previous infection. Differences between individuals and species in these immune parameters can reflect differences in infection risk, life expectancy, and biological function. In honeybees which show an age-related division of labor within the worker caste, previous studies demonstrated that foragers show a strongly reduced number of hemoctyes compared to the younger nurse bees. This loss of immune competence has been regarded advantageous with respect to an already high mortality rate due to foraging and to redistribution of energy costs at the colony level. Based on the idea that abandoning hemocytes in all adults would be a reasonably direct regulatory mechanism, we posed the hypothesis that abandoning hemocytic immunity is not restricted to worker honeybees. We tested our hypotheses by performing a comprehensive analysis of hemocyte number and phenoloxidase (PO)-activity levels in immunologically naive workers, queens, and drones. We found that in all three adult phenotypes hemocyte number is dramatically reduced in early adult life. In contrast, we found that the dynamics of PO-activity levels have sex and caste-specific characteristics. In workers, PO activity reached a plateau within the first week of adult life, and in queens enzyme levels continuously increased with age and reached levels twice as high as those found in workers. PO-activity levels slightly declined with age in drones. These data support our hypothesis, from which we infer that the previously reported reduction of hemocyte in foragers is not worker specific but represents a general phenomenon occurring in all honeybee adult phenotypes.

Mutation Accumulation Affects Male Virility inDrosophilaSelected for Later Reproduction

An intensive study of longevity, female fecundity, and male reproductive behavior in Drosophila melanogaster was undertaken in order to establish whether late-life fitness characters in short-lived populations might be affected by the increase in deleterious alleles due to random genetic drift. We also sought to determine whether selection for late-life fertility could eliminate alleles that produce a decline in later fitness components in short-lived populations, as predicted by the mutation accumulation hypothesis for the evolution of aging. These experiments employed long-lived (O) populations, short-lived (B) populations, and hybrids made from crosses of independent lines from within the O and B populations. No detectable longevity differences were seen between hybrid B males and females and purebred B males and females. Reproduction in aged B purebred females was significantly less than in hybrid females at 3 wk of age only. A full diallel cross of the five replicate B lines showed a steady increase in hybrid male reproductive performance after the first week of adult life, relative to the parental lines. A full diallel cross of the five replicate O lines revealed no significant increase in hybrid O age-specific male reproductive success compared with the purebred O lines when assayed over the first 5 wk of adult life. The results on male reproductive behavior are consistent with the idea that relaxed age-specific selection in the B populations has been accompanied by an increase in deleterious, recessive traits that exhibit age-specific expression. Consequently, we conclude that a mutation accumulation process has been at least partly responsible for the age-specific decline in male B virility relative to that of the O populations.

ARE THE STRUCTURAL CHANGES IN ADULT DROSOPHILA MUSHROOM BODIES MEMORY TRACES? STUDIES ON BIOCHEMICAL LEARNING MUTANTS

SUMMARYThe pre-imaginal development of Drosophila mushroom bodies is under the influence of an unknown variable which causes populations of wild-type flies at eclosion to differ in the average number of Kenyon cell fibers. During the first week of adult life the number adjusts to an intermediate level which depends upon the experience of the flies. Under olfactory deprivation or social isolation it reaches a lower level than under favorable rearing conditions (J. Neurogenet., 1 (1984) 113–126). The biochemical learning mutants dunce and rutabaga show no experince-dependent modulation of fiber number (Fig. 2). In both strains the mushroom bodies of young adults seem to develop abnormally; in dunce a loss of aboout 600 fibers is observed, in rutabaga fiber number is low at eclosion and does not increase (Fig. 1a). The following model for long-term memory is proposed: in mushroom bodies outgrowth and decay of Kenyon cell fibers occur simultaneously. The fibers randomly form transient synapses onto extrinsic output neurons of the mushroom bodies and receive synapses from modulating neurons. Experience consolidates certain synapses, thus prolonging survival of the respective Kenyon cell fibers and increasing the steady state level of fiber number (Fig. 3).

FIBER NUMBER IN THE MUSHROOM BODIES OF ADULT DROSOPHILA MELANOGASTER DEPENDS ON AGE, SEX AND EXPERIENCE

SUMMARYThe mushroom bodies are two characteristically shaped structures of the insect central brain. In Drosophila melanogaster they contain more fibers in females than in males. Within the first week of adult life the total number of fibers increases by about 15% and decreses again in flies older than 3–4 weeks. The number of mushroom body fibers is significantly reduced in flies kept under social isolation or deprived of their antennal input, but not in flies subjected to visual deprivation.

Biological and ecological studies on Scymnus syriacus and Scymnus levaillanti (Coleoptera: Coccinellidae)

Both Scymnus syriacus Mars. and Scymnus levaillanti Muls. are aphidophagous coccinellids. In the laboratory they con- sumed and successfully reproduced on several species of aphids. Larvae suck the prey contents from aphid appendages, while adults consume the whole aphid, except for parts of the appendages. Extra-oral digestion is practiced during feeding. The mean number of aphids consumed by the larval stage of S. syriacus when reared at 25°C was 95, and 130 aphids at 30°C. For S. levaillanti it was 125 and 139 aphids at 25°C and 30°C, respectively. The mean number of eggs deposited daily by S. syriacus for the first three weeks of adult life was 19.5, with a range of 3-30 eggs at 25°C. Longevity of adults ranged from 3 to 4 months at 25°C and 2.5-3 months at 30°C.

Diachasmimorpha longicaudata and D. kraussii (Hymenoptera: Braconidae), potential parasitoids of the olive fruit fly

The olive fruit fly, Bactrocera oleae (Tephritidae), is a significant threat to California's olive industry. As part of a classical biological control program started in 2002, the parasitoids Diachasmimorpha kraussii and D. longicaudata (Hymenoptera: Braconidae) were imported to California from laboratory colonies in Hawaii. Studies on their biology and behavior as parasitoids of the olive fruit fly were conducted in quarantine. Both species tend to oviposit into 2nd and young 3rd instars, with the offspring completing development in the flies’ puparia. Most eggs are deposited in the first two weeks of adult life. Observed lifetime fecundity was low, possibly as a consequence of the relatively poor quality of the harvested olives used as a host substrate. Both pre-imaginal development and adult longevity were limited at constant temperatures above 30°C, which may indicate that these species will have difficulty establishing in the warmest regions of California.

ハスモンヨトウ（チョウ目：ヤガ科）幼虫の内部寄生蜂であるハスモンサムライコマユバチMicroplitis manilae Ashmead（ハチ目：コマユバチ科）の生活史特性に及ぼす温度の影響

Microplitis manilae is new to Japan, and has been found to parasitize the larvae of Spodoptera litura in Okinawa Island, one of the southernmost islands of Japan. The parasitoids showed solitary endoparasitism and arrhenotokous parthenogenesis. They parasitized S. litura larvae from the first to antepenultimate instar, and greatly suppressed the feeding of host larvae, but they failed to parasitize penultimate and final instars, and eggs. Based on the developmental rates of M. manilae reared at constant temperatures between 15 and 30°C, developmental zero was calculated as 11.5°C and effective accumulative temperature from egg to adult emergence as 217.4 degree days. Oviposition and adult emergence of M. manilae were greatly suppressed when parasitoids were reared at a constant 15°C, while such suppression did not appear when they were reared at 15°C on average but at two different temperatures within a day. A female laid more than 300 eggs during 2 weeks of adult life at 20–30°C and survived for 60 days without egg laying at 15°C. The temperature dependency of development and fecundity in this species was compared with those of Meteorus pulchricornis, which is a well-known parasitoid of S. litura.

Genotypic differences in space use and movement patterns in Drosophila melanogaster

We used five Drosophila melanogaster recurrent F1s to investigate genotypic differences in space use and movement patterns, focusing on the behaviour of teneral females and individually marked young adults that were allowed free access to large, structurally complex environments. Teneral females from the five F1s differed in their propensity to hide after emergence and in the height at which they perched above the substrate. During the first 2 weeks of adult life, F1s of both sexes showed consistent differences in site fidelity, the proportion of time spent in areas located far from food items, and their choice of substrate when perching near food items. As larvae, these same five F1s differed with respect to the distances travelled while foraging, distances moved after disturbance at natal fruits, and pupation distance from natal fruits. The results of this study may help to shed light on related questions involving this species, including the effects of natal experience on habitat preference, and the effect of structural features near pupation sites on the ability of teneral females to avoid predators or forced copulations.

Biology and Descriptions of Nymphal and Adult <I>Jadera choprai</I> (Hemiptera: Rhopalidae)

The biology of nymphs and adults of the Neotropical scentless bug Jadera choprai Göllner-Scheiding feeding on mature seeds of the balloon vine, Cardiospermum halicacabum (L.) (Sapindaceae), was studied in the laboratory. Most nymphs (>75%) successfully reached adulthood when feeding on this food. Nymphs reared individually had lower mortality (14.0%) and shorter developmental times (35.7 d) than did bugs reared in groups (23.3% and 39.9 d). All adult females oviposited when fed on seeds of balloon vine. Mean adult longevity was 86.0 d for males and 47.7 for females. Mean fecundity was ≈147 eggs per female, and ≈85% of the eggs hatched. Fresh body weight of females increased significantly during the first week of adult life; males, however, lost weight significantly during this period. Females lost weight during their second week posteclosion, but they regained the weight subsequently. However, males did not. Nymphs and adults (macropterous and brachypterous forms) of J. choprai are described and illustrated, as are their setal patterns.

Hormetic protection of Drosophila melanogaster middle-aged male flies from heat stress by mildly stressing them at young age

Previous studies have shown that exposing flies to hypergravity (3g or 5g) for the first 2 weeks of adult life slightly increases longevity of male flies and survival time at 37 degrees C for both sexes, and delays an age-linked behavioral change. The present experiment tested whether the hypergravity could also protect flies from four successive deleterious non-lethal heat shocks at 4 and 5 weeks of age. Males that lived in hypergravity for the first 2 weeks of adult life lived slightly longer (ca. +15% or 1.2 day) after heat shocks (30 min or 45 min at 37 degrees C) than flies that always lived at 1g, but this positive effect of hypergravity was not observed in females. Therefore, hypergravity exposure at young age can help the male flies recovering from a heat shock at older ages.

Laboratory adaptation ofBactrocera tryoni(Diptera: Tephritidae) decreases mating age and increases protein consumption and number of eggs produced per milligram of protein

A significant reduction in age of mating occurred during the first four generations (G1-G4) of laboratory adaptation of wild Bactrocera tryoni (Froggatt) and this was associated with the earlier attainment of peak egg load although no significant differences were detected in the peak egg load itself. A long term laboratory (LTL) strain had a significantly earlier mating age and higher peak egg load than flies of wild origin or those from the first four laboratory generations. The amount of protein consumed by females in the first week of adult life was significantly higher in the LTL strain than in flies of wild origin or G1-G4 but there were no significant changes (or only slight changes) with laboratory adaptation in the amounts of protein consumed up to the ages of mating and peak egg load. Laboratory adaptation resulted in no significant changes in egg size, egg dry weight, puparial fresh weight and the dry weight of newly emerged females. The large increase in fecundity with laboratory adaptation is associated with a 4- to 5-fold increase in the rate of conversion of dietary protein to eggs (i.e. eggs produced per mg of protein consumed).

Drosophila lifespan enhancement by exogenous bacteria.

We researched the lifespan of Drosophila under axenic conditions compared with customary procedure. The experiments revealed that the presence of bacteria during the first week of adult life can enhance lifespan, despite unchanged food intake. Later in life, the presence of bacteria can reduce lifespan. Certain long-lived mutants react in different ways, indicating an interplay between bacteria and longevity-enhancing genes.

Effect of variation in host size on sex ratio, size, and survival of Syngaster lepidus, a parasitoid of Eucalyptus longhorned beetles (Phoracantha spp.): II

Larvae of the cerambycid beetle Phoracantha recurva Newman colonize the inner bark of stressed or dying Eucalyptus trees. These cryptic larvae are parasitized by the solitary ectoparasitoid Syngaster lepidus Brullé. When denied a choice of host sizes in a previous study, parasitoid females produced only male progeny in 2 week old larvae, but when given access to only large larvae, the sex ratio of the progeny was significantly female biased. When female wasps were simultaneously presented with a range of host sizes in the study presented here, the sex ratio was significantly male biased for wasps produced from the smallest host class (2 weeks old), but was not different among the 3, 4, or 5 week old hosts. The sex ratio of progeny remained constant throughout the life of the ovipositing females. Fertility peaked during the second week of adult life, then declined to zero by the fourth week, with females producing about 22 progeny during their lifetimes. Longevity of females was significantly greater than that of males. Significantly more progeny were produced from 3 week old hosts than from any other age class. There was no difference in the number of progeny emerging from 2 or 4 week old hosts, but significantly fewer progeny were produced from 5 week old hosts. The size of emerging wasps increased with host size for both males and females. In Australia, a complex of parasitoids, uses Phoracantha larvae as hosts. S. lepidus prefers to use younger, smaller larvae, while other members of the parasitoid guild exploit larger larval hosts. The results from this study suggest tradeoffs between sex allocation and percent survival in different host size classes, and reflect the observations from previous field studies of this host–parasitoid complex in Australia.

Synaptic organization in the adult honey bee brain is influenced by brood-temperature control during pupal development.

Recent studies have shown that the behavioral performance of adult honey bees is influenced by the temperature experienced during pupal development. Here we explore whether there are temperature-mediated effects on the brain. We raised pupae at different constant temperatures between 29 and 37 degrees C and performed neuroanatomical analyses of the adult brains. Analyses focused on sensory-input regions in the mushroom bodies, brain areas associated with higher-order processing such as learning and memory. Distinct synaptic complexes [microglomeruli (MG)] within the mushroom body calyces were visualized by using fluorophore-conjugated phalloidin and an antibody to synapsin. The numbers of MG were different in bees that had been raised at different temperatures, and these differences persisted after the first week of adult life. In the olfactory-input region (lip), MG numbers were highest in bees raised at the temperature normally maintained in brood cells (34.5 degrees C) and significantly decreased in bees raised at 1 degrees C below and above this norm. Interestingly, in the neighboring visual-input region (collar), MG numbers were less affected by temperature. We conclude that thermoregulatory control of brood rearing can generate area- and modality-specific effects on synaptic neuropils in the adult brain. We propose that resulting differences in the synaptic circuitry may affect neuronal plasticity and may underlie temperature-mediated effects on multimodal communication and learning.

BEHAVIOUR AND BEE BRAINS

The question of whether there are links between our genetic makeup and the way we behave has long puzzled humans. With the publication of the human genome we may finally be on the verge of answering this tantalising question. Some scientists hope ultimately to be able to predict behaviour by simply looking at our genetic makeup. Unfortunately, humans are probably too complex to begin answering this problem at the moment. However, undaunted by the enormity of the task, Charles Whitfield and his colleagues at the University of Illinois have set about tackling the problem, while setting their sights a little lower. They have turned their attention to a relatively simple creature, the honey bee (Apis mellifera), to start unravelling how(and if) our genes control what we do.Bees are fascinating because they form complex societies, where everyone has a particular role. For example, worker bees have two distinct forms of behaviour. During the first 2–3 weeks of adult life, female worker bees are confined to the hive, nursing and caring for the demanding young. As they mature, they switch roles and begin foraging, spreading their wings and flying far afield to search for pollen and nectar. The change from nurse to forager depends on the number of hungry mouths there are to feed and the needs of the colony, so the team decided to look at the bee's genetic brain profiles as they switched from one behaviour to the other.Comparing gene expression patterns across 40% of the genome, the team looked at 5–9-day-old nurses and 28–32-day-old foragers from a typical colony. There were significant differences in brain gene expression for 39% of the genes in the portion of the genome tested. The team then wanted to find out whether these differences were associated with the age of the bees or with the way the bees were behaving. Whitfield and his colleagues turned their attention to single cohort colonies, where all the worker bees are the same age. In these colonies, some bees begin foraging at a very early age in the absence of older bees, while others remain in their nursing role as there are no youngsters to replace them. Knowing that all of these bees were the same age, regardless of their roles, the team measured gene activity in the brains of young and old nurses and precocious and old foragers to see whether the brain expression patterns were due to old age or experience.What they found was that there is a strong relationship between behaviour and brain gene expression; so it is not how old you are, but what you are doing that is important if you are a bee. Having shown that there is a molecular signature, like a fingerprint, that is strongly related to behaviour, the team were able to identify individual's activities from their molecular fingerprint alone, distinguishing nurses from foragers with a 92–95% accuracy! And with the publication of the honey bee genome pending, Whitfield and his colleagues are optimistic they can unravel the complex web of genetic interactions that transform bees from caring nurses to roaming foragers.

Looking Farther Afield

Looking Farther Afield

Metabolic rate in female Culex tarsalis (Diptera: Culicidae): age, size, activity, and feeding effects.

We used flow-through respirometry on female mosquitoes to observe individual ventilatory pattern and to measure metabolic rate at rest, during activity and after a blood-meal. At rest, young adult females of the species Culex tarsalis ventilated cyclically with an average VCO2 of 6.5 nl/min and frequency of 45 mHz. Both resting metabolic rate and body mass of females increased between emergence and 4 d, but only body mass continued to increase until 12 d. Mating status had no effect on the body mass or resting metabolic rate of the females. Both lipid and carbohydrate stores strongly increased during the first week of adult life, in particular between emergence and 4 d, in which lipid mass increased 8.3-fold and carbohydrate mass increased 3.6-fold. Hourly metabolic rate after a blood or sugar meal was measured over a 6-d period in two groups of 14 females. Sugar-fed mosquitoes remained calm during the day and had nocturnal increases in metabolic rate associated with flight activity. Blood feeding elicited a specific dynamic action lasting approximately 55 h, at the peak of which metabolic rate of the blood-fed females was twice that of the sugar-fed group. Eggs were laid on the third night. The increase in metabolic rate presumably reflected the cost of blood digestion and egg production. The females were not active during digestion, so that although their metabolic rate was increased, the overall energy expenditure of the blood-fed group was not very different from that of the sugar-fed group.

Maturation of muscle properties and its hormonal control in an adult insect.

The oviposition of female locusts requires longitudinal muscles to tolerate remarkable lengthening. Whether this ability together with concomitant properties develops during maturation or is present throughout life was investigated. The properties of the locust abdominal muscles involved in oviposition behaviour were investigated with respect to their maturation, segment- and gender-specificity and regulation by juvenile hormone (JH). Muscles from the sixth abdominal segment (an oviposition segment) of mature females (>18 days old) were able to tolerate large extensions (>8 mm). At this length, muscles were still able to generate considerable neurally evoked twitch tension. In contrast, muscle fibres from females less than 5 days old did not tolerate extension of more than 4 mm. At this length, tension generation was negligible. The maximum tension generated at different stimulus frequencies was significantly higher in muscles of females more than 18 days old than in females less than 5 days old. Furthermore, the cross-sectional area of muscle fibres increased significantly during reproductive development. Current-clamp recordings from denervated muscle fibres of females more than 18 days old revealed their ability to generate overshooting action potentials. The potentials were tetrodotoxin (TTX)-insensitive (0.5 micromol l(-1) TTX), but were blocked by Cd(2+) (50 micromol l(-1)) or nifedipine (50 micromol l(-1)), which suggests the involvement of L-type Ca(2+) channels. Action potentials recorded from females less than 5 days old differed considerably in amplitude and shape from those recorded from females more than 18 days old, suggesting their maturation during the first 2 weeks of adult life. Inactivation of the corpora allata (CA) by precocene inhibited the maturation of these muscle properties, whereas injection of JH into precocene-treated females reversed this effect. Homologous muscles from the third abdominal segment (a non-oviposition segment, M169) and muscles from males (M214) revealed no comparable changes, although some minor changes occurred during reproductive development. The results suggest a gender- and segment-specific maturation of muscle properties that is related to reproductive behaviour and controlled by JH.