Stimulate Egg Production Research Articles

A cost of reproduction in Drosophila melanogaster: stress susceptibility.

Little is known about physiological mechanisms that underlie the cost of reproduction. We tested the hypothesis that stress susceptibility is a cost of reproduction. In one test of our hypothesis, Drosophila melanogaster females were exposed to a juvenile hormone analog (methoprene) to stimulate egg production followed by stress assays. A sterile stock of D. melanogaster was employed as a control for reproduction. Exposure of fertile females to methoprene resulted in an increase in female reproduction and increased susceptibility to oxidative stress and starvation (compared to solvent controls). Sterile females did not exhibit a decrease in stress resistance. Mating also stimulated egg production. As a second test of our hypothesis, mated females were compared to virgin females. Mated fertile females were relatively susceptible to oxidative stress, but this relationship was not evident when mated and virgin sterile females were compared. The results of the present study support the hypothesis that stress susceptibility is a cost of reproduction.

A COST OF REPRODUCTION IN DROSOPHILA MELANOGASTER: STRESS SUSCEPTIBILITY

Little is known about physiological mechanisms that underlie the cost of reproduction. We tested the hypothesis that stress susceptibility is a cost of reproduction. In one test of our hypothesis, Drosophila melanogaster females were exposed to a juvenile hormone analog (methoprene) to stimulate egg production followed by stress assays. A sterile stock of D. melanogaster was employed as a control for reproduction. Exposure of fertile females to methoprene resulted in an increase in female reproduction and increased susceptibility to oxidative stress and starvation (compared to solvent controls). Sterile females did not exhibit a decrease in stress resistance. Mating also stimulated egg production. As a second test of our hypothesis, mated females were compared to virgin females. Mated fertile females were relatively susceptible to oxidative stress, but this relationship was not evident when mated and virgin sterile females were compared. The results of the present study support the hypothesis that stress susceptibility is a cost of reproduction.Corresponding Editor: T. Mousseau

Role of juvenile hormone-esterase in mating-stimulated egg development in the moth Heliothis virescens

Juvenile hormone (JH) titer in virgin females of Heliothis virescens is significantly lower than that in mated females of the same age. The JH titer in virgin females follows a diel pattern in which it begins to increase towards the end of photophase, remains high around the onset of scotophase, and declines during scotophase. The titer reaches its lowest levels at the onset of photophase, and remains low during the first half of photophase. In mated females, the diel pattern of JH titers is not as pronounced. JH-esterase (JHE) activity in mated females is significantly lower than that of virgin females during photophase; JHE levels in the former are similar to levels seen in newly emerged females. JHE activity in mated females also exhibits a diel pattern, in which activity is low during photophase and high at the onset of scotophase. Evidence for the indirect involvement of JHE in the mating-stimulated egg development is provided by the effect of selected JHE inhibitors in inhibiting JHE activity and stimulating egg production in virgin females.

Reproductive Management of Captive Parrots

Studies of the behavior of Amazon parrots throughout a reproductive trial indicate that activities such as food gathering, which may occupy large fractions of the activity budget of wild parrots, occupy little time in captivity. This may be one factor contributing to the large percentage of time during which Amazon parrots are generally inactive in typical captive conditions. The extent of inactivity in captive Amazons creates an open time niche wherein enrichment devices might play a role in improving their well being. Studies of the reproductive endocrinology and the behavior of parrots suggest that hand rearing may impair adult fertility and nest box use. Hand rearing may also cause adult Cockatiels to lay eggs on cage floors rather than in nest boxes. However, the use of nest boxes with oversized nest entrances can be very effective in alleviating chronic floor laying in Cockatiels. Another egg-laying problem in Cockatiels, unwanted egg laying, can be prevented by the use of long-acting formulations of the superactive GnRH agonist, leuprolide acetate, which presumably [figure: see text] acts in birds, as in mammals, by down-regulating pituitary GnRH receptors. Manipulations to limit the increases in prolactin normally seen during incubation in poultry can significantly increase egg production. As clutch size in Cockatiels may also be limited by rising prolactin levels, such manipulations may be effective in stimulating egg production in parrots. An alternative approach for increasing flock egg production is to place foster eggs in nests of Cockatiel pairs that are slow to lay. This technique stimulates males to increase their nest-oriented behavior and, subsequently, may stimulate egg laying in some females that might not otherwise have laid eggs. The parental phases of reproduction in Amazon parrots are often a time of heightened aggressiveness towards humans, but low levels of serum testosterone in males during that time suggest that this particular interspecies aggressiveness may not be dependent on elevated testosterone levels. Occasional human handling during the nestling stage may produce a degree of tameness comparable with hand-reared chicks, yet not impair adult reproductive performance. Such handling may also alter the immune status of captive parrots, and possibly reduce the serum corticosterone response to handling. If so, occasional human handling during the nestling stage could improve the adaptation of parrots to captivity.

Responses of Laying Hens to Forced Molt Procedures of Variable Length With or Without Light Restriction

The importance of the length of the rest period and of photoperiod as components of the forced molt procedure was evaluated in 650- and 560-d-old Lohman hens. The procedure included an 8-d feed withdrawal phase and rest periods varying from 0 to 35 d, during which the birds were fed for maintenance only. In the first trial, forced molt was applied with or without omission of artificial illumination. The rest period varied between 2 and 20 d. In the second trial, all treatments included omission of artificial illumination, and a variable rest period between 0 and 35 d. Egg production ceased, after 4 to 5 d of feed withdrawal and resumed 8 to 15 d after the end of the rest period, without any consistent response to its length. Forced molt stimulated egg production rate and diminished its age-dependent rate of decline, reduced the proportion of broken and shell-less eggs, and improved shell quality. Following wide oscillations proportional to the length of the rest period, egg weight stabilized at levels similar to that of the unmolted controls. Feed intake was stimulated by forced molt to levels exceeding those of the control hens. Body weight increased during the postmolt period to levels slightly exceeding those of unmolted controls.Results of one trial show that omission of artificial illumination was essential for the full expression of the molt responses. In the other trial, production rate and shell quality were improved and the percentage of broken eggs was reduced when the length of the rest period was increased. Maximal improvements appears to have been reached with rests periods of 14 to 21 d.

Growth, fecundity and glycogen utilization in Lymnaea palustris exposed to atrazine and hexachlorobenzene in freshwater mesocosms

AbstractFreshwater mesocosms were used to study the long‐term sublethal effects of atrazine and hexachlorobenzene (HCB) on a basommatophoran gastropod, Lymnaea palustris (Müller). Growth, fecundity, and biochemical parameters related to polysaccharide metabolism (glycogen content and polysaccharide‐hydrolyzing enzyme activity) of pesticide‐exposed snails were compared with those of control animals maintained in untreated mesocosms. HCB inhibited body growth and stimulated egg production, whereas atrazine had no relevant effect on these physiological parameters. Also, HCB stimulated the activity of polysaccharide‐hydrolyzing enzymes, suggesting that changes in the metabolism of reserve polysaccharides (glycogen) may be involved in the inhibition of growth and increase of fecundity. In contrast, atrazine had no effect on the metabolism of polysaccharides. It is concluded that the effects of HCB are related to its neurotoxicity that would have affected the neurohormonal control of growth and reproduction of exposed snails. It is suggested that polysaccharide‐hydrolyzing enzymes may be used as biomarkers to predict the effects of neurotoxic pesticides on freshwater snail populations.

Critical Day Lengths for Egg Production and Photorefractoriness in the Domestic Turkey

Critical day lengths (CDL) for ovarian growth, egg production, and photorefractoriness were estimated in turkey hens during winter and summer seasons. In two experiments, one in each season, fixed day length treatments ranging from 10.5 to 16 h/d were applied to photosensitive hens at 30 wk of age. Daily egg production was used to estimate CDL for the induction of egg production as well as optimal egg production. After 24 wk on light treatments, hens used during the winter season were exposed to 20 h light:4 h dark and subsequent changes in egg production were used to evaluate photorefractoriness. In two additional experiments, a night-interruption design was used to evaluate CDL and ovarian photoresponsiveness during winter and summer.The CDL for inducing egg production varied by season and was estimated to be 10.5 h or less during winter and about 11 h during summer. Likewise, the CDL for optimal egg production varied by season, being 11 to 11.5 h during winter and >14 h during summer. The CDL for photorefractoriness in winter photostimulated hens was between 12 and 12.5 h.It was concluded that CDL vary by season and are not fixed, but are dynamic characteristics of photoperiodic processes. Thus, photoresponsiveness of turkey hens changes by season. In addition, CDL for initiating egg production, stimulating egg production, and inducing photorefractoriness are all different, with the CDL for photorefractoriness being longest.

Variable egg development among Anopheles (Nyssorhynchus): control by mating?

Abstract. Among ten species of neotropical malaria vectors the frequency of egg development by virgin females fed both sugar and blood varied from 23% to 100% and was positively correlated with their mean fecundity. The mean volume of male accessory glands of these same species varied more than 10‐fold and was negatively correlated with population‐ or species‐specific incidence of egg development by virgin females. The accessory glands of Anopheles nuneztovari Gabaldon and Anopheles rangeli Gabaldon, Cova Garcia & Lopez are much greater in size than those of the other eight species and are believed to contain secretory materials that stimulate egg production following mating. Insemination did not stimulate egg development in Anopheles albimanus Wiedemann whose males possess comparatively small accessory glands.

The Effect of Photoperiodic History on Egg Laying in Dwarf Broiler Hens

An experiment was conducted in dwarf broiler breeders to determine whether the decrease in egg production towards the end of a laying year is due to the development of photorefractoriness or to age per se. The birds were reared on short days (8 h light/day) and subjected to dietary restriction to prevent BW exceeding the minimum required to support egg production. They were transferred at 22 wk of age to long days (20 h light/day) while controls were maintained on short days for a further 2, 14, or 30 wk. At the end of these periods, dietary restriction was relaxed to stimulate egg production, and the control short-day birds were transferred to long days. The number of days to the onset of egg laying after lifting dietary restriction was less in short-day controls than in hens exposed to long days for 14 wk [19.5 ± .5 (SE) versus 24.0 ± 1.1 days, P < .01] or 30 wk (26.4 ± 1.3 versus 41.2 ± 1.1 days, P < .001). The number of eggs laid during the 12 wk after first oviposition in hens exposed to long days for 2, 14, or 30 wk before relaxing dietary restriction was not significantly different from that of the short-day controls. The numbers of eggs laid during the 12 wk after first oviposition decreased (P < .001) as the hens became older irrespective of photoperiodic history. These observations indicate that in dwarf broiler breeders, photoperiodic history, and therefore the development of photorefractoriness, is less important than age per se in maintaining intensity of egg laying in the 1st laying yr.

Effect of courtship and repeated copulation on egg production in the simultaneously hermaphroditic land snailArianta arbustorum

Summary An experiment was conducted to examine whether extended courtship display (a major component of mating behaviour) or repeated copulation in the course of a reproductive season stimulates egg production in the simultaneously hermaphroditic land snail Arianta arbustorum. Repeated copulation was found to increase the number of eggs produced while courtship display did not appear to affect egg production. However, repeated copulation neither accelerated the onset of egg laying nor increased the hatching success of eggs. These results suggest that reciprocal intromission and/or receipt of a spermato-phore, but not the long-lasting courtship behaviour, stimulates egg production in A. arbustorum.

Synthesis of two Drosophila male accessory gland proteins and their fate after transfer to the female during mating

The male accessory gland of Drosophila is an adult secretory tissue which contributes many products to the male ejaculatory fluid. The secretions of the accessory gland affect the behavior and physiology of the female fly after mating, reducing her receptivity to courtship and stimulating egg production and oviposition. We have examined the developmental and mating-stimulated expression of two accessory gland proteins in the male and their transfer to and fates in the mated female. One of these proteins, msP 355a, has features of a prohormone and contains a region with amino acid sequence similarity to the egg-laying hormone of Aplysia; the other, msP 355b, is a small acidic protein. Both proteins are first detected in the accessory gland only after eclosion, although their transcripts are already present in late pupae. Both proteins are initially detected in the two morphologically distinct secretory cell types of the accessory gland, the main cells, and the secondary cells. In the glands of aged virgin males, they are only detected in the large vesicles of the secondary cells and in the lumen of the gland. Copulation results in an increase in the mRNAs for both proteins, as well as renewed translation of the proteins at least in the main cells. Both proteins are transferred to the female genital tract during copulation, and rapidly enter the female hemolymph. msP 355a is subject to rapid and specific cleavage within the female genital tract, but not in the hemolymph; msP 355b is not cleaved in either the female genital tract or the hemolymph.

Stimulation of egg production in the grain miteAcarus siro by the juvenile-hormone analogue fenoxycarb

The insect juvenile-hormone analogue fenoxycarb (ethyl [2-(phenoxyphenoxy) ethyl] carbamate) has been shown to stimulate egg production in the flour miteAcarus siro L. Incorporation of fenoxycarb into mite food at 10 mg kg−1 and 100 mg kg−1 increased egg production by 43% and 99%, respectively. In addition, total mite populations were significantly higher in fenoxycarb-treated media than in controls. These results are discussed in relation to the possible gonadotropic role of juvenilehormone-like molecules in mites, and to the use of fenoxycarb as a grain protectant.

Physiological role of HMG-CoA reductase in regulating egg production by Schistosoma mansoni.

Pathological lesions observed in humans infected with Schistosoma mansoni are due to the eggs produced by the female parasite. Mevinolin, a potent inhibitor of the enzyme hydroxymethylglutaryl-CoA (HMG-CoA) reductase, blocks egg production by this parasite. In this report, we demonstrate that cholesterol precursors, mevalonate and farnesol, stimulate egg production by the female parasite and that these precursors can reverse the mevinolin-induced inhibition of egg production. Because the parasite cannot synthesize cholesterol, we incubated parasites in a culture media containing radiolabeled acetate with and without mevinolin. We isolated nonsterol lipids from the parasite and observed that mevinolin dramatically reduced the conversion of acetate into the polyisoprenoid (dolichols) lipids of the parasite. Dolichols and other nonsterol lipids did not stimulate egg production. HMG-CoA reductase activity was observed in homogenates of the parasite and was inhibited by mevinolin (Ki = 52 nM), but its activity was tripled when the parasite was chronically exposed to low doses of the drug. Parasites with increased reductase activity produced five to six times more eggs. Lastly, chronic administration of large doses of mevinolin to infected mice resulted in a marked reduction of the pathology associated with the infection. These results suggest that egg production in S. mansoni is associated with the parasite's HMG-CoA reductase activity and that a nonsterol lipid produced in the biochemical pathway regulated by this enzyme stimulates egg production.

Interaction of Photoperiod, Grouping and Isolation in Female Reproduction ofLymnaea stagnalis

Summary A study was made of the effects of the photoperiod on female reproductive activities in grouped and isolated specimens of the hermaphrodite freshwater snail Lymnaea stagnalis. Isolation of snails rapidly increased (< 3 days) egg production. The effect was long-lasting, and was probably caused by deprivation of copulation. Changes of photoperiod had similar effects in isolated and grouped snails. Compared to the effects of isolation, the photoperiodic effects were relatively slow in appearing (> 14 days). In comparison with a medium day (MD) (12 hr light/12 hr dark), a long day (LD; 16 hr light/8 hr dark) stimulated egg production whereas a short day (SD) (8 hr light/16 hr dark) lowered egg production. The LD effects were clearer in grouped than in isolated snails, but SD effects were clearer in isolated than in grouped snails. It is argued that the effects of grouping, isolation and photoperiod on egg production are mediated by the neuroendocrine system. It is suggested that the photoperiod plays an important role in the control of the egg laying season. Mating is probably important in the control of fecundity in relation to population density.

Vitamin B12 nutriture of chickens fed raw soybean meal.

Experiments were conducted to investigate a possible interference by raw soybean meal (RSM) with B12 nutriture of chickens. In Experiment 1, day-old chicks were fed B12-free isonitrogenous and equienergetic diets containing 0 or 40% RSM to determine if RSM accelerated storage losses of B12. After 42 days, RSM decreased growth (P less than .01), decreased hepatic (P less than .01) and blood (P less than .05) concentrations of glutathione (GSH), and increased (P less than .01) pancreas and liver weights. However, statistically significant differences due to treatment were not detected in hepatic B12 concentration, indicating that RSM does not enhance B12 turnover in chicks. To ascertain the effect of RSM on B12 absorption, 9 micrograms B12/kg diet was added to diets containing 0 or 40% RSM and fed to chicks to 42 days of age. Raw soybean meal depressed growth (P less than .001) and hepatic GSH (P less than .01) and increased (P less than .001) pancreas weights. The RSM had no effect on hepatic B12 concentration, suggesting that RSM trypsin inhibition does not impair B12 absorption in chicks. A third experiment was designed to test the hypothesis that vitamin B12 stimulates egg production or feed intake of hens fed a diet with 27% RSM. Vitamin B12-depleted hens were fed RSM or heat-treated soybean meal (HSM) diets containing equivalent amounts of soybean protein, oil, and hulls. Hens received either 26 micrograms B12/kg BW per os or 13 micrograms B12/kg BW intramuscularly twice within a 30-day period.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of feeding, mating and ovariectomy on degeneration of indirect flight muscles of Dysdercus cingulatus (Heteroptera: Pyrrhocoridae)

Degeneration of indirect flight muscles takes place during the first gonotrophic cycle in females. Feeding and mating stimulate egg production and muscle histolysis. Starved virgin females do not histolyse the flight muscles. Mating has greater effect on muscle degeneration than feeding. Ovariectomy inhibits degeneration to a certain extent.

Effects of Ddt and Fenitrothion on Field-Collected Larvae of a Eucalypt-Defoliating Beetle, Paropsis Atomaria Ol. I. Mortality, Relative Toxicity, Development of Treated Larvae, and Effect of the Primary Parasitoids.

Insecticide concentrations within the range 0.025-0.1% (DDT) or 0.002-0.02% (fenitrothion) were applied to populations of third- and fourth- instar larvae of Paropsis atomaria Ol. collected from the field. The susceptibility of larvae varied with insecticide and its concentration, larval age, generation, and with the level of parasitization in the batches of larvae tested. Fenitrothion was 10-14 times more toxic than DDT. Third-instar larvae were more susceptible than fourth instars to both insecticides. LC*50 for DDT at 48 h was about 0.02% w:v for third-instar, and 0.06% w:v for fourth-instar larvae; for fenitrothion it was about 0.004% w:v for both instars. For both insecticides, more than half of the batches of larvae showed significant heterogeneity of response. This was caused mainly by parasitization of some of the larvae, and in large part depended on which species of parasitoid was present. LC*50 for DDT applied to fourth instars was 0.066% for non-parasitized, 0.047% for parasitized larvae: 0.043% for those parasitized by the braconid Eadya paropsldis Huddleston &amp; Short, and 0.06% for those parasitized by the tachinid flies. For fenitrothion, LC*50 for fourth-instar larvae was 0.0045% for non-parasitized, 0.0033% for total parasitized, 0.0031% for those containing Eadya, and 0.0038% for those containing tachinids. Non-parasitized prepupae and the adults from larvae which survived insecticide treatments showed a general decrease in body weight with increase in concentration: prepupal weight decreased further when parasitoids were present. Larval and pupal developmental periods were not significantly altered by treatments. The insecticides applied to the larvae stimulated egg production in the adults and speeded up embryogenesis, but did not affect the reproductive system and fecundity.

Artificial Insemination of the Boll Weevil 12

When the boll weevil, Anthonomus grandis Boheman, was artificially inseminated by a new technique, fertile eggs were obtained from 68.7% of the females; however, the number that laid fertile eggs dropped quickly over a 2-week period. Not as many spermatozoa reached the spermathecae of artificially inseminated females, and the spermatozoa were apparently not as active as those of normally inseminated females. The presence of active spermatozoa in the copulatory pouch stimulated egg production and normal oviposition behavior. The behavior of females artificially inseminated with only male accessory gland material was indistinguishable from that of virgin females.

EFFECT OF OVIPOSITION SITES ON EGG PRODUCTION AND LONGEVITY OF TROGODERMA PARABILE (COLEOPTERA: DERMESTIDAE)

AbstractPairs of adults of Trogoderma parabile Beal were held in glass vials and provided with one of seven types of oviposition sites. Among the types of oviposition sites tested, the highest mean egg production was recorded on cotton balls and the lowest in empty glass vials. Egg production was not increased by adding food to vials that contained cotton balls. A suitable oviposition site, which provided crevices for insertion of the ovipositor, was more important than food in stimulating egg production. Non-ovipositing females lived longer than productive females on the various oviposition media. Adults fed, but did not require food to lay eggs. Mated females laid practically the same number of eggs during the oviposition period whether or not males were present.

Analysis of Host-Parasite Relationships of Root-Knot Nematodes By Single-Larva Inoculations of Excised Tomato Roots

This report describes a bacteria-free culture unit to be used in large numbers for detailed analysis of host-parasite relationships of Meloidogyne sp. The unit consists of an excised tomato root growing in agar medium in a test tube to which one nematode larva has been added. Almost every nematode which penetrates induces a gall; a high proportion of these galls have eggs externally after 3 weeks of incubation at 28° C. Galls appear from the 1st to the 9th day, eggs from the 18th to the 26th day, and larvae from the 25th to the 32nd day after inoculation. Infectivity of Meloidogyne incognita acrita was 53%. Variations in nutrient composition had no marked effects except that high potassium stimulated egg production without affecting incidence of gall formation; high concentrations of iodine increased brown discoloration of galls. Addition of juice from a resistant plant (Cornus florida) depressed the infectivity of M. incognita acrita for tomato roots. A resistant variety of tomato, Nemared, maintained its resistance to Meloidogyne in excised root culture.