[Stimulation of silkworm fecundity by heterogeneous insemination].
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Animals↗
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Effect of granulosa cell apoptosis on fecundity?
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Apoptosis↗
Testing whether male age or high nutrition causes the cessation of reproductive aging in female Drosophila melanogaster populations.
Fecundity seems to stop declining and plateaus at low levels very late in Drosophila melanogaster populations. Here we test whether this apparent cessation of reproductive aging by a population, herein referred to as fecundity plateaus, is robust under various environmental influences: namely, male age and nutrition. The effect of male age on late age fecundity patterns was tested by supplying older females with young males before average population fecundity declined to plateau levels. The second possible environmental influence we tested was nutrition and whether late-life fecundity plateaus arise from a decline in the calories available for reproduction. This hypothesis was tested by comparing average daily female fecundity with both low- and high-lifetime nutrition. Both hypotheses were tested by measuring mid- and late-life fecundity for each cohort under the various environmental influences, and statistically testing whether fecundity stops declining and plateaus at late ages. These experiments demonstrate that mid- and late-life population fecundity patterns are significantly affected by the age of males and nutrition level. However, male age and nutrition level did not affect the existence of late-life fecundity plateaus, which demonstrates the robustness of our earlier findings. These results do not address any issue pertaining to the possible role, if any, of lifelong inter-individual heterogeneity in Drosophila fecundity.
Aging↗
Selection on body size and sexual size dimorphism differs between host species in a seed-feeding beetle.
Sexual size dimorphism varies substantially among populations and species but we have little understanding of the sources of selection generating this variation. We used path analysis to study how oviposition host affects selection on body size in a seed-feeding beetle (Stator limbatus) in which males contribute large ejaculates (nuptial gifts) to females. Females use nutrients in these ejaculates for egg production. Male body size, which affects ejaculate size, affects female fecundity and is thus under fecundity selection similar in magnitude to the fecundity selection on female body size. We show that when eggs are laid on a host on which larval mortality is low (seeds of Acacia greggii) fecundity predicts fitness very well and fecundity selection is the major source of selection on both male and female adult size. In contrast, when eggs are laid on a host on which larval mortality is high (seeds of Parkinsonia florida) fecundity poorly predicts fitness such that fecundity selection is relaxed on both male and female size. However, because egg size affects larval mortality on this poor host (P. florida) there is selection on female size via the female size --> egg size --> fitness path; this selection via egg size offsets the reduction in fecundity selection on female, but not male, body size. Thus, differences in host suitability (due to differences in larval mortality) affect the relative importance of two sources of selection on adult body size; fecundity selection on both male and female body size is lower on the poor quality host (P. florida) relative to the high quality host (A. greggii) whereas selection on female body size via effects of egg size on offspring survival (body size --> egg size --> fitness) is greater on the poor quality host relative to the high quality host. Because selection via the egg size path affects only females the difference in larval survival between hosts shifts the relative magnitude of selection on female vs. male size. Researchers working on other study systems should be alerted to the possible importance of subtle, but consequential, indirect selection on their study organisms.
Animals↗
Geographic variations in probability of pregnancy in four cities of France.
BACKGROUND: Several studies have described geographic variations in human fecundability, but this phenomenon has almost exclusively been studied at an international level rather than within a given country. Our aim was to describe geographic variations in fecundability, the monthly probability of pregnancy, between four cities of France. METHODS: We conducted a cross-sectional study in four French maternity units from Toulouse, Rennes, Lyons and Paris, among partners of pregnant women. Women were asked about the time to pregnancy (TTP) of their current pregnancy. TTP was analysed with a discrete Cox model allowing to estimate fecundability ratios (FR). RESULTS: Time to pregnancy was defined for 894 couples. There was no strong evidence of heterogeneity in fecundability between the four compared cities (p=0.05 without adjustment and p=0.25 after adjustment for behavioural and medical factors). The highest fecundability was observed in Rennes and the lowest in Toulouse (fecundability ratio (FR)=1.28, 95% CI: 1.01-1.63). Differences in fecundability were smaller between the other cities. CONCLUSION: We highlighted a possibly slightly higher fecundability in Rennes compared to Toulouse. Possible explanations for this finding are discussed. We note that the finding is consistent with previous observations indicating a higher sperm concentration among semen donors in Rennes than in Toulouse.
Cross-Sectional Studies↗
Time to pregnancy among male workers of the reinforced plastics industry in Denmark, Italy and The Netherlands. ASCLEPIOS.
OBJECTIVES: The relationship between occupational styrene exposure and male fecundity was examined. METHODS: Among 1560 Danish, Italian, and Dutch reinforced plastics workers, 220 styrene-exposed workers and 382 unexposed referents who had fathered a child were identified. A total of 768 historical styrene measurements conducted in 1970-1996 in the study companies formed the basis for semiquantitative exposure assessment in combination with measurements of urinary styrene metabolite levels. All the subjects were interviewed about work conditions and other factors potentially related to reduced fecundity. Fecundity was measured as the reported time to pregnancy (number of months a couple needed to conceive their youngest child). RESULTS: A statistically nonsignificantly reduced fecundity was observed for the styrene-exposed workers [fecundity ratio 0.79, 95% confidence interval (95% CI) 0.59-1.05]. But no consistent pattern of a detrimental effect on fecundity was found when time to pregnancy was related to worktasks indicating higher styrene exposure levels or semiquantitative or quantitative measures of styrene exposure. The workers with high exposure showed a fecundity ratio of 1.09 (95% CI 0.69-1.72). CONCLUSIONS: It is unlikely that styrene exposure has a strong effect on male fecundity.
Adult↗
Variation in adult life history and stress resistance across five species of Drosophila.
Dry weight at eclosion, adult lifespan, lifetime fecundity, lipid and carbohydrate content at eclosion, and starvation and desiccation resistance at eclosion were assayed on a long-term laboratory population of Drosophila melanogaster, and one recently wild-caught population each of four other species of Drosophila, two from the melanogaster and two from the immigrans species group. The relationships among trait means across the five species did not conform to expectations based on correlations among these traits inferred from selection studies on D. melanogaster. In particular, the expected positive relationships between fecundity and size/lipid content, lipid content and starvation resistance, carbohydrate (glycogen) content and desiccation resistance, and the expected negative relationship between lifespan and fecundity were not observed. Most traits were strongly positively correlated between sexes across species, except for fractional lipid content and starvation resistance per microgram lipid. For most traits, there was evidence for significant sexual dimorphism but the degree of dimorphism did not vary across species except in the case of adult lifespan, starvation resistance per microgram lipid, and desiccation resistance per microgram carbohydrate. Overall, D. nasuta nasuta and D. sulfurigaster neonasuta (immigrans group) were heavier at eclosion than the melanogaster group species, and tended to have somewhat higher absolute lipid content and starvation resistance. Yet, these two immigrans group species were shorter-lived and had lower average daily fecundity than the melanogaster group species. The smallest species, D. malerkotliana (melanogaster group), had relatively high daily fecundity, intermediate lifespan and high fractional lipid content, especially in females. D. ananassae (melanogaster group) had the highest absolute and fractional carbohydrate content, but its desiccation resistance per microgram carbohydrate was the lowest among the five species. In terms of overall performance, the laboratory population of D. melanogaster was clearly superior, under laboratory conditions, to the other four species if adult lifespan, lifetime fecundity, average daily fecundity, and absolute starvation and desiccation resistance are considered. This finding is contrary to several recent reports of substantially higher adult lifespan and stress resistance in recently wild-caught flies, relative to flies maintained for a long time in discrete-generation laboratory cultures. Possible explanations for these apparent anomalies are discussed in the context of the differing selection pressures likely to be experienced by Drosophila populations in laboratory versus wild environments.
Adaptation, Physiological↗
Epidemiology of male reproductive function: a field searching for tools.
BACKGROUND: An increase in the frequency of disorders of the male human reproductive organs has been described over recent decades. Neither its causes nor its consequences on fecundity, the ability of the couples to produce a live child, are clearly known. This lack of knowledge may partly be due to methodological difficulties specific to reproductive epidemiology. METHODS: We discuss the relevance and limits of some markers of the male aspects of human reproduction, focusing on semen parameters and fecundability, a measure of the probability of pregnancy. RESULTS: Semen parameters are associated with fecundability, although they have a relatively low sensitivity to detect couples with low fecundability. The study of semen parameters proved central to describe the influence of environmental factors on the male side of reproductive function. The main limitation of semen studies is low participation rates and the possible selection biases ensuing. Fecundability can be estimated by collecting waiting time to pregnancy. Its assessment in retrospective studies often excludes the least fecund, those couples remaining childless, which entails a bias and a decrease in statistical power. The prospective approach and an approach relying on the enrollment of a cross-sectional sample of the couples currently trying to obtain a pregnancy (current duration approach) do not have these limitations. Although it has never been used, the assessment of fecundability using the current duration approach is promising both for aetiologic research and monitoring. CONCLUSION: Most of the potential markers of male reproductive function are not assessed in the general population of France, with the exception of the incidence rate of testis cancer, which is currently increasing. We present some alternatives for a monitoring system of reproductive function.
Adult↗
Obesity and time to pregnancy.
BACKGROUND: Obesity may reduce fecundity. We examined the obesity-fecundity association in relation to menstrual cycle regularity, parity, smoking habits and age to gain insight into mechanisms and susceptible subgroups. METHODS: Data were provided by 7327 pregnant women enrolled in the Collaborative Perinatal Project at 12 study centres in the United States from 1959 to 1965. Prepregnancy body mass index (BMI) was analysed continuously and categorically [underweight (<18.5 kg/m2), optimal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2) and obese (>or=30.0 kg/m2)]. Adjusted fecundability odds ratios (FORs) were estimated using Cox proportional hazards modelling for discrete time data. RESULTS: Fecundity was reduced for overweight [OR=0.92, 95% confidence interval (95% CI): 0.84, 1.01] and obese (OR=0.82, 95% CI: 0.72, 0.95) women compared with optimal weight women and was more evident for obese primiparous women (OR=0.66, 95% CI: 0.49, 0.89). Fecundity remained reduced for overweight and obese women with normal menstrual cycles. Neither smoking habits nor age modified the association. CONCLUSIONS: Obesity was associated with reduced fecundity for all subgroups of women and persisted for women with regular cycles. Our results suggest that weight loss could increase fecundity for overweight and obese women, regardless of menstrual cycle regularity, parity, smoking habits and age.
Adult↗
How would a decline in sperm concentration over time influence the probability of pregnancy?
BACKGROUND: Reports have suggested a decline in sperm concentration during the second half of the 20th century. The effect of this decline on fecundability (the monthly probability of pregnancy) could be detected in principle by a study of time to pregnancy. In practice, the amplitude of this expected effect is not well known and the statistical power of time-to-pregnancy studies to detect it has not been explored. METHODS: We developed a nonparametric model to describe a temporal decline in sperm concentration using data on French semen donors. We then applied this model to 419 Danish couples planning a first pregnancy in 1992, to predict their time to pregnancy as if the pregnancy attempt had begun during earlier decades with higher sperm concentrations. Finally, we used bootstrap simulations to estimate the statistical power of prospective or retrospective studies that compared fecundability (estimated from time to pregnancy) across these time periods. We express the change in fecundability over time as a fecundability ratio (FR), with values less than 1 indicating decreased fecundability. RESULTS: We estimate that the median sperm concentration decreased by 21% from 1977 to 1992 and by 47% from 1947 to 1992. The estimated decline in fecundability with those semen changes was 7% from 1977 to 1992 (FR = 0.93, adjusted) and 15% from 1947 to 1992 (FR = 0.85, adjusted). The total numbers of couples that would be needed in prospective studies of time to pregnancy to detect these changes in fecundability (with a power of 80%) were 12,000 when comparing 1977 to 1992, and 2000 when comparing 1947 to 1992. Retrospective studies of the same size that excluded childless couples had much lower statistical power and were biased toward the null. CONCLUSION: The effect of realistic declines in sperm concentration on time to pregnancy may be observed only with studies that include several thousand couples.
Adult↗
[The reproductive history of female blood-sucking mosquitoes (Diptera, Culicidae)].
The author classifies current data on the morphology and function of normal and abnormal mosquito ovarioles, obtained with the use of intraovarian oil injections. A combined method for analysis of the female reproductive history is described, that helps elucidate the female reproductive age (the number of ovipositions), the initial fecundity (the number of normal and abnormal ovarioles), the potential fecundity in each gonotrophic cycle (the number of ovarioles with functional germarium), the total potential fecundity (the sum of potential fecundity values in each gonotrophic cycle), the actual fecundity (the number of eggs laid by females) in each gonotrophic cycle, and the total actual fecundity (the number of eggs laid over the female life). The method consists of 3 steps: (1) obtaining of an ovarian preparation, making use of an intraovarian oil injection, that permits a detailed study of every ovariole; (2) inventory of all the ovarioles in the ovary (3 methods are offered for the purpose); (3) quantitative analysis of female reproductive history. The general rule for determination of the reproductive age is as follows: every dilatation, the vestigial ones included, and every granulated site of an egg sac correspond to one reproductive cycle in a normal ovariole. Their sum in an ovariole represents the value of the female reproductive age. The number of the eggs developing in each ovariole corresponds to the number of granulated sites of the egg sac. The potential fecundity may reduce from cycle to cycle, because some ovarioles may become sterile.
Aging↗
Effect of controlled ovarian hyperstimulation on pregnancy rates after intrauterine insemination.
OBJECTIVE: Our objective was to evaluate the effect of controlled ovarian hyperstimulation on pregnancy rates after intrauterine insemination of washed husband's sperm. STUDY DESIGN: In a private practice setting at the Infertility, Gynecology, and Obstetrics Medical Group in San Diego, 79 treatment programs included intrauterine insemination during natural cycles, 195 included clomiphene stimulation, and 53 had human menopausal gonadotropin stimulation. Pregnancy rates and monthly fecundabilities were calculated by life-table analysis and compared by the Z test. RESULTS: By life-table analysis the cumulative probability of pregnancy after intrauterine insemination with no ovulation induction is 21.0% after six cycles with a monthly fecundability of 3.4%. With clomiphene the pregnancy rate is 32.7% with a monthly fecundability of 6.1%, and with human menopausal gonadotropin the pregnancy rate is 60.7% with a monthly fecundability of 13.0%. The human menopausal gonadotropin group had a significantly higher pregnancy rate and monthly fecundability as compared with the other two groups. There were no differences between the no-stimulation and the clomiphene groups. CONCLUSIONS: Human menopausal gonadotropin stimulation results in a significantly higher pregnancy rate and monthly fecundability after intrauterine insemination as compared with no stimulation or clomiphene use.
Female↗
Effect of age on intrauterine insemination with frozen donor sperm.
OBJECTIVE: To assess the effect of variables that influence the pregnancy outcome of intrauterine insemination with frozen donor sperm. METHODS: A retrospective analysis of 408 cycles of frozen donor sperm inseminations were studied. Cycle fecundity and cumulative probability of pregnancy were compared according to several variables. RESULTS: The pregnancy rate was 13.5% per treatment cycle and 57.3% per patient. By life-table analysis, the cumulative probability of pregnancy was 75.6% after 12 cycle attempts, but there was a plateau after seven cycles. The cycle fecundity after the seventh cycle was 0.05, compared with 0.16 during the first seven cycles. Age had a profound impact on cycle fecundity. The cycle fecundity for women age 35 or less, 35-40, and over 40 years old were 0.2, 0.12, and 0.06, respectively. The cumulative probability of pregnancy after seven cycles for women 35 years or younger was 88%, compared with 65 and 42% in women 35-40 and over 40 years old, respectively. The number of motile sperm inseminated for pregnant cycles was higher than that for nonpregnant cycles. The fecundity rates for cycles with five or fewer, five to ten, greater than ten to 20, and over 20 million motile sperm inseminated were 5, 11, 16, and 20%, respectively. CONCLUSION: The most significant predictors of the fertility of intrauterine insemination with frozen donor sperm were the women's age and the total number of motile sperm inseminated. Fecundity dropped after seven cycles of treatment.
Adult↗
Systemic mechanisms of individual reproductive life history in female Medflies.
This paper is the second one in a series of two papers hypothesizing and testing systemic grounds of reproductive life history in the female fruit fly. In the first paper, we analyzed mechanisms of individual fecundity scheduling and have drawn the following conclusions. Individual fecundity in female flies is endowed as a flat pattern with a steady-state period of a constant rate of egg-laying. An individual female reveals three stages in her adult life history: maturation, maturity, and senescence. The first stage is a transient period of achieving a steady state at maturity, which can be maintained until the senescence stage. Thus, an individual fecundity pattern has no maximum. The maximums observed experimentally are averaging-caused artifacts. Two natural causes of deaths exist in flies, senescence-caused ones and premature deaths, probably due to a reproductive overload. In this paper, to confirm these findings, we use individual daily scores of egg-laying in four populations of Mediterranean fruit flies. Based on fecundity scores, we divide each Medfly population into four classes, namely zero-egg, short-, medium- and long-lived egg-layers. We demonstrate that, indeed, the three above findings definitely exist in Medflies. Our procedure allows the efficient storage of individual fecundity in parametric form, with only five numbers for each fly. Finally, this protocol will allow a more precise analysis of fecundity-energy trade-offs in flies carrying appropriate longevity mutations.
Animals↗
Stability effects of a juvenile period in age-structured populations.
Prior theoretical studies have shown that the juvenile period's length is an important determinant of local stability in age-structured population dynamics. For example, both short and long periods produce stability, but intermediate lengths can cause instability. Short juvenile periods significantly increase stability (compared to no juvenile period) if fecundity is independent of adult age. Here I re-examine these and other patterns, using a model which includes a variable juvenile period, juvenile mortality, density-dependent fecundity and adult mortality, and age-dependence is adult fecundity. Among other things, the results confirm the stable-unstable-stable pattern with increasing juvenile period length, but show that the stabilizing effect of short periods disappears when fecundity varies with adult age. Broadly speaking, the results suggest that age-dependence in adult fecundity has important dynamical consequences, and that models assuming that fecundity is independent of adult age may be unreliable guides to the dynamics of populations for which this assumption is not reasonably accurate.
Animals↗
Evaluation of the postcoital test in cycles involving exogenous gonadotropins.
OBJECTIVE: To evaluate the hypothesis that a postcoital test, optimally performed in the periovulatory period of cycles in which gonadotropin-induced superovulation was used, correlates with cycle fecundity. METHODS: Of 1135 total consecutive cycles, 367 first cycles were analyzed from the reproductive endocrinology and infertility service of a university medical center. This referral population had a mean age of 34.6 years for the female partner, a nulliparity rate of 81%, and a mean length of infertility of 4.8 years. Postcoital tests were performed 36-40 hours after hCG administration in gonadotropin-stimulated cycles. Clinical pregnancy was defined as fetal cardiac activity as seen on transvaginal ultrasound examination. RESULTS: Couples with no sperm observed per high-power field in the cervical mucus achieved a 16% fecundity rate (21 pregnancies in 129 cycles), one to ten sperm a 18% fecundity rate (28 pregnancies in 154 cycles), and more than ten sperm a 15% fecundity rate (13 pregnancies in 84 cycles). There was no significant difference between groups (n = 367, P = .85); the power to detect a statistically significant difference was .82. As validation of optimal cervical mucus, fecundity rates were compared with these postcoital test values across the entire range of peak periovulatory serum estrogen levels, and no correlation was seen (P = .61, .86, and .96 for estrogen levels of 201-500, 501-1500, and 1501-3433 pg/mL, respectively). CONCLUSION: With precise periovulatory timing and supraphysiologic estrogen levels optimizing qualitative cervical mucus characteristics in gonadotropin-induced cycles, the number of sperm observed per high-power field does not correlate with cycle fecundity.
Adult↗
Reproduction response of Chinese mitten-handed crab (Eriocheir sinensis) fed different sources of dietary lipid.
The effect of feeding three semi-purified diets containing different lipid sources (anchovy oil, soybean oil and pork lard) on fecundity, hatchability and egg fatty acid composition of Chinese mitten-handed crab (Eriocheir sinensis) broodstock was compared with a fresh clam diet in a 6-month feeding trial. Broodstock crabs fed the diet containing pork lard showed poor fecundity and low hatchability. Crabs fed the diet containing soybean oil showed improved fecundity; however, no significant improvement in hatchability was observed. Broodstock fed the diet containing anchovy oil showed the highest fecundity and egg hatchability. Eggs from broodstock fed anchovy oil as sole dietary lipid had a higher n-3 polyunsaturated fatty acid (PUFA) content (33.3%) compared with those of crabs fed diets with soybean oil (20.1%) and pork lard (16.3%) as lipid sources. The results indicate a close correlation between: (1) the 20:5n-3 content of the egg lipid and fecundity; (2) the 22:6n-3 content and hatchability; and (3) fecundity, hatchability and n-3/n-6 fatty acid ratio. The results also suggest that each of these n-3 HUFAs may play different and specific roles in crab reproduction and that either must be adequate in the broodstock diet.
Animal Feed↗
Effect of X-irradiation at larval stage on adult lifespan in Drosophila melanogaster.
The effects of X-ray irradiation at larval stage with doses of 1.2, 2.1, 4.2, 7.5 and 17.1 Gy on adult longevity and fecundity in Drosophila melanogaster fruit flies were studied. A significant negative trend with increasing dose of irradiation was detected for the median lifespan in both sexes. In all experimental groups, both male and female mortality rates in irradiated flies were above control levels approximately for one month after emergence, and below control levels at older ages. The irradiation with 1.2 and 2.1 Gy resulted in 11.5% and 12.7% increase of male maximum lifespan, respectively. Irradiated females had in most cases a lower fecundity than control females. In all studied age groups, the decrease of fecundity was dose-related, and the negative effect of irradiation on fecundity was no longer observed in flies older than two weeks of age. Mean fecundity for the 4-25-day period of the irradiated females was shortened and dose-related [one-way ANOVA: F(5,414) = 10.56, P < 0.001], but significant differences from control were observed only for flies irradiated with doses of 4.2, 7.5 and 17.1 Gy. Mean fecundity for females irradiated with doses of 1.2 and 2.1 Gy did not differ from that of control females.
Aging↗