Experimental Studies on Male and Female Reproductive Success: Effects of Variation in Spur Length and Pollinator Activity on Platanthera mandarinorum ssp. hachijoensis (Orchidaceae)

Abstract Field experiments on an orchid, Platanthera mandarinorum ssp. hachijoensis , were carried out to investigate the effects of variations in spur (nectary) length and pollinator activity on reproductive success (RS) of individual plants. Experiments comprised two kinds of treatments: spur shortening and bagging to restrict pollinator activity. Plants with a natural spur lengths range show nearly equal RS, whereas plants with shortened spurs had decreased RS proportional to spur length reduction. Pollinaria attachment (a measure of male RS) to the pollinators seems to demand stricter morphological correspondence than pollen receipt (female RS). Decrease of male and female RSs in spur-treatments was smaller in the case of high pollinator activity than low pollinator activity. Results of the bagging experiments indicated that female RS was greater than male RS in cases of high pollen carryover. These facts suggest that (1) fecundity selection operates more intensely on both male and female functions in the case of low pollinator activity and more intensely on the male function in the case of high pollen carryover, and (2) individuals with different spur lengths in natural populations have nearly equal probabilities of RS after excluding the extreme variants through the reduction of male RS.     

延迟交配对昆虫生殖行为的影响以及与性信息素防治害虫的关系

对鳞翅目昆虫延迟交配对昆虫生殖力、卵孵化率、交配成功率、成虫寿命等进行了总结。雌虫延迟交配降低雌虫的生殖力、卵的孵化率及与雄虫成功交配率,但可以延长雌虫寿命。雄虫延迟交配降低雌虫的生殖力、卵的孵化率、产卵时间,雄虫的精子质量下降但寿命有所增加。已发现延迟交配在迷向法中控制害虫起着重要的作用,对进一步认识迷向法中不同作用机理以及延迟交配在迷向法防治害虫中的潜力进行了探讨。     

Effects of delayed mating on the fecundity,fertility and longevity of females of diamondback moth,Plutella xylostella

Abstract The effects of delayed mating on the copulation duration, female fertility, fecundity, egg fertility, longevity and the number days alive after mating of females of diamondback moth (DBM), Plutella xylostella, were studied. When male mating was delayed, the female fertility, fecundity, egg fertility, longevity and number days alive after mating of DBM decreased, and there was a negative correlation between the age of the moth with those variables except copulation duration. When female mating was delayed, the female fertility, fecundity, percent egg fertility and number days alive after mating of DBM also decreased, but the longevity increased, which also showed a negative relationship between the age of the moth with the variables except copulation duration and longevity. When both males and females delayed mating, the female fertility and fecundity decreased; egg fertility was affected marginally, and the longevity of females increased. The moth age was negatively correlated with those variables.     

Effects of exposure to short-term heat stress on fitness components in Drosophila melanogaster

Effects of thermal stress on survival and reproductive success in ten recently collected isofemale lines of Drosophila melanogaster were compared for flies treated as follows: always held at 25° C, placed in an incubator set at 37° C for 120 min, or exposed to 40° C in an incubator for 90 min, with or without previous exposure to 37° C. Short-term exposure to the higher temperature greatly reduced adult survival, the mating frequency of males and females, and female fecundity, which was measured as offspring produced over ten days. Male fertility, measured as the progeny produced by a female mated once, differed little among treatments. Previous exposure to a high, but non-lethal, temperature before exposure to the higher one, improved survival of males and females, and improved offspring production of females. Genetic variation was present among lines for offspring production, but genetic variation for survival was not significant, and genotype by environment interactions for fitness components of females were small. These results indicated low genetic variation in thermal resistance in the studied population, such that a threshold for temperature stress probably exists, above which local extinction is more likely than the evolution of resistance.     

The postmarsupial development of Porcellio siculoccidentalis, with some data on reproductive biology (Crustacea, Isopoda, Oniscidea)

In the broader context of research on the Sicilian Porcellio imbutus-complex, the postmarsupial development of Porcellio siculoccidentalis Viglianisi, Lombardo & Caruso, 1992 was studied in detail. This research was conducted in the laboratory under controlled conditions, allowing us to follow the stages of development, from the formation of the marsupium in ovigerous females until the larval stages and development of the seventh pair of legs. The timing of developmental stages and the morphological modifications of appendages in the postmarsupial manca stages (M I-M III) are described. The manca stage M I had a duration of about one hour. Ovigerous females were collected and reared separately, and the number of parturial molts in the absence of males was counted. The results showed a maximum of four successive parturial molts. Fecundity and fertility were evaluated as the number of eggs and embryos, respectively, inside the marsupium of the ovigerous females. Both parameters were positively correlated with the size of the females. The maximum numbers of eggs and embryos in the marsupium were 113 and 141, respectively. Data describing the total number of postmarsupial mancas released per month indicated that the highest release occurred in April.     

Females Remate for Sperm Replenishment in a Seed Bug: Evidence from Offspring Viability

Females of many insects mate multiply but why they do so remains controversial. Here we investigated the effects of multiple matings on female reproductive success of a New Zealand seed bug, Nysius huttoni. We found little evidence for females to gain material (nutritional) benefits through multiple matings because the number of matings did not have significant effect on female fecundity. Females remated to the same males or different males produced similar number of viable offspring, suggesting that females do not obtain genetic benefit from remating in terms of offspring viability. With the increase of the number of matings, however, overall fertility rate significantly increased and daily fertility rate declined significantly slower over time. These results suggest that females remate for the replenishment of sperm. Five matings are sufficient for females to maximize their reproductive success, and additional matings appear to be superfluous. However, the females of this bug mate as many as 68 times if males and females are paired for lifetime. This can be explained by the convenience hypothesis, i.e., females remate superfluously to minimize the costs of harassment by promiscuous males.     

The song of the old mother: Reproductive senescence in female drosophila

Among animals with multiple reproductive episodes, changes in adult condition over time can have profound effects on lifetime reproductive fitness and offspring performance. The changes in condition associated with senescence can be particularly acute for females who support reproductive processes from oogenesis through fertilization. The pomace fly Drosophila melanogaster is a well-established model system for exploring the physiology of reproduction and senescence. In this review, we describe how increasing maternal age in Drosophila affects reproductive fitness and offspring performance as well as the genetic foundation of these effects. Describing the processes underlying female reproductive senescence helps us understand diverse phenomena including population demographics, condition-dependent selection, sexual conflict, and transgenerational effects of maternal condition on offspring fitness. Understanding the genetic basis of reproductive senescence clarifies the nature of life-history trade-offs as well as potential ways to augment and/or limit female fertility in a variety of organisms.     

Effect of male and female multiple mating on the fecundity, fertility, and longevity of diamondback moth, Plutella xylostella (L.)

Abstract:  The effect of diamondback moth (DBM), Plutella xylostella (Lep., Plutellidae) male and female multiple mating on fecundity, fertility, and longevity was studied. Males could mate for five times with virgin females during scotophase. The successful copulation rates, fecundity of female, and longevity of both females and males decreased when male mating times increased, whereas copulation duration increased. Correlation coefficient between copulation duration and male mating times was significant ( r  = 0.7358, P = 0.0001, spearman rank-order correlation). There were linear relationships between mating history of males and longevities of males and females, and regression relationships between them were significant. Mated females had similar daily reproductive pattern, which laid the most eggs on the first day after mating in spite of their mates' mating history. Virgin females laid some infertile eggs before they died. Most of the females mated once during their lifespan but 19.9% of females mated twice when one female kept with one male during scotophase. There were no significant differences in the fecundity, fertility and longevity between the single- and twice-mated females. Correlation coefficient between copulation duration and female mating times was not significant ( r  = 0.0860, P = 0.8575). Results suggested that DBM females may be monandrous. Multiple mating did not increase male or female mating fitness.     

Altered reproductive success in rat pairs after environmental-like exposure to xenoestrogen

Endocrine-disrupting compounds (EDCs) have the capacity of altering the normal function of the endocrine system. EDCs have shown dramatic effects on the reproductive biology of aquatic wildlife and may affect human reproduction as well. Studies on EDCs in mammalian species have often investigated the effects of short-term, high doses on male and female reproductive physiology. However, it is difficult to predict from such studies the effects of EDC on populations that are exposed to very low doses throughout their life via contaminated food and water. We studied the effects of EDC on mammalian reproduction with an environmental-like protocol where the endpoint is the reproductive success of exposed pairs. We focused on a subclass of EDC, the xenoestrogens, which mimic the action of natural oestrogen hormones. Male and female rats were exposed to low doses of the pure oestrogen, ethynyloestradiol, during development, by oral administration to their mothers during pregnancy and lactation, and to them until puberty. We evaluated the effects of the exposure on development and reproductive physiology of individuals, and on fertility and fecundity of pairs in which both members had been exposed to the same treatment. We found that low doses caused major reproductive deficits in the experimental animals. Very low, environmentally relevant doses did not have evident effects on exposed animals; however, the fecundity of exposed pairs was substantially altered. Environmentally relevant doses of xenoestrogens which have no evident physiological effects can alter the reproductive success of exposed pairs in natural populations.     

Hunter-gatherer energetics and fertility: A reassessment of the !Kung San

This paper examines the question of why the total fertility rate of the !Kung San hunter-gatherers of the Northern Kalahari desert is as low as 4.69 births. When the intermediate variables involved are examined through the employment of a reproductive equation, it becomes clear that low fecundity is a major issue. Arguments offered previously to explain the low fertility of !Kung women, depending on factors such as nutrition, health status, and lactational practices are insufficient. Drawing upon recent data from sports medicine and endocrinology, I suggest that the pattern of San female energetics in their gathering and subsistence routine has a direct effect upon their fecundity. Such a correlation between activity patterns, endocrine function, and reproductive capacity may also be important for understanding the fertility of other mobile hunter-gatherer groups.     

Remating Behavior of Cnephasia jactatana Walker Females (Lepidoptera: Tortricidae)

Cnephasia jactatana Walker is an important pest of kiwifruit in New Zealand. We investigated, under laboratory conditions, the effects of multiple mating on the reproductive performance of C. jactatana females and how such effects varied with male virginity and larval nutrition. We found that in permanent pairs, remating increased female fecundity and fertility but suboptimally fed females benefited more from remating. Regardless of this benefit, mass-reared pairs had a lower remating frequency. Females remating with a virgin male or a male that had delivered a spermatophore presented similar fecundity and fertility; however, females receiving a second ejaculate from a virgin male had increased daily fecundity. Female weight clearly affected remating behavior since those that received a second ejaculate were significantly heavier. Neither mating length nor size of the first spermatophore influenced female remating. Further, mass-reared and individually reared males produced spermatophores of similar size.     

Fecundity and life table parameters of Campoletis sonorensis (Hymenoptera: Ichneumonidae), an endoparasitoid of the Cabbage Looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae), under laboratory conditions

The fecundity and life table parameters of Campoletis sonorensis females were measured using thirty 4-day-old Trichoplusia ni larvae daily at 24°C, 60% RH and a photoperiod of 12 h L:12 h D. The mean longevity was 34.5±2.8 days, the mean oviposition period was 22.7±1.9 days, and the mean constant oviposition period and the mean post-oviposition period were 15.9±1.3 and 11.9±2.2 days, respectively. The mean realised fecundity and the mean fertility differed significantly at 66.9±7.8 and 60.4±7.8 parasitoids per female, respectively. The mean sex ratio for the mean oviposition period (23 days) was 0.13±0.07, indicating a highly female biased ratio. The life table parameters were: intrinsic rate of natural increase (r _m), 0.135 female/day; gross reproductive rate (GRR), 50.30; net reproductive rate (R _o), 49.96; finite capacity for increase (λ), 1.14 female/day; mean generation time (T), 28.97 days; doubling time (DT), 5.13; capacity for increase (r _c), 0.33; and cohort generation time (T _c), 11.69. Campoletis sonorensis may be a suitable candidate for a biocontrol program of T. ni populations mostly because the primary selection criterion, r_m , obtained for this parasitoid can be similar to or larger than the rate obtained for T. ni.     

Effect of radiation on fecundity and fertility of codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) from South Africa

Codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is the key pest of pome fruit in South Africa, and it’s control in apple and pear orchards relies on the application of insecticides and pheromone‐mediated mating disruption. Development of resistance to insecticides and placement of restrictions on the use of certain insecticides has made control of codling moth in South Africa increasingly problematic. The use of the sterile insect technique (SIT) as a control tactic for codling moth is under investigation as a potential addition to the current control strategy. We investigated the radiosensitivity of a laboratory strain of codling moth that was established from moths collected from commercial and organic orchards in the Western Cape, South Africa. Fecundity and fertility of this strain following radiation were consistent with values for the codling moth strain in the Canadian rearing facility in British Columbia. For both strains, the female codling moth was considerably more radiosensitive than the male. At a radiation dose of 100 Gy or higher, treated females were 100% sterile. The fertility of the South African strain was higher (86.3%) than for the Canadian strain (71.9%). This difference in fertility between the two strains was maintained when the dose of radiation was 100 Gy. However, the level of fertility was very similar between the two strains for doses ≥150 Gy. Therefore, based upon previously published work and the data from this study, an operational dose of 150 Gy is recommended for future codling moth SIT programmes in South Africa.     

Quantitative studies on the pathogenicity of Nosema carpocapsae,a microsporidian pathogen of the codling moth,Cydia pomonella,in New Zealand

The pathogenicity of Nosema carpocapsae for codling moth was studied using dose-infectivity experiments. The IC₅₀ (median infective concentration) was similar for the five larval instars (range 4.0 × 10³ to 6.7 × 10⁴ spores/ml). Spore loads in moths ranged from 6.0 × 10⁶ to 7.1 × 10⁷ spores per moth and varied with dose and with larval age at infection. The infection does not cause mortality but does reduce the fecundity and fertility of infected moths. Nosema carpocapsae is transmitted transovarially as well as horizontally. Infected eggs were not produced by healthy females mated with infected males, although such pairs generally produced fewer eggs than healthy pairs.