Progeny Sex Ratio Research Articles

Influence of Nest Hole Selection on Sex Ratio and Progeny Size in Osmia lignaria propinqua (Hymenoptera: Megachilidae)

The effect on sex ratio and size of progeny produced was examined for a greenhouse population of the gregarious bee Osmia lignaria propinqua Cresson under conditions of unlimited nest holes of four diameters. Significantly more female progeny (the larger sex) were produced in wide-diameter holes than in narrow-diameter holes. Progeny of both sexes were significantly larger in wider holes than in narrow holes. A significant interaction of sex and straw diameter suggests that females increased in size more than males with increasing hole diameter. Females made little selection based on hole diameter with two exceptions: few nests were made in the narrowest hole diameter (5 mm); and there was a minor, but statistically significant tendency for larger bees to make a greater proportion of their nests in the widest hole sizes (7 and 8 mm), but this trend accounted for only 17% of the variance. Possible reasons for the lack of specialization by females are discussed. Workers who want to use this bee as a commercial pollinator should provide them with nesting holes of 7 and 8 mm diameter.

Laboratory studies on the biology ofSpalangia nigra [Hym.: Pteromalidae

At 21 °C,Spalangia nigra Latreille (Hymenoptera: Pteromalidae) averaged 29.3 days between exposure and emergence of 1st progeny from host house flies,Musca domestica L. (Diptera: Muscidae). At 27 °C, the average developmental time to 1st emergence was reduced to 26.6 days, and a majority of adult wasps emerged from host house fly puparia between 29 and 40 days postoviposition. The sex ratio of progeny ranged from 1.4 to 1.8 female-to-male, but all progeny of virgin females were male. Male wasps lived from 6.8–15 and females 11–17.8 days at 27 °C; honey as a food source increased longevity. No significant differences in parasitism byS. nigra were associated with host house fly pupal densities ranging from 1 to 200 pupae per female-male pair of wasps, but average percent parasitism decreased at host densities greater than 50. House fly pupae exposed to parasitism at ages ranging from 4 to 96 h did not differ in subsequent production of adult flies.S. nigra did not demonstrate preference for house flies or stable flies,Stomoxys calcitrans (L.) (Diptera: Muscidae) as hosts. The results of these studies indicate thatS. nigra may contribute significantly to previously unexplained mortality of house flies and stable flies.

Effect of prolonged frequency of mating by the male rat on his fertility and on the sex ratio of his offspring

Sixteen male rats were allowed to mate with five intact primiparous females over a period of 5 days at the beginning (initial mating), middle (second mating) and end (third mating) of an experiment lasting 89 days. During the intervals between matings (Period 1 and 2) each male was housed with two ovariectomized, oestrogen and progesterone treated stimulus females changed every day to utilize the “Coolidge effect”. Males copulated with stimulus females throughout the experiment. There was a significant trend toward a decrease in the number of inseminated females towards the end of the experiment. Of 240 females mated during the matings 162 gave birth. The proportion of females which gave birth did not significantly decrease with each mating. The sex ratio of progeny (males/females) following the second (mean ± S.E., 0.91 ± 0.10) and third (0.86 ± 0.08) matings was significantly lower than after the initial mating (1.24 ± 0.15). In conclusion, continual ejaculatory activity did not influence a male's fertilizing ability even after a prolonged period (65 days). On the other hand, it did affect the sex ratio of offspring, decreasing the proportion of male progeny.

Constant Sex Ratios of Progeny in Nutritionally Stressed Wild House Mice

Constant Sex Ratios of Progeny in Nutritionally Stressed Wild House Mice

Birth Measurements, Parturition Dates, and Progeny Sex Ratio of Dama dama in Donana, Spain

Birth Measurements, Parturition Dates, and Progeny Sex Ratio of Dama dama in Donana, Spain

Alternation of Sex Ratio in a Partially Bivoltine Bee, Megachile rotundata (Hymenoptera: Megachilidae)

Data on offspring production by the alfalfa leafcutting bee, Megachile rotundata (F.), from three site-years were used to examine predictions of parental investment and sex ratio theory. In northern Utah, spring-emergent adults produce two types of offspring: those that develop directly to the adult stage and emerge in midsummer, and those that develop to the prepupal stage and enter diapause until the following year. For species with this kind of life cycle, it has been hypothesized that spring parents should bias their investment in summer emergent progeny towards females if spring males survive to participate in the summer mating. Results from all site-years support the theory. The sex ratio of summer-emergent progeny is always biased towards females, that of diapausing progeny is usually biased towards males, and there is always a significant difference between the two; and there is no difference in the sex ratio of diapausing offspring, whether produced by the spring or summer generations. However, the main premise of the theory remains unsubstantiated: in a preliminary estimate, we found the probability that spring males participate in summer matings to be very low. The import of the unexpected finding that diapausing progeny are 50% larger than summer-emergent progeny is discussed.

REARING AND HOST AGE SUITABILITY OF FANNIA CANICULARIS (L.) (DIPTERA: MUSCIDAE) FOR PARASITIZATION BY MUSCIDIFURAX ZARAPTOR KOGAN AND LEGNER (HYMENOPTERA: PTEROMALIDAE)

AbstractThe fecundity and sex ratio of progeny of Muscidifurax zaraptor Kogan and Legner were assessed on <1-day-old to >9-day-old Fannia canicularis (L.) pupae. Two age classes of parasites (1 day old and 2–3 days old) were used. Host age did not significantly affect production of progeny. Mean number of progeny per female increased in both parasite age groups on 3 successive days of host-exposure as the parasites aged: 4.5, 7.4, and 10.4 progeny per female were produced for the 1-day-old parasites and 7.6, 10.4, and 11.8 progeny per female were produced for the 2- to 3-day-old parasites. Sex ratio of progeny was not significantly affected by host age, averaging 77% females (range 63–92%). Mass rearing of F. canicularis on used M. domestica medium is described.

Influence of Some Environmental Factors on the Laboratory Production of Cotesia melanoscela (Braconidae: Hymenoptera): A Larval Parasitoid of Lymantria dispar

Environmental factors hypothesized to affect production of the Korean strain of the parasitoid, Cotesia melanoscela Ratzeburg, from larvae of the gypsy moth, Lymantria dispar L., were examined to determine the optimum conditions for mass rearing. Maximum parasitoid production occurred with an exposure time of 24 h, a parasitoid : host (P:H) density of 5:50, an oviposition temperature of 28°C, use of first- and second-instar hosts, use of 8-d-old ovipositing females, and with exposure of ovipositing females to a light intensity of 1,452 lux. Neither the presence of males within oviposition cups nor time of day (a.m. or p.m.) significantly influenced the number of progeny produced or their sex ratio (P = 0.05). Among those external factors examined, only age of female parasitoid significantly altered the sex ratio of progeny.

Reproductive Response of Glyptapanteles flavicoxis (Hymenoptera: Braconidae) to Various Densities and Instars of the Gypsy Moth, Lymantria dispar (Lepidoptera: Lymantriidae)

The reproductive response of the gregarious parasite, Glyptapanteles flavicoxis (Marsh), to instars 2-5 of Lymantria dispar (L.) was examined for five host densities (1, 2, 4, 8, and 16 hosts per d). Fecundity was the same at all host densities and instars, but was positively correlated with female longevity. Production of progeny was generally highest on the day females emerged and decreased as the parasites aged. The most hosts parasitized during a 24-h period for any parasite was 12, with an average of 3.7 hosts for parasites exposed to 16 hosts per d. The parasitization rate of G. flavicoxis exhibited a type 2 functional response, such that total numbers of hosts parasitized increased with host densities, but the percentage declined. Females attacked greater numbers of early (second-third) instars than late (fourth-fifth) instars, but the number of progeny per parasitized host increased with host instar. Conversely, fewer progeny were produced per parasitized host as host density increased. Host density did not have any effect on sex ratio (percentage of females), but the sex ratio in progeny of females ovipositing in late instars was higher than in those ovipositing in early instars.

Labile Sex Ratios in Wasps and Bees

separate sexes, it is a question about sex ratios of a female's progeny. In this article, I describe recent work on sex allocation in wasps and bees. Wasps and bees do not change sex, as do some plants and other animals. However, they have an impressive ability to control the sex of their offspring (facultative or labile sex-ratio control), and do so in some amazing ways. Insights gained from studies of these insects apply to many other reproductive systems.

Effects of mating on the oviposition behaviour of the parasitic wasp,Apanteles glomeratus L. (Hymenoptera: Braconidae)

The oviposition behaviour of mated or virgin females of the parasitic wasp,Apanteles glomeratus L., was investigated. Virgin females laid fewer eggs in a shorter time than did mated females (P<0.01), though the attack ratio and attack time of these 2 female types were the same. Progeny sex ratios of mated females suggested the occurrence of sperm shortage, because old mated females produced clutches of a high male proportion, sometimes consisting of males only. Recopulation of females was also observed, but actual insemination did not occur, and therefore,A. glomeratus females are considered to be fundamentally monogamous.

Plasticity in life-history traits of the bark beetle Ips calligraphus as influenced by phloem thickness.

Reproduction and development of Ips calligraphus (Germar) (Coleoptera: Scolytidae) occur primarily in the phloem (inner bark) tissue of its pine hosts. In slash pine (Pinus elliottii Engelm. var. elliottii), phloem thickness can vary widely from tree to tree. We compared adult residence time and fecundity and progeny development time, body size, and sex ratio of this beetle when reared in slash pine bolts and bark slabs with phloem thicker or thinner than average adult body width. Most studies were conducted at 20°, 25°, and 30° C. Residence time of parent males and females decreased with increasing temperature but it was not affected by phloem thickness. Residence time of parent males was about 2 days shorter than that of parent females at each temperature. Reproductive fitness was greater in thick phloem at all temperatures as measured by faster larval development, earlier emergence of progeny (F 1 ) adults, and emergence of more progeny adults per parent female. Progeny survival was similar between phloem those from thick phloem, and their sex ratio was female biased (1:2 vs 1:1, male:female). When allowed to inhabit thick phloem, the progeny (F 2) of adults from thin phloem were just as large and of similar sex ratio (1:1) as were progeny of F 1 adults from thick phloem. The high degree of plasticity in the life-history traits of this beetle may enable it to successfully colonize pines that vary widely in phloem thickness.

Evolutionary conflict over the control of offspring sex ratio

There are many theories which predict how animals should control the sex ratio of their offspring. In diploids, however, such control is rarely seen. Two explanations have been suggested for this. One is that parents are simply unable to control the sex ratio of their offspring. The other is that sperm actively oppose such control. This paper examines the possibilities and consequences of parent-gamete conflict over the sex ratio. Such conflict may occur between any of the parties concerned--sperm, ova, fathers, mothers, offspring. It is concluded that gametes are indeed almost always opposed to any parental manipulation of the sex ratio. However, it is probable that the rarity of adaptive parental control of progeny sex ratio in diploids is because parents are physiologically incapable of altering the sex ratio.

雌性発生2倍体キンギョの同胞群別性比について

雌性発生2倍体キンギョの同胞群別性比について

The reproductive strategy of the gregarious parasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae) : 2. Host size discrimination and regulation of the number and sex ratio of progeny in a single host.

Host size of Pteromalus puparum, a gregarious pupal parasitoid, shows a wide inter- and intraspecific variation. Experiments were made to study the regulation of the number and sex ratio of progeny per host by the parasitoid. The parasitoid could discriminate inter- and intraspecific size differences of the host and regulate the number of eggs according to the host size when a single female attacked the host. The sex ratio of progeny (proportion males) was about 0.1. The number of progeny laid by the female agreed with the energetically most efficient number og eggs in order to maximize total weight of progeny per host but not with the reproductively most efficient number of eggs to maximize the total fecundity of the progeny. The parasitoid laid smaller number of eggs in a half buried host, but the number was much larger than a half of those in a fully exposed host. When more than one female attacked a single host, the number and sex ratio of progeny per host increased with the number of females attacking the host, but the number of progeny per female decreased. The change of the sex ratio agreed with the prediction of the local mate competition model.

Nesting Behavior of Ammophila harti (Fernald) (Hymenoptera: Sphecidae)

The nesting behavior of Ammophila harti was studied during 1982-1984 in a sandy region of central New York. Two to three generations occurred per year. First generation females were more active in the morning while second generation females were equally active in the morning and afternoon; in addition, the activity rate (observed behaviors/female/hr) of second generation females was greater than that of first generation females. Females maintained several nests simultaneously; first generation females maintained fewer nests per week but more nests per lifetime than second generation females. The nest was short and unicellular, contained a single wasp larva, and was provisioned progressively with mostly Geometridae and Noctuidae larvae over several days. Cell depth decreased over the summer and was influenced by the moisture content of the sand; nests located in wetter sand were consistently shallower than nests located in drier sand. Use of nests differed between generations with more use occurring in the first generation. Active success (nests containing wasp progeny/nests used) and reproductive efficiency (nests containing wasp progeny/all constructed nests) were equal in both generations. The sex ratio of the wasp progeny of each generation differed; a 1:3.13 ratio (males: females) occurred in the first generation progeny and a 1.2:1 ratio in the second generation progeny.

Influence of Age of Female Glyptapanteles flavicoxis (Marsh) (Hymenoptera: Braconidae) and Its Periodicity of Oviposition Activity on Levels of Parasitism and Reproductive Output

Glyptapanteles flavicoxis oviposition activity, progeny production, and progeny sex ratio were studied in relation to parental female age in the laboratory. The daily percentage of hosts successfully parasitized, total number of progeny produced, and percentage of female progeny all declined with parental female age. Greater success in parasitizing hosts was achieved in the morning (9–12 a.m.) than in the afternoon (1–4 p.m.) when given equal numbers of hosts. Female age had no significant effect on this trend.

SEX RATIO, PARENTAL INVESTMENT, AND INTERPARENT VARIABILITY IN NESTING SUCCESS IN A SOLITARY BEE.

Observations of uniquely marked females of the solitary, twig-nesting bee, Osmia bruneri, were conducted under greenhouse conditions to test several predictions of sex-ratio and parental-investment theory. In support of Fisher's (1958) theory, we found that the observed sex-ratio of progeny in this dimorphic species did not differ from that expected on the basis of average male and female weights. Investment patterns also exhibited a seasonal component: female parents produced more female than male offspring early in the nesting season but reversed this pattern later. Interfemale variability was large for all nesting parameters examined. Neither female-parent size nor the rate at which females completed cells was significantly related to several estimates of parent fitness. Parent-offspring heritability for size was also low. We found no evidence to support the hypothesis that progeny sex-ratios are influenced by maternal condition. Variance in progeny sex-ratios was large, but the population sex-ratio probably departs frequently from the equilibrium value. The results marginally support Kolman's (1960) prediction of large variance in progeny sex-ratios in large panmictic populations. We conclude that variability among females in investment patterns and variability in size among progenies are probably maintained by such factors as resource heterogeneity and the shape of the adult survivorship curve.

The relationship of relative gene dose to the complex phenotype of the daughterless locus in Drosophila.

The daughterless (da) gene provides an essential maternally supplied component for Drosophila sex determination and dosage compensation. In this connection, it is required as a positive regulator of a female-specific master regulatory gene, Sex-lethal (Sxl). In addition, zygotic da gene function is required for male and female viability. Thus, the phenotype da is complex; it includes both maternal and zygotic aspects, as well as both sex-specific and nonsex-specific aspects. Assessment of wild-type da function has relied on the characterization of only a single leaky mutant da allele. In order to better understand the nature of this allele and the relationships between the various aspects of its complex phenotype, tandem duplications of both the mutant and wild-type da alleles were isolated and used in a dose study of this gene's function. Three conclusions were reached: 1) by the most stringent genetic criteria, the mutant da allele is a simple hypomorph, an allele with reduced but non-zero levels of wild-type functions; 2) since increased dose of da+ had no effect on viability or progeny sex ratio, this gene seems not to be a dose-sensitive element of the X/A ratio sex determination signal; and 3) expression of the maternal da+ allele does make a contribution to the nonsex-specific developmental processes that require zygotic da+ function; however, that contribution is clearly minor. In contrast, the zygotic genotype with respect to da appears to have no effect on the expression of Sxl+ in the zygote, the sex-specific process that requires maternal da+ function.

Anti-male (anti-H-Y) male treatment influences progeny sex ratio

Published data on progeny sex ratio changes resulting from induction or administration of anti-male antibody in parental generation were compared by Fisher's independent test of significance. Sex ratio (males/total) depression is highly significant ( P < 0.001). Our large sample size data confirm this result; significant progeny sex ratio decrease follows active anti-H-Y maternal immunization in mice or passive immunization in D. melanogaster.