Phenotypic Sex Ratio Research Articles

Selection of the families with high growth rate and high female proportion in half-smooth tongue sole(Cynoglossus semilaevis)

The present study aims to uncover the relationship between the phenotypic sex and genotypic sex and the growth rate of male and female half-smooth tongue sole and to select the excellent families with high female proportion.In this paper,we firstly established 22 half-smooth tongue sole families which were cultured in the same pond.Secondly,we identified the offspring's phenotypic sex and genotypic sex of 5 normal male families and 5 neo-male families.This study shows that there are significant differences not only in growth rate but also in proportion of male to female.Two fast-growing families(No.16 and No.61)whose relative weight gain rate were 0.81 g/d and 0.56 g/d and 4 relatively fast-growing families(No.21,No.28,No.57 and No.63),the relative weight gain rate ranges from 0.48 g/d to 0.53 g/d were selected;12 commonly-growing and 4 slow-growing families were selected also.The average ratios of genotypic female and phenotypic female of the 5 normal male(ZZ)families were 51.87% and 42.94%,and the ratio of genotypic female reversing to phenotypic male was 14.08%.Instead,the average genotypic female and phenotypic female ratio of the 5 neo-male(ZW)families was 49.34% and 4.45%,respectively,and the ratio of genotypic female reversing to phenotypic male was 91.41%.In the present study we found for the first time that there were significant differences in phenotypic sex ratio between different families.We also found that the genotypic females in neo-male families were more easily reversed to phenotypic males,which increased the number of phenotypic males in cultured populations.It initially showed that the families with high female proportion and fast growing rate could be selected via family selection,which could provide theories and new technical methods for the breeding and the production of high quality seeding of half-smooth tongue sole.

Mode of sexual differentiation and its influence on the relative sensitivity of the fathead minnow and zebrafish in the fish sexual development test

Exogenous treatment of fish with natural sex hormones and their mimics has been shown to influence gonadal differentiation resulting in biased phenotypic sex-ratios. This has lead to the development of the Fish Sexual Development Test (FSDT) as a method for the detection of endocrine active chemicals. Proposed test organisms include the medaka, zebrafish (ZF) and stickleback, although the guideline also allows for inclusion of species such as the fathead minnow (FHM), provided the test duration allows for sufficient sexual differentiation. However, although the processes underlying sexual differentiation are known to differ for each of these species, it is not known how, or if, these differences would influence the results of the FSDT. In the experiments reported here, responses of the ZF and FHM to prochloraz, a sterol biosynthesis inhibitor and androgen antagonist, were characterized and compared. Exposure to 320 μg/L of prochloraz, from embryo until 60 (ZF) or 95–125 (FHM) days post hatch inhibited somatic growth of both species, but while a negative impact on ZF larval survival was observed (LOEC 32 μg/L) there was no evidence for an effect on FHM larval survival. Prochloraz influenced sexual differentiation in both species by decreasing the proportion of females (LOEC 100 μg/L (ZF), 320 μg/L (FHM)) and delaying completion of sexual differentiation; manifest as an increased incidence of ovotestis in the ZF (LOEC 100 μg/L) and as an increased number of fish with undifferentiated gonads in the FHM (LOEC 320 μg/L). However, while exposure to 320 μg/L prochloraz delayed maturation of the differentiated FHM testis, there was no such effect in the ZF. These results demonstrate that the different strategy of sexual differentiation in the ZF and FHM influences the profile of responses of their gonads to the masculinising effects of prochloraz, but does not affect their overall sensitivity.

Contrasting sex ratios in juvenile and adult chinook salmon Oncorhynchus tshawytscha (Walbaum) from south‐west Alaska: sex reversal or differential survival?

A sex‐specific genetic marker (growth hormone pseudogene) and age‐at‐maturation data were used to infer the cause of male‐biased phenotypic sex ratios in adult chinook salmon Oncorhynchus tshawytscha from the Kwethluk and Tuluksak Rivers, south‐west Alaska. The results showed that: (1) adult genetic and phenotypic sex ratios were similar and were male biased, (2) genetic sex ratios of pre‐smolts were not male biased and (3) the average age‐at‐maturation for males was significantly less than for females. These results suggest that the sex ratio distortion is due to gender bias in marine survival probably related to gender differences in marine life‐history strategies.

Persistent sex-reversal and oviducal agenesis in adult Xenopus ( Silurana) tropicalis frogs following larval exposure to the environmental pollutant ethynylestradiol

It is known that estrogen-like environmental pollutants can feminise gonadal differentiation in frogs resulting in female-biased sex-ratios at metamorphosis. The long-term effects on reproductive function in frogs following larval exposure to pollutants are less known. Amphibian test systems which allow life-cycle studies are therefore needed. The aim of the present study was to characterise long-term estrogenic effects on the reproductive system of the emerging model species Xenopus ( Silurana) tropicalis following larval exposure to ethynylestradiol (EE 2). EE 2 is a synthetic estrogen that has been detected in sewage effluents and in surface waters. Newly hatched tadpoles (Niewkoop Faber (NF) stage 48) were exposed to the nominal EE 2 concentrations 0 (control), 1, 10, and 100 nM (with analytical chemistry support) until complete metamorphosis (NF stage 66). Effects on the reproductive organs were determined in juveniles (1 month after metamorphosis) and in 9-month-old frogs. Larval exposure to EE 2 caused female-biased phenotypic sex-ratios in both juvenile and adult frogs, which is in agreement with previous work on other frog species. Nearly all (97%) of the 63 EE 2-exposed 9-month-old frogs had ovaries. Histological evaluation of the gonads of the 9-month-old frogs showed that they were sexually mature. Among the adult frogs with ovaries there was a dose-dependent increase in the frequency of individuals lacking oviducts. Adult frogs exposed to 100 nM EE 2 that had ovaries but no oviducts had lower levels of estrogen receptor alpha (ERα) mRNA in the brain than control animals and those exposed to 100 nM EE 2 that had ovaries as well as oviducts. EE 2 exposure did not cause any significant changes in ERα mRNA levels in the ovaries of the adult frogs. The reduced level of ERα mRNA in the brain of individuals with ovaries lacking oviducts suggests an organizing effect of EE 2 on the central nervous system. The results show that transient early life-stage exposure to an environmental pollutant can induce effects on the reproductive organs and the central nervous system that persist into adulthood. Overall, our data suggest that X. tropicalis, which has a shorter generation time than the well-established model species Xenopus laevis, is a suitable model organism for research on developmental reproductive toxicity in anuran species.

Defective Reproductive Organ Morphology and Function in Domestic Rooster Embryonically Exposed to o,p′-DDT or Ethynylestradiol1

Environmental pollutants with estrogenic activity have a potential to disrupt estrogen-dependent developmental processes. The objective of this study was to investigate if embryonic exposure to the environmental estrogens o,p'-DDT (1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane; 37, 75, 150 or 300 microg/g egg) and EE2 (17alpha-ethynyl estradiol; 60 ng/g egg) affects the reproductive system in domestic roosters. Following egg injection on Embryonic Day 4, the newly hatched chicks were sexed by cloacal inspection. A skewed phenotypic sex ratio with overrepresentation of chicks deemed as females was observed in the groups exposed to the three highest doses of o,p'-DDT but not in the EE2-exposed group. Normal sex ratios were observed in all groups at adulthood. However, a cloacal deformation seemed to remain in the adult roosters, causing an abnormal semen flow upon semen collection. Semen yield was significantly reduced in both o,p'-DDT-exposed and EE2- exposed birds, whereas semen quality was unaffected. When killed, deformations of the left testis were found in all treatment groups. Image analysis revealed a reduced seminiferous tubular area in the roosters exposed to the two highest doses of o,p'-DDT. Embryonic exposure to o,p'-DDT caused decreased comb weight and right-spur diameter, while EE2 only affected right-spur diameter. In conclusion, this study shows that embryonic exposure to estrogenic compounds can induce permanent effects in male birds. The effects of the two studied compounds were partly similar but o,p'-DDT also induced alterations not seen in the EE2-treated birds.

Daily temperature shifts during the embryonic period do not alter the phenotypic sex ratio of spring-run chinook salmon

The purpose of this study was to determine whether daily-elevated water temperature shifts during the embryonic period in spring-run chinook salmon (Oncorhynchus tshawytscha) could influence the phenotypic sex ratio. Three families of salmon embryos were divided into two groups; one was moved between 7.5 °C and 12 °C each day (6–8 hours) for 105 days while the other (control) remained at a constant 7.5 °C. Sex ratios varied between the three families, but no significant sex ratio differences were observed between the control and temperature shifted groups.

Development of sex control techniques for European sea bass ( Dicentrarchus labrax L.) aquaculture: effects of dietary 17 α-methyltestosterone prior to sex differentiation

The purpose of this study was to develop a method for the hormonal masculinization of sea bass ( Dicentrarchus labrax L.) reared under natural conditions of photoperiod and temperature. Sexually undifferentiated sea bass were fed 17α-methyltestosterone (MT) at 10 mg kg −1 food during three distinct periods of 100 days each: Period I, 126–226 days post fertilization (DPF) (July–November); Period II, 226–326 DPF (November–February); Period III, 326–426 DPF (February–May), and their combinations. Phenotypic sex ratios after hormone treatment were determined by histological examination of the gonads. MT significantly increased the proportion of juvenile males from controls (79%), to 93–100% in groups for which treatment included Period I. In contrast, no significant alterations in the phenotypic sex ratio were observed when MT treatment started after this period. In groups treated with MT for more than 100 days, including Period I, growth was significantly depressed. Furthermore, when MT was given for 300 days (126–426 DPF), 7% of the fish were intersex. The effects of MT on the developing gonads were confirmed by a significant reduction of the gonadosomatic index (GSI) when treatment included Period I regardless of treatment duration. The visceral fat index (VFI) decreased with increasing durations of MT administration, denoting a lipolytic effect. However, 200 or more days after MT withdrawal, the mean VFI of MT-treated groups showed no differences with respect to that of the controls, indicating that the effects of MT on visceral fat mobilization were transitory. Similarly, reduction of the hepatosomatic index (HSI) and increase of the carcass index were found to be related to the length of MT administration, but values similar to those of controls were obtained after suppression of hormonal treatments. Survival of the treated groups was not compromised (average 76% vs. 78% in controls), and no teratological phenomena were observed. No treatments starting before Period I or of less than 100 days of duration were tested in this study; however, the acquisition of complete and functional sex reversal without any deleterious effects after MT administration during this period and the lower effectiveness of MT treatment in progressively more advanced stages of development, shows that Period I is effective for the complete and permanent masculinization of sea bass.

Sex Preselection in Swine: Altered Sex Ratios in Offspring following Surgical Insemination of Flow Sorted X‐ and Y‐Bearing Sperm

Contents: Flow cytometric sorting of X and Y chromosome‐bearing sperm into separate populations, followed by surgical insemination into the isthmus of the oviduct of mature gilts, produced litters with phenotypic sex ratios skewed in the direction of male or female according to the predicted sex of the sperm population inseminated. The skewing of the sex ratio of the offspring was predicted from flow cytometric DNA reanalysis of flow sorted sperm populations. Gilts inseminated with intact, viable flow‐sorted X‐bearing sperm produced litters of off spring that were 74% female (P < .01). Gilts inseminated with intact, viable flow‐sorted Y‐bearing sperm gave off spring that were 68% male (P < .04). These results validate the use of DNA as a marker for pre‐selecting the sex of offspring when used in conjunction with flow cytometric sorting of sperm.

Effect of using ram testis in a fry diet for Oreochromis niloticus (L.) on growth, survival and resultant phenotypic sex ratio

Effect of using ram testis in a fry diet for Oreochromis niloticus (L.) on growth, survival and resultant phenotypic sex ratio

Coning Phenology of the Cycad Macrozamia riedlei (Zamiaceae) Over a Five- Year Interval

ORNDuFF, R. (Department of Integrative Biology, University of California, Berkeley, CA 94720). Coning phenology ofthe cycad Macrozamia riedlei (Zamiaceae) over a five-year interval. Bull. Torrey Bot. Club 118: 6-11. 1991.-Phenotypic sex ratios and estimates of coning frequencies of seven populations of the Western Australian cycad Macrozamia riedlei (Fisch. ex Gaud.) C. A. Gardner have been published based on fieldwork conducted in 1983. These populations, plus two additional ones, were sampled five years later for the same traits. In addition, size classes were determined for known males, females, and plants of unknown sex, cone numbers of males and females with 1988 cones were determined, and insects associated with male cones shedding pollen were collected and identified. Of the five populations with males and females having 1983 cones, three had no individuals of either sex with 1988 cones, one had males but no females with 1988 cones, and one had males and females with 1988 cones. Two additional populations with no 1983 cones also had no 1988 cones, although these had evidence of very low levels of cone production in the intervening period. One population with a male-biased phenotypic sex ratio in 1983 had a 1:1 male: female sex ratio in 1988; two populations not sampled in 1983 had a male bias and a 1:1 phenotypic sex ratio, respectively. For the two sampling periods, a male bias prevails. Considerable interpopulation differences were present in average leaf numbers of plants with 1988 cones. Males and females were of equal size within all populations but one, where females had twice the leaf number of males. Plants with cones were larger than plants lacking cones. Cone numbers produced by males equaled those of females except in two populations, where males produced more cones than females. For males, there was no correlation between leaf number and cone number, and in all samples but one this was true for females. In one population of females, leaf number increased with cone number. The two studies support earlier suggestions that males and females of M. riedlei under natural conditions rarely produce cones in successive years, and that males produce cones more frequently than females. The absence of 1988 cones in some populations is attributed to competition and shading effects, but may also be related to the marginal conditions under which these populations grow. Fire appears to stimulate cone production by reducing competition and increasing nitrogen fixation by root-inhabiting Cyanobacteria. The percentage of plants judged to be mature in various populations ranged from 45 to 90 percent. Four species of Coleoptera, two of which are weevils, were collected from male cones shedding pollen, suggesting that insects may play a role in the pollination of this cycad.

Costs of reproduction in Nyssa sylvatica: sexual dimorphism in reproductive frequency and nutrient flux.

We examined the influence of differential reproductive frequency between the sexes on tertiary (phenotypic) sex ratios in the the dioecious tree Nyssa sylvatica (Nyssaceae). Reproduction was evaluated in relation to sex, size and canopy exposure using flowering data collected from 1229 marked trees over a four year period. For subsets of each population we used data on flower number, fruit crop size, fruit/flower ratios, and individual flower and fruit mass to compare biomass invested in reproductive structures of males and females. We also examined seasonal changes in stem nitrogen and soluble carbohydrate content in relation to flower and fruit production for trees of each sex. Our results indicate that: 1) Male-biased tertiary sex ratios could be explained by more frequent reproduction by male trees; 2) Estimated secondary sex ratios based on sums of all known males and females were not significantly different from 1:1; 3) Flowering frequency of males and females was significantly related to plant size (DBH) and exposure of the canopy to light; 4) Estimtes of reproductive biomass allocation ranged from 1.36 to 10.8 times greater for females relative to males; 5) Flower production was related to stem nutrient status for both sexes, but nutrient depletion and its effect on subsequent flowering was much more pronounced for female trees. We conclude that less frequent flowering by female trees may result from depletion of stored reserves, and that differential flowering frequency in N. sylvatica may ultimately reduce apparent sexual differences in the costs of reproduction.

Transitional range of temperature, pivotal temperatures and thermosensitive stages for sex determination in reptiles

Abstract The function relating phenotypic sex ratio to incubation temperature in reptiles can vary in a number of ways in addition to simple differences in the temperatures giving 50% of each sex. This paper offers terminology and definitions for describing these relationships. These definitions accomodate interactions between genetic and environmental effects on sexual differentiation, and variability within populations. The paper also discusses the concept of a sensitive stage/period within incubation during which temperature can affect the direction of sexual differentiation. Thermosensitive period has previously been assessed in a variety of ways. A suggestion for a more general way of defining thermosensitive stage/period is made.

Sex preselection in rabbits: live births from X and Y sperm separated by DNA and cell sorting.

Intact, viable X and Y chromosome-bearing sperm populations of the rabbit were separated according to DNA content with a flow cytometer/cell sorter. Reanalysis for DNA of an aliquot from each sorted population showed purities of 86% for X-bearing sperm and 81% for Y-bearing sperm populations. Sorted sperm were surgically inseminated into the uterus of rabbits. From does inseminated with sorted X-bearing sperm, 94% of the offspring born were females. From does inseminated with sorted Y-bearing sperm from the same ejaculates, 81% of the offspring were males. The probability of the phenotypic sex ratios differing from 50:50 were p less than 0.0003 for X-sorted sperm and p less than 0.004 for Y-sorted sperm. Thus, the phenotypic sex ratio at birth was accurately predicted from the flow-cytometrically measured proportion of X- and Y-bearing sperm used for insemination.

Size distribution and coning behaviour of the Australian cycad Lepidozamia peroffskyana

AbstractLeaf numbers as an estimate of sexual maturity and presence of current and previous season's cones were determined for individuals sampled in two populations of Lepidozamia peroffskyana near Dorrigo and Sealy Lookout, New South Wales, Australia. Average leaf numbers of known males and females were not significantly different. Average leaf numbers of plants showing no evidence of coning were lower than for coning individuals, suggesting that both populations contain substantial numbers of immature plants. About half the plants in both populations were putatively mature, but only 12% of such individuals in the Dorrigo population bore current season's cones compared with 51% in the Lookout population; 28% of the Dorrigo plants and 5% of the Lookout plants showed evidence of prior coning. Thus, in each population, not all mature plants produce cones during a given reproductive episode. The proportion that does so appears to vary from year to year. Cone production by individuals of each sex appears to be separated by several‐year intervals. The few plants with current season's cones in the Dorrigo population prevented determining a phenotypic sex ratio there, but for the Lookout population it was not statistically different from 1:1 male:female. The weevil Tranes lyterioides was abundant on two male cones that were entering the pollination phase in the Lookout population, suggesting that it may be involved in the pollination of this cycad.

Sex Ratios and Coning Frequency of the Cycad Zamia pumila L. (Zamiaceae) in the Dominican Republic

In January 1985, features of coning behavior were examined in three populations of the cycad Zamia pumila (Zamiaceae) growing in different environmental conditions in the Dominican Republic. One population exists in a state of semi-cultivation in the relatively open lawns of the National Botanical Garden, Santo Domingo. A second occurs in moderately open areas at the edge of a second-growth forest at Boca Chica, and a third occupies shaded areas under the canopy of a relatively undisturbed forest at Bayahibe. One-third of the botanical garden females bore cones from the current and previous season, whereas only 9 percent of the Boca Chica females showed successive coning and none of the Bayahibe plants did. Four percent of the mature individuals in the botanical garden showed no evidence of coning in either season, whereas one-third and two-thirds of those in the latter two populations, respectively, fell into this non-coning category. The phenotypic sex ratio for the botanical garden and the Boca Chica populations was 1:1. Since nearly all individuals at the first site produced cones and thus were assignable to sex, the genotypic sex ratio of that population was 1:1. A male bias was evident at Bayahibe, where 73 percent of the coning individuals were male. Where environmental conditions are most favorable, the energetically costly female cones appear to be produced more frequently and by a greater proportion of females than where these conditions are less favorable. These environmental differences thus influence the phenotypic sex ratio, which is equality under good to excellent environmental conditions, but male-biased under less favorable environmental conditions under which fewer females than males produce cones each season. DESPITE CONSIDERABLE RECENT INTEREST in the population biology of dioecious seed plants, little attention has been paid to gymnosperms, even though some of these, such as the cycads, show striking sexual dimorphism in their allocation of resources to cones during episodes of sexual reproduction. Of the 75 taxa of seed plants for which published sex ratios were summarized by Willson (1983), only two are gymnosperms (two species of Dacrydium, Podocarpaceae). Since Willson's summary appeared, a study including data on sex ratios and coning frequencies for a population of the New World cycad Zamia pumila L. in Puerto Rico was published by Newell (1983), and another has been published dealing with similar features of the cycad Macrozamia riedlei (Fisch. ex Gaud.) C. A. Gardner in Western Australia (Ornduff 1986). The present paper is concerned with coning behavior and sex ratios in Zamia pumila, and extends observations from the Puerto Rican population studied by Newell to three populations growing under different environmental conditions in the Dominican Republic.

Maternal dietary sodium chloride levels affect the sex ratio in rat litters

Eighty-eight adult female rats were fed diets containing either 0.08, 0.12, 1, 3, or 4% NaCl for at least one week prior to breeding and throughout gestation. Within 24 hours of birth, all pups were sexed based on anogenital distance, and the numbers of males and females were recorded. The amount of sodium chloride in mother rats' diets was inversely related to the proportion of phenotypic males in the litter. As dietary salt increased, the proportion of males decreased. These alterations in dietary NaCl affected the sex ratio without disrupting litter size or the general health of the offspring. Dietary mineral content may affect the phenotypic sex ratio through changes in the genotypic sex ratio, or alternatively, via changes in the environment in which the genes are expressed. These findings are important for basic research concerning maternal nutrition and development.