ST Males Research Articles

Impacts of Sex Ratio Meiotic Drive on Genome Structure and Function in a Stalk-Eyed Fly.

Stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio (SR) meiotic drive and impact the fitness of male and female carriers. Here, we assemble and describe a chromosome-level genome assembly of the stalk-eyed fly, Teleopsis dalmanni, to elucidate patterns of divergence associated with SR. The genome contains tens of thousands of transposable element (TE) insertions and hundreds of transcriptionally and insertionally active TE families. By resequencing pools of SR and ST males using short and long reads, we find widespread differentiation and divergence between XSR and XST associated with multiple nested inversions involving most of the SR haplotype. Examination of genomic coverage and gene expression data revealed seven X-linked genes with elevated expression and coverage in SR males. The most extreme and likely drive candidate involves an XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and associated with regulation of TE expression. In addition, we find evidence for rapid protein evolution between XSR and XST for testis expressed and novel genes, that is, either recent duplicates or lacking a Dipteran ortholog, including an X-linked duplicate of maelstrom, which is also involved in TE silencing. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species.

Effects of sex and early rearing condition on adult behavior, health, and well-being in captive chimpanzees (Pan troglodytes)

Scientific evaluation of management strategies for captive species is part of the establishment of best practices for animal welfare. Here we report the effects of sex, rearing, and a sex-by-rearing interaction on adult, captive chimpanzees’ (Pan troglodytes) behavior, health, well-being, personality, and orientation towards humans based on multiple methods (observation, animal records, and surveys). Chimpanzees raised in three conditions, mother-reared (MR), standard nursery (ST) and an experimental nursery (RC), were assessed approximately 20 years after their differential rearing experiences concluded. Sex had a significant effect on behavior towards conspecifics (aggression [M > F]; affiliation [F > M]), on abnormal behavior (rocking [M > F]), and on likelihood of incurring at least one injury (between ages 6 and 10 [M > F]). Rearing condition had a significant impact on behavior towards humans (negative solicitation [RC = ST > MR = ST]; neutral behavior [RC > ST > MR], yawning (RC = ST > MR = ST), subjective well-being (MR = ST > RC = ST), and on GI illness frequency (RC > ST = MR). Sex interacted with rearing on aggression towards humans (for males, RC > MR = ST), frequency of upper respiratory infection (URI: for males RC > MR = ST)) and likelihood of at least one URI between the ages of 11 and 15 (RC males > ST males). Our findings support the conclusion that there are long-term effects of both early rearing and sex on captive adult chimpanzee welfare.

Gender and Circadian Effects of Myocardial Infarctions

This study determines if there are differences in circadian effects of myocardial infarctions (MIs) and MI type, non-ST elevation MI (NSTEMI) and ST elevation MI (STEMI), between females and males. A two-group, nonexperimental chart review was conducted. A total of 273 randomly selected patients with an acute MI were included. Data analysis included descriptive statistics, t test and chi square to determine differences between the groups. Of the 109 females, 26% had MI symptoms begin at night, 30% in the morning, 29% in the afternoon, and 15% in the evening (p = .067). In comparison, of the 164 males, 27% had MIs at night, 30% morning, 32% afternoon, and 11% evening (p < .001). There was no circadian difference between females and males and the time of day MI-related symptoms began (p = .887) or a MItype circadian effect (p = 0.466). The majority of patients had MIs during the daytime hours.

SEX RATIO DISTORTER REDUCES SPERM COMPETITIVE ABILITY IN AN INSECT

Selfish genetic elements (SGEs) are ubiquitous in animals and often associated with low male fertility due to reduced sperm number in male carriers. In the fruit fly Drosophila pseudoobscura, the meiotic driving X chromosome "sex ratio" kills Y-bearing sperm in carrier males (SR males), resulting in female only broods. We competed SR males against the ejaculates of noncarrying standard males (ST males), and quantified the number of sperm transferred by SR and ST males to females. We show that SR males are very poor sperm competitors, which is partly related to transfer of fewer sperm during mating. However, sperm numbers alone cannot explain the observed paternity reduction, indicating SR males' sperm may be of reduced quality, possibly due to damage during the killing of the noncarrying Y-sperm. The reduction in sperm competitive ability due to SR is large enough to potentially stabilize the spread of sex ratio drive through populations. The poor sperm competitive ability of SR males coupled with their low fitness as mates could favor increased remating by females to reduce paternity by SR males. Given the generally poor performance of SGE-carrying males in sperm competition, this may generate strong selective pressure favoring polyandry in many species.

Sperm development, age and sex chromosome meiotic drive in the stalk-eyed fly, Cyrtodiopsis whitei.

The cytological basis of X chromosome meiotic drive or sex ratio (SR) has been reported for several species of Drosophila but not for other species. Here we describe how sperm development in the stalk-eyed fly, Cyrtodiopsis whitei, influences progeny sex proportion, in order to determine if a common developmental mechanism could cause meiotic drive in these distantly related taxa. Because age has been found to affect the degree of segregation distortion in some Drosophila, we tested flies from six to 26 weeks of age. We find that spermatocyst bundles in SR males frequently contain incompletely elongated spermatid nuclei independently of male age. Older males have, however, more spermatocyst bundles in their testes than younger males. Abnormal spermatid elongation affects male fertility since SR males produce 74% as many progeny per week as ST males. The proportion of spermatocyst bundles with improperly elongated spermatid nuclei explains 71% of the variation in progeny sex proportion. After reviewing the literature on sperm development and meiotic drive, we conclude that the cytological basis of meiotic drive in diopsids closely resembles Drosophila. Across species in both groups, the production of fertile males is associated with less than half of all spermatids not elongating normally in a spermatocyst bundle. We discuss the possibility that frequency-dependent selection on male fertility could stabilize the drive polymorphism in these unusual flies.

Reproductive performance in male European sea bass ( Dicentrarchus labrax, L.) fed two PUFA-enriched experimental diets: a comparison with males fed a wet diet

Reproductive performance of male European sea bass ( Dicentrarchus labrax) fed a wet diet (WD) was compared to that of fish fed two commercial pelleted diet enriched with polyunsaturated fatty acids (PUFAs) by the use of Northern hemisphere fish oil (ST) or tuna orbital oil (RO). Broodstock growth, spermiation duration, milt production, milt spermatozoa density, sperm motility, milt lipid composition, and fertilization rates were compared during the reproductive season. RO and ST males exhibited longer spermiation periods producing statistically higher milt volumes and milt spermatozoa densities as compared to WD; no differences in quality or motility of sperm were observed between groups. Although the fertilization rates of RO, ST and WD milt at 3 and 24 h after fertilization were similar (88–90%), significantly higher rates of embryonic and larval survival were observed at 48 and 72 h after fertilization from eggs fertilized with ST (13.9% and 15.5%) and RO milt (20.9% and 20.6%) as compared to WD (1.0% and 1.2%). Analysis of milt PUFA profiles revealed several differences between groups. Although total PUFAs were increased in all groups as compared to diet PUFA composition, a greater increase was noted for ST and RO. In January and March, fish fed the WD exhibited more weight gain and attained significantly higher weights, respectively, than RO fish. Results showed that although fish fed the WD displayed increased weight gain, reproductive performance was enhanced in males fed the commercially fabricated diets possibly reflecting benefits of PUFA-enrichment.

How does the immune network learn?

Scientific evaluation of management strategies for captive species is part of the establishment of best practices for animal welfare. Here we report the effects of sex, rearing, and a sex-by-rearing interaction on adult, captive chimpanzees’ (Pan troglodytes) behavior, health, well-being, personality, and orientation towards humans based on multiple methods (observation, animal records, and surveys). Chimpanzees raised in three conditions, mother-reared (MR), standard nursery (ST) and an experimental nursery (RC), were assessed approximately 20 years after their differential rearing experiences concluded. Sex had a significant effect on behavior towards conspecifics (aggression [M > F]; affiliation [F > M]), on abnormal behavior (rocking [M > F]), and on likelihood of incurring at least one injury (between ages 6 and 10 [M > F]). Rearing condition had a significant impact on behavior towards humans (negative solicitation [RC = ST > MR = ST]; neutral behavior [RC > ST > MR], yawning (RC = ST > MR = ST), subjective well-being (MR = ST > RC = ST), and on GI illness frequency (RC > ST = MR). Sex interacted with rearing on aggression towards humans (for males, RC > MR = ST), frequency of upper respiratory infection (URI: for males RC > MR = ST)) and likelihood of at least one URI between the ages of 11 and 15 (RC males > ST males). Our findings support the conclusion that there are long-term effects of both early rearing and sex on captive adult chimpanzee welfare.

Sexual selection in mice. VI. Effects of fostering.

Individually, 10 male mice of both the albino (ST/bJ) and black-agouti (CBA/J) strains were taken at birth, fostered to females of the other strain, and reared with their litters. At weaning each male was paired with one of its foster brothers and placed in a separate cage. When the males were 90 days of age, a single albino (ST/bJ) female was placed in each pen. Ten litters were obtained from each competition cage, yielding a total of 100 litters for each type of fostering. In those cases where CBA males had been reared with ST litters, both males were equally successful in reproduction. However, in the reverse situation, where ST males had been reared with CBA litters, the ST males enjoyed a distinct reproductive advantage. These results are compared to those obtained in a previous sexual selection experiment, using the same strains of mice but without fostering. In addition, the results of fighting experiments between males from these strains and the implications of those results for the present study are discussed.

MULTIPLE MATING AND THE "SEX-RATIO" TRAIT IN DROSOPHILA PSEUDOOBSCURA.

The sex-ratio polymorphism (SR) of Drosophila pseudoobscura provides a particularly interesting system for study since it appears to be maintained in nature by a balance between and selection. The trait is a sex-linked condition which causes males to produce predominantly X-bearing sperm. Approximately 99% of progeny of their mates are females. Since corresponding value for normal males is 50%, SR chrolaosome may enjoy nearly a two-fold advantage in transmission over standard X chromosome (ST). A two-fold advantage is an extremely powerful force in evolutionary terms. Herein lies problem: despite advantage, SR is maintained in apparent equilibrium through much of southern portion of species range (Dobzhansky, 1958). In cage populations, SR is rapidly reduced in frequency or eliminated (Wallace, 1948; Anderson, 1968), and although Wallace found some of SR genotypes, particularly SR/SR females, to be at a selective disadvantage, fitnesses he measured were insufficient to account for its elimination (Edwards, 1961). Policansky and Ellison (1970) proposed a solution: since mechanism of SR involves elimination of half of spermatids per spermatid bundle in SR males, they suggested that SR males transfer fewer sperm and therefore fertilize fewer eggs than ST males. Policansky (1974) provided experimental evidence of a fertility deficiency of SR males and suggested that SR-mated females run out of sperm and remate sooner than ST-mated females. He concluded that the SR X-chromosome is not driven (i.e., has no advantage by virtue of aberrant segregation ratios) with respect to normal X-chromosome. It should be noted that this use of term is somewhat broader than definition originally provided by Sandler and Novitski (1957) since it includes fertility differences between SR and ST males in addition to effect of segregation ratios. To sharpen distinction between and fitness parameters, term meiotic drive will be used in this paper to denote advantage which aberrant segregation ratios would produce in absence of any fitness differences between SR and ST males. Thus any differences in fertility, mating success or sperm displacement will be considered fitness parameters even if differences are direct results of mechanism of the. SR trait. I attempted to study fertility differences between SR and ST males, but was able to demonstrate fertility disadvantage to SR males only under two conditions: when males were very young (20-33 h from eclosion) or after their supply of sperm had been previously reduced by repeated matings (Beckenbach, 1978). I also found that females inseminated by males whose supply of sperm had been partially depleted by previous matings showed no reduction in either fecundity or egg hatchability early in their reproductive period, compared to more heavily inseminated females. Thus fertility deficiency proposed by Policansky and Ellison is conditional at best, and populational consequences of any deficiency are minimized by pattern of fertilized egg production of females. Thus on basis of information obtained by studying singly-mated females, deficiency is insufficient to account for failure of SR to increase in frequency in nature or to cause its rapid elimination from experimental populations. However, picture may be radically different if multiple mating of females is allowed.

Fertility Differences as a Factor in the Maintenance of the "Sex Ratio" Polymorphism in Drosophila pseudoobscura

"Sex ratio" (SR) males of Drosophila pseudoobscura produce more than 95% female progeny. Previous workers have had varying opinions on the roles played by differential mating success and fertility of SR and normal (ST) males, if any, in the maintenance of the SR/ST polymorphism. In order to assess the importance of these roles, virgin D. pseudoobscura females were marked and released in the Santa Catalina mountains near Tucson, Arizona. Marked and unmarked females, and males, were collected over a period of about 2 wk, and total numbers of male and female progeny produced by individual flies were counted. The results show that SR males, which appear to produce about half as many sperm as ST males, fertilize as many eggs per insemination as ST males but inseminate only half their share of females. This means that SR males produce as many daughters as ST males, and is consistent with earlier observations that natural populations appear to be in Hardy-Weinberg equilibrium for SR. If the mating disadvantage of SR males is caused directly by reduced sperm production, then SR is not a case of meiotic drive balanced by selection, and the population dynamics of SR in D. pseudoobscura may be representative of other species having SR. If the mating disadvantage is not directly related to reduced sperm production, then SR is a case of meiotic drive balanced by selection. The selection in this case would be the mating disadvantage. If this is the correct explanation then the equilibrium involving SR may be different in every population.

"Sex Ratio," Meiotic Drive, and Group Selection in Drosophila pseudoobscura

"Sex ratio" (SR) is a widespread genetic condition of the X-chromosome in Drosophila species which causes males to produce progenies consisting almost entirely of females. Results of samples from natural populations of Drosophila pseudoobscura and results of some laboratory experiments indicate that SR males produce only about half as many sperm as normal (ST) males; because of this deficiency, SR males are able to fertilize only about half as many eggs as ST males. These results explain the observed equilibria of frequencies of SR in natural populations, and suggest that, at least in the case of D. pseudoobscura, male fertility may be partly limited by the number of sperm males can produce.

Dysfunctional sperm production in Drosophila melanogaster males homozygous for the segregation distorter elements.

Drosophila males heterozygous for the segregation distorter chromosome show a reduction in fecundity which is correlated with the degree of distortion of their segregation ratio. When males are made homozygous for the segregation distorter elements, their fecundity is lowered to just that extent expected if each SD were independently causing the sperms carrying the other to dysfunction. In three cases tested, Sd Ac/Ac, Sd Ac/Sd Ac, and Sd Ac St/Sd Ac St, the fecundity of the males is consistent with the dysfunction model, whereas the females are normal. The Sd Ac St/Sd Ac St males are almost completely sterile. They do produce sperms, however, which are motile and which look morphologically normal in the phase contrast microscope. They are transferred to the female during copulation and are stored in apparently normal numbers in the seminal receptacle and spermathecae.

Mating behaviour of two inbred strains of mice

Observations were made of the mating patterns of males from two inbred strains, ST/J and CBA/J, with females from both of these strains. Experiment I involved single males that were housed separately, while experiment II involved inter-strain pairs of males that were housed together. In three out of the four possible situations, the ST males had a significantly greater rate of mating success than the CBA males. In all four situations the mating pattern of the ST male was significantly different from that of the CBA male in at least two respects (thrusts per mount and genital lickings per mating). It is not possible, at this time, to attribute the greater mating success of the ST male to any specific aspects of his mating pattern. The mating success of each of the two types of males, under paired conditions with ST females, in this experiment corresponds closely to the reproductive success of these males in a previous experiment.

Interaction of aggressive and sexual behavior in male mice.

I. Eleven albino males (ST/J) and eleven black-agouti males (CBA/J) were fought interstrain, in round-robin fashion, once a week for eleven weeks in the presence of an estrus induced albino female (ST/J). 2. The CBA males were superior in both fighting ability and mating success. 3. A comparison of the present results with those of our previous fighting experiments conducted without females present, shows that the presence of an estrus female significantly reduced the aggressiveness of the CBA males while affecting the ST males only by increasing their attack latency. 4. A comparison of the present results with those of our previous mating experiments conducted when the two types of males are housed together permanently and given natural estrus ST females, shows that mating success varies with experimental conditions, for in the earlier experiment the ST males were superior in mating. 5. The influence of hereditary background on the behavior of mice and the dependency of fighting ability and mating success upon the situation in which these behaviors are elicited are discussed.

Interstrain fighting in male mice

Interstrain fighting between males of the ST J (albino) and the CBA J (black-agouti) strains was studied under three different sets of conditions: ( a) contests terminated after first victory using males isolated since weaning; ( b) 30-minute contests with males isolated since weaning; ( c) contests terminated after the first victory using socially experienced males. It was found that: 1. (1) Under all three sets of conditions, the CBA males achieved fighting superiority. 2. (2) The CBA superiority in fighting was not evident in the first contests but developed rapidly thereafter. 3. (3) When the contests are conducted for a 30-minute period, rather than until first submission, the conditioning of the ST males to defeat occurs more rapidly. 4. (4) Social experience before fighting has different effects on the two types of males. It drastically reduces all aspects of aggressiveness of the ST males. Its only effects on the CBA males are to increase their attack latency and to extend the number of contests required to achieve their superiority in fighting. The above results are compared with those obtained elsewhere. The dependency of fighting ability upon the situation in which the behaviour is elicited is discussed.