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PubMed2001

Seasonal variation in androgen-metabolizing enzymes in the diencephalon and telencephalon of the male European starling (Sturnus vulgaris).

In seasonally breeding songbirds, seasonal fluctuations occur in serum testosterone (T) concentrations and reproductive behaviours. Many T-dependent behaviours are regulated by the activity of androgenic and oestrogenic metabolites within specific brain regions. Male European starlings breed in spring when circulating T concentrations peak. T and its metabolites act within portions of the diencephalon to regulate the pituitary-gonadal axis and to activate courtship and copulation. Song in male starlings is critical for mate attraction during the breeding season and is regulated by steroid-sensitive nuclei in the telencephalon and diencephalon. Outside the breeding season, T is undetectable, however, males continue to sing at high levels. This suggests that singing outside of the breeding season might not be T-dependent as it appears to be in the spring. Alternatively, singing when T is low might continue to be regulated by T due to increased sensitivity of the brain to the action of the steroid. This increased sensitivity could be mediated by changes in intracellular T metabolism leading to increased production of active or decreased production of inactive metabolites. To explore the relationship between T-metabolism and reproductive behaviour, we analysed seasonal changes in the activity of four brain T-metabolizing enzymes: aromatase, 17beta-hydroxysteroid dehydrogenase (17beta-HSDH), 5alpha-reductase (all three convert T into active metabolites) and 5beta-reductase (converts T into an inactive metabolite) in the diencephalon and telencephalon. In the anterior and posterior diencephalon, the highest aromatase was observed in spring when this region is critical for courtship and copulation. In the telencephalon, aromatase was highest and 5beta-reductase was lowest throughout the winter months well prior to the reproductive season and these enzymes presumably maximize T-activity within this region. Although these data do not indicate whether the metabolic changes occur specifically within song nuclei, these findings are compatible with the idea that singing in male starlings outside the breeding season may be regulated by steroids despite the presence of low serum T concentrations. Overall, seasonal changes in T-metabolizing enzymes appear to play a significant role in seasonal changes in behaviour and reproductive physiology.

17-Hydroxysteroid Dehydrogenases↗

PubMed2001

Microsatellite determination of male reproductive success in a natural population of the territorial ornate dragon lizard, Ctenophorus ornatus.

It is now evident that the genetic mating system can be very different to the observed mating system. However, it is less well known what makes particular individuals more (or less) successful than expected from the observed system. In this study the observed territorial structure of a field population of the agamid lizard, Ctenophorus ornatus, was compared with the mating system as evidenced by microsatellite parentage assignment. This study also investigated whether any male traits predicted reproductive success. Sixty-five per cent of clutches were sired at least partially by a male other than the main territory-holding male and 35% of clutches were sired by a male with no overlap of the female's territory. Multiple paternity was moderately frequent at 25% of clutches. Male chest patch size predicted territory size and the number of females in the territory, but did not predict reproductive success. Instead, male head depth and body size were independently related to the number of offspring sired. As male head depth also predicted the number of females in a territory, these males are likely to be gaining increased reproductive success as a consequence of the higher number of females in their territories. Larger body size males, however, did not have a greater number of females in their territory and instead had more extra-territorial copulations. Whether these extra-territorial copulations are due to female choice or success in male competition is unknown.

Animals↗

PubMed2003

Evidence for genetic monogamy and female-biased dispersal in the biparental mouthbrooding cichlid Eretmodus cyanostictus from Lake Tanganyika.

In this study, we investigate whether apparent social monogamy (where a species forms a pair bond but may participate in copulations outside the pair bond) corresponds with genetic monogamy (where individuals participate only in copulations within a pair bond) in a biparental mouthbrooding cichlid fish, Eretmodus cyanostictus, from Lake Tanganyika, Africa. Our findings suggest that E. cyanostictus is both socially and genetically monogamous and that monogamy may result from limited opportunities for polygyny, rather than from reproductive benefits of monogamy. Mating systems are believed to influence the relative rate of dispersal of the sexes, and our results suggest that E. cyanostictus displays female-biased dispersal, providing some support for the 'resource competition' hypothesis driving sex-biased dispersal.

Animals↗

PubMed2003

Social pairing and female mating fidelity predicted by restriction fragment length polymorphism similarity at the major histocompatibility complex in a songbird.

Female birds often copulate outside the pair-bond to produce broods of mixed paternity, but despite much recent attention the adaptive significance of this behaviour remains elusive. Although several studies support the idea that extra-pair copulations (EPCs) allow females to obtain 'good genes' for their offspring, many others have found no relationship between female mating fidelity and traits likely to reflect male quality. A corollary to the good genes hypothesis proposes that females do use EPCs to increase the quality of young, but it is the interaction between maternal and paternal genomes - and not male quality per se - that is the target of female choice. We tested this 'genetic compatibility' hypothesis in a free-living population of Savannah sparrows (Passerculus sandwichensis) by determining whether females mated nonrandomly with respect to the major histocompatibility complex (Mhc). During both the 1994 and 1995 breeding seasons, female yearlings (but not older birds) avoided pairing with Mhc-similar males (P < 0.005). The Mhc similarity between mates also predicted the occurrence of extra-pair young in first broods (P < 0.007) and covaried with estimates of genome-wide levels of similarity derived from multilocus DNA fingerprinting profiles (P = 0.007). The overall genetic similarity between adults tended to predict female mating fidelity, but with less precision than their Mhc similarity (P = 0.09). In contrast, females appeared insensitive to the size, weight or age of males, none of which explained variation in female mating fidelity. Taken together, these results are consistent with the hypothesis that females sought complementary genes for their offspring and suggest either that the benefits of heterozygosity (at the Mhc) drive female mating patterns or that the avoidance of inbreeding is an ultimate cause of social and genetic mate choice in Savannah sparrows.

Animals↗

PubMed2003

Sexual conflict in Sepsis cynipsea: female reluctance, fertility and mate choice.

Sexual conflict can elevate mating costs via male inflicted damage to females. Possible selective advantages to males include decreasing the likelihood that females remate and/or increasing females' current reproductive investment in a manner analogous to terminal reproductive investment. We investigated female mating behaviour relative to their number of previous copulations in the fly Sepsis cynipsea, and whether males accepted as first mates were more likely to be accepted again. Females were more likely to remate with new rather than original males, although there was no associated fitness benefit, and in contrast to theoretical predictions, females became less reluctant to remate as the number of previous copulations increased. Additionally, females did not increase reproductive investment as would be expected if they were ensuring their final reproductive efforts were maximized by remating. This suggests that damaging females is a pleiotropic effect which inadvertently leads to increased, not decreased, polyandry.

Animals↗

PubMed2004

Floral evolution and pollinator mate choice in a sexually deceptive orchid.

Sexually deceptive orchids mimic sex pheromones and appearance of female insects to attract males, which pollinate the flowers in an attempted mating. This study examines the effects of pollinator mate choice on orchid floral evolution using the Thynnine wasp Neozeleboria cryptoides (Smith) (Hymenoptera: Tiphiidae), which pollinates the sexually deceptive orchid Chiloglottis trapeziformis Fitzg. (i) When male wasps were given the choice between two female dummies of different sizes and identical amount of synthetic pheromone, they preferentially attempted to copulate with medium-sized dummies over small dummies. (ii) When given the choice between two dummies of identical size but different amounts of pheromone, males preferred the larger amount of pheromone. Larger amounts of pheromone generally attracted more males than smaller amounts. (iii) Orchid flower labella, which mimic a female body, were significantly longer and broader than female wasp bodies, and the flowers also produced on average 10 times more 'pheromone' than females. The evolution and maintenance of these exaggerated mating signals is likely to be mediated by the male pollinator behaviour demonstrated here. (iv) When five dummies were offered simultaneously in a 10 cm circular array, males rarely attempted copulation on more than one dummy during a single visit. This behaviour may foster the evolution or maintenance of clonality in C. trapeziformis, as it will minimize pollen exchange within clones.

Animals↗

PubMed2003

Peptidergic modulation of male sexual behavior in Lymnaea stagnalis: structural and functional characterization of -FVamide neuropeptides.

In the simultaneous hermaphrodite snail Lymnaea stagnalis, copulation as a male is controlled by neurons that send axons to the male copulatory organs via a single penis nerve. Using direct mass spectrometry of a penis nerve sample, we show that one of the molecular ions has a mass corresponding to GAPRFVamide, previously identified from the buccal ganglia, and named Lymnaea inhibitory peptide (LIP). The identity of this peptide is confirmed by partial peptide purification from the penis nerve, followed by post source decay mass spectrometry. We cloned the LIP-encoding cDNA, which predicts a prohormone that gives rise to five copies of LIP (now re-named LIP A), two other -FVamide peptides (LIPs B and C), and five structurally unrelated peptides. The LIP gene is expressed in neurons of the right cerebral ventral lobe that send their axons into the penis nerve. We show that the LIP A peptide is present in these neurons and in the penis nerve, and confirmed the presence of LIP B and C in the penis nerve by post source decay mass spectrometry. Finally, we demonstrate that LIP A, B and C inhibit the contractions of the penis retractor muscle, thereby implicating their role in male copulation behavior.

Amino Acid Sequence↗

PubMed2002

The effect of a partial Y chromosome deletion in B10.BR-Ydel mice on testis morphology, sperm quality and efficiency of fertilization.

Males of the mouse strain B10.BR/SgSn and its congenic mutant strain B10.BR-Ydel, with a partial deletion of the Y chromosome, were used to examine factors related to poor sperm quality and quantity in the mutant strain. The testes of males from the two strains did not differ in their immunohistochemical reaction to androgen receptors or in the number of Sertoli and germ cells in tubules with normal morphology. However, mutants showed a greater frequency of degenerated tubules, a higher level of X-Y chromosome dissociation at meiosis (18% v. 10% in control males), and a lower content of resistant sperm heads in testis homogenates. In the cauda epididymidis, there was a higher percentage of spermatozoa with abnormal heads (88% v. 31%) and of spermatozoa with a cytoplasmic droplet still attached (74% v. 51%). Many sperm heads with flat acrosomes, occurring only in mutants (30% of sperm population), were deficient in proteolytic enzymes, as evidenced by the reaction on gelatine membranes. Most copulations of mutant males (11/18) were sterile in spite of the presence of spermatozoa in the uterus, but in the remaining copulations the fertilization rate was reasonably good (79%). Low numbers of spermatozoa were recovered from the oviducts, and those with the most severely deformed heads were less frequent there than in the uterus. The results show that a partial deletion of the Y chromosome affects efficiency of spermatogenesis, morphology of spermatozoa, their epididymal maturation and capacity to reach the ampulla and fertilize eggs.

Acrosome↗

PubMed2002

Experimental analysis of sperm competition mechanisms in a wild bird population.

Recent work on wild birds has revealed the importance of sperm competition as a source of sexual selection, but behavioral and paternity studies have previously provided only indirect evidence for mechanisms of sperm competition in wild birds. In a field study of collared flycatchers Ficedula albicollis we used a previously uncharacterized method to determine the frequency and timing of extra-pair inseminations. By counting the number of sperm trapped on the perivitelline layer of eggs, we determined the timing of inseminations and estimated, on a day-to-day basis, the amount of sperm females stored. Our results showed that female collared flycatchers preferentially engaged in extra-pair copulations when mated to an unattractive male with a small white forehead patch. These copulations were timed for the middle part of their fertile period, at least 2 days after the last within-pair insemination. Although the mean number of extra-pair insemination events was only 1.33 per cuckolding female, the ratio between the number of sperm from extra-pair and pair inseminations was at least 5 to 1. Thus a single, well timed extra-pair insemination caused by female behavior could greatly bias fertilization probability in favor of an attractive extra-pair male. Our results suggest a possible behavioral mechanism for female control of sperm competition.

Animals↗

PubMed2001

Assessing mating performance of male Glossina pallidipes (Diptera: Glossinidae) using a walk-in field cage.

To monitor the quality of male tsetse for use in the sterile insect technique (SIT), a field cage test was developed and evaluated. Mating competitiveness was tested with male Glossina pallidipes Austen that emerged from pupae stored for different periods at 15 degrees C. Control males emerged from pupae stored at 23-24 degrees C and emerged at 26.5 degrees C. Each sample of test males was divided into two groups with one group being irradiated at 120 Gy; the other group was not irradiated. More than 70% of the maximum possible number of mating pairs occurred in all tests. Males emerged from pupae kept at low temperature and then irradiated formed a greater proportion of mating pairs than the controls. Males emerged from pupae kept at 15 degrees C generally started mating more quickly than the standard colony males although there was no significant difference. Insemination rates were above 99%. Pooled data indicated that mean spermathecal values for females mated with irradiated males were significantly lower than for control males. The duration of copulation varied significantly between treatment groups and was significantly longer for irradiated male flies; there was no correlation between duration of copulation and mean spermathecal value.

Animals↗

PubMed2005

An advantage for young sperm in the house cricket Acheta domesticus.

We show that males of the house cricket Acheta domesticus regularly expel sperm packages (spermatophores) independently of copulation and at a rate that is not affected by the presence of females. We then show for the first time that the age of sperm affects their likelihood of being stored by females after copulation; younger sperm were overrepresented in the female sperm storage organ and therefore in the sperm population used for fertilization. Our results suggest that the reproductive success of males may increase if they deliver ejaculates with young sperm, and the results may explain why the males of several species are regularly observed to discard ejaculates. Our results also suggest that phenomena such as female multiple mating, paternity bias, and/or exaggerated ejaculate sizes may be related to the advantage both genders gain by using young sperm.

Animals↗

PubMed1982

Control of female reproduction in Drosophila: genetic dissection using gynandromorphs.

The sexual behavior of Drosophila melanogaster gynandromorphs was studied to analyze the relationship between different steps in the female reproductive pathway. It was assumed that, in some gynandromorphs, certain female functions are missing because the corresponding control sites (foci) are either composed of male tissue or did not develop. A given gynandromorph can show elements of both male and female reproductive pathways. None of the steps of the female reproductive pathway appeared to be dependent on any other, in contrast to male behavior where, for example, following of females is a prerequisite for attempted copulation. By correlating each of the behaviors with the genotype of the cuticle, we confirmed previous findings that the focus for the female sex appeal is located in the abdomen, but receptivity to copulation is controlled by a site in the head. Many of the gynandromorphs did not lay eggs, presumably because either the focus controlling egg transfer from the ovaries to the uterus or the one controlling egg deposition was composed of male tissue. Many of the nonovipositing gynandromorphs laid eggs while dying or could be induced to deposit eggs after implantation of hormone-producing glands or topical application of a juvenile hormone analog. Some of the noninseminated gynandromorphs laid eggs at the rate characteristic for inseminated females, suggesting that an oviposition focus (mapping in the head region) suppresses oviposition in virgin females, but not in gynandromorphs whose focus is composed of male tissue. Some of the inseminated gynandromorphs oviposited eggs at a low rate, possibly because the focus responsible for detection of insemination could not function properly. Some of the inseminated gynandromorphs laid unfertilized eggs, revealing the importance of the focus controlling sperm release from the seminal receptacle. Foci controlling egg transfer, egg deposition and sperm release are located in the thorax, according to mosaic fate mapping results and studies on the reproductive behavior of decapitated females. The location of egg deposition in the culture vial seems to be controlled by a brain site. Sexual behavior in Drosophila does not depend on the presence (or absence) of the ovary or germ line.

Animals↗

PubMed1979

Control of male reproductive behavior by the central nervous system of Drosophila: dissection of a courtship pathway by genetic mosaics.

In gynandromorphs of Drosophila, a detailed examination was made of the association between male courtship behavior and the chromosomal genotype of various parts of the central nervous system. Mosaic flies that behave as males repeatedly show a shorter courtship than normal males. If there is to be male behavior, the posterior dorsal brain must be haplo-X on at least one side for occurrence of the early courtship events. Tapping, following of females and wing extension. Licking (proboscis extension) has nearly the same focus but is submissive; that is, male tissue must be present in both left and right dorsal brain. The next courtship step, attempted copulation, has a focus (especially for actual genital contact) located in the thoracic ganglia, though apparently not in a discrete region. Attempted copulation, which can occur even in mosaics with a gravid abdomen, may be correlated with the presence of sex combs. The role of courtship foci are interpreted in terms of known sensory inputs to and functions of the major insect ganglia.

Animals↗

PubMed2003

Reproductive capacity of sperm obtained after germ cell transplantation in a mouse model.

BACKGROUND: The testicular stem cell transplantation technique has become an established research model in the mouse. This technique may also become useful for clinical applications. Therefore, it is necessary to investigate whether sperm obtained after testicular stem cell transplantation retain their full functional capacity and whether they are able to produce normally-developing embryos. This study aimed at evaluating the fertilizing and developmental abilities of sperm obtained after stem cell transplantation. METHODS: First, transplanted male mice were mated with females in order to evaluate in-vivo conception. Subsequently, functionality of sperm obtained after testicular germ cell transplantation was investigated by performing both IVF and ICSI. RESULTS: After in-vivo conception we found that in the control group 90% of the mice with a copulating plug became pregnant. In the experimental group only 35% of the mice with a copulating plug became pregnant (P = 0.006). After IVF, fertilization and blastocyst developmental rates were significantly lower in the transplanted group (P < 0.0001). Fertilization and blastocyst developmental rates after ICSI were comparable with control sperm. CONCLUSIONS: Our study showed that in the mouse, sperm obtained after stem cell transplantation are able to fertilize oocytes on the basis of assisted reproduction. It is recommended to further investigate this method in the human, as well as to investigate the post-implantation development of the embryo.

Animals↗

PubMed1996

Colonization and bionomics of Forcipomyia taiwana (Diptera:Ceratopogonidae) in the laboratory.

An improvement in colonizing the biting midge Forcipomyia taiwana (Shiraki) was achieved by a new technique that facilitated the rearing of the midges and induced them to mate in the laboratory. At temperature of 15, 20, 25, and 30 degrees C, the development duration of the egg, 4 larval instars, and pupa decreased as temperature increased. Among 7 different diets, the blue green algae, Anabaena sp.Ch3, was the best food for rearing the midges. When the larvae were fed on the blue green algae at 25 degrees C, they needed 12 d to pupate, the pupation rate was 71.4%, the emergence rate was 80.2%, and the average longevity of the male and the female 38.3 and 22.6 d, respectively. When 120 paris were kept in a plastic cage (60 by 60 by 60 cm), swarming and copulation occurred during 0700-0900 and 1700-1800 hours. Swarm occurred throughout the cage and consisted of 10 males. The copulation was performed on the wall and the bottom of the cage, and the average duration was 290 s.

Animals↗

PubMed1987

The effect of season on the induction of sexual behavior by estradiol in female rhesus monkeys.

Rhesus monkeys housed in an outdoor environment are seasonal breeders, with ovulations and concomitant sexual behavior limited to the fall and winter months. To determine if there is a seasonal difference in the capacity of physiological levels of estradiol (E2) to induce sexual behavior in ovariectomized rhesus monkeys housed outdoors, subjects living in a social group were treated with subcutaneous E2 implants in a counter-balanced design during the nonbreeding season (May-July) and during the breeding season (September-November). Serum E2 levels were monitored by obtaining blood samples twice a week. Three levels of E2 were studied: baseline (less than 30 pg/ml), follicular (100 pg/ml), and periovulatory (200 pg/ml). Two of five adult males in the group were injected with human chorionic gonadotropin (hCG) twice a week to insure that males with high testosterone levels were present during each season. Focal observations of behavior of 15 minutes' duration on each subject were conducted 5 days per week, with frequencies and durations of social, sexual, and solitary behaviors recorded. Concomitant 2-h group scans were made to record all occurrences of mounting behavior. Neither heterosexual serial mounting nor seminal plugs were ever observed in E2-treated females during the summer months. In contrast, copulation and seminal plugs were observed in subjects at both treatment levels during the fall. While E2-treated females engaged in homosexual mounting behavior during both summer and fall, E2 treatment resulted in heterosexual copulation only during the fall. Changes in patterns of social behavior paralleled changes in sexual behavior and were significantly affected by treatment and season, with more male-female interactions during the fall months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Developmental competence of domestic cat embryos fertilized in vivo versus in vitro.

Development of in vitro-fertilized (IVF) cat embryos was compared to that of naturally produced cat embryos in vivo and in vitro. To obtain in vivo-fertilized embryos, queens were mated three times daily on the second and third days of natural estrus and ovariohysterectomized at 64, 76, 100, 124, or 148 h after the first copulation. Embryos were flushed from the reproductive tract, evaluated for developmental stage, and cultured. For IVF, oocytes from gonadotropin-stimulated queens were inseminated with electroejaculated cat sperm in Ham's F-10 and evaluated for fertilization (cleavage to > or = 2 cells) at 30 h. In vitro development of embryos fertilized in vivo (n = 109) and in vitro (n = 46) was evaluated every 24 h for up to 10 days. High-quality embryos recovered at 64, 76, 100, 124, and 148 h after the first copulation were typically 1 to 2 cells (13 of 20), 5 to 8 cells (18 of 28), 9 to 16 cells (14 of 24), morulae (15 of 21), and compact morulae (11 of 18), respectively, suggesting blastomere cleavage once per day in vivo after the first three rapid cell divisions. A similar developmental rate to the morula stage (p > or = 0.05) was achieved in vitro by embryos derived from both in vitro and in vivo fertilization. Additionally, the proportion (p > or = 0.05) of in vivo-generated embryos (2 to 16 cells) that developed to morulae (64 of 83; 77.1%) was similar to that of IVF embryos (28 of 46; 60.9%). However, none of the IVF embryos (0/46), but 70.6% (77 of 109) of the in vivo-produced embryos, achieved blastocyst formation in culture (p < or = 0.05). Furthermore, 66.2% (51 of 77) of these blastocysts exhibited zona hatching. Incidence of morula and blastocyst formation in the in vivo group was influenced by stage of the embryo at collection. Embryos that were at the 9- to 16-cell stage at recovery were more likely (p < or = 0.05) to achieve morula or blastocyst status and emerge from the zona pellucida than younger-stage counterparts. In summary, the in vivo and in vitro growth rate of cat embryos produced after natural mating was comparable to that of embryos fertilized and cultured in vitro. However, developmental ability to the blastocyst stage was superior for embryos produced in vivo after natural mating.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

The postpartum llama: fertility after parturition.

Fertility was evaluated at various times during the postpartum period in the llama. Fifty-six parous female llamas chosen at random were bred at 10, 20, and 30 days postpartum with six intact males. Half of the females copulated only once and the other half twice within an interval of 24 h. Ovarian activity was monitored by ultrasonography and analysis of urinary estrone sulfate and pregnanediol glucuronide (PdG). At the time of copulation, all females had developed ovulatory-size follicles. Ovulation was confirmed by the presence of a CL at 8 days after breeding and PdG concentrations > 1 ng/mg creatinine (Cr). Conception was defined as PdG concentrations > 1 ng/mg Cr at 15 days after breeding and the presence of a CL. Pregnancy was defined as the presence of a CL, PdG concentrations > 1 ng/mg Cr and an embryonic vesicle 20 days postbreeding. There were no significant differences in the proportion of females ovulating after breeding at different times postpartum; however, conception and pregnancy were significantly greater in females bred at Day 20 or 30. Ovarian follicle size was significantly larger at 30 days (9.1 mm) than at 10 and 20 days (7.9 and 8.8 mm, respectively) of breeding, with no difference in concentrations of estrone sulfate. The proportion of females conceiving as a result of breeding at 10 days postpartum (6 out of 10) was significantly less than for females bred at 20 (13 out of 15) or 30 days (16 out of 18).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗