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Selection for increased female sexual receptivity in raised stocks of Drosophila melanogaster.

Two third-chromosome mutations in raised (rsd) stocks, when homozygous, cause the wings of Drosophila melanogaster adults to be held upright. Males expressing these mutations cannot vibrate their wings to produce the courtship song, which functions to increase female receptivity to copulation. As expected, rsd males are less successful when courting wild-type females. However, females from long-established rsd stocks are more receptive to courtship stimuli and mate more readily with both rsd and wild-type males than do wild-type females. Genetic analysis reveals dominant factors on the X and third chromosomes that, in combination, are responsible for the increased receptivity of rsd females. These observations suggest that the lack of courtship song in rsd stocks, which would be expected to reduce the vigor of the stock, may have functioned as a selective force, favoring mutations that increased female receptivity. Possible consequences of selection favoring the development of differential female receptivity on speciation are discussed.

Animals↗

Nuptial feeding of spermless spermatophores in the Hawaiian swordtail cricket, Laupala pacifica (Gryllidae: Triginodiinae).

Crickets in the genus Laupala (subfamily Trigonidiinae) have an elaborate courtship system, defined by a highly ritualized serial transfer of multiple spermatophores. Males produce multiple "micro" spermatophores followed by a final "macro" spermatophore during a single mating bout. Remarkably, the microspermatophores of L. cerasina, the first species whose mating system was studied in detail, were discovered to be spermless. However, in a study of another species, L. pacifica, sperm transfer was reported after every copulation suggesting that L. pacifica microspermatophores contain sperm. The presence or absence of sperm in the microspermatophore has important implications for the evolution of this exaggerated courtship system and the origin of nuptial gifts. In this study, we systematically examined L. pacifica spermatophore contents for sperm using a fluorescent nuclear stain. We detected sperm only in macrospermatophores. This finding suggests that spermless microspermatophores are typical for Laupala; thus, to determine the origin of this highly modified phenotype will require comparative analyses with closely related outgroups that exhibit less exaggerated courtship systems.

Animals↗

Discrimination of conspecific sex and reproductive condition using chemical cues in axolotls ( Ambystoma mexicanum).

Chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. We investigated the behavioral effects of conspecific whole-body odorants in axolotls, Ambystoma mexicanum, a salamander species that is fully aquatic. We found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. Although males showed no difference in courtship displays across testing conditions, females performed courtship displays only in response to male odorants. We also found that electro-olfactogram responses from the olfactory and vomeronasal epithelia were larger in response to whole-body odorants from the opposite sex than from the same sex. In males, odorants from gravid and recently spawned females evoked different electro-olfactogram responses at some locations in the olfactory and vomeronasal epithelia; in general, however, few consistent differences between the olfactory and vomeronasal epithelia were observed. Finally, post hoc analyses indicate that experience with opposite-sex conspecifics affects some behavioral and electrophysiological responses. Overall, our data indicate that chemical cues from conspecifics affect general activity and courtship behavior in axolotls, and that both the olfactory and vomeronasal systems may be involved in discriminating the sex and reproductive condition of conspecifics.

Action Potentials↗

Effects of an NO synthase inhibitor on aggressive and sexual behavior in male crickets.

The mechanisms of the effects of some types of behavior on others have received little study. The present investigation addresses the phenomenon present in male crickets of the species Gryllus bimaculatus, consisting of the powerful activation by transient flight (3 min) of aggression to another male and of the female courtship program. We found that flight did not evoke these behavioral changes in males injected with the NO synthase inhibitor LNNA. The intensity and duration of fights with another male, the frequency of ritual singing by the victor, and the intensity with which the victor pursued the vanquished only increased significantly after flight in control male crickets injected with Ringer's solution, but not in experimental crickets. Similarly, flown males injected with LNNA were no different from unflown males in terms of the intensity of female courtship (the latent period and relative duration of courtship singing); in controls, the latent period was significantly shorter and the duration of singing was significantly greater in flown crickets. LNNA had no effect on aggressive or sexual behavior in unflown males. These results demonstrate that flight may increase NO synthesis, making a significant contribution to the formation of the flight-evoked behavioral state.

Aggression↗

The effects of exogenous neuropeptide Y on feeding and sexual behavior in the red-sided garter snake (Thamnophis sirtalis parietalis).

Actively courting adult male red-sided garter snakes were injected with one of two dosages of neuropeptide Y (NPY) or saline into the third cerebral ventricle. Courtship and feeding responses were assessed prior to surgery, 4-5 h and 24 h post-surgery. Feeding behavior was tested by the presentation of a favored food, an earthworm. NPY significantly reduced courtship behavior scores at both low (0.16 nmol) and high (0.77 nmol) doses 4-5 h after surgery. Snakes also took much longer to reach the criterion courtship score at the high dose. Feeding occurred only in snakes treated with NPY. At the low dose 29% ate at 4-5 h and 24 h after surgery; 43% of the snakes treated with the high dose ate 4-5 h post-surgery. When tested the day following injection, animals were courting at levels comparable to presurgery levels and refused food.

Animals↗

Behavioral and physiological control of yolk synthesis and deposition in the female red-sided garter snake (Thamnophis sirtalis parietalis).

Ovarian recrudescence in female garter snakes, Thamnophis sirtalis parietalis, follows spring emergence from hibernation and mating. In the laboratory, courtship and mating stimuli significantly increased the proportion of female garter snakes becoming pregnant, although some noncourted nonmated controls also became pregnant. Females given artificial mating stimuli under anesthetic, without courtship stimuli, were no more likely than either noncourted, nonmated or anesthetized controls to become pregnant. Hormonal changes and yolk synthesis rapidly followed mating in both laboratory and field females; serum estradiol increased more than 10-fold in 2 days and serum calcium, a measure of yolk precursor lipoprotein (vitellogenin) concentration, increased more than two times in 10 days. Administration of exogenous estradiol stimulated yolk synthesis, but did not result in yolk deposition into ovarian follicles. However, administration of ovine follicle-stimulating hormone induced both hepatic yolk synthesis and yolk deposition. Our results are consistent with the hypotheses that courtship and copulation are facilitatory to ovarian recrudescence but neither alone nor in combination is necessary nor sufficient, and in this species yolk synthesis and yolk deposition are separately regulated.

Animals↗

Psychobiology of sexual behavior in a whiptail lizard, Cnemidophorus inornatus.

This study investigated the effects of social environment on gonadal recrudescence and sexual behavior in male and female Little Striped Whiptail lizards (Cnemidophorus inornatus). The presence of sexually active males facilitates ovarian recrudescence in conspecific females. Similarly, the presence of reproductively active females facilitates testicular recrudescence in conspecific males. Males housed with females, however, had lower average circulating concentrations of testosterone and dihydrotestosterone, and higher average concentrations of corticosterone compared to intact males housed in isolation. In other studies, the presence of reproductively active females partially restored courtship behavior in castrated males compared to castrated males housed in isolation. Despite the stimulatory effects of females on castrates, exogenous androgens are required for complete restoration of all components of sexual behavior in male C. inornatus. Females are receptive to male courtship and copulatory behavior only during the vitellogenic stages; females in previtellogenic or postovulatory ovarian stages aggressively reject male courtship advances. These findings demonstrate reciprocal effects of sexual behaviors of males and females upon each other's reproductive behavior and physiology.

Animals↗

Steroid control of sexual behavior and brain aromatase in the dove: effects of nonaromatizable androgens, methyltrienolone (R1881), and 5 alpha-dihydrotestosterone.

This study examines the effects of nonaromatizable androgens, methyltrienolone (R1881) and 5 alpha-dihydrotestosterone (DHT) on aggressive courtship and vocal behavior in the male ring dove. Since androgens may influence behavior by increasing the formation of estrogen in the brain, the effects of R1881 and DHT on brain aromatase activity were also studied using an in vitro microassay. Under conditions in which testosterone induced aggressive courtship patterns, the nonaromatizable androgens were ineffective. But DHT and R1881 induced vocal behavior with equal efficiency, indicating that androgens can influence mechanisms of vocal behavior without conversion to estrogens. The behavioral effectiveness of both hormones was reduced (approximately 50%) when the period between castration and treatment was doubled. Testosterone propionate increased formation of E2 from 3H-testosterone in both the preoptic (POA) and anterior hypothalamic areas. Neither of the nonaromatizable androgens affected POA aromatase activity. The results suggest that only the aromatizable androgen, testosterone, which is also required specifically for male courtship, increases preoptic formation of estrogen.

Aggression↗

Wood duck hatch date: relationship to pairing chronology, plasma luteinizing hormone, and steroid hormones during autumn and winter.

We examined variation in courtship activity and hormone levels of male and female wood ducks (Aix sponsa) in relation to hatch date. Young wood ducks were assigned in groups of 8 (4 males and 4 females) to 4 experimental pens; 2 pens contained early-hatched ducks (3-12 April) and 2 pens contained late-hatched ducks (7-16 June). Courtship behaviors occurred less frequently in October and November than in December and January-February for both early- and late-hatched groups. Early-hatched wood ducks participated in courtship more frequently and formed pair bonds sooner than late-hatched individuals. Testosterone (T) and androstenedione (AD) levels of males did not differ between treatment groups; however, average levels of luteinizing hormone (LH) were greater for early-hatched males. Differences in LH occurred in 2 of 12 samples (6 October and 3 November); otherwise, LH did not vary by treatment. Levels of T and LH in males varied temporally, but there was no significant temporal variation in AE levels. Temporal variation in hormone levels was similar for early- and late-hatched males. Estradiol (E), progesterone (P), and LH levels of females did not differ between treatment groups. There was temporal variation in levels of E and LH, but not of P; this variation was similar for early- and late-hatched females. These data indicate that behavioral differences occurring temporally and between early- and late-hatched wood ducks were not related to corresponding differences in hormone levels.

Animals↗

Antiphonal duetting and sex hormones in the tropical bush shrike Laniarius funebris (HARTLAUB).

We investigated changes in antiphonal duetting with phases of reproduction and circulating levels of luteinizing hormone, testosterone, and estradiol in slate-colored boubous (Laniarius funebris) breeding in aviaries. Frequency of overall male singing did not vary with reproductive phase while frequencies of female singing and female vocal responses to male song were reduced during incubation and feeding of nestlings. This resulted in significant changes in frequency of duetting. Males sang the sexual song type M1 more often during courtship and nest building than during the nestlings phase. Their territorial song types M2 and M4 did not vary with breeding phase. Females were less responsive to M1 during incubation and to M2 during the nest building and nestlings than during the courtship phase. Plasma levels of luteinizing hormone and testosterone increased in males from the prebreeding to the courtship phase. While testosterone decreased already during nest building and remained low during subsequent phases of reproduction, luteinizing hormone decreased during incubation and feeding of nestlings. Female luteinizing hormone levels were highest during nest building. Female estradiol levels decreased from nest building to incubation and increased again during subsequent nest building. Female testosterone levels were low but not basal and did not vary with phase. Neither the overall male and female singing frequencies nor the frequencies of male song types were correlated with hormonal state. However, female participation in territorial duets M4 correlated positively with their testosterone levels. It is suggested that in this monogamous, duetting species with prolonged pairbonds behavioral cues between the mates are more important than the hormonal state in control of male and female singing.

Animals↗

Androstenedione therapy reinstates normal, not supernormal, song structure in castrated adult male zebra finches.

In previous studies, androstenedione (AE) replacement therapy restored the highest levels and intensities of courtship song displays in castrated male zebra finches of any hormone tested. Furthermore, female zebra finches responded strongly to AE-treated males and preferred intact males given small AE implants to unsupplemented males. In this study, we asked whether AE treatment might alter song structure, since male song is an important cue in mate choice by female zebra finches. Songs of adult males were recorded. The males were then castrated and given AE therapy and recorded again. No differences were found between the courtship or undirected songs males sang before castration and after AE treatment. As in previous studies, the structure of a male's courtship song differed significantly from his undirected song, and the structural differences between these two song types were not altered by AE treatment.

Androstenedione↗

Effects of olfactory tract lesions on sexual and feeding behavior in the goldfish.

The paired olfactory tracts (OTs) of goldfish each have a lateral (LOT) and medial (MOT) olfactory tract, the latter with medial (mMOT) and lateral (lMOT) subdivisions. Bilateral OT section (OTX) reduced, while unilateral OT section (UNI) did not impair, male sexual behavior and feeding responses to a complex food odor; in contrast, female sexual behavior, induced in both sexes by prostaglandin treatment, was little affected by OTX. Experiments in which control fish were given UNI and treatment groups received UNI plus selective section of the remaining OT assessed the role of the OT subdivisions in the two olfactory-influenced behaviors (male sexual behavior and feeding). LOT section did not affect courtship, while MOT section reduced courtship to the low levels seen in OTX males; within the MOT, the mMOT may be more important than the lMOT for courtship expression. In contrast to male sexual behavior, feeding responses were less affected by MOT than LOT section. With respect to male sexual behavior, these findings demonstrate differential functions for the anatomically distinct subdivisions of the goldfish olfactory tracts, possibly related to their distinct terminal fields within the telencephalon.

Animals↗

Effect of morphine and naloxone on LH response and sexual behavior of rams (Ovis aries).

Effects of the opiate agonist, morphine, and antagonist, naloxone, on LH release, courtship behavior and ejaculation frequency of mature, sexually active or sexually inactive rams were investigated. Plasma LH concentrations were monitored from blood samples collected every 15 min for 10 hr (0800 to 1800 hr) from eight rams that were isolated from or in contact with estrous females. Plasma LH concentration was higher (P < .05) in sexually active rams exposed to receptive females compared with hormone concentration of rams isolated from ewes. Intravenous infusion of morphine sulphate (1 mg/kg) into rams 4 and 6 hr after exposure to ewes reduced (P < .05) plasma LH concentration as compared to rams given saline. Morphine did not affect (P > .05) courtship behavior (investigatory sniff, mount attempt, foreleg kick, flehmen, vocalization) but diminished (P < .05) number of ejaculations. In another trial, LH concentrations were higher (P < .05) in seven sexually active rams given naloxone iv or when given to three rams through an intracerebroventricular cannula (icv) as compared to LH response of sexually inactive rams. LH did not differ (P > .05) in seven sexually inactive rams before or after administration of naloxone. Investigatory sniffs by sexually active rams were increased (P < .03) after treatment with the opiate antagonist. Four of the seven sexually active rams had more ejaculations after naloxone compared with the pretreatment period, but mean ejaculation frequency after treatment did not differ (P = .31). Naloxone did not stimulate courtship behavior of sexually inactive males.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Relationship between male-male and male-female sexual behavior in 5-6-month-old male lambs.

To characterize male-male sexual behavior during lamb development, to relate it with lamb body and testicular growth, and with sexual behavior toward estrual ewes, 40 Milchschaf male lambs, weaned at 45 days of age, were kept with ewes that were nursing younger lambs. Experimental lambs were weighed and scrotal circumference was measured every 2 weeks. Male-male sexual behavior was observed during 1-2 h every 2 weeks after birth until 7 months of age. Observations were recorded more intensively (3-4 h on five different days) for 2 weeks (5-6 months of age) as male-male sexual behavior increased during that period. Both mounting and mounted lambs were identified. An individual mounting index (MI) was calculated. To study male-female sexual behavior, lambs were individually located with two estrual ewes, and during 5 min the number of ano-genital sniffing, lateral approaches, mounts, and mounts with ejaculation were recorded. From those data, a libido index was also calculated. Male-male mounts (n=308) were observed. Courtship behavior was displayed in 25% of interactions; mounts were accepted in 72.1% of attempted mounts. Mounts without previous courtship were accepted more frequently than mounts with previous courtship (P=0.002). Lamb weight and scrotal circumference were not different according to MI groups. Lambs that mounted more times estrual ewes (first tertile) had greater (P=0.04) MI (0.61+/-0.10) than lambs with medium (0.27+/-0.09) and less (0.30+/-0.10) MI. The regression between MI and heterosexual libido index was r=0.33 (P<0.05). In summary, intensive male-male sexual activity during a short period of male lamb development was observed. There was a positive relationship between sexual behavior of male lambs towards other male lambs and towards estrual ewes.

Aging↗

Multiple mechanisms of phenotype development in the bluehead wrasse.

Despite having detailed information on mechanisms mediating sex-typical behavior in many species, we have little understanding of whether the same mechanisms regulate these behaviors when they are performed in the same species under different social contexts. In the five field experiments of this study of bluehead wrasses (Thalassoma bifasciatum), a sex-changing fish, we examined the roles of arginine vasotocin (AVT) and the potent teleost androgen 11-ketotestosterone (11KT) in mediating sexual and aggressive behaviors typical of dominant males. We demonstrated that AVT appears necessary for the assumption of dominant territorial status in males and females, but is sufficient only in the socially dominant terminal phase (TP) male phenotype. Specifically, an AVP V(1) receptor antagonist prevented both TP males and females from gaining dominance over recently vacated territories. However, unlike TP males in a previous study, neither females nor initial phase males responded to AVT treatment with increases in display of TP male typical behaviors when under social conditions that inhibit sex change. Treating females with 11KT did not alter responsiveness to AVT, but did induce male coloration and courtship behavior that was not observed in oil-treated females. Combined with the results of a previous study, these results indicate that the ability of AVT to induce male-typical behavior differs among sexual phenotypes and that this differential responsiveness appears to be dependent on social context and not directly on exposure to 11KT. Furthermore, since 11KT can induce courtship behavior in females that is not affected by AVT, there may be different hormonal mechanisms mediating courtship behavior under different social contexts.

Aggression↗

Immunohistochemical colocalization of Yellow and male-specific Fruitless in Drosophila melanogaster neuroblasts.

The Drosophila melanogaster fruitless gene encodes multiple male-specific transcription factors that are hypothesized to regulate a hierarchy of genes responsible for the development of male courtship behavior. Here we show that there are dramatically increased levels of the protein product of the male courtship behavior gene yellow associated with male-specific Fruitless protein in a subset of neuroblasts in third-instar larval male brains. We hypothesize that yellow is downstream of fruitless in a male courtship behavior developmental genetic pathway.

Animals↗

The effects of sex steroids and vasotocin on behavioral responses to visual and olfactory sexual stimuli in ovariectomized female roughskin newts.

Previous studies have found that vasotocin (AVT) administration to male roughskin newts (Taricha granulosa) enhances courtship clasping as well as appetitive responses to specific sexual stimuli and that treating female newts with androgens plus AVT induces the expression of male-typical courtship clasping (the selective clasping of females). However, the unique and/or interactive effects of sex steroids and AVT on appetitive responses to specific sexual stimuli have not yet been determined. To first identify male-typical, sexually dimorphic appetitive responses to female sexual stimuli, we tested intact newts during the breeding season and found that males, but not females, are attracted to female visual and pheromonal sexual stimuli. We then used ovariectomized (ovx) females implanted with empty silastic capsules (Blk) or with capsules containing testosterone (T), dihydrotestosterone (DHT), or estradiol (E2) and then injected with either saline or AVT to determine the effects of steroids and AVT, alone or in combination with each other, on male-typical behavioral responses to those stimuli. E2 treatment depressed responses toward female visual stimuli independently of AVT. On the other hand, only T-implanted, AVT-injected females displayed male-typical behavioral responses toward female olfactory stimuli, preferring to spend more time in proximity to female-scented than unscented newt models and selectively clasping the female-scented models. Together, these results support the conclusion that sex steroids and AVT influence behavioral responses to sexual stimuli via sensory-specific mechanisms. Furthermore, they suggest that T and AVT interact within the brain to influence sensorimotor processing in the pathways that integrate olfactory sexual stimuli into male-typical courtship behaviors.

Animals↗

Social stress effects on territorial marking and ultrasonic vocalizations in mice.

Acute social defeat (SD) leads to transient and persistent physiological and behavioral changes. We examined the effects of acute SD on territorial urine marking and ultrasonic courtship vocalizations in DBA/2 male mice. Both behaviors are considered androgen dependent and are influenced by social status, with dominant mice displaying more of both behaviors. In Experiment 1, male mice that received SD displayed prolonged inhibition of territorial urine marking, relative to nondefeated control mice (NOSD). In addition, territorial marking increased with repeated tests. In Experiment 2, male mice that received 3 successive days of SD displayed fewer ultrasonic courtship vocalizations at 30 min. post-SD1 and 30 min. post-SD2, relative to NOSD mice. In Experiment 2, we also observed decreased territorial marking 4 weeks post-SD. In sum, SD induced prolonged inhibition of territorial marking, but had only transient effects on ultrasonic courtship vocalizations, suggesting that different mechanisms may mediate the maintenance of these behaviors.

Aggression↗