A potential mate influences reproductive development in female, but not male, pine siskins.

The role of photoperiod in avian reproductive timing has been well studied, and we are increasingly recognizing the roles of other environmental cues such as social cues. However, few studies have evaluated the extent to which males and females of the same species respond similarly to the same type of cue. Moreover, previous studies have rarely examined how variation in the quality or nature of a given social cue might modulate its effect. Here, we examine the sensitivity of male and female pine siskins (Spinus pinus) to a potential mate as a stimulatory cue for gonadal recrudescence, and we investigate whether variation in the relationship between a bird and its potential mate modulates the effect of that potential mate. Birds were initially housed without opposite sex birds on a 12L:12D photoperiod with ad libitum food. After gonadal recrudescence had begun males and females were randomly paired with an opposite sex bird or housed alone. An additional group of males was paired with estradiol-implanted females. In males, these social treatments had no effect on testis length, cloacal protuberance length, luteinizing hormone (LH) levels, or testosterone levels. In females, presence of a potential mate had a significant and positive effect on ovary score, defeathering of the brood patch, and LH levels. Among paired birds, the degree of affiliation within a pair corresponded to the extent of reproductive development in females, but not males. Thus, reproductive timing in females appears to be sensitive to both the presence of a potential mate and her relationship with him.

Disruption of the temporally regulated cloaca endodermal ß-catenin signaling causes anorectal malformations.

The cloaca is temporally formed and eventually divided by the urorectal septum (URS) during urogenital and anorectal organ development. Although congenital malformations, such as anorectal malformations (ARMs), are frequently observed during this process, the underlying pathogenic mechanisms remain unclear. ß-Catenin is a critical component of canonical Wnt signaling and is essential for the regulation of cell differentiation and morphogenesis during embryogenesis. The expression of ß-catenin is observed in endodermal epithelia, including URS epithelia. We modulated the ß-catenin gene conditionally in endodermal epithelia by utilizing tamoxifen-inducible Cre driver line (Shh(CreERT2)). Both ß-catenin loss- and gain-of-function (LOF and GOF) mutants displayed abnormal clefts in the perineal region and hypoplastic elongation of the URS. The mutants also displayed reduced cell proliferation in the URS mesenchyme. In addition, the ß-catenin GOF mutants displayed reduced apoptosis and subsequently increased apoptosis in the URS epithelium. This instability possibly resulted in reduced expression levels of differentiation markers, such as keratin 1 and filaggrin, in the perineal epithelia. The expression of bone morphogenetic protein (Bmp) genes, such as Bmp4 and Bmp7, was also ectopically induced in the epithelia of the URS in the ß-catenin GOF mutants. The expression of the Msx2 gene and phosphorylated-Smad1/5/8, possible readouts of Bmp signaling, was also increased in the mutants. Moreover, we introduced an additional mutation for a Bmp receptor gene: BmprIA. The Shh(CreERT2/+); ß-catenin(flox(ex3)/+); BmprIA(flox/-) mutants displayed partial restoration of URS elongation compared with the ß-catenin GOF mutants. These results indicate that some ARM phenotypes in the ß-catenin GOF mutants were caused by abnormal Bmp signaling. The current analysis revealed the close relation of endodermal ß-catenin signaling to the ARM phenotypes. These results are considered to shed light on the pathogenic mechanisms of human ARMs.

Dysregulation of Wnt inhibitory factor 1 (Wif1) expression resulted in aberrant Wnt-ß-catenin signaling and cell death of the cloaca endoderm, and anorectal malformations.

In mammalian urorectal development, the urorectal septum (urs) descends from the ventral body wall to the cloaca membrane (cm) to partition the cloaca into urogenital sinus and rectum. Defective urs growth results in human congenital anorectal malformations (ARMs), and their pathogenic mechanisms are unclear. Recent studies only focused on the importance of urs mesenchyme proliferation, which is induced by endoderm-derived Sonic Hedgehog (Shh). Here, we showed that the programmed cell death of the apical urs and proximal cm endoderm is particularly crucial for the growth of urs during septation. The apoptotic endoderm was closely associated with the tempo-spatial expression of Wnt inhibitory factor 1 (Wif1), which is an inhibitor of Wnt-ß-catenin signaling. In Wif1(lacZ/lacZ) mutant mice and cultured urorectum with exogenous Wif1, cloaca septation was defective with undescended urs and hypospadias-like phenotypes, and such septation defects were also observed in Shh(-/-) mutants and in endodermal ß-catenin gain-of-function (GOF) mutants. In addition, Wif1 and Shh were expressed in a complementary manner in the cloaca endoderm, and Wif1 was ectopically expressed in the urs and cm associated with excessive endodermal apoptosis and septation defects in Shh(-/-) mutants. Furthermore, apoptotic cells were markedly reduced in the endodermal ß-catenin GOF mutant embryos, which counteracted the inhibitory effects of Wif1. Taken altogether, these data suggest that regulated expression of Wif1 is critical for the growth of the urs during cloaca septation. Hence, Wif1 governs cell apoptosis of urs endoderm by repressing ß-catenin signal, which may facilitate the protrusion of the underlying proliferating mesenchymal cells towards the cm for cloaca septation. Dysregulation of this endodermal Shh-Wif1-ß-catenin signaling axis contributes to ARM pathogenesis.

Testosterone manipulation postcastration does not alter cloacal gland growth differences in male quail selected for divergent plasma corticosterone stress response.

Japanese quail selected for reduced (low-stress, LS) rather than exaggerated (high-stress, HS) plasma corticosterone response to brief restraint have consistently shown greater cloacal gland (CG) development, an androgen-dependent trait. In this study, the effects of testosterone implants on levels of plasma testosterone and CG development in castrated LS and HS quail were determined. Stress-line males were castrated and randomly allocated to 1 of 3 testosterone treatments: the empty testosterone (ET), low testosterone (LT), or high testosterone (HT) implant group. Cloacal gland volume was determined at 4 weekly intervals that represented ranges of 1 to 9 d, 8 to 17 d, 15 to 24 d, and 22 to 31 d after castration and testosterone implantation. Levels of plasma testosterone were also assessed at the end of the study. Development of the CG was affected by quail line (LS > HS), testosterone treatment (HT > LT > ET), and time of measurement (1 to 9 d < 8 to 17 d < 15 to 24 d = 22 to 31 d after castration and testosterone implantation). A significant interaction between testosterone treatment and time of measurement on CG volume was also detected (with CG volume generally increasing with time in LT- and HT-treated quail, but not in ET-treated quail). However, even though HT implant treatments induced higher CG development than did LT treatments beyond the first interval of CG volume measurement, and despite the finding of greater CG volumes in LS than HS quail during the last 2 measurement intervals within each of the LT and HT groups, no interaction was observed between testosterone implant dosages and quail stress line on CG volume. Thus, by the end of the study, regardless of testosterone dose, CG volume was consistently greater in LS quail than in their HS counterparts. In addition, although, as expected, the testosterone implant treatment significantly altered levels of plasma testosterone (HT > LT > ET), neither quail line nor its interaction with testosterone treatment affected plasma testosterone. The present findings suggest that the often-observed depressed CG development in the HS line may be independent of testosterone effects.

Embryonic and posthatching treatments with sex steroids demasculinize the motivational aspects of crowing behavior in male Japanese quail.

Demasculinizing action of embryonic estrogen on crowing behavior in male Japanese quails was examined. Eggs were treated with either 20 microg of estradiol benzoate (EB) or vehicle on the 10th day of incubation. Chicks hatched from both groups of eggs were injected daily with either testosterone propionate (TP; 10 microg/g b.w.), 5alpha-dihydrotestosterone (DHT, a non-aromatizable androgen; 10 microg/g b.w.), or vehicle from 11 to 50 days after hatching, and during this period their calling behaviors were observed. Irrespective of embryonic treatments, all birds received posthatching treatment with either TP or DHT, but not with vehicle, emitted crows in place of distress calls in a stress (non-sexual) context of being isolated in a recording chamber. The posthatching TP, but not posthatching DHT, induced crowing in a sexual context (crowing in their home-cages) from much earlier age than posthatching vehicle in the birds received control embryonic treatment with vehicle. The same TP treatment, however, completely eliminated the crowing in a sexual context in the birds received EB during their embryonic life. In the birds treated with either posthatching DHT or posthatching vehicle, the crowing in a sexual context was only slightly decreased by embryonic EB treatment. These data suggest that posthatching estrogen, derived from testosterone aromatization, enhances the demasculinizing action of embryonic estrogen, and thus strongly reduces the sexual motivation for crowing behavior. This demasculinizing action, however, would not influence vocal control system which generates acoustic pattern of crowing in the presence of androgens allowing the birds to crow in a non-sexual context.

Dietary phytoestrogens and photoperiodic response in a male songbird, the Dark-eyed Junco (Junco hyemalis).

Many commercial bird diets are made with soy products that contain phytoestrogens (i.e., plant compounds that have weak agonist activity at estrogen receptors), but the effects of these compounds on bird physiology and behavior are largely unknown. The primary phytoestrogens present in soy are the isoflavones genistin and diadzin, which have been shown to affect reproductive measures in many taxa. Two groups of wild-caught male Dark-eyed Juncos (Junco hyemalis) were fed a diet either made with water-washed soy protein (soy(+)) or made with soy protein that had been alcohol-washed to extract isoflavones (soy(-)). Both groups exhibited a photoperiodic response to long days. Plasma luteinizing hormone (LH) concentrations increased within the first week of long day (LD) exposure for both groups, and over the course of the experiment LH was higher in the soy(+) group, although concentrations for both groups were lower than have been reported in free-living juncos. The rate of cloacal protuberance (CP) growth was significantly affected by diet, with the soy(-) birds beginning to increase their CPs about a week faster than soy(+) birds after exposure to LD. There was no group difference in food intake, fat score, body mass, or behavioral measures during the study or in testis weight at the end of the study. Although effects of dietary phytoestrogens detected were subtle (i.e., rate of CP growth), those investigating subtle effects of hormonally active substances (e.g., endocrine disruptors) or environmental cues affecting the reproductive axis in songbirds may want to consider eliminating phytoestrogens from their experimental diets.

Cloacal gland growth differences in high and low plasma corticosterone stress response line male quail reared under short daylengths.

Mail quail selected (generation 32) for reduced [low stress (LS)] or exaggerated [high stress (HS)] plasma corticosterone stress response to brief mechanical restraint (5 min of immobilization) were studied for differences in the growth of their cloacal glands when reared essentially lifelong on short day lengths of 8L:16D. Post-brooding, at 4 wk of age, 96 quail (48 LS+48 HS) were housed in cages (1 LS and 1 HS male/cage), and the short day light treatment was instigated. Using a digital caliper, cloacal gland (CG) size measurements (length and width, mm) were made biweekly beginning at 42 d of age and ending at 196 d of age (28 wk old). The CG volume (CVOL) was calculated from these measurements using a literature-proposed formula. The CVOL in both lines increased similarly with increasing age from 6 to 12 wk of age. However, beginning at 14 wk of age and thereafter, LS males showed greater (P<0.05) CVOL than HS ones. No further increases in CVOL were observed in either line at 24 wk of age beyond that seen at 22 wk. This study demonstrated that although both lines show CG development under short days, eventually CG growth becomes comparatively stymied in the HS males. Furthermore, the maintenance of similarly lower CVOL in HS than LS males, CVOL that showed no further increase from 22 to 24 wk of age, suggests that holding these quail lifelong on short days results in, comparatively, yet another permanent negative reproductive consequence in quail selected for exaggerated plasma corticosterone stress responsiveness.

Cloacal gland and testes development in male Japanese quail selected for divergent adrenocortical responsiveness.

The time course of sexual development in male quail from lines selected for either a reduced (low stress, LS) or an exaggerated (high stress, HS) plasma corticosterone response to brief restraint was determined. Sexual development was assessed by examination of cloacal gland area (CAREA) and volume (CVOL), proportion of individuals that produced cloacal gland foam, and the intensity of cloacal gland foam production (CFP) at 4, 5, 6, 8, 10, 14, and 16 wk of age. These intervals encompass ages during which growing, photostimulated quail would be expected to evolve from being totally prepubescent to well into adulthood. Testes weight (TW) and the proportion of individuals that had achieved a combined TW of 500 mg (PI500) were also measured at 6 and 16 wk of age. Mean CAREA and CVOL were similar in LS and HS quail at 4 wk of age. Beginning at 5 wk of age and thereafter, CAREA was greater (P < 0.05) in LS than in HS quail. Similarly, beginning at 6 wk of age and thereafter, CVOL was greater (P < 0.05) in LS than in HS quail. More LS than HS birds also expressed foam at 4 (P < 0.05), 5 (P = 0.15), and 6 wk (P < 0.05) of age. From 8 wk on, all birds were in foam production. CFP results mimicked those found for CAREA and CVOL in that LS quail tended toward higher CFP values than HS quail at all intervals of measurement. TW were higher (P < 0.02) in LS than HS quail when data from the 2 ages at which testes were harvested were combined. At 6 wk of age, the LS and HS birds showed a PI500 line difference (P < 0.08) of 1.0 and 0.91, respectively; by 16 wk, all birds exhibited a maximum PI500. The results suggest that 1) selection for reduced adrenocortical responsiveness in Coturnix is accompanied by an accelerated onset of puberty in males, and 2) enhanced reproductive development in LS males remains extant throughout early to middle-age adulthood.

Interrelationship of day length and temperature on the control of gonadal development, body mass, and fat score in white-crowned sparrows, Zonotrichia leucophrys gambelii.

We tested the effects of naturally relevant environmental temperatures on long day-induced reproductive development in male and female white-crowned sparrows, Zonotrichia leucophrys gambelii. Transfer from short days (8L 16D) to long days (20L 4D) resulted in rapid testicular development and partial ovarian development as has been reported many times previously. Exposure of experimental groups to low (5 degrees), moderate (20 degrees), and high (30 degrees) temperature during photostimulation had only subtle effects on plasma levels of follicle-stimulating hormone and luteinizing hormone over time and no effects on the size of testes, cloacal protuberance, ovaries, or brood patch at Day 30 of treatment. Long days resulted in the well known increase in body mass and fat score, indicative of preparations for migration. In females, treatment with low temperature resulted in a reduction in the premigratory increase in fat and body mass when transferred to long days. This was accompanied by an increase in plasma levels of corticosterone during the early stages of photostimulation at low temperature. Temperature regimes had no effects on fattening or body mass in males, despite an early increase in plasma corticosterone at low temperature. Circulating levels of thyroxine (T4) and triiodothyronine (T3) increased to varying degrees following photostimulation. Temperature treatment had no effect on plasma levels of thyroid hormones in males, but low temperature did inhibit thyroid hormone secretion (particularly T4) in females. Although reproductive development appears to be resistant to naturally relevant temperature extremes in both sexes, low environmental temperature impaired preparations for migration in females but not males. This effect may be mediated through glucocorticosteroids and not thyroid hormones. Reasons for the sexual dimorphism in this response are unknown, but may be related to sexual selection for males to arrive on the breeding grounds ahead of females regardless of local weather conditions.

Influence of different photoperiods on development of gonad, cloacal gland and circulating thyroid hormones in male Japanese quail Coturnix coturnix japonica.

One day old chicks of Japanese quail were exposed to different photoperiods (LD, 8:16, 13.5:10.5, 16:8 and LL) and observations (testes weight, cloacal gland size, body weight and circulating thyroxine and triiodothyronine) were taken at the age of 3, 5, 7, 9 and 16 weeks. Results indicate that immediate reproductive development occurred in birds exposed to long photoperiods (greater than 12 hr). Growth under LD 8:16, was not apparent till 7th week and by 16 weeks, degree of gonadal development was similar in all the birds, irrespective of photoperiodic treatment. Whereas body weight of the intermediate and long day (LD 13.5:10.5, 16:8 and LL) treated birds increased upto 5th week and remained constant thereafter. But the chicks maintained under short day length (LD 8:16), showed spontaneous increase till the end of the study and birds were much heavier compared to all other groups. Plasma T4 concentration increased with increasing age till 9th week and remained unaltered thereafter. On the other hand T3 level did not change till 7th week followed by a decline. It is suggested that the initiation and degree of gonadal growth in quail depends on the availability of daily photoperiod, until the achievement of full breeding condition. Peak level of T4 observed in 9 week old birds may be involved in the development of photorefractoriness at that age.

Effects of surgical deafening and exposure to continuous darkness on cloacal gland size in scotorefractory Japanese quail.

Adult male quail were transferred to short days (SD) and exposed simultaneously to conspecific vocalizations of males on long days (CVMLD). Cloacal glands did not regress in some males while in others their glands regressed then spontaneously recrudesced. Of the birds that exhibited cloacal gland regression, 80% recrudesced by 8 weeks and all birds recrudesced by 25 weeks on SD. Three experiments are reported. The first experiment analyzed the effects of transfer to SD. The remaining two experiments examined the role of auditory stimuli. In Experiment 2, deafening males whose cloacal glands had not regressed after 17 days exposure to SD and CVMLD produced a significant decrease in cloacal gland size. In Experiment 3, quail whose cloacal glands had regressed and recrudesced while exposed to SD and CVMLD were deafened and/or transferred to complete darkness (DD). Cloacal gland size was significantly smaller in deafened males kept on SD or kept in DD than in sham controls retained on SD. Surprisingly, the cloacal glands of sham controls in DD were similar to those of intact birds which remained on SD. These results suggest that scotorefractoriness which has been attributed to an insensitivity to short photoperiods may be due to a sensitivity to vocalizations of birds on LD. Perhaps there is a hierarchy of physical and social cues so that a decrease in the photoperiod unmasks the effects of auditory stimuli. Furthermore, an interval timer mechanism or some alternative to the external coincidence model of time keeping seems to account for the refractoriness to SD.

Developmental sex differences in brain aromatase activity are related to androgen level.

Sex differences in the metabolism of testosterone (T) in the developing brain of quail were examined using an in vitro microassay. During each developmental stage (day before hatching, hatching and 2 days after hatching) aromatase activity was higher in hypothalamic areas than in a control neostriatal area. There was no sex difference in oestradiol-17 beta (E2) formation in the late embryonic brain or at hatching. But aromatase activity in the male preoptic-anterior hypothalamic area was 50% higher than in females by day 2. No regional differences in brain 5 beta-reductase activity were detected at any of the developmental stages sampled. There was a sex difference in production of catabolic 5 beta-reduced metabolites. Male 5 beta-reductase activity declined continuously from high embryonic levels in all areas, whereas female enzyme activity showed an increase at hatching. In contrast to plasma progesterone, levels of T were higher in the male than in the female by day 1 after hatching. We suggest that elevated circulating T in the male after hatching may account for the sexual dimorphism in brain aromatase activity.

Relationship between throat feather-color pattern and photodependency of testicular function in the athens randombred control line of Japanese quail.

The relationship between throat feather-color and testicular regression and recrudescence under short photoperiods of 6 hr light (L):18 h dark (D) was examined in the Athens randombred control line of Japanese quail. In contrast to earlier studies, no differences were found in testicular regression when quail with brick red, mixed red and white, central red surrounded by white, or all white throat feathers were shifted from a photoperiod of 16L:8D to one of 6L:18D. The cloacal protuberance areas (CPA) of all groups ranged between 1.81 +/- .09 and 1.90 +/- .19 cm2 while birds were housed on the long photoperiod. Cloacal protuberance areas of all groups were markedly reduced after 3 wk of exposure to 6L:18D. Testes weights of all groups ranged between 46.7 and 54.8 mg after 3 wk of exposure to the short photoperiod. In a second experiment, cloacal foam gland development of males of the four throat feather patterns was examined during 26 wk after changing the photoperiod from 16L:8D to 6L:18D. Foam glands of all groups regressed within 3 wk of exposure to 6L:18D. Glands of birds with brick red throats or mixed red and white feathers recrudesced by 11 wk under the short photoperiod. Foam glands of birds with white throats or a band of white surrounding a patch of red did not show recrudescence at 11 or 14 wk but did so by 26 wk.

Effect of the injection solvent on steroid activity.

The effects of testosterone, 5 alpha-dihydrotestosterone, and androstenedione on cloacal gland and sternotracheal muscle growth and on luteinizing hormone plasma levels were studied in Japanese quail. The steroids were given to the animals in daily intramuscular injections and were dissolved either in propylene glycol or in ethanol:saline (1:1). The three steroids had significant effects on the responses which were measured, but the magnitude of this effect was clearly related to the type of vehicle in which the steroids were dissolved. Furthermore there was a significant interaction between the effects of solvents and of steroid; for example, testosterone was much less androgenic than 5 alpha-dihydrotestosterone when dissolved in propylene glycol, but both had similar effects when dissolved in ethanol:saline. The effects of the mode of administration of different steroids on a given physiological response should be taken into consideration.

Testosterone induces hypothalamic aromatase during early development in quail.

The effects of testosterone on androgen metabolizing enzymes were examined in the developing hypothalamus of male and female quail using an in vitro radiometric assay which measures metabolite formation in individual brain samples. Testosterone (T) administered by subcutaneous silastic implants to gonadectomized 4-day-old chicks increased formation of estradiol-17 beta (E2) in both preoptic area + anterior hypothalamus (PA) and posterior hypothalamus + tuberal area (HT) to adult levels. The T-induced increase in E2 formation occurred to the same degree in both sexes. The increase was very small in control non-target areas, neostriatum intermediale + hyperstriatum ventrale (VN), of either sex. Testosterone had no effect on formation of 5 alpha-dihydrotestosterone (5 alpha-DHT), 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta-androstane 3 alpha, 17 beta-diol (5 beta, 3 alpha-diol) in PA. Kinetic analysis of the rate of E2 production by hypothalamic tissue from castrated chicks (CX-chicks) and castrates treated with T (CX + T-chicks) indicates that the increase in hypothalamic aromatase activity by T corresponds to induction of the enzyme: the Vmax (maximum velocity) was increased by T (CX-chicks, 21; CX + T-chicks, 91 fmol/mg FW/h), whereas the Km was unaffected (CX-chicks, 5.5; CX + T-chicks, 4.7 X 10(-8) M). Testosterone treatment, effective for inducing PA and HT aromatase activity, also activated crowing and caused cloacal gland development; neither of these effects were sexually dimorphic. Our results indicate that: (1) T induces aromatase specifically in the hypothalamus during early post-hatching development, other pathways of T metabolism are not affected; and (2) the inducible aromatase is not sexually dimorphic in the developing brain. Since there are sex differences in adult brain aromatase, we conclude that capacity for induction of the hypothalamic aromatase becomes sexually differentiated after the post-hatching period.

Environmental and endocrine control of reproduction in the song sparrow, Melospiza melodia. I. Temporal organization of the breeding cycle.

Endocrinologic investigations of free-living populations of song sparrows, Melospiza melodia, have revealed temporal patterns of secretion of reproductive hormones that differ from those of other monogamous avian species. Males arrive in the breeding area in March whereas females arrive 1-2 weeks later. In males the periods of territory establishment and attraction of a mate are characterized by high circulating levels of luteinizing hormone (LH) and testosterone (T), whereas testis mass is low, and growth of the cloacal protuberance (CPL) is just beginning. In April, testes and CPL develop rapidly reaching a peak in early May when females are laying eggs, and when most copulations occur. Plasma LH and T decline in early April, but increase for a second time in late April and early May coincident with the egg-laying period. Thereafter, circulating LH and T decline during the parental phase, but not to basal levels. Although there is an increase in LH during the egg-laying period for the second clutch, there is no change in T levels. Testis mass, CPL, plasma LH, and T all decline to basal levels simultaneously in late July and August. The high levels of LH and T in March, followed by a temporary decline and resurgence in April and May, indicate that environmental factors in addition to the well known effects of increasing day length can regulate secretion of these hormones. In females, plasma levels of T and dihydrotestosterone (DHT) are also elevated in March and early April, and decline to low levels as the nesting phase progresses. A further decline, to basal levels, occurs in August during the molt. LH and estradiol (E2) titers in females show two peaks coincident with the egg-laying periods for each clutch. Plasma levels of corticosterone (B) increase during the breeding season in males, but not females. In both sexes B levels are basal during the moult and increase in October after moult is completed. Body mass and fat depot decline in males as the nesting phase progresses, and then increase dramatically after breeding is terminated. As expected, females show two peaks of body mass and fat depot coincident with the two periods of egg laying. The postbreeding increases in body mass and fat depot are much less pronounced in females than in males.

Relative potencies of testosterone and 5 alpha-dihydrotestosterone on crowing and cloacal gland growth in the Japanese quail (Coturnix coturnix japonica).

It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5 beta-reductase in the young brain, which converts testosterone to inactive 5 beta-reduced metabolites. This hypothesis was tested indirectly by comparing the relative potencies of 5 alpha-dihydrotestosterone (5 alpha-DHT), which cannot be converted to 5 beta-metabolites, and testosterone at inducing crowing in young gonadectomized male and female quail. The promotion of cloacal gland growth by these treatments was also assessed since there are no age-related changes in 5 beta-reductase in this organ. Silicone elastomer implants (2 X 5, 5 and 10 mm) containing 5 alpha-DHT were more effective at stimulating crowing than similar implants of testosterone whilst there was little difference in their potency at inducing cloacal gland growth. These results are consistent with the hypothesis that brain steroid 5 beta-reductase regulates the behavioural activity of testosterone in the brain of young birds.

Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone.

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males.

Variations in the photoperiodic cloacal response of Japanese quail: association with testes weight and feather color.

The size of the cloacal gland was found to be a reliable indicator of testicular activity of Japanese quail. Six experiments were performed to examine the effects of alternating long and short photoperiod on the size of the cloacal gland of male Japanese quail. Three types of photoperiodic cloacal responses were distinguished. Type I birds became refractory to short photoperiods after they had experienced 5 weeks or more of short days. They maintained large cloacal glands under subsequent condition of alternating long and short photoperiod. Type II birds were intermediate types I and III birds did not become refractory to short photoperiods after experiencing 5 weeks or more of short days. The cloacal glands responded to conditions of alternating long and short photoperiods with increases or decreases in size. Feather color on the throat was found to correspond to the type of cloacal response. Type I birds had brick-red throat feathers. Type II birds had white feathers intermingled with brick-red feathers. Type III had white throat feathers. The percentages of types I, II, and III observed in the experimental population was 67, 18, and 15%, respectively. Type III birds were used to study the effects of blinding on the cloacal response to short photoperiod. Five out of eight blinded type III birds did not lose the responsiveness to short photoperiod. These results are consistent with the view that extraocular photoreceptors participate in the photoperiodic gonadal response of Japanese quail.