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Abstracts from VI International Symposium on Avian EndocrinologyMarch 31 - April 5, 1996 Chateau Lake Louise, Alberta Continued Behavioral and Hormonal Development in a Small Parrot, the Peach-Faced Lovebird (Agapornis roseicollis)E. Pröve, a. Reichmann Universität Bielefeld, Fakultät für Biologie, Postfach
100131, D-33501 Bielefeld, Germany Previous investigations revealed that gonadal steroids are not important in the control of social and sexual behaviour patterns of adult peachfaced lovebirds. This investigation proved whether there might be an influence of gonadal hormones on the development of social and sexual behaviour patterns early in ontogeny (day 2 until day 120 of life). Behavioral development of female and male birds is nearly identical and could be divided into three phases. Only weak correlations are found according to the production of gonadal steroids. Manipulation of developing birds with androgens revealed a negative influence on development, with respect to forming pair bonds (which takes place very early in development). Endocrine Mechanisms of Cooperative Breeding in Florida Scrub Jays (Aphelocoma coerulescens)S.J. Schoech Department of Biology, Indiana University, Bloomington, IN
47405, USA Cooperatively breeding species are characterized by the presence of helpers that provide parent-like care to nondescendant young. Although helpers in some species also breed, Florida scrub jay helpers are nonbreeders that may delay breeding for up to five years. To determine whether fundamental physiological differences between breeders and helpers might explain delayed breeding in helpers, gonadal and adrenal steroid hormone levels and gonad dimensions were compared in male and female breeders and nonbreeders. Additionally, because prolactin is often associated with parental behaviors, the relationship between prolactin and helping behaviors was also examined. Male helpers had lower testosterone (T) levels and smaller testes than breeders, however, helpers' T titres and testes volumes exhibited significant seasonal increases. Female helpers had estradiol levels that were equivalent to (1992 and 1994) or higher than (1993) breeders. Whereas helpers' ovarian follicles were not as developed as breeders, they were not completely regressed. Additionally, in both males and females, neither baseline corticosterone levels (1 min post-capture) nor levels following administration of a prolonged stressful stimulus differed between breeders and helpers. These data suggest that male and female helpers are reproductively competent but, nonetheless, remain as nonbreeders. This is not due to physiological differences, but is more likely because there are a shortage of breeding opportunities, i.e. suitable habitat. Previous researchers have postulated that helpers are reproductively inhibited, however, the corticosterone data show that if helpers are inhibited it is independent of the adrenal axis. Prolactin levels were highest while caring for nestlings, although breeders had higher levels than helpers. Prolactin titres of helpers were correlated with the amount of food that they delivered to nestlings. Not all helpers provisioned nestlings: those that did had higher prolactin titres than those that did not help. These data suggest that prolactin facilitates helping in the Florida scrub jay. The Effects of Testosterone on Reproductive Success in the Dark-Eyed Junco, Junco hyemalis carolinensisS.a. Raouf, P.G. Parker1, E.D. Ketterson, V. Nolan Jr Department of Biology, Program in Animal Behavior, Indiana
University, Bloomington, IN 47405, USA; 1Department of Zoology,
1735 Neil Avenue, Ohio State University, Columbus, OH 43210, USA We are studying how the hormone testosterone (T) affects male fitness by altering male reproductive behavior in the darkeyed junco, a monogamous territorial passerine. Previously, we have shown that manipulating plasma T levels by giving male birds T implants alters their phenotype in several ways: elevating song rate, increasing homerange size, decreasing nest attendance, and enhancing attractiveness to females. Here we present the results of a fouryear field study in which we compare the reproductive success at home (by withinpair copulations) and away (by extrapair copulations, EPFs) of control and Ttreated male darkeyed juncos using multilocus DNA fingerprinting. Our results show that in the nests belonging to Tmales fewer eggs hatched than in the nests of control males. However, by the time nestlings were six days old the number of young in the nest genetically related to the caregiving father was not affected by male treatment. The percent of offspring produced by EPFs in this population varied from 20% to 40%. In all 4 years Tmales were significantly more likely to have fathered the extrapair young than control males. In summary, treating darkeyed juncos with T alters a suite of traits, some of which affect male behaviour and male attractiveness to females. Our results show that these differences do not result in a loss of genetic fitness with the social mate, but enhances fitness gained through extrapair fertilizations. Plasma Corticosterone Response Characteristics in Mallard DucksD. Guéméné, G. Guy1, J. Noirault, J.M. Faure Station de Recherches Avicoles, INRA, Centre de Tours, 37380
Nouzilly, France;1Station Expérimentale des Palmipèdes à Foie
Gras, INRA, Artiguères, 40280 Benquet, France In view of the public concern about stress and welfare of domestic animals, we intend to investigate the effect of force feeding upon physiological indicators of stress. As a preliminary we have characterised corticosterone (B) secretion in male mallard ducks between 10 and 14 wk of age. In a first experiment three serial blood samples were drawn at 15 min intervals by either venipuncture (VP) or occipital sinus puncture (OSP), to assess the effects of blood sampling. B levels were lower in the samples drawn by OSP and significant differences were observed on the first 2 sampling. The OSP procedure was therefore used in all other trials. In a second experiment we investigated the effect of a single i.m. injection upon B levels, measured 15 min later. Results showed no effect of a single i.m. injection of 1ml 0.9% saline solution. In trial 3, ACTH (Synacthen) was i.m. administrated (5mg/kg B.W.) and different ducks were sampled at 10 min intervals. The B levels rose significantly (P < 0.05) above control values. B levels were maximum 10 min after injection and decreased thereafter and were no different from controls 60 min post-injection. In trial 4, ACTH was injected i.m. at doses ranging between 0.625 to 20mg/kg B.W. and B levels measured in samples taken 15min post-injection. B levels rose significantly (P < 0.05) above control values for all tested doses and the maximum response was measured with a dose as low as 1.25mg/kg B.W. It is concluded that the OSP procedure can be used for B measurement, that a delay of 15min is adequate to perform sampling and ACTH doses of 0.625 and greater than 1.25mg/kg B.W are adequate to measure suboptimal and maximum B responses in male mallard ducks. Prevention of Incubation Expression Using Passive Immunization Against ProlactinS. Crisóstomo-Pinto1,2, D. Guéméné1, M. Garreau-Mills1, D. Zadworny3 1Station de Recherches Avicoles, INRA-Centre de Tours, 37380
Nouzilly, France; 2Faculdade Veterinária, UECE Dpto. de Medicina
Veterinária, 60715 Fortaleza-Ce-Brasil; 3Department of Animal
Science, McGill University H9X-3V9 Canada Active immunization against prolactin has recently been shown to be an effective approach to delay and/or to prevent incubation behavior expression in domestic birds (Guémené et al., 1994, 1995; March et al., 1994). In this experiment we investigate whether passive immunization against prolactin could also prevent incubation behavior in turkey hens. Medium White turkey hens (n=30) were injected 3 times per week during 4 consecutive week starting on week 5 of egg production. The hens were injected i.m. with a volume of 1.0 ml per injection for the first week and 0.5 ml thereafter, of normal rabbit serum or serum containing antibodies raised against turkey prolactin (Guémené, et al., 1994). None of the passively immunized hens exhibited incubation behavior, whereas more than half (53%) of the control hens did. Plasma prolactin concentrations in the two groups were comparable until week 9 and from week 19 of egg production onward. Differences were observed from week 10 until week 16. Nonimmunized hens had higher plasma prolactin concentrations than immunized hens. This difference can be related to the presence of incubating hens in the control group. No change in plasma LH and oestradiol concentrations were seen after immunization. We conclude that prevention of incubation behavior can be achieved by passive immunization against prolactin; a technique that resulted in a higher rate of egg production under our experimental system. Regulation of Food Intake by Metabolic Fuels in Migratory BirdsT. Boswell*, M. Ramenofsky, R.D. Richardson, R.J. Seeley, J.C. Wingfield, S.C. Woods Departments of Zoology and Psychology, University of
Washington, Seattle, WA 98195, USA; *Present address: Roslin
Institute, Roslin, Midlothian EH25 9PS UK Migratory birds show increased storage and utilization of fat, promoted by increased feeding before migration, as an adaptation for long-distance flight. To determine whether their food intake is sensitive to carbohydrate and/or lipid utilization, white-crowned sparrows maintained on short days (9L15D) were injected intraperitoneally (i.P.) with carbohydrate utilization inhibitors (2-deoxy-D-glucose (2-DG) or 2,5-anhydro-D-mannitol; 2,5-AM). Food intake was decreased by high doses of 2-DG (100 and 300 mg/kg) or 2,5-AM (300 and 600 mg/kg). No dose of 2-DG or 2,5-AM increased feeding. Plasma glucose levels were manipulated by injecting insulin (0.5, 1, 2, 4 U/kg, intramuscular) and glucagon (1, 10, 25, 50 mg/kg, i.P.). Insulin significantly decreased plasma glucose while glucagon induced a significant increase. While exerting opposing effects on glucose levels, the effect of both hormones on food intake was similar, in that low doses did not affect feeding and higher doses (insulin, 2 and 4 U/kg; glucagon 25 and 50mg/kg) induced significant decreases. Furthermore, injections of glucose (10, 50, 100 mg/kg, i.P.) had no significant effect on food intake. Together, these data suggest that feeding is not sensitive to changes in plasma glucose levels, and that, unlike mammals, white-crowned sparrows do not increase food intake in response to decreased carbohydrate utilization. However, 2-DG, 2,5-AM, insulin and glucagon had the common effect of significantly increasing plasma free fatty acid levels, as well as decreasing feeding. Moreover, injections of the lipid tributyrin (100, 300, 600 or 2000 mg/kg i.P.) significantly depressed food intake in a dose-dependent manner. Increased levels of plasma lipids may, therefore, inhibit feeding. Thus, food intake in white-crowned sparrows appears to be more sensitive to signals from lipid metabolism than to those from carbohydrate metabolism. Localization of cGnRH-I and pre-pro-GnRH-I mRNA in Laying and Refractory Turkey HensG.F. Ball, H.R. Besmer, T.P. Hahn, J.a. Proudman1, M.a. Ottinger2, M.M. McCarthy3 Department of Psychology, Johns Hopkins University, Baltimore,
MD 2128, USA; Germplasm Laboratory, ARS-USDA, Beltsville, MD
20805, USA; 2Department of Animal Science, University of
Maryland, College Park, MD 20742, USA; 3University of Maryland
School of Medicine, Baltimore, MD 21201, USA Turkey hens placed on long photoperiods (>12L:12D) will lay for approximately 25 weeks and many will cease laying due to broodiness or photorefractoriness. In many avian species the onset of refractoriness is associated with marked changes in the hypothalamic content of chicken gonadotropin-releasing hormone-I (cGnRH-I). We collected brains from turkey hens who had been held on a photoperiod of 14L:10D for 25 weeks. Birds were either still egg laying or had ceased egg laying for at least 6 weeks and appeared to be refractory. Brains were collected and cGnRH-I was measured either by enzyme immunoassay (EIA) from microdissected brain areas or via immunocytochemistry. An in situ hybridization procedure (using a ssDNA probe generated by asymmetric PCR and internally labelled with 32P-CTP) was also used to localize the mRNA for preproGnRH-I. Cells containing preproGnRH-I were located in the preoptic and septal areas, identical to the localization of cGnRH-1 immunoreactivity. This is the first demonstration of prepro GnRH-1 localization in avian species, although the distribution of cGnRH-I immunoreactive cells is in good agreement with a previous report by Millam et al. (JCN 333:68-82, 1993) for turkey hens. cGnRH-I immunoreactivity and preproGnRH-I mRNA in hens was not significantly different from that in refractory hens, though there were differences the cGnRH-I content of the median eminence, measured by EIA. Corticosterone, Body Condition, and Dispersal Behavior in Screech-Owls: a New ModelA.M. Dufty, J.R. Belthoff Raptor Research Center and Department of Biology, Boise State
University, Boise, ID 83725, USA In virtually all birds and mammals, juveniles of one or both sexes leave their natal area before breeding. In western screechowls (Otus kennicottii), both sexes of young disperse, but there is variation in the timing of dispersal within and among broods. We present a model that explains the timing of dispersal in screechowls and similar nonmigratory species where young birds obtain and defend territories following dispersal. The model is based on interactions among hormones, body condition and social stimuli. We hypothesize that corticosterone (B), which is known to stimulate increased locomotor activity and foraging behavior in birds, increases just prior to dispersal through a combination of endogenous and exogenous events. Although rising plasma corticosterone may stimulate increased movement, the precise effect on dispersal timing depends on the body condition of the bird. Juveniles in good body condition (i.e., those with sufficient fat reserves) are prepared to disperse and will leave when corticosterone initially rises. Birds in poor body condition will not disperse, but the rise in B will stimulate increased foraging activity, resulting in improved body condition and dispersal. Preliminary laboratory studies support predictions of the model: both B and locomotor activity increase in captive juvenile owls at the time that freeliving owls disperse, and B stimulates increased body mass. Age-Related Differences in Vocal Control Region Size in Adult Dark-Eyed Juncos (Junco hyemalis)C.C. Gulledge, P. Deviche Institute of Arctic Biology, University of Alaska Fairbanks,
Fairbanks, AK 99775, USA Oscines have an interconnected set of brain regions (vocal control regions, VCRs) that control song learning and production. VCR volumes increase dramatically during development, then are relatively stable through the first breeding season. Some VCRs decrease in size after breeding, but then increase again before the next breeding season via recruitment of new neurons and cell growth. Birds entering their first breeding season (FBS) have never experienced post-breeding shrinkage in these regions, whereas older birds (>FBS) have experienced cyclic VCR volume changes. To determine whether >FBS birds fully increase their VCRs to match FBS volumes, we measured the volumes of four VCRs (Area X, MAN, HVC, and RA) in FBS and >FBS male dark-eyed juncos (Junco hyemalis) captured during the breeding season. We found that the volumes of two regions (Area X and MAN) involved in song learning and perception are larger in FBS than in >FBS birds. In contrast, the volumes of two regions (HVC and RA) regulating song expression did not differ with respect to age. Birds of both ages must be able to produce songs in order to defend territories and attract mates. In some species, FBS males modify their own song repertoires to match older males on neighbouring territories. One explanation for the observed differences in VCR volumes may, therefore, be that FBS males require more brain space devoted to song learning and perception in order to match neighbouring song repertoires. In addition, when occupying a territory and breeding for the first time, FBS males must learn to acoustically identify neighbouring conspecifics. In contrast, >FBS male juncos return in the spring to a previously occupied site and so are already familiar with some characteristics of their acoustic environment. We propose that this difference may explain why >FBS males do not increase brain space involved in learning and conspecific song perception to match that of FBS males. (Supported by NSF Award BNS-9121258 to P.D.) Short Term Increases in Activity in Gambel's White Crowned Sparrow due to Non Invasive Corticosterone AdministrationC.W. Breuner, a.L. Griffith, J.C. Wingfield Department of Zoology, Box 351800, University of Washington,
Seattle, WA 98195-1800, USA There is emerging evidence that corticosteroids influence the facultative behavioral changes associated with stressful events. An increase in locomotor activity in response to a stressor could be adaptive if it removes the organism from the vicinity of the stressor, such as low food availability. This increase in locomotor activity has been associated with rising levels of corticosteroids. Many aspects of this action, however, are still unclear: 1) does corticosterone directly activate locomotor activity; 2) after the onset of a stressor, how quickly does corticosterone affect activity; 3) do activity levels increase with higher doses of corticosterone, or is it solely a threshold response; and 4) is there a seasonal regulation of this behavioral response? A non invasive method of corticosterone delivery has therefore been devised to address these questions in Gambel's white crowned sparrow (Zonotrichia leucophrys gambelii). Injecting meal worms with corticosterone and feeding those worms to the birds increases circulating corticosterone levels to a discrete, repeatable level which peaks within seven minutes and is cleared within 60 minutes. Controls receive meal worms injected with vehicle and there is no increase in corticosterone. These experiments demonstrate that corticosterone increases activity within 30 minutes of application, this activity does not increase with higher levels of corticosterone, and the response varies seasonally. Mechanisms for Seasonal Modulation of the Corticosterone Response to Stress in Free-Living and Captive White-Crowned SparrowsL.M. Romero, J.C. Wingfield Department of Zoology, Box 351800, University of Washington,
Seattle, WA 98195, USA Whitecrowned sparrows (Zonotrichia leucophrys, abbr. WCS) can modulate their corticosterone (B) response to stress seasonally, so that the amount of B released in response to a standard stimulus depends upon the time of year. To further examine this phenomenon, we tested three questions: do changes in (1) adrenal sensitivity to ACTH or (2) pituitary sensitivity to ACTHreleasing factors contribute to modulation of the B response; and (3) do captive birds also modulate their B responses? Freeliving Gambel's WCS were captured during breeding in Alaska and during fall migration in Washington and subjected to a standardized 30 min stress of capture and handling. Baseline B levels (within 3 min of capture) were 5fold higher during breeding. B increased after stress at both times, but stressinduced levels during migration were equivalent to baseline levels during breeding. The maximal B response to stress could be further augmented during breeding with an ACTH injection, but ACTH was ineffective during migration. Furthermore, during breeding ACTHreleasing factors (CRF, arginine vasotocin , and mesotocin) could further augment B release, an effect again lacking in migrating birds. We also measured responses in captive molting Gambel's and Pugetensis WCS and captive Gambel's WCS, 2 weeks after capture and before molt. Baseline B levels in all captives were slightly elevated at all times compared to migrating freeliving birds. All captives had stressinduced B levels similar to migrating birds, but only in Pugetensis and in recently captured Gambel's did ACTH augment that response. At no time were ACTHreleasing factors effective in captives.These data suggest that (1) captive WCS can modulate their B responses to stress, and (2) both the adrenal and pituitary undergo changes in their sensitivities to their respective releasing factors. Testosterone Implants Increase Song but not Aggression in an Arctic Bird, the Lapland Longspur (Calcarius lapponicus)K.E. Hunt, J.C. Wingfield, T.P. Hahn Department of Zoology, Box 351800, University of Washington,
Seattle, WA 98195, USA Arctic birds have an extremely short breeding season, with rapid changes in behavior that may involve different relationships of hormones and behavior than those normally seen in lowerlatitude birds. We studied the effect of exogenous T on song and aggression in freeliving male Lapland longspurs (Calcarius lapponicus), a tundranesting arctic passerine. Male Lapland longspurs have an unusually high (1020 ng/ml) and brief (13 days) peak of circulating T in early spring, and much lower T during incubation (Hunt et al. 1995). We gave highT implants to 16 birds, lowT implants to 7 birds, and empty or no implants to 23 control birds, and measured their circulating T levels, cloacal protuberance lengths, and behavior during incubation. HighT birds had larger cloacal protuberances than controls, but lowT birds did not. We measured aggression (threat posture and attacks) and song by placing a live decoy with taped song playback near the focal bird's nest, and recording behaviors for the next 30 minutes. HighT birds were no more aggressive than controls, but were significantly more likely to sing. LowT birds did not behave differently from controls. Overall, birds with higher T levels stayed further away from the decoy and sang, while birds with lower T levels stayed closer to the decoy and did not sing. Song occurrence was not correlated with aggression occurrence. These results suggest that the high, brief T peak of male Lapland longspurs may be related more to song than to direct territorial aggression. We speculate that the hormonebehavior patterns demonstrated in this study may be adaptations for breeding in the short Arctic summer. The Lapland longspur's very high, brief T peak may be a mechanism for limiting high song rate to a brief period in early spring, facilitating a sudden transition into breeding condition and a very brief courtship phase of just 13 days, while allowing other Trelated functions to continue for several weeks more at lower T levels. Reductase Activity, Aggression and Reproduction in Bearded TitsJ. Dittami, H. Hoi1, E. Möstl2 Institute of Zoology, Althalstr. 14, A-1090 Vienna; 1KLIVV,
Savoyenstr. la, A-1160; 2Institute of Biochemistry,
Linkebahngasse 11, A-1030 Vienna, Austria Bearded tits exhibit an abnormal seasonal pattern of androgens, aggressive behavior and reproductive behavior compared to other marsh breeding species. Pair bonds are formed in autumn and mating occurs in spring. Male aggression peaks in fall and is non-existent in spring, the reverse pattern of females. Polyandrous mating occur before egg-laying, in which up to 30 males are involved in an attempt to isolate and copulate with a female after a courtship flight. Male genitalia (measured by CPL) in this species are extremely large for any bird species with comparable mass (<10mm and 30g). The disparity between reproduction and aggression is evident in androgen patterns in males and females. Males have elevated testosterone levels in fall but baseline levels in spring. An immunogram was constructed for blood from spring males by combining HPLC and RIA data. Results showed that 17-ß-dihydrotestosterone levels peak in males in spring. Females, conflict frequencies and androgen titres reflect the males' nest defence and, later in the season, resource defence patterns, which we have described for other species: high nesting values and then slow increases over summer with minimal levels in fall. It is interesting that the levels of conflict in males but not the genital development or sexual behavior is effected by reducing the androgens in circulation. Trade off's are assumed here between the costs and benefits of mate guarding and the need for a high copulatory potential, where genital size and flight speed may play important roles. Effect of `Chemical Adrenomedullectomy' on the Testis of PigeonsA. Ghosh, S. Ghosh, S. Sengupta Histophysiology Laboratory, Department of Zoology, University
of Calcutta, 35, Ballygunge Circular Road, Calcutta-700 019,
India As a result of intensive investigations over the last few decades, a large body of information has accumulated which suggests that both environmental and hormonal factors are involved separately or jointly, in the regulation of avian gonadal cycle. Amongst peripheral hormones, adrenomedullary hormones also seem to be involved in the control of avian reproduction, although this is a controversial view. To explore the direct and indirect influence of the adrenal medulla upon the avian gonad, the chromaffin tissue should be ablated. This is, however, impossible in birds because of intermingling of cortical and medullary tissues. Guanethidine sulphate is, however, known to be a selective destroyer of the adrenal medulla and a depletor of catecholamines. Hence, to know the direct influence of the adrenal medulla upon the testis, guanethidine was administered to pigeons (single dose: 5 mg/bird for 96 hours). Histologically remarkable changes were observed after guanethidine treatment. Medullary areas were drastically disorganized, whereas the cortical areas remained normal. In the testis, overall degeneration of germinal epithelium and leydig cell disruption took place after treatment. Biochemically, epinephrine and norepinephrine contents were drastically decreased after guanethidine treatment, but the corticosterone level remained unchanged. Plasma testosterone showed a lowered titre in the guanethidine treated pigeons. In conclusion, `chemical adrenomedullectomy' causes spermatogenetic disruption, along with the fall in plasma testosterone level in pigeons, which clearly indicates a `direct' role of catecholamines in the testicular physiology of this avian species. [Supported by grants from the Indian National Science Academy to AG (BS/SS/73/95), LPB Trust, Calcutta to SG and R.D. Birla Smarak Kosh, Bombay to SS] |