Effect of female sexual displays on the endocrine physiology and behaviour of male white-crowned sparrows, Zonotrichia leucophrys

In photoperiodic birds, endocrine responses to behavioural interactions between males and females may be involved in temporally "fine-tuning" the onset of reproduction to yearly variations in the environment. This study examined the endocrine and behavioural responses of male White-crowned sparrows ( Zonotrichia leucophrys ) to changes in the endocrine state of the female, as signalled by changes in her behaviour. Males on different photoperiodic regimes were paired with oestrogen-treated, sexually receptive females. Males exposed to gonadostimulatory long days mounted and copulated with oestrogen-treated females even before gonadal development was complete. These males had higher plasma levels of testosterone and luteinizing hormone and maintained enlarged testes longer than control males paired with untreated, nonreceptive females. Males maintained on nonstimulatory short days also mounted oestrogen-treated females; however, testes of these males remained nonfunctional and their plasma levels of testosterone and luteinizing hormone were basal. Thus, reproductive function of photostimulated males is profoundly affected by changes in the endocrine state and behaviour of the female. However, male sexual behaviours are expressed in response to visual and auditory stimuli from the female regardless of male hormonal condition or photoperiodic treatment.     

The prolactin cell of the white-crowned sparrow,Zonotrichia leucophrys pugetensis

Summary The anterior pituitaries from a series of female White-crowned Sparrows,Zonotrichia leucophrys pugetensis, in the periods of oviposition, incubation, and brooding under natural conditions, have been investigated by electron microscopy. The prolactin cells occur in cephalic lobe and are characterized by large (ca. 300–600 m), polymorphic electron-dense secretory granules and an extremely well developed, lamellated endoplasmic reticulum. During incubation and brooding it is only these prolactin cells that are in an activated secretory phase, as indicated by increase in number and size, extremely well developed endoplasmic reticulum, decrease in number of mature secretory granules, and by active formation of granules in the enlarged Golgi apparatus. In the late stages of brooding, and post-breeding, the prolactin cells regress with involution of the endoplasmic reticulum and Golgi apparatus, reaccumulation of granules, and the appearance of lysosomes.The gonadotropes of both the cephalic and caudal lobes undergo progressive morphologic changes through the course of the breeding period. They are numerous and active in the ovulating bird. They undergo gradual regression during the periods of incubation and brooding to become typical broody cells.This investigation was supported by Grant No. GF-33334, U.S.-Japan Cooperative Science Program of the National Science Foundation and by Grant No. GB-28080X, also from the National Science Foundation, to Professor Farner; and by Grant No. 5R040 Japan-U.S. Cooperative Science Program of Japan Association of Science Promotion, to Professor Mikami.     

Hormonal, behavioral, and thermoregulatory responses to bacterial lipopolysaccharide in captive and free-living white-crowned sparrows (Zonotrichia leucophrys gambelii)

Exposing vertebrates to pathogenic organisms or inflammatory stimuli, such as bacterial lipopolysaccharide (LPS), activates the immune system and triggers the acute phase response. This response involves fever, alterations in neuroendocrine circuits, such as hypothalamo-pituitary-adrenal (HPA) and -gonadal (HPG) axes, and stereotypical sickness behaviors that include lethargy, anorexia, adipsia, and a disinterest in social activities. We investigated the hormonal, behavioral, and thermoregulatory effects of acute LPS treatment in a seasonally breeding songbird, the white-crowned sparrow (Zonotrichia leucophrys gambelii) using laboratory and field experiments. Captive male and female sparrows were housed on short (8L:16D) or long (20L:4D) day lengths and injected subcutaneously with LPS or saline (control). LPS treatment activated the HPA axis, causing a rapid increase in plasma corticosterone titers over 24 h compared to controls. Suppression of the HPG axis occurred in long-day LPS birds as measured by a decline in luteinizing hormone levels. Instead of a rise in body temperature, LPS-injected birds experienced short-term hypothermia compared to controls. Birds treated with LPS decreased activity and reduced food and water intake, resulting in weight loss. LPS males on long days experienced more weight loss than LPS males on short days, but this seasonal effect was not observed in females. These results paralleled seasonal differences in body condition, suggesting that modulation of the acute phase response is linked to energy reserves. In free-living males, LPS treatment decreased song and several measures of territorial aggression. These studies highlight immune-endocrine-behavior interrelationships that may proximately mediate life-history tradeoffs between reproduction and defense against pathogens.     

Plasma corticosterone increases during migratory restlessness in the captive white-crowned sparrow Zonotrichia leucophrys gambelli

Plasma corticosterone increases during the period of spring migration in a variety of bird species. Long-distance migrants show elevations in corticosterone specifically in association with the stage of flight, suggesting that corticosterone may support flight-related processes, for example, locomotor activity and/or energy mobilization. The pattern of corticosterone secretion as it relates to migratory flight has hitherto not been clearly described in migrants that frequently interrupt flight to refuel, for example, the Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii). The Gambel's white-crowned sparrow fuels by day and expresses peak migratory activity during the first few hours of night. To determine if plasma corticosterone increases in association with the stage of migratory flight also in this short-bout migrant, we induced captive white-crowned sparrows to enter into the migratory condition by placing photosensitive birds on long days (16L:8D) and then evaluated birds for plasma corticosterone and locomotor activity during four time points of the day. Patterns found in long-day birds were compared to those observed in short-day controls (8L:16D). Differences in energy metabolism as determined from plasma metabolites were also evaluated. We found that locomotor activity and corticosterone were significantly elevated at the onset of the dark period, but only in long-day birds. Plasma beta-hydroxybutyrate (a ketone body) was also elevated. Thus, findings suggest that plasma corticosterone and ketogenesis increase in association with migratory restlessness in a short-bout migrant. In fact, corticosterone may play a regulatory role, because it shows a trend to increase already before night-time activity.     

Migratory sleeplessness in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

Twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations between their wintering and breeding grounds. If and how songbirds sleep during these periods of increased activity has remained a mystery. We used a combination of electrophysiological recording and neurobehavioral testing to characterize seasonal changes in sleep and cognition in captive white-crowned sparrows (Zonotrichia leucophrys gambelii) across nonmigratory and migratory seasons. Compared to sparrows in a nonmigratory state, migratory sparrows spent approximately two-thirds less time sleeping. Despite reducing sleep during migration, accuracy and responding on a repeated-acquisition task remained at a high level in sparrows in a migratory state. This resistance to sleep loss during the prolonged migratory season is in direct contrast to the decline in accuracy and responding observed following as little as one night of experimenter-induced sleep restriction in the same birds during the nonmigratory season. Our results suggest that despite being adversely affected by sleep loss during the nonmigratory season, songbirds exhibit an unprecedented capacity to reduce sleep during migration for long periods of time without associated deficits in cognitive function. Understanding the mechanisms that mediate migratory sleeplessness may provide insights into the etiology of changes in sleep and behavior in seasonal mood disorders, as well as into the functions of sleep itself.     

Signals of status in wintering white-crowned sparrows, Zonotrichia leucophrys gambelii

The possibility of plumage status signalling within the social systems of wintering birds has been a controversial issue. Our results are the first to demonstrate conclusively the reality of such signalling. Data from eight groups of captive white-crowned sparrows (Zonotrichia leucophrys gambelii), each with 8 to 11 different individuals, show that immature and adult females with crowns painted to resemble more brightly coloured, dominant adult males consistently win encounters with control birds of their own age and sex. These experiments demonstrate that signals that correlate with age (adult versus immature) and sex (adult male versus adult female) are used by the birds as reliable indicators of relative dominance position. Our demonstration of status signalling draws attention to the need to explain how such a system can be evolutionarily stable and we discuss some suitable models.     

Biosynthesis of fatty alcohols,alkane-1,2-diols and wax esters in particulate preparations from the uropygial glands of white-crowned sparrows (Zonotrichia leucophrys)

Biosynthesis of sebaceous gland waxes was studied with the uropygial gland of the white-crowned sparrow as the experimental tissue. A 27,000g particulate preparation from this gland catalyzed reduction of palmitoyl-CoA to hexadecanol at an optimum pH near 5.0 with NADPH as the preferred reductant. At low protein concentrations, palmitoyl-CoA inhibited the reductase and bovine serum albumin prevented this inhibition. An apparent K_m of 0.3 mm was calculated for palmitoyl-CoA from linear double-reciprocal plots ignoring the inhibitory concentration of the substrate. An apparent K_m of 3 mm was calculated for NADPH from linear double-reciprocal plots. Palmitoyl-CoA reduction was inhibited by thiol directed reagents such as p-chloromercuribenzoate, N-ethylmaleimide, and iodoacetamide. The particulate fraction also catalyzed esterification of hexadecanol with endogenous C₁₆ and C₁₈ acyl moieties with an optimum pH of 7.5. Stimulation of esterification of hexadecanol by ATP and CoA as well as by low concentrations of palmitoyl-CoA suggests that the CoA esters of fatty acids are involved in esterification. Tween-20 stimulated esterification of hexadecanol and hexadecyl dodecanoate was the major wax ester formed in the presence of Tween-20 suggesting that the C₁₂ acid of Tween-20 participated in esterification. Ignoring the inhibitory concentrations of hexadecanol (>0.2 mm), an apparent K_m of 0.1 mm was calculated from linear double-reciprocal plots. α-Hydroxylation of palmitic acid was demonstrated in cell-free extracts of the uropygial gland. A 27,000g particulate preparation from the gland catalyzed the reduction of α-hydroxypalmitic acid to hexadecane-1,2-diol with NADPH as the preferred reductant at an optimum pH near 6.5. This reduction required both ATP and CoA, suggesting that α-hydroxyacyl-CoA was the true substrate for the reductase. With stereospecifically labeled NADP³H, it was shown that both acyl-CoA reduction and α-hydroxy acid reduction involved transfer of the hydride specifically from the B-side of the nicotinamide ring of NADPH. Subcellular fractionation using sucrose density gradient centrifugation strongly suggested that the enzymes which catalyzed reduction of palmitoyl-CoA and α-hydroxypalmitic acid as well as the esterification of hexadecanol are localized in the microsomal membranes of the gland.     

Light-microscope studies of the cytology of the adenohypophysis of the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary Adenohypophyses from more than two hundred white-crowned sparrows of both sexes and different ages, and from different periods of their annual reproductive cycle, have been used for this investigation. In addition to examination of these normal birds, we have also studied the adenohypophyses of 23 castrates and 24 controls held in different photoperiodic conditions.Cytologically the pars distalis of the adenohypophysis of the white-crowned sparrow is typically avian with distinct cephalic and caudal lobes, each with characteristic cell-types.Four basic cell-types, the acidophils, basophils, amphophils, and chromophobes, have been identified in the pars distalis by means of Matsuo tetrachrome and Matsuo modified PAS-methyl blue staining methods.Three types of acidophils, orange, red, and small, are confined to the caudal lobe of the pars distalis. Their possible functions are discussed.Light basophils (PAS-light red cells) and deep basophils (PAS-deep red cells) are equally distributed in both lobes. It is suggested that basophils may be involved in gonadotropic function since their appearance correlates well with the annual gonadal cycle and photoperiodic stimulation of gonadal growth and with the results of castration.The amphophils or PAS-purple cells (aldehyde-fuchsin positive) are found only in the cephalic lobe. Their probable function is discussed.Two types of chromophobes, specific and ordinary chromophobes, have been observed. The specific chromophobes are found only in the cephalic lobe and are similar to the Kernhaufen described by Romeis (1940). The ordinary chromophobes are similar to those of the pars distalis of other avian species and of mammals.The castration cells are found in both lobes of the photosensitive castrates under natural photoperiodic conditions as well as in those subjected artificially to photostimulation (20-hour daily photoperiods). Similar cells have also been observed in the pars tuberalis of the castrated photostimulated birds.The relations of the rostral and caudal groups of the portal vessels to the cell-types found in the cephalic and caudal lobes are discussed.Dedicated to Professor Dr. Y. Kato, Department of Anatomy of the Domestic Animals, Kyushu University, Fukuoka, Japan, and to President Dr. H. Mimura, Shinshu University, Matsumoto, Japan, in honor of their retirement.The investigation reported herein was supported by a research grant (5RO 1-HEO7240 NEUA) from the National Institutes of Health to Professor Vitums, by funds for biological and medical research made available by State of Washington Initiative Measure No. 171 to Professor Vitums; by a Research Career Development Award (5K3 AM-18, 370) from the National Institutes of Arthritis and Metabolic Diseases to Professor King; and by a research grant (5RO 1 NB 06 187) from the National Institutes of Health to Professor Farner. The senior author is greatful to Professor Dr. Hideo Murai and Doctor Yasukuni Watanabe, Department of Animal Science, Shinshu University,Ina,Japan, for their cooperation and support in this investigation. We wish to thank Mrs. Sumiko Sumida for technical assistance, and Miss Kathleen Reinhardt for the preparation of the drawings.     

Investigations of the butylcholinesterase-containing cells of the adenohypophysis of the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary In the adenohypophysis of Zonotrichia leucophrys gambelii two types of cells with butylcholinesterase(BuChE) activity can be demonstrated histochemically. Type I occurs in the cephalic lobe of the pars distalis and in the pars tuberalis; it consists of oval and round cells. It is a distinctive cell type that is identical with the amphophilic cells described by Matsuo, Vitums, King and Farner (1969). Whereas castration or inhibition of thyroid gland activity causes only minor changes in these cells, blocking of adrenal cortex activity, or adrenalectomy, causes conspicuous hyperplasia and hypertrophy suggesting that these cells are involved in the production or release of ACTH. The second type, which occurs in both cephalic and caudal lobes, consists mostly of irregularly formed cells. Various observations indicate that it is a composite group, consisting, at least in part, of degenerating cells.These investigations were supported by grants from the National Institutes of Health (S ROI NB 06812) and the National Science Foundation (GB 5969) to Professor Farner.     

Electron microscopic and experimental studies of the pineal organ in the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary The structure of the pineal organ of Zonotrichia leucophrys gambelii, as revealed by light- and electron-microscopy, resembles that of Passer domesticus (Oksche and Kirschstein, 1969; Ueck, 1970). The typical cellular element is the pinealocyte with certain basic structural features of the pineal photoreceptors of lower vertebrates (see Oksche, 1971). However, instead of the characteristic, cone-like outer segments, there are, as in other species of birds, only bulbous cilia with ectopic whorls of lamellae. This structure of the outer segment is, in a sense, contrary to the demonstration of synaptoid contacts, numerous unmyelinated, and occasional myelinated nerve fibers by electron microscopy. In Nissl preparations it was possible to demonstrate typical nerve cells. The pinealocytes of Z. l. gambelii are secretory; their Golgi complex forms granulated vesicles (800–1,400 Å in diameter) that belong to the group of granular inclusions characteristic of monoamines. Autonomie nerve fibers course within the connective tissue capsule of the pineal organ. In many pinealocytes of Z. l. gambelii, the granular endoplasmic reticulum contains extensively expanded cisternae that are filled with a flocculent material and closely associated with bundles of filaments. In a number of cases such loop-like structures are selectively stainable with aldehyde fuchsin. It was not possible to demonstrate specific secretory activity in the supporting cells. Extirpation of the pineal organ in Z. l. gambelii had no definitely detectable influence on the photoperiodic control of testicular growth.Aves, Passeriformes, Fringillidae.Supported by grants from the Deutsche Forschungsgemeinschaft to Professor Oksche and by the National Science Foundation (GB 11905) to Professor Farner. A part of this investigation was effected while Professor Kobayashi held a Visiting Professorship at the University of Giessen.     

The ACTH-immunoreactive system in the brain of the white-crowned sparrow,Zonotrichia leucophrys gambelii (Passeriformes,Emberizidae)

Summary The ACTH-immunoreactive (ir) system of the avian brain is particularly conspicuous in the male white-crowned sparrow (Zonotrichia leucophrys gambelii). The irperikaryal population is concentrated mainly within the tuberal region, projecting primarily in a dorsal direction: (i) into the striatum; (ii) into rostral diencephalic, septal, hyperstriatal, and thalamic areas; and (iii) into dorsal and ventral areas of the brain stem. Ir-fibers seemingly contact local non-immunoreactive neurons mainly in the accumbens nucleus, septum, dorsal thalamic nuclei, infundibular and interpeduncular nuclei, and in the rostral diencephalon. Neurohemal zones are not supplied by ACTH-ir terminals. Immunocytochemical problems arising from the complexity of the proopiomelanocortin molecule and its derived peptide components are discussed in relation to phylogenetically directed studies, and contradictory results.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday     

Hypothalamic and hormonal control of photoperiodically induced vernal functions in the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary The effects of implantation of testosterone propionate (TP) in various sites in the hypothalamus on the photoperiodically induced vernal premigratory functions in the White-crowned Sparrows were investigated in order to assess the role of the hypothalamo-hypophysial-testicular axis in the induction of these responses.Implantation of glass capillary tubes containing TP in the basal infundibular nucleus (IN), in the median eminence, or in the pars distalis inhibited the photoperiodically induced increase in plasma levels of luteinizing hormone (LH), as measured by radioimmunoassay, and testicular growth. The effective implants significantly lowered the levels of LH in birds held on nonstimulatory short days. These TP implants apparently inhibited release from the pars distalis of both LH and follicle-stimulating hormone (FSH). It is concluded that the site of sensitivity in the negative feedback by testosterone is either the basal IN or the pars distalis, or both. The implants of TP that inhibited the increase in plasma LH and testicular growth completely did not prevent the birds from fattening.These investigations were supported, in part, by research grants from the National Institutes of Health (HD-6527) and National Science Foundation (BMS 79-13933) to Professor Donald S. Farner. This paper is based on a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy from the University of WashingtonThe author is grateful to Professor Donald S. Farner for his guidance throughout the course of these investigations. The assistance of Mr. Philip W. Mattocks, Jr. in performing radioimmunoassays is sincerely appreciated     

Steroid hormone interrelationships with territorial aggression in an Arctic-breeding songbird,Gambel's white-crowned sparrow,Zonotrichia leucophrys gambelii

The breeding season is very brief for arctic-breeding passerines, and any interruptions of parental care by aggressive interactions over territory may reduce reproductive success. We tested both the "testosterone insensitivity" and "corticosterone insensitivity" hypotheses in the arctic-breeding Gambel's white-crowned sparrow, Zonotrichia leucophrys gambelii. Additionally, we tested whether simulated territorial intrusions (STIs), known to stimulate increases in luteinizing hormone (LH) and testosterone (T) in mid-latitude breeding Z. l. pugetensis, would also be effective in either the early or late phases of the brief breeding season of Z. l. gambelii. Plasma levels of T and LH were high early in the breeding season and declined as egg laying began. Exposure of free-living males to 10 min of STI significantly increased LH but not T secretion. Nonetheless, the pituitary-gonadal axis is sensitive as jugular injection of gonadotrophin-releasing hormone increased plasma T at 10 min relative to saline-challenged controls. T implants failed to increase territorial aggression following STI during incubation. These data are consistent with the T insensitivity hypothesis and contrast sharply with the response of the southerly breeding subspecies, Z. l. pugetensis, in which the territorial response to T administration is retained throughout its relatively long breeding season. However, corticosterone implants during the incubation period decreased territorial aggression during STI. This responsiveness to corticosterone is not consistent with the corticosterone insensitivity hypothesis of stress modulation. Z. l. gambelii retain sensitivity to corticosterone levels that may occur naturally in response to environmental perturbations resulting in suppression of territorial behavior.     

Twenty-one novel microsatellite DNA loci isolated from the Puget Sound white-crowned sparrow, Zonotrichia leucophrys pugetensis

The white‐crowned sparrow, Zonotrichia leucophrys, has served as a model species for studies of song and reproductive physiology. Here, we describe primers for 21 novel microsatellite loci isolated from the Puget Sound subspecies, Zonotrichia leucophrys pugetensis, which will be useful for parentage and population genetic analyses. Based on genotypes from seven to 22 adult birds from one population, the average number of alleles per locus was 10.9 (four to 21 alleles) and observed heterozygosity varied from 0.50 to 1.00. All loci also amplified products in at least one of three other passerine species tested.