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Sexual Difference (sexual + difference)

Distribution by Scientific Domains

Humanities and Social Sciences	45%
Life Sciences	40%
Medical Sciences	12%

Selected Abstracts

THROUGH A DIFFERENT LENS: RETHINKING THE ROLE OF SEXUAL DIFFERENCE IN THE THEOLOGY OF HANS URS VON BALTHASAR

MODERN THEOLOGY, Issue 1 2009
BARBARA K. SAIN
Sexual difference plays a pivotal role in Balthasar's thought, as an analogy for the Trinity and as an analogy for the relation between Christ and the church. This essay examines the influence of the analogy of being on his interpretations of these analogies, his understanding of created masculinity, and his use of the language of sexual difference for the Holy Spirit. Ultimately many of Balthasar's best insights about human love as an analogy for divine love can be retained without connecting femininity uniquely with creation, and his trinitarian theology provides the best interpretive key for doing so. [source]

The Substance of Sexual Difference: Change and Persistence in Representations of the Body in Eighteenth,Century England

GENDER & HISTORY, Issue 2 2002
Karen HarveyArticle first published online: 16 DEC 200
The claims of Thomas Laqueur for a shift from a one,sex to a two,sex model of sexual difference are incorporated into many recent histories of gender in England between 1650 and 1850. Yet the Laqueurian narrative is not supported by discussions of the substance of sexual difference in eighteenth,century erotic books. This article argues that different models of sexual difference were not mutually exclusive and did not change in linear fashion, but that the themes of sameness and difference were strategically deployed in the same period. Thus, there was an enduring synchronic diversity which undermines claims for linear transformation. [source]

Interval, Sexual Difference: Luce Irigaray and Henri Bergson

HYPATIA, Issue 1 2008
REBECCA HILL
Henri Bergson's philosophy has attracted increasing feminist attention in recent years as a fruitful locus for re-theorizing temporality. Drawing on Luce Irigaray's well-known critical description of metaphysics as phallocentrism, Hill argues that Bergson's deduction of duration is predicated upon the disavowal of a sexed hierarchy. She concludes the article by proposing a way to move beyond Bergson's phallocentrism to articulate duration as a sensible and transcendental difference that articulates a nonhierarchical qualitative relation between the sexes. [source]

The Unacknowledged Socrates in the Works of Luce Irigaray

HYPATIA, Issue 2 2006
SHAUN O'DWYER
In Luce Irigaray's thought, Socrates is a marginal figure compared to Plato or Hegel. However, she does identify the Socratic dialectical position as that of a ,phallocrat' and she does conflate Socratic and Platonic philosophy in her psychoanalytic reading of Plato in Speculum of the Other Woman. In this essay, I critically interpret both Irigaray's own texts and the Platonic dialogues in order to argue that: (1) the Socratic dialectical position is not ,phallocratic' by Irigaray's own understanding of the term; (2) that Socratic (early Platonic) philosophy should not be conflated with the mature Platonic metaphysics Irigaray criticizes; and (3) that Socratic dialectical method is similar in some respects with the dialectical method of Diotima, Socrates' instructress in love and the subject of Irigaray's "Sorcerer Love" essay in An Ethics of Sexual Difference. [source]

Asymmetrical Genders: Phenomenological Reflections on Sexual Difference

HYPATIA, Issue 2 2005
SILVIA STOLLER
One of the most fundamental premises of feminist philosophy is the assumption of an invidious asymmetry between the genders that has to be overcome. Parallel to this negative account of asymmetry we also find a positive account, developed in particular within the context of so-called feminist philosophies of difference. I explore both notions of gender asymmetry. The goal is a clarification of the notion of asymmetry as it can presently be found in feminist philosophy. Drawing upon phenomenology (Merleau-Ponty, Levinas) as well as feminist difference theory (Irigaray), I argue that a gender asymmetry does exist that cannot,as in the first assumption,be transformed into symmetry. [source]

Transforming Sacrifice: Irigaray and the Politics of Sexual Difference

HYPATIA, Issue 4 2002
ANNE CALDWELL
This essay examines Irigaray's analysis of politics and the political implications of her critique of sacrificial orders that repress difference/matter. I suggest that her descriptions of a fluid "feminine" can be read as an alternative symbolic not dependent on repression. This idea is politically promising in opening a possibility for justice and a nonantagonistic intersubjectivity. I conclude by assessing Irigaray's concrete proposals for sexuate rights and a civil identity for women. [source]

Bridging the Social and the Symbolic: Toward a Feminist Politics of Sexual Difference

HYPATIA, Issue 3 2000
EMILY ZAKIN
By clarifying the psychoanalytic notion of sexual difference (and contrasting it with a feminist analysis of gender as social reality), I argue that the symbolic dimension of psychical life cannot be discarded in developing political accounts of identity formation and the status of women in the public sphere. I discuss various bridges between social reality and symbolic structure, bridges such as body, language, law, and family. I conclude that feminist attention must be redirected to the unconscious since the political cannot be localized in, or segregated to, the sphere of social reality; sexual difference is an indispensable concept for a feminist politics. [source]

Diversity and Equality: Three Approaches to Cultural and Sexual Difference

THE JOURNAL OF POLITICAL PHILOSOPHY, Issue 1 2003
Avigail Eisenberg
First page of article [source]

Horrifying Sex: Essays on Sexual Difference in Gothic Literature

THE JOURNAL OF POPULAR CULTURE, Issue 1 2009
Jay R. Clarkson
No abstract is available for this article. [source]

THROUGH A DIFFERENT LENS: RETHINKING THE ROLE OF SEXUAL DIFFERENCE IN THE THEOLOGY OF HANS URS VON BALTHASAR

Male-biased size dimorphism in ichneumonine wasps (Hymenoptera: Ichneumonidae) , the role of sexual selection for large male size

ECOLOGICAL ENTOMOLOGY, Issue 3 2005
Tiit Teder
Abstract., 1.,Sexual differences in body size are expected to evolve when selection on female and male sizes favours different optima. 2.,Insects have typically female-biased size dimorphism that is usually explained by the strong fecundity advantage of larger size in females. However, numerous exceptions to this general pattern have led to the search for selective pressures favouring larger size in males. 3.,In this study, the benefits of large size were investigated in males of four species of ichneumonine wasps, a species-rich group of parasitoids, many representatives of which exhibit male-biased size dimorphism. 4.,Mating behaviour of all ichneumonine wasps are characterised by pre-copulatory struggles, in the course of which males attempt to override female reluctance to mate. A series of laboratory trials was conducted to study the determinants of male mating success. 5.,A tendency was found for larger males as well as those in better condition to be more successful in achieving copulations. Size dimorphism of the species studied, mostly male-biased in hind tibia length but female-biased in body weight, indicates that sexual selection in males favours longer bodies and appendages rather than larger weight. 6.,The qualitative similarity of the mating patterns suggests that sexual selection cannot completely explain the considerable among-species differences in sexual size dimorphism. 7.,The present study cautions against using various size indices as equivalents for calculating sexual size dimorphism. 8.,It is suggested that female reluctance in ichneumonine wasps functions as a mechanism of female mate assessment. [source]

Olfactory responses of two species of grasshoppers to plant odours

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2000
H.H. Chen
Abstract Electroantennogram (EAG) responses were recorded from two species of oedipodine grasshoppers, Oedaleus decorus asiaticus L. (graminivorous) and Angaracris barabensis Pall. (forbivorous), to volatiles emitted by chopped leaves of ten plant species. Male O. d. asiaticus showed much stronger EAG responses than conspecific females and both sexes of A. barabensis. Sexual differences in EAG responses correspond to different numbers of antennal sensilla of both sexes and to certain behavioural and morphological factors as well. The overall EAG response profiles of the two grasshopper species to the ten plant odours were similar. However, adaptation to host odour might have occurred because of differences in their feeding habits. Females of the graminivorous O. d. asiaticus possess a significantly higher olfactory sensitivity for poaceous plant species than A. barabensis, while the forbivorous A. barabensis showed significantly higher EAG responses to Allium senescens (Liliaceae), and a tendency of high responses to composite plant species in comparison with O. d. asiaticus. [source]

Sex-specific food provisioning in a monomorphic seabird, the common guillemot Uria aalge: nest defence, foraging efficiency or parental effort?

JOURNAL OF AVIAN BIOLOGY, Issue 1 2009
Chris B. Thaxter
Sexual differences in food provisioning rates of monomorphic seabirds are well known but poorly understood. Here, we address three hypotheses that attempt to explain female-biased food provisioning in common guillemots Uria aalge: (1) males spend more time in nest defence, (2) females have greater foraging efficiency, and (3) males allocate a greater proportion of foraging effort to self-maintenance. We found that males spent no more time with chicks than females but made longer trips and travelled further from the colony. There was extensive overlap between sexes in core foraging areas, indicating that females were not excluding males from feeding opportunities close to the colony. However, as a result of their longer trips, the total foraging areas of males were much greater than those of females. There was no difference between sexes in overall dive rate per hour at sea, in behaviour during individual dives or in a number of other measures of foraging efficiency including the frequency, depth and duration of dives and the dive: pause ratio during the final dive bout of each trip, which was presumably used by both sexes to obtain prey for the chick. These data strongly suggest that sexes did not differ in their ability to locate and capture prey. Yet males made almost twice as many dives per trip as females, suggesting that males made more dives than females for their own benefit. These results support the hypothesis that female-biased food provisioning arose from a difference between sexes in the allocation of foraging effort between parents and offspring, in anticipation of a prolonged period of male-only post-fledging care of the chick, and not from differences in foraging efficiency or time spent in nest defence. [source]

Sexual differences and effect of photoperiod on melatonin receptor in avian brain

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2001
Nicoletta Aste
Abstract Several data suggest that melatonin may influence avian reproduction by acting at the level of the hypothalamic-hypophisial-gonadal axis, and/or on neural circuits controlling reproductive behaviours. The action of melatonin is exerted through specific receptors whose distribution and pharmacological properties have been extensively investigated. This review will focus on the distribution, sexual dimorphism, and dependence upon the photoperiod of melatonin binding sites in avian species with a special emphasis on Japanese quail. Melatonin receptors are widely distributed in avian brain. They are mostly present in the visual pathways of all the investigated species and in the song controlling nuclei of oscine birds. Sexual dimorphism of melatonin binding sites (higher density in males than in females) was detected in some telencephalic nuclei of songbirds, in the visual pathways, and in the preoptic area of quail. The last region plays a key role in the activation of male quail copulatory behaviour and it hosts a large population of gonadotropin-releasing hormone-containing neurons. Sexual dimorphism of melatonin-binding sites in the above-mentioned regions suggests a differential role for this hormone in the modulation of visual perception, gonadotropin production, and seasonally activated behaviours in male and female quail. Further studies are necessary to understand interrelationships among photic cues, gonadal steroids, density, and sexually dimorphic distribution of melatonin receptors. Microsc. Res. Tech. 55:37,47, 2001. © 2001 Wiley-Liss, Inc. [source]

Lifetime sexual dimorphism in Juniperus communis var. communis

PLANT SPECIES BIOLOGY, Issue 1 2007
LENA K. WARD
Abstract The sexes of dioecious Juniperus communis were differentially affected over their lifetime in response to ecological and physiological stress in populations of different ages studied over 23 years in southern England. In a young population, the female survival rate was less than the male rate, with more females dying during a severe attack by rabbits and later with fungus disease in the roots. The sex ratio (female : male) in marked individuals was predicted by age, changing from 1:1.13 in 1983 to 1:1.32 in 2005. In an old senescing population, where two-thirds of the individuals died, the sex ratio varied, but overall became more male biased (1:1.51,1:2.10). Males had a greater resistance to terminal disease, and were slightly older than females at death (110 years compared to 106). Young females grew less than males, presumably because of greater trade-offs with reproductive effort: the mean annual shoot growth was 6.7 cm compared to 8.1 cm in males. By approximately 30 years of age, heights of the sexes were significantly different. The annual growth of old females (4.8 cm) was greater than that in males (4.3 cm), possibly because males survived longer in poor health. Sexual differences in height in the old population were progressively lost. Cone abundance in females was less than that in males and cone production had greater periodicity; the young population outperformed the old. There were slightly longer time lags in inverse correlations between growth and reproductive indices in females. [source]

Achieving high sexual size dimorphism in insects: females add instars

ECOLOGICAL ENTOMOLOGY, Issue 3 2007
TOOMAS ESPERK
Abstract 1.,In arthropods, the evolution of sexual size dimorphism (SSD) may be constrained by a physiological limit on growth within each particular larval instar. A high SSD could, however, be attained if the larvae of the larger sex pass through a higher number of larval instars. 2.,Based on a survey of published case studies, the present review shows that sex-related difference in the number of instars is a widespread phenomenon among insects. In the great majority of species with a sexually dimorphic instar number, females develop through a higher number of instars than males. 3.,Female-biased sexual dimorphism in final sizes in species with sexually dimorphic instar number was found to considerably exceed a previously estimated median value of SSD for insects in general. This suggests a causal connection between high female-biased SSD, and additional instars in females. Adding an extra instar to larval development allows an insect to increase its adult size at the expense of prolonged larval development. 4.,As in the case of additional instars, SSD is fully formed late in ontogeny, larval growth schedules and imaginal sizes can be optimised independently. No conflict between selective pressures operating in juvenile and adult stages is therefore expected. 5.,In most species considered, the number of instars also varied within the sexes. Phenotypic plasticity in instar number may thus be a precondition for a sexual difference in instar number to evolve. [source]

Differential effect of oestradiol and astroglia-conditioned media on the growth of hypothalamic neurons from male and female rat brains

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000
M. J. Cambiasso
Abstract To determine whether soluble products from different CNS regions differ in their ability to support oestrogen-stimulated neurite growth, hypothalamic neurons from sexually segregated embryos were cultured with astroglia-conditioned medium (CM) derived from cortex, striatum and mesencephalon, with or without 17-,-oestradiol 100 n m added to the medium. After 48 h in vitro, neurite outgrowth was quantified by morphometric analysis. Astroglia-CM from mesencephalon (a target for the axons of hypothalamic neurons) induced the greatest axogenic response in males and in this case only a neuritogenic effect could be demonstrated for oestradiol. On the other hand, astroglia-CM from regions that do not receive projections from ventromedial hypothalamus inhibited axon growth. A sexual difference in the response of hypothalamic neurons to astroglia-CM and oestradiol was found; growth of neurons from female foetuses was increased by astroglia-CM from mesencephalon, but no neuritogenic effect could be demonstrated for oestradiol in these cultures. Blot immunobinding demonstrated the presence of receptors for neurotrophic factors in cultures of hypothalamic neurons; Western blot analysis of these cultures demonstrated that oestradiol increased the concentration of trkB and IGF-I R,, whereas trkA was not detected and the concentration of trkC was not modified. These results support the hypothesis that target regions produce some factor(s) that stimulate the growth of axons from projecting neurons and further indicate that in the case of males this effect is modulated by oestradiol, perhaps mediated through the upregulation of trkB and IGF-I receptors. [source]

The Substance of Sexual Difference: Change and Persistence in Representations of the Body in Eighteenth,Century England

Freud's Oedipus and Kristeva's Narcissus: Three Heterogeneities

HYPATIA, Issue 1 2005
SARA BEARDSWORTH
The paper shows that three heterogeneities in Freud and Kristeva (unconscious/conscious, semiotic/symbolic, and imaginary/symbolic) expose the historical emergence, significance, and demise of psychic structures that present obstacles to our progressive political thinking. The oedipal and narcissistic structures of subjectivity represent the persistence of two past, bad forms of authority: paternal law and maternal authority. Contemporary psychoanalysis reveals a humankind going through the loss of this past in a process that opens up a different future of sexual difference in Western cultures. [source]

Bridging the Social and the Symbolic: Toward a Feminist Politics of Sexual Difference

Allometry, bilateral asymmetry and sexual differences in the vocal tract of common eiders Somateria mollissima and king eiders S. spectabilis

JOURNAL OF AVIAN BIOLOGY, Issue 2 2007
Edward H. Miller
Intraspecific sexual differences, high variation, and positive allometry of sexually-selected external display structures are common. Many sexually-selected anatomical specializations occur in the avian vocal tract but intraspecific variation and allometry have been investigated little. The tracheal bulla bulla syringealis occurs in males of most duck species. We quantified variation and size-scaling of the bulla, plus sexual differences in size of trachea, bronchi, and vocal muscles, for 62 common eiders Somateria mollissima and 51 king eiders S. spectabilis. Trends were similar in both species. Bullar ossification and definitive size occurred early in life: bullar size did not differ between first-year and older males. Bullar size did not vary more than size of other body parts (CVs of 3.4,7.0% for bullar length and breadth). Bullar size scaled to body size with negative allometry or isometry. Vocal muscles were 10,50% thicker in males than females, a much greater sexual difference than in body size (CVs of 3,6% on linear body-size variables). Vocal muscles were larger on the left side in both sexes and bilateral asymmetry was slightly more pronounced in males. Low variation and a trend towards negative allometry suggest that bullar size is under stabilizing selection; if bullar size affects vocal attributes of voice, then the latter cannot be condition-dependent. We recommend comparative research on vocal communication, vocal individuality and vocal-tract anatomy and function in eiders and other ducks. [source]

Melanocytic nevi of the breast: a histologic case-control study

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 2 2004
F. Rongioletti
Background:, Melanocytic nevi in the genital, acral, and flexural sites often display clinical and histologic features that may simulate melanoma. We verified whether this is the case also for nevi of the breast. Methods:, Eleven dermatopathologists, from nine Italian Institutions, collected the specimens of melanocytic lesions from the breast and other body sites, excluding the acral, genital, and flexural areas, as controls. Cases and controls were matched for sex and age. All nevi were observed ,blindly' and simultaneously by all participants. For each lesion, 10 histological parameters were analyzed: asymmetry, absence of lateral demarcation of melanocytes, lentiginous proliferation, nested and dyshesive pattern, intraepidermal melanocytes above the basal layer, involvement of the hair follicle, absence of maturation of dermal melanocytes, melanocytic atypia, fibroplasia of the papillary dermis, and lymphocytic dermal infiltrate. Each parameter was scored 2 when present and 1 when absent or not valuable. A total score was calculated for each lesion. Results were statistically analyzed by the chi-square test and the Mann,Whitney U -test. Results:, One hundred and one nevi came from the breast area and 97 from elsewhere. Breast nevi exhibited significantly more atypical features than nevi from other sites. In particular, breast nevi with intraepidermal melanocytes, melanocytic atypia, and dermal fibroplasia were significantly more numerous. We did not find any sexual difference. Conclusions:, To avoid undue concerns, dermatopathologists should be aware that melanocytic nevi of the breast may show a high degree of atypical features. [source]

How to do the History of Heterosexuality: Shakespeare and Lacan

LITERATURE COMPASS (ELECTRONIC), Issue 4 2010
Will Stockton
This essay argues against two presumptions: first, that the psychoanalytic approach to sexuality is ahistorical; and second, that critics cannot speak of heterosexuality before its 19th-century invention. Looking to Lacanian psychoanalysis, and particularly to Lacan's theory of sexuation (or sexual difference), this essay develops a queer history of heterosexuality premised on the idea that ,heterosexuality' is simply the latest way of describing a structural relation between the sexes. Lacan calls this structure ,the sexual relation', and describes it as a fantasy that man and woman are two halves of the same whole. At the same time, he insists that ,the sexual relation does not exist': that neither sex can actually make the other whole. Lacan's own reading of Shakespeare's Hamlet, focused in part on Hamlet's antagonism toward Ophelia following the prince's discovery of his father's ,castration', offers an example of how to queer heterosexuality in pre-19th-century texts. My reading of Measure for Measure offers a second example, one that likewise evokes Freud's mytho-historical account of the murder of the primordial father and the subsequent creation of a disinterested ,law' in the father's name (Lacan's Name of the Father). This essay concludes by suggesting that the fantasy of the sexual relation falters in both plays on the ,obscene' revelation of the law's/the Father's sinfulness. [source]

THROUGH A DIFFERENT LENS: RETHINKING THE ROLE OF SEXUAL DIFFERENCE IN THE THEOLOGY OF HANS URS VON BALTHASAR

WONDER BETWEEN TWO: AN IRIGARAYAN READING OF GENESIS 2:231

MODERN THEOLOGY, Issue 1 2008
ROLAND J. DE VRIES
Luce Irigaray, in the course of engagement with René Descartes, argues that we must return wonder to its first locus,that of sexual difference. I suggest that Irigaray's notion of wonder finds resonance in the poetic declaration of the first man in Genesis 2:23. While the creation narratives affirm the equality of woman and man, they also affirm the irreducibility of woman and man to each other. This insistence on wonder has implication for communicative exchange between woman and man. I also argue, however, against Irigaray, that wonder is as appropriate between humans and God as between the sexes. [source]

A Nietzschean Feminist Rejoinder to the Mädchenbuch Controversy

ORBIS LITERARUM, Issue 3 2010
Elsa Asenijeff's Unschuld.
While sexual difference and cultural norms still largely limited the opportunities of most Wilhelmine girls and women to express themselves on issues of sexuality, gender, education, and class difference, a range of feminist writers encouraged their young audiences to question the radical social developments of the late Wilhelmine era. Few Mädchenbücher, however, seem to have been written by feminists who rejected both a traditional, cultural conservative ideology as well as a more radical socialist outlook. The eighteen short works of the Nietzschean feminist Elsa Asenijeff (1867,1941) that comprise Unschuld. Ein modernes Mädchenbuch (1901), illustrate her strategies in unsettling notions of Wilhelmine cultural and sexual (re)production by valorizing the creativity and radical individualism of young girls. Asenijeff's enthusiasm for Genie and individual freedom, and her attempts to reconcile this with Nietzsche's arguments regarding women's biological destiny, position her as another example of the complex yet largely positive reception of Wilhelmine feminists to his teachings. [source]

Correlation of hemocyte counts with different developmental parameters during the last larval instar of the tobacco hornworm, Manduca sexta

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2008
Susann Beetz
Abstract We determined the changes in hemocyte titer and in the abundance of hemocyte types of the tobacco hornworm Manduca sexta during the fourth and fifth larval stadium and the beginning of the pupal stadium. As we analyzed the samples of individual insects at daily intervals, we were able to correlate phenotypical features, body weight, as well as total protein content and lysozyme activity in the hemolymph with the observations on hemocytes. In the course of the fifth larval stadium, the hemocyte titer decreased slightly and declined further after pupation. Using calculated values for total hemocyte numbers, females had about five times and males three times more hemocytes in the circulating population at the beginning of the wandering stage (in the middle of the fifth larval stadium) than immediately after the last larval,larval molt (from the fourth to the fifth larval stadium). This sexual difference was mainly due to an increase in the number of plasmatocytes, which was more prominent in females than in males. Granular cells were dominant in early fifth larval stadium while plasmatocytes were the most abundant cells in pupae. Oenocytoids and spherule cells disappeared during the wandering stage. Lysozyme activity in the hemolymph rose to a maximum during the wandering stage, with females having lysozyme values twice as high as those for males. These changes in lysozyme activity, however, did not correlate with the increase of total hemolymph protein titer which occurred already at the beginning of the wandering stage. We postulate that changes in hemocyte titers are under direct hormonal control, which has to be proven in future experiments. Arch. Insect Biochem. Physiol. 2007. © 2007 Wiley-Liss, Inc. [source]

SEXING THE CANVAS: CALLING ON THE MEDIUM

ART HISTORY, Issue 4 2009
NICHOLAS CHARE
The first part of this article explores current art-historical approaches to gender through three case studies: the Venus of Willendorf; Michelangelo; and Artemisia Gentileschi. The second part employs case studies to examine how ideas about gender have historically been articulated and performed through the use of specific media and techniques. There has been little research devoted to how mediums (such as fresco, oil, and watercolour) and techniques (including drip, impasto, and staining) materialize femininity and masculinity. The article seeks to redress this neglect through an examination of some of the ways in which the gendering of materials and modes of art-making has contributed to the construction and deconstruction of sexual difference in the visual field. Artists whose works are considered include Francis Bacon, Thomas Girtin, J.M.W. Turner, and Jack Vettriano. [source]

Double-nesting behaviour and sexual differences in breeding success in wild Red-legged Partridges Alectoris rufa

IBIS, Issue 4 2009
FABIÁN CASAS
Double-nesting behaviour, a rare breeding system in which females lay in two nests, one incubated by herself and the other one by her mate, could be considered an intermediate stage in the evolutionary trend from biparental to uniparental care of single clutches. We examined the occurrence and success of double-nesting behaviour in Red-legged Partridges Alectoris rufa in Central Spain. Clutch size and hatching success were recorded, as well as the variation in these between years and between incubating sexes. Participation in incubation was higher for females (94.76%) than males (41.0%), and the proportion of incubating males varied markedly between years, with no incubating males in one dry year and approximately 50% of males incubating in other years. There was significant variation among years and between sexes in laying date, clutch size and hatching success. Clutch size decreased with later laying date in males and females. The probability of clutch loss to predation differed between sexes, being much higher for nests incubated by females. Our results suggest that both rainfall and predation influence the occurrence and success of double-nesting. [source]

Physiological response to stress in fledgling Lesser Kestrels Falco naumanni: the role of physical condition, sex and individual genetic diversity

IBIS, Issue 3 2009
JOAQUÍN ORTEGO
Exposure to chronic stress early on during development has important deleterious consequences later in life, reducing important components of individual fitness such as survival and future reproduction. In this study, we evaluate the factors associated with physiological response to stress in fledgling Lesser Kestrels Falco naumanni, paying particular attention to the potential role of individual genetic diversity. For this purpose, we used heterophil/lymphocyte ratios (H/L ratio) as a haematological stress indicator and typed the analysed individuals at 11 highly polymorphic microsatellite loci, which allowed us to estimate their genetic diversity. We found that the H/L ratio decreases with fledgling physical condition, suggesting that this parameter is a good indicator of nutritionally based physiological stress. Physiological response to stress was higher in males than in females and this effect was independent of physical condition, suggesting that the observed pattern is due to inherent sexual differences in the factors influencing H/L ratios. Finally, the H/L ratio was positively associated with the genetic diversity of offspring. Previous experimental studies have found that individuals with higher genetic diversity show increased levels of circulating glucocorticoids, which in turn are directly responsible for increasing H/L ratios. On this basis, we suggest that a positive effect of genetic diversity on corticosterone levels may explain the observed association between H/L ratios and individual heterozygosity. Overall, this study highlights the utility of leucocyte profiles to study stress in wild bird populations and poses an interesting question about the effects of individual genetic diversity on haematological response to stress. [source]