Testosterone-induced male traits in female ruffs (Philomachus pugnax): autosomal inheritance and gender differentiation

A balanced polymorphism in male mating behaviour exists in male ruffs, with no obvious parallel expression in females. Pedigree data of male phenotypes support an autosomal model of inheritance, in contrast to sex-linked inheritance patterns found in other taxa with sex-limited alternative mating strategy polymorphisms. We tested this model by inducing male courtship behaviour in gonad-intact female ruffs, using subcutaneous testosterone implants that produced physiological concentrations of testosterone. The implants rapidly induced in females both types of male mating behaviour, an increase in body mass typical of pre-breeding males, and the growth of normally male-limited breeding plumage. As predicted under an autosomal model, the distributions of induced male behaviour types in females paralleled those of their brothers and half-brothers, and were inconsistent with sex-linked models. Effects were reversible, and experimental females bred normally in subsequent years. Our results show that genotype-specific male characteristics can be induced by testosterone in female adults that have presumably not undergone neural organization for them early in life, showing direct use of genetic information in intra- and intersexual differentiation.     

Schaubalz und geschlechtliche Auslese beim Kampfl?ufer(Philomachus pugnax)

Ohne ZusammenfassungAus dem Englischen mit freundlicher Genehmigung des Verfassers frei übertragen von H. Culemann, durchgesehen von F. Steinbacher.Observations tending to throw light on the question of sexual selection in birds, including a day-to-day diary on the breeding habits of the Ruff (Machetes pugnax); The Zoologist 1906 und 1907.     

On the maintenance and origin of alternative strategies in the Ruff Philomachus pugnax

This paper has tried to answer the question of how the independent and the satellite strategy of the Ruff originated and has been maintained during evolution. It is not intended as a report of a piece of completed research but gives a number of tentative, but testable hypotheses. Data are presented that independent males and satellites are equally successful in copulating, provided that almost all copulations occur on leks, and independent males and satellites spend an equal proportion of their time on leks. The extent that males with the different strategies are attached to leks is analysed. Within the group of independent males, considerable differences exist: a resident male is strongly attached to only one particular lek and a marginal male seems to sample many leks. A satellite male behaves intermediately: he is attached to a limited number of leks. The mechanism for the maintenance of both strategies could not be explained by competition for resources (copulations). Contests between independent males and satellites are asymmetric, the satellite being the weaker contestant. The mechanism seems to be due to enlarging the accessibility of the resource by cooperation between both strategies. The ideas on the origin of the system are based mainly on the behaviour of females. There is no relation between the distribution of leks and the size of a female's foraging area, except that most leks are situated along the migration route. It further seems that the number of copulating females in the Netherlands is larger than the number of males on leks, but the number of breeding females is much lower. It is suggested that many females copulate on migration, which is related to extreme breeding conditions in the north of the range. Apart from a change in the sex ratio from south to north, a change in the proportion of satellites is also predicted. The origin of the system is ascribed to the incompatibility between favourable food conditions for chicks and further possibilities for inter-male competition on leks in the same area. The satellite strategy is considered as being derived from a non-competitive strategy accompanying females on migration. In the phase of cooperation between resident and satellite males, individual recognition became important. This could be the factor underlying the evolution of white plumages in satellites and the extreme plumage diversity in independent males.     

Relationships between body composition, body size and alternative reproductive tactics in a lekking sandpiper, the Ruff (Philomachus pugnax)

1. The Ruff is a lekking sandpiper in which males have two genetically determined alternative mating strategies: 'satellite' or 'independent'. Satellite males are non-territorial, following groups of females on and off leks. Independent males attempt to establish territories on leks and can be either 'resident' territory holders, or non-territorial 'marginals'. The time budgets of the three behavioural tactics (resident, marginal and satellite) differ notably in time allocated to foraging, aggression and display activity. These differences have led to the suggestion that the benefits of size and energy stores may vary with mating tactic.
2. In this paper in vivo estimates of body composition (fat, fat-free mass) for breeding male Ruffs using total body electrical conductivity (TOBEC) are presented.
3. Satellite males have significantly shorter tarsi and wings than independent males.
4. After correcting for size, independent males are significantly heavier and fatter than satellites, and marginals in particular are heavier and fatter than both residents and satellites.
5. Estimates of energy expenditure during flight suggest that satellites may maintain reduced energy reserves to minimize flight costs, while the larger fat stores of independent males are consistent with the benefits of endurance as a territory holder.     

The Social Implications of traditional use of lek sites in the ruff Philomachus pugnax

In almost every letting vertebrate, adult males use traditionallek sites. This paper attempts to explain this phenomenon byinvestigating the social implications of traditional use oflek sites. A population of ruffs Philomachus pugnax was observedduring six breeding seasons, and lek stability, site fidelity,male copulatory success, and male dominance relationships werestudied. Ninety percent of the territorial males were site-faithfulwithin and between years, and male dominance, copulatory success,and order of territory establishment were all inter-correlated.Males that were relatively dominant and successful as first-yearterritorials were more likely to return to the area, establishedthemselves even earlier in their second year, and rose in successrank. The frequency of disrupted copulations was very low, despitethe tightly clustered territories on leks. This suggests thatwell-developed dominance relationships exist between males.Site-faithful males are more likely to acquire accurate informationabout the competitive abilities of other males, and such informationis probably necessary for stable dominance relationships todevelop. Such relationships reduce the intensity of male aggression,thereby reducing the risk of male injury. High levels of maleaggression also deter females. Furthermore, stable dominancerelationships enables low-and medium-ranked males to remainon the leks while waiting for the top males to drop out. Thehigh site-fidelity of lekking males, thus, is suggested to haveevolved to facilitate the establishment of stable dominancerelationships, which are beneficial to all territorial males,irrespective of rank     

Seasonal changes in vertebrate immune activity: mediation by physiological trade-offs

Animals living in temporally dynamic environments experience variation in resource availability, climate and threat of infection over the course of the year. Thus, to survive and reproduce successfully, these organisms must allocate resources among competing physiological systems in such a way as to maximize fitness in changing environments. Here, we review evidence supporting the hypothesis that physiological trade-offs, particularly those between the reproductive and immune systems, mediate part of the seasonal changes detected in the immune defences of many vertebrates. Abundant recent work has detected significant energetic and nutritional costs of immune defence. Sometimes these physiological costs are sufficiently large to affect fitness (e.g. reproductive output, growth or survival), indicating that selection for appropriate allocation strategies probably occurred in the past. Because hormones often orchestrate allocations among physiological systems, the endocrine mediators of seasonal changes in immune activity are discussed. Many hormones, including melatonin, glucocorticoids and androgens have extensive and consistent effects on the immune system, and they change in systematic fashions over the year. Finally, a modified framework within which to conduct future studies in ecological immunology is proposed, viz. a heightened appreciation of the complex but intelligible nature of the vertebrate immune system. Although other factors besides trade-offs undoubtedly influence seasonal variation in immune defence in animals, a growing literature supports a role for physiological trade-offs and the fitness consequences they sometimes produce.     

Seasonal variations in cytokine expression and cell-mediated immunity in male rhesus monkeys

Our objectives in this study were to examine seasonal changes in immune responses including cytokine profiles of male rhesus monkeys housed under natural lighting conditions. We also monitored circannual changes in the secretion of several immunomodulatory hormones as potential mediators of the seasonal shifts in immune status. Retrospectively, the medical records of a large group of rhesus monkeys were examined to determine whether a common disease (campylobacteriosis) in this species shows a seasonal pattern of prevalence. Results of the study showed that there was a seasonal shift in the frequency of cells expressing TH1 cytokines (interleukin-2 and interferon-gamma) versus the TH2 prototype cytokine (interleukin-4) by peripheral blood mononuclear cells (PBMC) collected during the winter and summer. The frequency of TH1-type cytokine synthesis in the summer was markedly greater than in the winter whereas TH2-type cytokine expression did not vary between the two seasons. The proliferative response of PBMC to mitogens and natural killer cell activity of PBMC also varied with the season. Several hormones (testosterone, leptin, and prolactin) that modulate immune function exhibited circannual patterns of secretion. The prevalence of Campylobacter infections was higher in the spring than during the summer, fall, or winter. The data suggest that seasonal fluctuations in immune system status may alter the ability of primates to successfully respond to pathogens, and this may be related to circannual patterns of secretion of immunomodulatory hormones.     

Ectoparasites and reproductive trade-offs in the barn swallow (Hirundo rustica)

Parents are predicted to trade offspring number and quality against the costs of reproduction. In altricial birds, parasites can mediate these costs because intensity of parasitism may increase with parental effort. In addition, parasites may mediate a trade-off between offspring number and quality because nestlings in large broods may have reduced anti-parasite immune defence. In this study, we experimentally analysed the effect of brood size on infestation by an ectoparasitic mite in nests of barn swallows (Hirundo rustica). Nests with an enlarged brood had larger prevalence and intensity of infestation than those with a reduced brood. Importantly, each nestling in enlarged broods was exposed to a larger number of mites, even when measured on a per nestling basis, than in reduced broods. Nestlings in enlarged broods had smaller body mass and T-cell-mediated immune response compared to reduced broods. T-cell-mediated immune response and feather growth were negatively correlated with per nestling intensity of infestation in enlarged but not in reduced broods. The results suggest that nestlings in enlarged broods have depressed immunity leading to larger per nestling mite infestation. Hence, exposure to parasites of offspring and parents increases with brood size, and parasitism can thus mediate trade-offs between reproduction and number and quality of the progeny in the barn swallow.     

Seasonal polyphenism and developmental trade-offs between flight ability and egg laying in a pierid butterfly

Butterflies have competing demands for flight ability depending on, for example, mating system, predation pressure, the localization of host plants and dispersal needs. The flight apparatus, however, is costly to manufacture and therefore trade-offs are expected since resources are limited and must be allocated between flight ability and other functions, such as reproduction. Trade-offs between flight and reproduction may be difficult to reveal since they interact with other factors and can be confounded by differences in resource consumption. Previous studies have shown that adults of the summer generation of Pieris napi have relatively larger thoraxes compared with the spring generation. To study whether difference in thorax size results in a trade-off between flight ability and reproduction among the two generations, we conducted a split-brood experiment under common garden conditions. Our results show that summer generation adults have a higher dispersal capacity measured as flight duration in five different temperatures. Reproductive output differed between the two developmental pathways; spring generation females had a significantly higher output of eggs compared with summer generation females. We suggest that this is a consequence of a resource-allocation trade-off made during pupal development implemented by different demands for flight between the spring and summer generations. The significance of this finding is discussed in relation to reproduction and mobility in butterflies.     

Most susceptible stage of rice panicle development to Oebalus pugnax (Hemiptera: Pentatomidae)

Oebalus pugnax (F.) (Hemiptera: Pentatomidae) damage to rice, Orya savita L., reduces rough and head rice yields, and grain quality. O. pugnax feeds on developing kernels, introducing pathogenic fungi and causing a discoloration of the grain known as "peck." The objective of this study was to determine the stage of rice panicle development most susceptible to O. pugnax attack. During 2005 and 2006, in greenhouse and field experiments, rice plants were caged at the boot stage and then infested with adult or nymphal O. pugnax. Plants were infested during one of three stages of panicle development: heading, milk, or soft dough. Insects were allowed to feed on the plants for the duration of each stage and then killed. After maturation, panicles were harvested, and grain was hulled and milled. Grain weight, percentage of pecky grain, and percentage of whole grain after milling were recorded. No differences were found in the weight of rough, brown, or milled rice infested with O. pugnax during different stages of panicle development. Number of filled grains per cage was not affected by O. pugnax, and number of empty grains per cage was affected in two of four experiments. Higher percentage of peck was found in grain from panicles infested during dough and milk than in grain from panicles infested during heading. Adult O. pugnax caused higher percentage of peck than nymphs in all stages of panicle development. An inverse relationship was found between percentage of peck and percentage of whole grain weight only in one of the experiments.     

Attractiveness of stages of rice panicle development to Oebalus pugnax (Hemiptera: Pentatomidae)

Greenhouse experiments were conducted during 2004 and 2005 with male and female Oebalus pugnax (F.) (Hemiptera: Pentatomidae) caged on rice plants at different stages of panicle development with the objective of determining the most attractive stage to O. pugnax. Field-collected insects were released inside cages containing potted plants and observed during morning and afternoon hours for 5 d. Results showed that attractiveness of male and female O. pugnax to plants with panicles at milk and soft dough stages was greater than plants at preheading and heading stages. Preheading plants were the least attractive to the insects, confirming field observations. Results imply that insecticide applications during the preheading stage are likely ineffective and that monitoring efforts during the milk and soft dough stages of panicle development should be intensified.     

The effects of Muramyldipeptide (MDP) in cell-mediated immunity

Summary N-acetylmuramyl-l-alanyl-d-isoglutamine (MDP) was tested in cell-mediated systems. A preparation of MDP, which yielded comparable activity to Freund's complete adjuvant in a humoral response against bovine serum albumin, was used to examine the degree of correlation between in vitro and in vivo models of cell-mediated immunity: (a) The proliferative T cell response in vitro was found to be most strongly enhanced by MDP at low antigen concentrations. The stimulation indices (SIs), however, were only enhanced at very low antigen concentrations because of a mitogenic effect of MDP in the absence of any added antigen. In vivo the proliferative response was measured in a graft-versus-host reaction where MDP caused a nonspecific (systemic) proliferation. In a host-versus-graft situation, however, MDP significantly enhanced the local proliferative response, besides causing an increased systemic background proliferation. (b) The cytotoxic T cell response in vitro was enhanced with suboptimal and optimal antigen concentrations; with supraoptimal antigen concentrations a strong decrease in lytic activity was observed. In vivo, MDP enhanced the cytotoxic activity of peritoneal exudate cells in the same allogeneic system (H-2^b anti H-2^a) as the one used in vitro. This enhanced activity did not, however, enhance adoptive protection in the immunoincompetent host. (c) Cytotoxic T memory function was unaffected by MDP, both in an in vitro system using subcellular material to elicit the cytotoxic response and in vivo, when an adoptive transfer system was used to assay T memory cells for their protective capacity against tumor in the immunoincompetent host. (d) Antibody-mediated cell cytotoxicity was slightly suppressed when MDP was present in vitro; in vivo-pretreated spleen cells exhibited enhanced activity, but only at low antibody concentrations where a macrophage activity was superimposed on the K cell activity. (e) Macrophages could be activated both in vitro and in vivo to kill tumor cells effectively.     

Sex-allocation trade-offs in Nigella sativa (Ranunculaceae) examined with flower manipulation experiments

Sex-allocation trade-offs have long been invoked as a primary factor underlying the evolution of separate sexes and the reduction of pollen production accompanying the evolution of selfing. In the present study, I conducted stamen and style removal experiments to explore the existence of such trade-offs in Nigella sativa, a hermaphroditic plant species whose flower structure allows early manipulation of both male and female function. Plants on which all stamens were removed at the bud stage had a higher rate of flower initiation and produced significantly heavier seeds than did plants whose flowers remained intact, apparently by using resources that were released when the stamens were removed. However, there was no effect of stamen removal on the number of flowers that reached anthesis, the total biomass allocated to seed production, or the vigour of plants in the progeny generation. In contrast, prevention of fruit production (style removal) increased the amount of biomass invested in stamen by 57% relative to plants whose flowers were allowed to set fruit. These observations verify the existence of a sexual trade-off in N. sativa but also raise the possibility that stamen-suppressing mutations sometimes lack the pleiotropic consequences of increasing female function, at least in species with large, expensive fruits.     

Energetic trade-offs between immunity and reproduction in male Japanese quail (Coturnix coturnix)

We investigated a postulated trade-off between reproduction and immune function by comparing the energetic costs of an immune response with phytohemagglutinin challenge (or injection) in castrated (low testosterone [T]) and intact (high T) Japanese Quail (Coturnix coturnix). Intact birds had higher resting metabolic rate (RMR) and significantly lower immune response than castrates. RMR of intact birds did not change in response to an immune challenge, suggesting that maintenance of reproductive tissues and associated high T is both immunosuppressive and energetically costly. Despite having a greater immune response than intact quail, castrates had a lower pre-challenge RMR than intact birds and paradoxically tended to decrease RMR during an immune challenge. This paradox may be because of pro-inflammatory cytokines that are released during immune responses. Cytokines promote energy conservation through malaise and soporific behaviors, possibly explaining the co-occurrence of a relatively strong immune response and a decrease in nocturnal RMR in castrates. The lower immune response in intact birds may not elicit as great a response of pro-inflammatory cytokines owing to an already elevated RMR from reproductive state, thus reducing any effect on RMR. The suppressed immune response and elevated RMR in intact birds may be because of T; however, we cannot separate the effects of T per se from the metabolic requirements of reproductive tissues.     

Lymphokine production in the cell-mediated immune response (author's transl)

In response to tuberculin, lymphocytes derived from BCG-sensitized guinea pigs elaborated soluble materials capable of inducing some reactions in vitro which correlated with the cell-mediated immune response in vivo. The lymphokine activity of these soluble materials was demonstrated by the following biological effects: macrophage migration inhibition, macrophage aggregation, cytotoxicity to HeLa cells and skin reaction.     

Speed-versus-accuracy trade-offs during nest relocation in Argentine ants (Linepithema humile) and odorous house ants (Tapinoma sessile)

Animals are often forced to accommodate disturbance to their territories or nests. When nest relocation becomes necessary, it is important to efficiently evaluate alternative nest sites to choose the one most suitable under current conditions. However, if time is limiting, species may experience a speed-versus-accuracy trade-off when searching for a new home. We examined nest site selection under duress (in the form of flooding) in two species of ants: Linepithema humile and Tapinoma sessile. We predicted that if ants are able to assess and evacuate to the most suitable location, colonies should move to higher elevation, relative to their current nest site, in response to flooding. To test for a speed-versus-accuracy trade-off, we presented colonies with new nest chambers that were either higher, lower, or at the same height as their current nest and examined if their ability to efficiently choose a new site was influenced by the rate of flooding. When flooding rates were slow, both species favored the highest nest site and nearly always moved their entire nest to the same chamber. However, when the rate of flooding was doubled, colonies of T. sessile less often chose the highest nest site and were also more likely to split their nests between two of the available chambers. These results demonstrate a trade-off between speed and accuracy in nest site selection for odorous house ants, while L. humile retained their ability to adequately assess new nest sites under the conditions we presented. These patterns may arise from differences in exploratory behavior and activity between the two species. Despite having identical colony sizes, L. humile had approximately ten times more workers exploring the alternate nest sites 30 min into the experiment than did T. sessile.     

Seasonal population dynamics in Lucilia eximia (Wiedemann) (Diptera: Calliphoridae)

In this study the seasonal variation of fecundity, wing and tibia sizes were investigated in natural populations of Lucilia eximia (Wiedemann) as an attempt to determine the variations in life history of the species associated to seasonality. Specimens of L. eximia were monthly collected in Botucatu, S?o Paulo, Brazil, during two years and the adult females dissected to estimate fecundity. Body size was estimated by measuring wing and tibia. Fecundity and body size were seasonally analysed. A relatively constant temporal trajectory was found for fecundity, wing and tibia size over twenty-four months. Strong positive correlations between wing and tibia size, fecundity and wing and fecundity and tibia were observed. The maintenance of stable values in L. eximia indicates that it has suffered little seasonal influence over the period analysed. This result confirms the demographics and life history stable profile of the species in spite of seasonal climatic changes observed in the study area.     

Interleukin-21 (IL-21)-mediated pathways in T cell-mediated disease

Interleukin-21 (IL-21) is produced mostly by activated CD4+ T cells and controls the differentiation and functional activity of effector T helper cells, counteracts the suppressive effects of regulatory T cells, and stimulates non-immune cells to make inflammatory mediators. IL-21-driven tissue damage has been demonstrated in a number of organs, such as the gut, pancreas, and brain. Therefore new treatment modalities to neutralise IL-21 in vivo would be a valuable addition to the therapeutic armamentarium to combat immune-mediated inflammation. Here we describe the emerging role of IL-21 in the initiation and progress of the tissue-damaging inflammatory response in immune-mediated pathologies.