Among-population variation in telomere regulatory proteins and their potential role as hidden drivers of intraspecific variation in life history.

Biologists aim to explain patterns of growth, reproduction and ageing that characterize life histories, yet we are just beginning to understand the proximate mechanisms that generate this diversity. Existing research in this area has focused on telomeres but has generally overlooked the telomere's most direct mediator, the shelterin protein complex. Shelterin proteins physically interact with the telomere to shape its shortening and repair.

Extensive regional variation in the phenology of insects and their response to temperature across North America.

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large-scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America.

Experimental ectoparasite removal has a sex-specific effect on nestling telomere length.

Parasites are a strong selective force that can influence fitness-related traits. The length of chromosome-capping telomeres can be used to assess the long-term costs of parasitism, as telomere loss accelerates in response to environmental stressors and often precedes poorer survival prospects. Here, we explored the sex-specific effects of ectoparasite removal on morphology and telomere length in nestling tree swallows ().

Morphology, performance and fluid dynamics of the crayfish escape response.

Sexual selection can result in an exaggerated morphology that constrains locomotor performance. We studied the relationship between morphology and the tail-flip escape response in male and female rusty crayfish (), a species in which males have enlarged claws (chelae). We found that females had wider abdomens and longer uropods (terminal appendage of the tail fan) than males, while males possessed deeper abdomens and larger chelae, relative to total length.

Size, shape, and sex-dependent variation in force production by crayfish chelae.

The ability to generate large closing forces is important for many animals. Several studies have demonstrated that bite or pinching force capacity is usually related to the linear dimensions of the closing apparatus. However, relatively few studies have applied geometric morphometrics to examine the effects of size-independent shape on force production, particularly in studies of crustacean pinching force.

Guanine-based structural coloration as an indicator of oxidative stress in a cichlid fish.

Vertebrate pigmentation is known to be influenced by oxidative stress, but few studies have tested the hypothesis that structural coloration can be similarly affected. We tested whether fish iridophores, which produce structural color using guanine stacks, might be affected by the prooxidant-antioxidant balance of the animal. Specifically, we hypothesized that convict cichlids (Amatitlania nigrofasciata) metabolize guanine present in iridophores to uric acid, an antioxidant, in response to oxidative damage.

Dietary carotenoids do not improve motility or antioxidant capacity in cichlid fish sperm.

Carotenoids may act as antioxidants under many circumstances. We examined the importance of carotenoids as antioxidants in the gonads of male convict cichlids (Amatitlania nigrofasciata), a species in which males lack the carotenoid-based breeding coloration that characterizes females. Male fish were fed one of four diets that included different combinations of xanthophyll and carotene carotenoids, and then we measured carotenoid concentration of the gonads, gonadosomatic index (GSI), sperm motility, and the antioxidant capacity of the gonads.

Carotenoid-based coloration in cichlid fishes.

Animal colors play important roles in communication, ecological interactions and speciation. Carotenoid pigments are responsible for many yellow, orange and red hues in animals. Whereas extensive knowledge on the proximate mechanisms underlying carotenoid coloration in birds has led to testable hypotheses on avian color evolution and signaling, much less is known about the expression of carotenoid coloration in fishes.

Exposure to environmentally relevant concentrations of genistein during activation does not affect sperm motility in the fighting fish Betta splendens.

Sperm collected from male fighting fish Betta splendens were activated in control water, water containing the ion-channel blocker gadolinium (a putative positive control), or water containing the isoflavone phytoestrogen genistein to determine the effects of acute genistein exposure on male reproductive function. Computer-assisted sperm analysis was used to quantify the proportion of sperm that were motile and the swimming velocity of those sperm. The highest concentration of gadolinium (100 μ M) tested was effective at reducing sperm motility and velocity, but neither concentration of genistein tested (3.

Dietary carotenoids increase yellow nonpigment coloration of female convict cichlids (Amantitlania nigrofasciata).

The carotenoid trade-off hypothesis states that diet-derived carotenoids are traded off among competing physiological demands, but this statement is rarely tested in ornamented females. In this study, reverse sexually dimorphic convict cichlids (Amantitlania nigrofasciata) were fed diets containing carotenoid supplementation at three biologically relevant levels for 12 wk. This treatment was followed by spectral, microscopic, and chemical analysis to determine how females allocated the pigments to tissues and how those decisions affected their ventral patch coloration.

Fighting fish (Betta splendens) bubble nests do not inhibit microbial growth.

Some organisms produce antimicrobial substances in nesting foam to favorably manipulate the environment to which their developing offspring are exposed. We tested if fighting fish Betta splendens foamy nest material, which is comprised of bubbles produced in the oral cavity of nesting males, has antimicrobial properties against a pathogenic bacteria (Edwardsiella tarda), a nonpathogenic bacteria (Escherichia coli), or a pathogenic oomycete (Saprolegnia parasitica). We also tested if exposure to nest material increases larval survival by performing in vitro fertilizations and individually incubating eggs in bubble nest extract or tank water (control).

Exposure to 17α-ethinylestradiol decreases motility and ATP in sperm of male fighting fish Betta splendens.

The synthetic estrogen 17α-ethinylestradiol (EE2) is an endocrine-disrupting chemical released into aquatic environments from sewage treatment facilities. We tested the effects of two environmentally relevant concentrations of waterborne EE2, 10 and 100 ng L(-1) , on reproductive endpoints in the teleost fish Betta splendens. In the first experiment, testes were removed from males and sperm were exposed to EE2 directly through the activation water.

Reproductive consequences of exposure to waterborne phytoestrogens in male fighting fish Betta splendens.

Phytoestrogens are plant compounds that can act as endocrine disruptors in vertebrates. Biologically active levels of phytoestrogens have been found in aquatic habitats near wood pulp and paper mills, biofuel manufacturing plants, sewage-treatment plants, and agricultural fields. Phytoestrogens are known to cause hormonal and gonadal changes in male fish, but few studies have connected these effects to outcomes relevant to reproductive success.

Testing the carotenoid trade-off hypothesis in the polychromatic Midas cichlid, Amphilophus citrinellus.

Many animals use carotenoid pigments derived from their diet for coloration and immunity. The carotenoid trade-off hypothesis predicts that, under conditions of carotenoid scarcity, individuals may be forced to allocate limited carotenoids to either coloration or immunity. In polychromatic species, the pattern of allocation may differ among individuals.

Experimental cooling during incubation leads to reduced innate immunity and body condition in nestling tree swallows.

Nest microclimate can have strong effects that can carry over to later life-history stages. We experimentally cooled the nests of tree swallows (Tachycineta bicolor). Females incubating in cooled nests reduced incubation time and allowed egg temperatures to drop, leading to extended incubation periods.

Modulation of monoamine neurotransmitters in fighting fish Betta splendens exposed to waterborne phytoestrogens.

Endogenous estrogens are known to affect the activity of monoamine neurotransmitters in vertebrate animals, but the effects of exogenous estrogens on neurotransmitters are relatively poorly understood. We exposed sexually mature male fighting fish Betta splendens to environmentally relevant and pharmacological doses of three phytoestrogens that are potential endocrine disruptors in wild fish populations: genistein, equol, and β-sitosterol. We also exposed fish to two doses of the endogenous estrogen 17β-estradiol, which we selected as a positive control because phytoestrogens are putative estrogen mimics.

Temperature and life history: experimental heating leads female tree swallows to modulate egg temperature and incubation behaviour.

1. Life-history decisions are strongly affected by environmental conditions. In birds, incubation is energetically expensive and affected significantly by ambient temperature.

Experimental heating reveals nest temperature affects nestling condition in tree swallows (Tachycineta bicolor).

Investment in one life-history stage can have delayed effects on subsequent life-history stages within a single reproductive bout. We experimentally heated tree swallow (Tachycineta bicolor) nests during incubation to test for effects on parental and nestling conditions. Females incubating in heated boxes maintained higher body condition and fed nestlings at higher rates.

Frequency-dependent performance and handedness in professional baseball players (Homo sapiens).

I used data on handedness and pitching and hitting performance in annual cohorts of professional baseball players (1957-2005) to test the hypothesis that handedness among pitchers was subject to negative frequency-dependent selection. As predicted by this hypothesis, right-handed pitchers were more successful (i.e.

Acorn mast drives long-term dynamics of rodent and songbird populations.

Resource pulses can have cascading effects on the dynamics of multiple trophic levels. Acorn mast is a pulsed resource in oak-dominated forests that has significant direct effects on acorn predators and indirect effects on their predators, prey, and pathogens. We evaluated changes in acorn mast, rodent abundance, raptor abundance, and reproductive success of a ground-nesting songbird over a 24-year period (1980-2004) in the southern Appalachian Mountains in an effort to determine the relationships among the four trophic levels.

Serotonin decreases aggression via 5-HT1A receptors in the fighting fish Betta splendens.

The role of the monoamine neurotransmitter serotonin (5-HT) in the modulation of conspecific aggression in the fighting fish (Betta splendens) was investigated using pharmacological manipulations. We used a fish's response to its mirror image as our index of aggressive behavior. We also investigated the effects of some manipulations on monoamine levels in the B.

Cerebral lateralization and its relationship to phylogeny and aggression in anabantoid fishes.

We examined the relationship between aggression and cerebral lateralization, as expressed by eye-use preference in a mirror-response paradigm, in six species of anabantoid fishes in the teleost family Belontiidae. Our objective was to test the hypothesis that frequency-dependent selection should decrease lateralization at the population level in more aggressive species. The mean laterality index did not differ significantly among the six species, nor did any of the species differ from zero, which suggests that populations of these fishes are neither left- nor right-eye biased.

Behavioral changes in fish exposed to phytoestrogens.

We investigated the behavioral effects of exposure to waterborne phytoestrogens in male fighting fish, Betta splendens. Adult fish were exposed to a range of concentrations of genistein, equol, beta-sitosterol, and the positive control 17beta-estradiol. The following behaviors were measured: spontaneous swimming activity, latency to respond to a perceived intruder (mirror reflection), intensity of aggressive response toward a perceived intruder, probability of constructing a nest in the presence of a female, and the size of the nest constructed.

Consequences of elevating plasma testosterone in females of a socially monogamous songbird: evidence of constraints on male evolution?

To explore whether selection for testosterone-mediated traits in males might be constrained by costs of higher testosterone to females, we examined the effects of experimental elevation of plasma testosterone on physiological, reproductive, and behavioral parameters in a female songbird, the dark-eyed junco (Junco hyemalis). We used subcutaneous implants to elevate testosterone (T) in captive and free-living female juncos. In captive birds, we measured the effects of high T on body mass, feather molt, and brood patch formation.