Growth of brown trout in the wild predicted by embryo stress reaction in the laboratory.

Laboratory studies on embryos of salmonids, such as the brown trout (Salmo trutta), have been extensively used to study environmental stress and how responses vary within and between natural populations. These studies are based on the implicit assumption that early life-history traits are relevant for stress tolerance in the wild. Here we test this assumption by combining two data sets from studies on the same 60 families.

Parental kinship coefficient but not paternal coloration predicts early offspring growth in lake char.

The 'good genes' hypotheses of sexual selection predict that females prefer males with strong ornaments because they are in good health and vigor and can afford the costs of the ornaments. A key assumption of this concept is that male health and vigor are useful predictors of genetic quality and hence offspring performance. We tested this prediction in wild-caught lake char (Salvelinus umbla) whose breeding coloration is known to reveal aspects of male health.

Sex-specific effects of inbreeding in juvenile brown trout.

Inbreeding depression, that is, the reduction of health and vigour in individuals with high inbreeding coefficients, is expected to increase with environmental, social, or physiological stress. It has therefore been predicted that sexual selection and the associated stress usually lead to higher inbreeding depression in males than in females. However, sex-specific differences in life history may reverse that pattern during certain developmental stages.

Sperm of more colourful males are better adapted to ovarian fluids in lake char (Salmonidae).

Fish often spawn eggs with ovarian fluids that have been hypothesized to support the sperm of some males over others (cryptic female choice). Alternatively, sperm reactions to ovarian fluids could reveal male strategies. We used wild-caught lake char (Salvelinus umbla) to experimentally test whether sperm react differently to the presence of ovarian fluid, and whether any differential sperm reaction could be predicted by male breeding coloration, male inbreeding coefficients (based of 4150 SNPs) or the kinship coefficients between males and females.

Adult sex ratios: causes of variation and implications for animal and human societies.

Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competition, mate choice, and social interactions. Here we review a growing literature, focusing on methodological developments that sharpen knowledge of the demographic variables underlying ASR variation, experiments that enhance understanding of the consequences of ASR imbalance across societies, and phylogenetic analyses that provide novel insights into social evolution.

Testing for population differences in evolutionary responses to pesticide pollution in brown trout ().

Pesticides are often toxic to nontarget organisms, especially to those living in rivers that drain agricultural land. The brown trout () is a keystone species in many such rivers, and natural populations have hence been chronically exposed to pesticides over multiple generations. The introduction of pesticides decades ago could have induced evolutionary responses within these populations.

Effects of global warming on sex ratios in fishes.

In fishes, sex is determined by genetics, the environment or an interaction of both. Temperature is among the most important environmental factors that can affect sex determination. As a consequence, changes in temperature at critical developmental stages can induce biases in primary sex ratios in some species.

Correction to: Sex-specific changes in gene expression in response to estrogen pollution around the onset of sex differentiation in grayling (Salmonidae).

An amendment to this paper has been published and can be accessed via the original article.

Embryo survival in the oviduct not significantly influenced by major histocompatibility complex social signaling in the horse.

The major histocompatibility complex (MHC) influences sexual selection in various vertebrates. Recently, MHC-linked social signaling was also shown to influence female fertility in horses (Equus caballus) diagnosed 17 days after fertilization. However, it remained unclear at which stage the pregnancy was terminated.

Low adaptive potential for tolerance to ethynylestradiol, but also low toxicity, in a grayling population (Thymallus thymallus).

Background: The presence of a novel pollutant can induce rapid evolution if there is additive genetic variance for the tolerance to the stressor. Continuous selection over some generations can then reduce the toxicity of the pollutant but also deplete the additive genetic variance for the tolerance and thereby slow down adaptation. One common pollutant that has been ecologically relevant for some time is 17alpha-ethynylestradiol (EE2), a synthetic compound of oral contraceptives since their market launch in the 1960s.

Sperm cryopreservation reduces offspring growth.

Sperm cryopreservation is routinely used in reproductive medicine, livestock production and wildlife management. Its effect on offspring performance is often assumed to be negligible, but this still remains to be confirmed in well-controlled within-subject experiments. We use a vertebrate model that allows us to experimentally separate parental and environmental effects to test whether sperm cryopreservation influences offspring phenotype under stress and non-stress conditions, and whether such effects are male-specific.

Sex-specific changes in gene expression in response to estrogen pollution around the onset of sex differentiation in grayling (Salmonidae).

The synthetic 17α-ethinylestradiol (EE2) is a common estrogenic pollutant that has been suspected to affect the demography of river-dwelling salmonids. One possibility is that exposure to EE2 tips the balance during initial steps of sex differentiation, so that male genotypes show female-specific gene expression and gonad formation. Here we study EE2 effects on gene expression around the onset of sex differentiation in a population of European grayling (Thymallus thymallus) that suffers from sex ratio distortions.

No additive genetic variance for tolerance to ethynylestradiol exposure in natural populations of brown trout ().

One of the most common and potent pollutants of freshwater habitats is 17-alpha-ethynylestradiol (EE2), a synthetic component of oral contraceptives that is not completely eliminated during sewage treatment and that threatens natural populations of fish. Previous studies found additive genetic variance for the tolerance against EE2 in different salmonid fishes and concluded that rapid evolution to this type of pollution seems possible. However, these previous studies were done with fishes that are lake-dwelling and hence typically less exposed to EE2 than river-dwelling species.

Consumption of carotenoids not increased by bacterial infection in brown trout embryos (Salmo trutta).

Carotenoids are organic pigment molecules that play important roles in signalling, control of oxidative stress, and immunity. Fish allocate carotenoids to their eggs, which gives them the typical yellow to red colouration and supports their resistance against microbial infections. However, it is still unclear whether carotenoids act mainly as a shield against infection or are used up during the embryos' immune defence.

Cycle-specific female preferences for visual and non-visual cues in the horse (Equus caballus).

Although female preferences are well studied in many mammals, the possible effects of the oestrous cycle are not yet sufficiently understood. Here we investigate female preferences for visual and non-visual male traits relative to the periodically cycling of sexual proceptivity (oestrus) and inactivity (dioestrus), respectively, in the polygynous horse (Equus caballus). We individually exposed mares to stallions in four experimental situations: (i) mares in oestrus and visual contact to stallions allowed, (ii) mares in oestrus, with blinds (wooden partitions preventing visual contact but allowing for acoustic and olfactory communication), (iii) mares in dioestrus, no blinds, and (iv) mares in dioestrus, with blinds.

Stallion semen quality depends on major histocompatibility complex matching to teaser mare.

The major histocompatibility complex (MHC) has repeatedly been found to influence mate choice of vertebrates, with MHC-dissimilar mates typically being preferred over MHC-similar mates. We used horses (Equus caballus) to test whether MHC matching also affects male investment into ejaculates after short exposure to a female. Semen characteristics varied much among stallions.

Major histocompatibility complex-linked social signalling affects female fertility.

Genes of the major histocompatibility complex (MHC) have been shown to influence social signalling and mate preferences in many species, including humans. First observations suggest that MHC signalling may also affect female fertility. To test this hypothesis, we exposed 191 female horses () to either an MHC-similar or an MHC-dissimilar stimulus male around the time of ovulation and conception.

Maternal allocation of carotenoids increases tolerance to bacterial infection in brown trout.

Life-history theory predicts that iteroparous females allocate their resources differently among different breeding seasons depending on their residual reproductive value. In iteroparous salmonids there is typically much variation in egg size, egg number, and in the compounds that females allocate to their clutch. These compounds include various carotenoids whose functions are not sufficiently understood yet.

Environmental stress linked to consumption of maternally derived carotenoids in brown trout embryos ().

The yellow, orange, or red colors of salmonid eggs are due to maternally derived carotenoids whose functions are not sufficiently understood yet. Here, we studied the significance of naturally acquired carotenoids as maternal environmental effects during embryo development in brown trout (). We collected eggs from wild females, quantified their egg carotenoid content, fertilized them in vitro in full-factorial breeding blocks to separate maternal from paternal effects, and raised 3,278 embryos singly at various stress conditions until hatching.

Demographic and genetic consequences of disturbed sex determination.

During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination.

Quality of seminal fluids varies with type of stimulus at ejaculation.

The theory of ejaculate economics was mainly built around different sperm competition scenarios but also predicts that investments into ejaculates depend on female fecundity. Previous tests of this prediction focused on invertebrates and lower vertebrate, and on species with high female reproductive potential. It remains unclear whether the prediction also holds for polygynous mammals with low female reproductive potential (due to low litter size and long inter-birth intervals).