Effects of maternal androgens and their metabolite etiocholanolone on prenatal development in birds.

Offspring phenotypes can be affected by maternal testosterone and androstenedione (A4), which are considered a tool of mothers to adjust offspring to a fluctuating environment. Yet testosterone and A4 are very rapidly metabolized by developing avian embryos, suggesting that either the maternal testosterone and A4 have potent organizational effects on the embryos extremely early before being metabolized or it is the metabolites that evoke phenotypic variation in the offspring. One of the metabolites, etiocholanolone, increases substantially during early embryonic development and is a likely candidate for mediating maternal effects as it can promote erythropoiesis.

Are lateralized and bold fish optimistic or pessimistic?

Cognitive bias is defined as the influence of emotions on cognitive processes. The concept of the cognitive judgement bias has its origins in human psychology but has been applied to animals over the past 2 decades. In this study we were interested in determining if laterality and personality traits, which are known to influence learning style, might also be correlated with a cognitive bias in the three-spined sticklebacks (Gasterosteus aculeatus).

Prolactin is associated with proximity to incubating partner rather than parental care in black-headed gulls.

The peptide hormone prolactin plays an important role in the expression of parental care behaviours across bird and mammal taxa. While a great deal is known about how plasma prolactin concentrations vary across the reproductive cycle, the few studies that investigate how prolactin relates to individual-level variation in parental care have reported mixed results. We argue that, since parental care is also affected by social interactions and environmental constraints, prolactin may better reflect behaviours that are indirectly related to parenting than the absolute level of care that is eventually expressed.

Effects of early predation and social cues on the relationship between laterality and personality.

Individual differences in laterality and personality are expected to covary, as emotions are processed differently by the two hemispheres, and personality involves emotional behavior. Fish species are often used to investigate this topic due to the large variability in personality and laterality patterns. While some species show a positive relationship between lateralization strength and boldness, others show a negative relationship, and some show no relationship.

The effect of light during embryonic development on laterality and exploration in Western Rainbowfish.

Several factors affect the development of lateralization such as hormones and light exposure during early development. Laterality also often correlates with other behavioral traits. To examine whether there is a common mechanism underlying the development of laterality and other behaviors, we manipulated laterality by exposing embryos of the Western rainbowfish () to light or continuous darkness during early development and determined whether a shift in laterality was associated with a change in behavior in a novel environment test at two different ages.

Egg-mediated maternal effects in a cooperatively breeding cichlid fish.

Mothers can influence offspring phenotype through egg-mediated maternal effects, which can be influenced by cues mothers obtain from their environment during offspring production. Developing embryos use these components but have mechanisms to alter maternal signals. Here we aimed to understand the role of mothers and embryos in how maternal effects might shape offspring social phenotype.

Position in the laying order has sex-specific consequences for reproductive success in adult black-headed gulls.

Mothers who produce multiple offspring within one reproductive attempt often allocate resources differentially; some maternally derived substances are preferentially allocated to last-produced offspring and others to first-produced offspring. The combined effect of these different allocation regimes on the overall fitness of offspring produced early or late in the sequence is not well understood, partly because production order is often coupled with birth order, making it difficult-to-separate effects of pre-natal maternal allocation from those of post-natal social environments. In addition, very little is known about the influence of laying order on fitness in later life.

Plasticity in metabolism of maternal androgens in avian embryos.

Mothers can influence offspring phenotypes by transferring non-genetic information to the young, which provides them with a flexible tool to adjust the developmental trajectory of the young in fluctuating environments. Mothers can differentially deposit their resources in the same reproductive attempt in relation to the offspring position in the sibling hierarchy. However, whether embryos from different positions can be plastic in their response to the maternal signals, potentially leading to a mother-offspring conflict, is yet unclear.

Dynamics of maternal androgens and its metabolites during early embryonic development: embryonic modification of a maternal effect.

In birds, exposure to maternal (yolk) testosterone affects a diversity of offspring post-hatching traits, which eventually affect offspring competitiveness. However, maternal testosterone is heavily metabolized at very early embryonic developmental stages to hydrophilic metabolites that are often assumed to be much less biologically potent. Either the rapid metabolism could either keep the maternal testosterone from reaching the embryos, opening the possibility for a mother-offspring conflict or the metabolites may facilitate the uptake of the lipophilic testosterone from the yolk into the embryonic circulation after which they are either converted back to the testosterone or functioning directly as metabolites.

Mesocosm experiment reveals scale dependence of movement tendencies in sticklebacks.

Habitat fragmentation can have negative impacts on migratory organisms that rely on the functional connectivity between growing and breeding grounds. Quantifying the population-level phenotypic consequences of such fragmentation requires fine-scaled tracking of individual behaviour and movements across relevant scales. Here we make use of a natural experiment where some populations of 'migrant' three-spined sticklebacks () became 'residents', following habitat fragmentation five decades ago.

Early conversion of maternal androgens affects the embryo already in the first week of development.

Maternal androgen exposure has potent effects on offspring development. As substantial levels of maternal androgens are deposited in avian egg yolks, avian eggs are frequently used to study maternal effects, with a strong focus on post-natal development. However, the underlying pathways are largely unknown.

Embryonic heart rate is affected by yolk androgens and egg laying sequence, and correlates with embryonic tissue growth: A study in rock pigeons.

Maternal androgen exposure can have crucial effects on offspring development. Bird eggs are frequently used for studying these effects and virtually all research in this field has focused on post-hatching offspring traits. Yet, much of the yolk, in which the maternal hormones are deposited, is consumed during the embryonic phase.

Maternally transferred thyroid hormones and life-history variation in birds.

In vertebrates, thyroid hormones (THs) play an important role in the regulation of growth, development, metabolism, photoperiodic responses and migration. Maternally transferred THs are important for normal early phase embryonic development when embryos are not able to produce endogenous THs. Previous studies have shown that variation in maternal THs within the physiological range can influence offspring phenotype.

Androgen Elevation Accelerates Reproductive Senescence in Three-Spined Stickleback.

Costs of reproduction shape the life-history evolution of investment in current and future reproduction and thereby aging. Androgens have been proposed to regulate the physiology governing these investments. Furthermore, androgens are hypothesized to play a central role in carotenoid-dependent sexual signaling, regulating how much carotenoids are diverted to ornamentation and away from somatic maintenance, increasing oxidative stress, and accelerating aging.

Exploration speed in captivity predicts foraging tactics and diet in free-living red knots.

Variation in foraging tactics and diet is usually attributed to differences in morphology, experience and prey availability. Recently, consistent individual differences in behaviour (personality) have been shown to be associated with foraging strategies. Bolder or more exploratory individuals are predicted to have a faster pace-of-life and offset the costs of moving more or in risky areas, with higher energetic gains by encountering profitable foraging opportunities and prey.

Is maternal thyroid hormone deposition subject to a trade-off between self and egg because of iodine? An experimental study in rock pigeon.

Maternal hormones constitute a key signalling pathway for mothers to shape offspring phenotype and fitness. Thyroid hormones (THs; triiodothyronine, T3; and thyroxine, T4) are metabolic hormones known to play crucial roles in embryonic development and survival in all vertebrates. During early developmental stages, embryos exclusively rely on exposure to maternal THs, and maternal hypothyroidism can cause severe embryonic maldevelopment.

Is imitational learning a driving factor for the population bias in human hand preference?

Lateral preference is a widespread organizational principle in human and nonhuman animals. In humans, the most apparent lateralized trait (handedness) is unique in the animal kingdom because of a very pronounced bias towards right-handedness on a population level. In this study, based on previous experiments, we test the hypothesis that this bias was-among other factors-shaped by evolution through the facilitation of social learning.

Testing the Darwinian function of lateralization. Does separation of workload between brain hemispheres increase cognitive performance?

Brain lateralization is a fundamental aspect of the organization of brain and behavior in the animal kingdom, begging the question about its Darwinian function. We tested the possibility that lateralization enhances cognitive performance in single- and dual-tasks. Previous studies reported mixed results on this topic and only a handful of studies have measured functional brain lateralization and performance independently and simultaneously.

Who listens to mother? A whole-family perspective on the evolution of maternal hormone allocation.

Maternal effects, or the influence of maternal environment and phenotype on offspring phenotype, may allow mothers to fine-tune their offspring's developmental trajectory and resulting phenotype sometimes long after the offspring has reached independence. However, maternal effects on offspring phenotype do not evolve in isolation, but rather within the context of a family unit, where the separate and often conflicting evolutionary interests of mothers, fathers and offspring are all at play. While intrafamilial conflicts are routinely invoked to explain other components of reproductive strategy, remarkably little is known about how intrafamilial conflicts influence maternal effects.

The importance of understanding function and evolution.

Ocklenburg et al. (2020, Laterality 2020: Entering the next decade. ) provided the field of laterality research with a stimulating research perspective for the coming decade, based on the current state of the art in both animal and human laterality research.

An examination of the influence of prenatal sex hormones on handedness: Literature review and amniotic fluid data.

Competing theories have posited roles for foetal androgen exposure in the development of human handedness. However, due to practical and ethical considerations, few studies have used hormonal measures to examine this possibility. The current paper reviews this literature and reveals a generally inconsistent pattern of results.

Testing the short-and long-term effects of elevated prenatal exposure to different forms of thyroid hormones.

Maternal thyroid hormones (THs) are known to be crucial in embryonic development in humans, but their influence on other, especially wild, animals remains poorly understood. So far, the studies that experimentally investigated the consequences of maternal THs focused on short-term effects, while early organisational effects with long-term consequences, as shown for other prenatal hormones, could also be expected. In this study, we aimed at investigating both the short- and long-term effects of prenatal THs in a bird species, the Japanese quail .

Testing different forms of regulation of yolk thyroid hormone transfer in pied flycatchers.

Hormones transferred from mothers to their offspring are considered a maternal tool to prepare progeny for expected environmental conditions, increasing maternal and offspring fitness. To flexibly influence offspring, mothers should be able to transmit the hormonal signals independent of their own hormonal status. However, the ability to regulate hormone transfer to the next generation is under debate.

Manipulation of Prenatal Thyroid Hormones Does Not Affect Growth or Physiology in Nestling Pied Flycatchers.

Hormones transferred from mothers to their offspring are thought to be a tool for mothers to prepare their progeny for expected environmental conditions, thus increasing fitness. Thyroid hormones (THs) are crucial across vertebrates for embryonic and postnatal development and metabolism. Yet yolk THs have mostly been ignored in the context of hormone-mediated maternal effects.