Brain Behavior and Evolution最新文献

Background: Astrocytes, a type of glial cell in the brain, show remarkable morphological and functional diversity across mammalian species.

Summary: This review explores astrocyte biology beyond the commonly studied rodent and primate models, focusing on nontraditional species to uncover evolutionary and adaptive features.

Key messages: By examining astrocytes in marsupials, monotremes, chiropterans, artiodactyls, carnivorans, and cetaceans, we highlight species-specific variations in astrocyte morphology, distribution, and molecular markers. These adaptations are linked to ecological demands, such as echolocation in bats or diving in cetaceans, and underscore the evolutionary pressures shaping astrocyte specialization. Additionally, we explore unique astrocytic subtypes, such as interlaminar astrocytes and their distribution across mammalian lineages, as well as the expression of connexins, GFAP, and other key markers across species. This comparative review provides insights into the evolutionary trajectory of astrocytes and their contributions to neural health and disease, emphasizing the need for broader taxonomic representation in astrocyte research.

Introduction: Noise associated with human activities in aquatic environments can affect the physiology and behavior of aquatic species which may have consequences at the population and ecosystem levels. Low-frequency sound is particularly stressful for fish since it is an important factor in predator-prey interactions. Even though behavioral and physiological studies have been conducted to assess the effects of sound on fish species, neurobiological studies are still lacking.

Methods: In this study, we exposed farmed salmon to low-frequency sound for 5 min a day for 30 trials and conducted behavioral observations and tissue sampling before sound exposure (timepoint zero; T0) and after 1 (T1), 10 (T2), 20 (T3), and 30 (T4) exposures, to assess markers of stress. These included plasma cortisol, neuronal activity, monoaminergic signaling, and gene expression in 4 areas of the forebrain.

Results: We found that sound exposure induced an activation of the stress response by eliciting an initial startle behavioral response, together with increased plasma cortisol levels and a decrease in neuronal activity in the hypothalamic tubercular nuclei (TN). At T3 and T4 salmon showed a degree of habituation in their behavioral and cortisol response. However, at T4, salmon showed signs of chronic stress with increased serotonergic activity levels in the dorsolateral and dorsomedial pallium, the preoptic area, and the TN, as well as an inhibition of growth and reproduction transcripts in the TN.

Conclusions: Together, our results suggest that prolonged exposure to sound results in chronic stress that leads to neurological changes which suggest a reduction of life fitness traits.

Background: Glial cells are important elements constituting the nervous systems and playing important roles. The characterization and exploration about their role are largely based on studies in mammals. Early in the history of modern science (in the distant 1896) is traced the first report of the existence of "bushy" glia cells in the brain of Octopus vulgaris. Subsequent studies focused on the nervous system of octopus and other cephalopods have largely ignored them, in favor of neuronal cells. As a result, there is a notable gap in scientific literature regarding a thorough and comprehensive description of the tissues that support and nourish nerve cells in cephalopods.

Summary: This review provides an overview of the intriguing world of glial cells in marine invertebrates, with a focus on octopus and allies. It highlights their significance and complexity while exploring functional analogies with mammalian glial cells.

Key messages: This review emphasizes the need for further research to understand the interaction between nerve cells and glial elements in cephalopods. Understanding these interactions can contribute to our knowledge of the evolution of complex cognition.

Introduction: A central question about the evolution of social behavior is how extensive diversity can arise when behaviors depend on shared neural, molecular, and hormonal mechanisms. Comparing close relatives can offer insights into which components of shared mechanisms are most evolvable.

Methods: We discriminate between two nonexclusive hypotheses by which conserved neural mechanisms might evolve to generate differences in social behavior: changes in the number or activity of neurons. We test these hypotheses in two recently diverged ecotypes of threespine stickleback (Gasterosteus aculeatus); the common ecotype provides parental care, while the white ecotype does not. We used double-label fluorescent immunohistochemistry with pS6, a marker of transcriptionally active neurons, to quantify the number and activity of two preoptic neuropeptidergic cell types that affect parental care across vertebrates: galanin (Gal) and oxytocin (OXT).

Results: Ecotypes did not differ in the overall activity of the preoptic area or the number of Gal and OXT neurons but did differ in the activity of Gal and OXT neurons. The activity of these neurons changed across reproductive stages in the common but not the white ecotype. Activity peaked after mating in commons when males began to care for their offspring, suggesting that changes in the activity of these specific preoptic neurons are required to transition from courtship to parenting.

Conclusion: Overall, our study suggests that rapid behavioral evolution occurred via changes in the activity but not the number of specific preoptic neuropeptidergic neurons.

Introduction: Raoellidae are small artiodactyls retrieved from the middle Eocene of Asia (ca. -47 Ma) and closely related to stem Cetacea. Morphological observations of their endocranial structures allow for outlining some of the early steps of the evolutionary history of the cetacean brain. The external features of the brain and associated sinuses of Raoellidae are so far only documented by the virtual reconstruction of the endocast based on specimens of the species Indohyus indirae. These specimens are however too deformed to fully access the external morphology, surface area, and volume measurements of the brain.

Methods: We bring here new elements to the picture of the raoellid brain by an investigation of the internal structures of an exceptionally well-preserved cranium collected from the Kalakot area (Jammu and Kashmir, India) referred to the species Khirtharia inflata. Micro-CT scan investigation and virtual reconstruction of the endocast and associated sinuses of this specimen provide crucial additional data about the morphological diversity within Raoellidae as well as reliable linear, surfaces, and volumes measurements, allowing for quantitative studies.

Results: We show that, like I. indirae, the brain of K. inflata exhibits a mosaic of features observed in earliest artiodactyls: a small neocortex with simple folding pattern, widely exposed midbrain, and relatively long cerebellum. But, like Indohyus, the brain of Khirtharia shows unique derived characters also observed in stem cetaceans: narrow elongated olfactory bulbs and peduncles, posterior location of the braincase in the cranium, and complex network of blood vessels around the cerebellum. The volume of the brain relative to body mass of K. inflata is markedly small when compared to other early artiodactyls.

Conclusion: We show here that cetaceans that nowadays have the second biggest brain after humans derive from a group of animals that had a lower-than-average expected brain size. This is probably a side effect of the adaptation to aquatic life. Conversely, this very small brain size relative to body mass might be another line of evidence supporting the aquatic habits in raoellids.

Introduction: Movement requires maneuvers that generate thrust to either make turns or move the body forward in physical space. The computational space for perpetually controlling the relative position of every point on the body surface can be vast. We hypothesize the evolution of efficient design for movement that minimizes active (neural) control by leveraging the passive (reactive) forces between the body and the surrounding medium at play. To test our hypothesis, we investigate the presence of stereotypical postures during free-swimming in adult zebrafish, Danio rerio.

Methods: We perform markerless tracking using DeepLabCut (DLC), a deep learning pose-estimation toolkit, to track geometric relationships between body parts. We identify putative clusters of postural configurations from twelve freely behaving zebrafish, using unsupervised multivariate time-series analysis (B-SOiD machine-learning software) and of distances and angles between body segments extracted from DLC data.

Results: When applied to single individuals, DLC-extracted data reveal a best-fit for 36-50 clusters in contrast to 86 clusters for data pooled from all 12 animals. The centroids of each cluster obtained over 14,000 sequential frames represent an a priori classification into relatively stable "target body postures." We use multidimensional scaling of mean parameter values for each cluster to map cluster centroids within two dimensions of postural space. From a posteriori visual analysis, we condense neighboring postural variants into 15 superclusters or core body configurations. We develop a nomenclature specifying the anteroposterior level/s (upper, mid, and lower) and degree of bending.

Conclusion: Our results suggest that constraining bends to mainly three anteroposterior levels in fish paved the way for the evolution of a neck, fore- and hind limb design for maneuverability in land vertebrates.

Background: The origin and maintenance of species is a unifying theme in evolutionary biology. Mate choice and selection on sexual signals have emerged as powerful drivers of reproductive isolation - the key pillar of the biological species concept. The mechanistic underpinnings of isolating behaviors lie in the circuit- and cellular-level properties of the brain and remain relatively understudied.

Summary: Here, I argue that temporal auditory selectivity in anuran amphibians offers a window into the proximate mechanisms of reproductive isolation. First, I discuss anuran behaviors as a longstanding neuroethological model with which to examine behavioral reproductive isolation and its neural correlates. Next, I review how modern neurobiological techniques are revealing the proximate mechanisms of the evolution of divergent mate preferences in anurans, highlighting cellular-level neural shifts in temporal coding. Finally, I discuss future research directions to reveal the neural mechanisms through which behavioral isolation is generated and maintained in anuran model systems.

Key messages: Anurans offer a powerful model for addressing questions about how neural barriers to gene flow arise across biological scales and how changes in the brain contribute to speciation. Modern evolutionary neurobiology will benefit from applying new tools to this longstanding neuroethological model clade.

Introduction: The factors shaping vertebrate brain evolution and cognition are broadly categorized as being either social or environmental. Yet, their relative importance is debated, partly due to the limitations associated with standard interspecific evolutionary comparisons. Here, we adopt a complementary strategy leveraging within-population variation in fish brain size to ask how variation in social and environmental factors correlates with individual brain size.

Methods: We investigated how overall brain size and brain part sizes varied between demes of the same population in the coral reef-associated batu coris Coris batuensis. This species is ideal for our approach because its local population densities are dissociated from both interspecific densities and habitat complexity.

Results: We found that individuals from demes with higher population densities possess larger overall brain volumes than those from lower population density environments, caused by an enlargement of all five main brain regions. Brain anatomical measures show no correlation with interspecific density or habitat complexity.

Conclusion: Our results suggest that variation in intraspecific social challenges is selected on individual batu coris brain size, either through phenotypic plasticity, differential survival, or habitat choice. These results conform with a broader version of the social brain hypothesis, emphasizing the importance of the entire brain over specific regions like the neocortex in mammals or the telencephalon in fishes.

Introduction: Chondrichthyans represent some of the earliest diverging lineages of jawed vertebrates, making them key models for studying the evolution of vertebrate brains. Despite their evolutionary significance, Mediterranean species remain understudied. This research focuses on the speckled skate (Raja polystigma), an endemic Mediterranean benthic species with distinct life history traits, such as bathymetric segregation and postnatal shifts in diet. These traits provide a unique opportunity to explore how ecological factors influence postnatal brain development and neuroecological adaptation in cartilaginous fishes.

Methods: We examined the allometric relationship between brain mass and body mass in postnatal individuals of R. polystigma and assessed the relative growth of major brain regions, including the olfactory bulbs, telencephalon, diencephalon, optic tectum, cerebellum, and medulla oblongata. Data were analyzed using log-transformed linear regressions to determine differential growth rates and patterns of regional specialization during development.

Results: Our analysis revealed that brain growth scales with negative allometry relative to body mass, indicating a slowdown in brain growth as individuals mature. Region-specific trends showed that the olfactory bulbs, cerebellum, and medulla oblongata grow at a faster rate than the rest of the brain, suggesting enhanced development of sensory and motor capacities. Conversely, the optic tectum exhibited slower growth, implying a reduced visual reliance in adults. The telencephalon and diencephalon scaled isometrically with brain mass, suggesting stable roles in cognitive and integrative functions throughout postnatal development.

Conclusion: These findings highlight how ecological and behavioral shifts during development shape brain organization in R. polystigma. Enhanced growth of non-visual sensory regions and motor centers may reflect adaptations to a benthic lifestyle and bathymetric niche. This study contributes to our understanding of neuroecological evolution in Mediterranean chondrichthyans and underscores the value of R. polystigma as a model for investigating brain development in relation to ecological specialization.