Journal of experimental zoology. Part B, Molecular and developmental evolution最新文献

Graph theory offers a conceptual framework for analyzing complex systems, providing complementary insights into the organization, development, and evolution of morphological structures in biological systems. Graphs describe interactions (edges or links) between entities (vertices or nodes) that can be directed or undirected, weighted or unweighted, and cyclic or acyclic. Over the past decade, a growing community of researchers in Argentina, including the authors of this contribution, has applied diverse graph-theoretical approaches to address questions in functional, evolutionary, and developmental morphology. In Latin America, Argentina stands out for incorporating graph theory and new approaches to network analysis into anatomical research. This review highlights the following particular areas where graph theory has been applied: (I) vertex parameters; (II) graph parameters; (III) graph modular organization and hierarchy; (IV) functional interpretations from modularity throughout graph parameters; (V) graph complexity; (VI) adding the temporal dimension to graphs; (VII) Gabriel graph and percolation in geometric networks; (VIII) dual networks; (IX) flow networks and Markov chains. By presenting these applications and original contributions, this work illustrates how graph theory can enrich morphological evo-devo research while reflecting the development of a growing research community in the region.

Cetaceans exhibit remarkable wound-healing abilities, an adaptation critical for survival in their aquatic environment. This study provides the first identification of leucine-rich alpha-2-glycoprotein 1 (LRG1) in the bottlenose dolphin (Tursiops truncatus), focusing on its potential role in wound healing. LRG1, a member of the leucine-rich repeat family, is involved in immune regulation, angiogenesis, and tissue remodeling in terrestrial mammals. We extracted and analyzed LRG1 from T. truncatus to detect basic evolutionary insights on cetacean wound healing. Comparative analyses indicated that T. truncatus LRG1 exhibits similarities with its terrestrial counterparts but may offer distinct adaptational characters. These findings represent a pivotal first step toward elucidating the molecular evolutionary mechanisms of cetacean wound healing and highlight LRG1 as a promising target for future veterinary clinical applications.

Ecomorphology examines how species' morphology adapt to their environments, providing insights into biodiversity and evolution. This field relies on three main components: a morphological matrix, an ecological matrix, and phylogeny. A major challenge in contemporary anuran ecomorphology is constructing the ecological matrix, as categorizing species' ecological roles lacks a standardized methodology, leading to inconsistencies across studies and complicating comparisons. In this study, we discuss the challenges of systematizing criteria for constructing the ecological matrix in anurans. To this end, we conducted a literature search, focusing on studies that consider microhabitats as ecological categories and locomotor abilities, using relevant keywords to the topic. A total of 31 studies from the last 46 years were selected for analysis, and information was extracted on the following aspects: analyzed species; microhabitat and locomotor mode categories; and whether or not own criteria for assigning ecological categories (i.e., microhabitat and locomotor modes) were specified. The analyzed studies reveal a high degree of consistency in the assignment of ecological categories for microhabitat classification but not for locomotor modes designation. The main discrepancies occur in the burrowing and/or fossorial categories, as well as climbing. Interestingly, these categories appear both as microhabitats and as locomotor modes. Key criteria include direct field observations and assignments based on primary literature sources. The variability in category assignments and data collection criteria underscores the need to develop more standardized protocols for ecological categorization to improve the accuracy and reproducibility of ecomorphological studies.

The mechanical loads from muscle contraction and gravity affect the biomechanical properties of long-bone limbs, varying according to the functional demands of each limb. In anurans, both limbs are used for locomotion, but the hindlimbs generate higher energy for jumping or swimming, and the forelimbs serve additional purposes (e.g., landing, amplexus, feeding, etc). This study examines the bone architecture of the forelimb bones (humerus and radioulna) and the hindlimb bones (femur, tibiafibula, tibiale, and fibulare) of 24 anuran species with different habitat uses within a phylogenetic context. Also, because of functional divergence among limbs, we investigate possible divergence in morphological integration among long bones depending on habitat use. Across all species, forelimb bones show significantly higher bone biomechanical properties values than hindlimbs, with aquatic and semiaquatic species exhibiting the most resistant bones to bending and fracture. The femur and tibiafibula of aquatic, semiaquatic, and terrestrial species showed similar and higher values, while arboreal species had the lowest values. The tibiale and fibulare bones show a unique stratified pattern across habitats, and in most species, these bones have higher values than the femur and tibiafibula. Although morphological integration varies across habitats-with terrestrial species showing the highest and aquatic and arboreal species the lowest, reflecting differences in limb specialization-the tibiale and fibulare uniquely exhibit significant covariation across all species. While phylogenetic factors may contribute to the observed variability, ecological factors play a crucial role in shaping bone geometry, highlighting the evolutionary adaptations of long bone resistance across ecological niches.

The tetrapod heart is characterized by three chambers in amphibians and non-avian reptiles, as opposed to four in birds, crocodilians and mammals. We explored this diversity via the most phylogenetically comprehensive comparison of heart transcriptomes undertaken to date. Transcriptomes representing the ontogeny of heart compartmentalization (septation) in alligator, chicken, frog, mouse, lizard and turtle embryos exhibited a clear species-specific signal, which was driven by genes involved in heart contraction. During the stage dominated by septation-related tissue transformations, the most highly expressed genes shared by species originated before the tetrapods diversified and were related to septum morphogenesis, ventricular development, and chamber formation. The expression of septation-related genes did not adhere to phylogeny or heart chamber number, and genes differentially expressed across developmental stages within species varied in their evolutionary ages and predicted functions. We discuss how the acquisition of novel structures in some lineages, convergent evolution of four heart chambers, embryonic metabolism, microstructural variation, and ontogenetic shifts (heterochronies), collectively, provide insight into evolved and conserved patterns of transcriptome-level variation. These data serve as a resource to further stimulate evo-devo research on complex organ systems, such as the heart.

During the origin of new niches, animals face novel situations and must adapt to access new resources. Innovative individuals may develop strategies and behaviors to take advantage of these resources, although these individuals often lack striking adaptations for the new niche. In these individuals, adequate performance must be achieved, even in cases where behaviors are not typical or usual, which does not necessarily imply optimal performance in terms of energy or speed, but rather the flexibility to choose a different scenario to pursue a biological purpose. Through experience, animals can improve their ability to perform complex movements and adapt to new conditions. We evaluated the existence of additional locomotor skills in a widespread anuran amphibian, Rhinella arenarum. This toad has a terrestrial niche, probably the ancestral condition within the genus. Therefore, it allows us to know the limits of these capacities to execute novel behaviors. Specifically, we analyzed whether the climbing abilities demonstrated by this terrestrial toad can be improved through learning. Adult male and female toads were tested in a climbing device during eight daily sessions. After training, animals improved climbing performance, measured by climbing latency, climbing speed, and stride frequency. The improvement by learning the ability to climb could thus represent an adaptation that allows the exploitation of arboreal niches. Our results indicate that it is possible that innovative individuals who manage to acquire and perfect the ability to climb could expand their range of available niches and, potentially, give rise to new evolutionary lines.

Behavioral stress responses allow animals to quickly adapt to local environments and are critical for survival. Stress responses provide an ideal model for investigating the evolution of complex behaviors due to their conservation across species, critical role in survival, and integration of behavioral and physiological components. The Mexican cavefish (Astyanax mexicanus) has evolved dramatically different stress responses compared to river-dwelling surface fish morphs, providing a model to investigate the neural and evolutionary basis of stress-like responses. Surface morphs inhabit predator-rich environments, whereas cave-dwelling morphs occupy predator-free habitats. While these key ecological variables may underlie differences in stress responses, the complexity of the behavioral differences has not been thoroughly examined. By leveraging automated pose-tracking and machine learning tools, we quantified a range of behaviors associated with stress, including freezing, bottom-dwelling, and hyperactivity, during a novel tank assay. Surface fish exhibited heightened stress responses characterized by prolonged bottom-dwelling and frequent freezing, while cavefish demonstrated reduced stress behaviors, marked by greater exploration and minimal freezing. Analysis of F2 hybrids revealed that a subset of behaviors, freezing and bottom-dwelling, co-segregated, suggesting shared genetic or physiological underpinnings. Our findings illustrate the power of computational tools for high-throughput behavioral phenotyping, enabling precise quantification of complex traits and revealing the genetic and ecological factors driving their evolution. This study provides a framework for understanding how integrated behavioral and physiological traits evolve, offering broader insights into the mechanisms underlying the diversification of animal behavior in natural systems.

The evolutionary change of the trigeminal nerve-innervation pattern is essential to reveal the mechanism underlying jaw acquisition. However, the homology of the branches between gnathostomes (jawed vertebrates) and cyclostomes (living jawless vertebrates) remains unclear. In this study, we focused on a subbranch called the ramus subpharyngeus, which belongs to the second branch of the lamprey trigeminal nerve and projects to the lower lip, investigating whether it contains motor components. To visualize motor fibers, we performed acetylcholinesterase (AChE) staining, a histochemical method that visualizes intrinsic activities of the catabolic enzymes produced by motor neurons and muscle fibers. As a result, we found AChE staining signals that correspond to the innervation course of the ramus subpharyngeus. To confirm that these signals in this region do not mark the motoneuronal somata nor muscle fibers, we conducted gene expression analysis by in situ hybridization. The results support that the signals mark the motor fibers. Based on these results, we propose that the lamprey oral apparatus is chiefly controlled by the second (i.e., premandibular) branch of the trigeminal nerve and further suggest that a drastic reorganization of the anterior craniofacial region occurred during the acquisition of the vertebrate jaw.