Integrative and Comparative Biology最新文献

Dermal denticles (scales) are important in influencing the movement of water around a shark's body. To date, most of the research on denticle morphology and their impacts on hydrodynamics has focused on the lateral flank of fast-swimming species. One understudied region where these interactions may be important is the nares of sharks. The constant flow of water through the nares is critical to olfaction and therefore a shark's survival. We imaged dermal denticles all around the incurrent and excurrent nares of the Pacific spiny dogfish (Squalus suckleyi), a benthopelagic species inhabiting eastern Pacific waters. At the incurrent naris, we quantified denticle morphological traits such as length, width, aspect ratio, ridge number, and angle of rotation off the anterior-posterior axis. We found that denticles at the incurrent naris display two primary morphologies: elongated with ridged crowns and rounded with smooth crowns. Moreover, we show denticles rotated to nearly 180 degrees off the anterior-posterior axis as denticles enter the incurrent naris at the cranial region. Using particle image velocimetry over a 3D printed model of a micro-computed tomography scan of the incurrent naris, we visualized the effects of this rotation on flow and found preliminary data for a reverse circulating vortex in addition to laminar flow into the olfactory chamber. Finally, we propose two hypotheses on the importance of this phenomenon. This work highlights the diversity of shark denticle morphology, particularly with respect to their role in fluid mechanics. Our findings challenge our current understanding of dermal denticle orientation and function, further supporting the need to investigate areas of interest across shark bodies that have not yet been studied in the literature.

Vertebral deformities such as abnormal curvatures and shapes may influence kinematics of fishes during swimming. Our study examines the vertebral deformities of hatchery-reared lumpfish (Cyclopterus lumpus) to better understand the effects of vertebral deformity on swimming kinematics. We recorded and analyzed videos of 50 juvenile lumpfish that were being raised as cleaner fish for salmonid farms. Each lumpfish was observed in 10-s video intervals and then euthanized for X-ray visualization of the skeleton. We used midline tracking to calculate speed, tailbeat amplitude, stride length, tailbeat frequency, and tail curvature during volitional swimming. Body shape analysis using 2D landmarking and principal component analysis showed that there was a significant relationship between the number of deformities and body shape from a dorsal view. We also found that body shape from a lateral view was a significant predictor of speed and stride length. We expected that an increase in deformity would cause a change in tail curvature and a decrease in speed, stride length, tailbeat frequency, and tail amplitude. Instead, we found that the lumpfish swimming was mostly unaffected by the deformity. There was only a significant relationship between tailbeat amplitude and number of early compressed vertebrae. Since vertebral deformities had a significant relationship with body shape, there was also an indirect effect of deformity on swimming speed.

Increasingly sophisticated taxonomic tools have enhanced our understanding of species diversity and phylogenetic relationships in elasmobranchs. Nevertheless, ichthyologists continue to face challenges in resolving the taxonomic placement and authentication of some taxa, particularly those originally described based on morphology. The recently described genus Fontitrygon comprises several Atlantic dasyatid stingrays whose phylogenetic positions have remained unresolved due to the lack of molecular data. In this study, we employed an integrative taxonomic approach to identify and determine the phylogenetic position of the understudied Fontitrygon garouaensis from Nigeria. Specimens were collected from freshwater ecosystems along the Jebba and Lokoja stretches of the River Niger in Nigeria. Comparative morphological analysis distinguished F. garouaensis from other Fontitrygon species by the presence of a depressed central-spine shaft with flanges extending along either side, a flattened oval disc, an obtuse snout, a whip-like tail bearing a sting, a broad and elongated snout, small pelvic fins, and radially arranged pectoral fins. Additionally, morphological measurements of the newly collected F. garouaensis were consistent with those of the syntype and holotype, confirming species identification. Phylogenetic analyses based on mitochondrial cytochrome c oxidase subunit I gene sequences recovered Fontitrygon as a monophyletic lineage and identified F. garouaensis as the sister taxon to F. margarita and F. margaritella. This study provides an integrative taxonomic assessment of F. garouaensis, clarifying its species identity and confirming the presence of F. garouaensis from the upstream of the Jebba stretch of the River Niger. We, therefore, propose an update to its IUCN geographic range.

Wildlife face a number of extrinsic stressors, such as habitat loss, pathogen infections, and contaminant exposure, which can increase the energy needed to maintain optimal health and survival. These multiple extrinsic stressors can also occur simultaneously during intrinsically stressful life stages such as reproduction, migration, or hibernation. To fully understand how to support healthy wildlife populations, we must quantify physiological and immunological phenotypes across a variety of stressors. We pose a framework for conducting field studies to collect individual-level samples that can be used for measuring physiological and immunological phenotypes as well as the potentially stressful intrinsic and extrinsic drivers of those phenotypes. We suggest that collaborative efforts should then be made to create broader, spatially coordinated hypotheses for determining patterns of wildlife health under intrinsically stressful time periods and across extrinsically stressful landscapes. We provide an example and preliminary findings for this multi-stressor, collaborative, and spatially coordinated approach with an ongoing study of North American bat health. Quantifying direct and critical measures of wildlife health and identifying key intrinsic and extrinsic stressors that drive physiological and immunological phenotypes will provide broad targets for conservation strategies and where and when those strategies should be prioritized in the future.

The increasing emergence of virulent pathogens necessitates novel approaches to predict and manage infectious disease risks. The importance of integrating observational and experimental approaches to studying host-pathogen interactions has long been recognized, as captive studies can mechanistically test hypotheses derived from field studies and identify causal factors shaping host susceptibility or tolerance of infection. However, captive experiments can also determine biomarkers of infection outcomes that could improve later interpretation of field data and identify at-risk hosts in wild populations. Such work could be especially useful in preempting or managing risks of pathogen spillover or spillback. SARS-CoV-2 emerged in humans in late 2019 and was rapidly followed by spillback into naïve wildlife, leading to both mortality events and novel enzootic cycles. Of special concern is whether SARS-CoV-2 could establish in bats in the Americas, given that sarbecoviruses coevolved with rhinolophid bats in the Eastern Hemisphere, and as coronavirus infection may exacerbate effects of white-nose syndrome. Here, we leverage residual plasma samples from a previous SARS-CoV-2 challenge study of Mexican free-tailed bats (Tadarida brasiliensis) to identify candidate protein biomarkers of susceptibility and test whether these can predict coronavirus risks in wild bats. We generated plasma proteomes from captive (n = 20; four resistant, five susceptible, 11 unchallenged) and wild (n = 15) bats using the S-Trap method and LC-MS/MS, identifying 475 proteins using data-independent acquisition and a species-specific genome annotation generated by the Bat1K Project. Receiver operator characteristic curves identified 27 potential biomarkers of SARS-CoV-2 susceptibility (AUC ≥ 0.8), and subsequent enrichment analyses of these proteins suggested downregulation of blood clotting and upregulation of complement activation and humoral immunity in susceptible bats. We then mined plasma proteomes from wild bats (sampled in 2022 from Bracken Cave Preserve, the largest known Mexican free-tailed bat population) to show that all candidate biomarkers were present in this population, with coefficients of variation ranging from 16 to 150% per protein. We detected coronaviruses in 20% of wild bats, with two cases of potential SARS-CoV-2 spillback. We demonstrate that at least four of these candidate susceptibility biomarkers classified bats with and without coronavirus infection in the wild. Our results inform the possible immune strategies underlying SARS-CoV-2 susceptibility in bats and give a preliminary example of how captive challenge studies can be coupled with field studies to inform zoonotic and conservation risks.

Comparative biomechanics describes investigating animal models to inform, understand, and improve health and locomotor understanding in humans and across biological organisms and species. In recent years, there has been an increased understanding of comparative biomaterials, which utilizes intincredibly diverse, yet can primarilyerdisciplinary techniques spanning physics, materials science, engineering, and biology to mimic and model the complex morphology and mechanics of biological structures. This perspective piece highlights some recent innovations in biological material characterization of mechanics, morphology, and composition, highlighting specific innovations that help address classical challenges in biomaterials analysis. It concludes with a review of highlights in material fabrication techniques that have expanded the scope of biomaterials through bio-inspired multi-material 3-dimensional printing, textiles, and bio-hybrids. This perspective serves as a starting guide for researchers to broaden their understanding of the innovations that different disciplines have made in characterizing biological materials across various length scales, which could be applied to bio-inspired design.

Emerging diseases threaten wildlife worldwide and understanding immune function in the context of the ecology of an organism is critical in predicting disease outcomes. The immune response in reptiles is especially understudied, leaving major gaps in the ability to address disease threats. Freshwater turtles are especially imperiled due to a swath of anthropogenic impacts, including bacterial, viral, and fungal diseases. Because multiple novel pathogen types threaten turtles, understanding nuances in their immune responses may help predict how populations may respond to challenges and shape conservation decisions. We aimed to characterize immune responses following exposure to 3 commercially available antigens representing bacterial, viral, and fungal pathogens in adult red-eared slider turtles (Trachemys scripta elegans) housed in natural conditions. We collected blood samples from red-eared sliders at 0, 12, 24, 48, and 72 h following an antigen treatment (lipopolysaccharide; LPS, polyinosinic-polycytidylic acid; poly(I:C), zymosan, or saline). We created blood smears at 0 and 72 h and the collected serum and buffy layer (serum + BL) were subjected to 3 manipulations (fresh, frozen, frozen + heat) for use in microbial killing assays against Escherichia coli, Candida albicans, and Staphylococcus aureus. The combination of antigen treatments on the turtles and manipulations to the collected blood allowed us to examine different immune responses and components. We also quantified corticosterone using enzyme-linked immunosorbent assays to understand energy mobilization following antigen treatment. Microbial killing was generally stable against microbes, regardless of antigen exposure and serum manipulations reveal differences in relative leukocyte and protein-based contribution to killing microbe classes. Overall, the low killing of Gram-positive S. aureus relative to E. coli and C. albicans further suggests that red-eared sliders rely on a robust complement response. Though we did not observe substantial differences among treatments, our results suggest that LPS elicited an increased complement response. The other antigens did not consistently stimulate stronger responses, but more work is needed to understand dose-dependent responses to poly(I:C) and zymosan and in turtles and other reptiles. Overall, our research demonstrates that microbial killing assays can be enhanced through deliberate serum + BL manipulation and microbe usage as ecoimmunological tools to gain a more robust understanding of the immune response in wild organisms.

The tongues of pangolins are among the more derived of other mammalian ant-eating specialists, extending nearly a body length to capture food. Pangolins pack portions of their hyolingual apparatus in their thoracoabdominal cavity. These muscles are responsible for protruding, retracting, and bracing the tongue through a large range of motion akin to that of muscular hydrostats. Using DiceCT and 3D muscle architectural modeling of a cadaveric Phataginus tricuspis (White-bellied pangolin), we show how the arrangement of muscle fascicles in a section of the thoracoabdominal portion of the tongue converges on the structure of a hydrostat. Rostrally, the body of the tongue is occupied by m. sternoglossus, paired, parallel-fibered muscle bellies that run the longitudinal distance of the first 2/3 of the tongue. Upon entering the abdominal cavity, the body tethers to coiled, elongate xyphoid bones via m. xiphisternalis. Xiphisternal muscle fibers envelop the caudal portion of m. sternoglossus and anchor to the distal portions of the xiphoid bones and aid in retracting the tongue. The coiled nature of the xiphisternal bones and attachments of tongue muscles suggests an elastic mechanism may help propel tongue extension. The body of the tongue resides in a glossal tube, an extension of geniohyoid muscles built by layers of circular and longitudinal fibers that modestly, helically wind around the long axis of the tongue, also aiding in tongue protraction. Together, these muscles act as a hydrostat in promoting hyolingual movements in pangolins.

Seventy percent of mammals copulate using repeated pelvic thrusting, while the transfer of sperm requires just a single intromission. Why did thrusting evolve to be the dominant form of sexual intercourse? In this study, we investigate how the rate of sexual pelvic thrusting changes with body size. By analyzing films of copulating mammals, from mice Mus musculus to elephants Elephantidae, we find that bigger animals thrust slower. The rate of pelvic thrusting decreases from 6 Hz for the pocket mouse Pergonathus to 1.3-1.8 Hz for humans to an absence of thrusting for the rhino Rhinocerotidae and elephant Elephantidae families. To understand this dependence on body size, we consider the spring-like behavior of the legs, which is associated with the elasticity of the body's muscles, tendons, and ligaments. For both running and thrusting, greater displacment and energy savings can be achieved if the system is oscillated at its resonant or natural frequency. Resonant frequencies, as measured through previous studies of running in dogs Canis familiaris and horses Equus ferus caballus, show good agreement with sexual thrusting frequencies. Running and sexual thrusting have nothing in common from a behavioral perspective, but from a physical perspective, they are both constrained by the same musculoskeletal systems, and both take advantage of resonance. Our findings may provide improved treatments for human sexual dysfunction as well as improving breeding strategies for domestic mammals.

Hydrostatic skeletons enable the transmission of mechanical work through a soft body. Despite the ubiquity of these structures among animals, we have a relatively rudimentary understanding of how they operate mechanically. Here we consider a mathematical model of the mechanics of a relatively tractable hydrostatic skeleton, the tube feet of sea stars. Tube feet drive locomotion by generating a pushing force against the environment. This pushing force is created by the transmission of pressure from one chamber, the ampulla, to another, the stem, which extends from the oral surface of the body. This system operates as a compound machine with a mechanical advantage (MA, the ratio of output to input force) that varies with the geometry of its two chambers. We present an analytical approach for parameterizing the model from morphometric measurements and formulating predictions for representative morphologies. Our analysis predicts that MA initially increases as the stem extends, but collapses to zero near maximum extension. The decrease in force output occurs because the angle of cross-helical fiber winding in the stem approaches the critical point of 54.7°, an angle at which the force components exactly balance the hoop and longitudinal forces from pressure. Though producing no axial force at full extension, a bent tube foot can still generate perpendicular forces that generate torque to lift and propel the body, a proposition that is supported by kinematic observations of the tube feet. These results provide a framework for understanding tube foot mechanics across echinoderms and highlight the functional significance of helical-fiber arrangements in hydrostatic skeletons.