Journal of Experimental Biology - Latest Issue
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An application of finite element analysis predicts unique temperatures and fates for flatback sea turtle embryos
ABSTRACTIncubation temperatures within sea turtle nests are governed by complex abiotic and biotic interactions. Established methods for estimating these temperatures include deploying temperature loggers at standard nest depths or using models to predict sand temperature. While these approaches capture abiotic drivers of incubation temperatures, they often fail to fully account for biotic factors, including the heat produced by the metabolism of embryos, despite its potential impact on hatchling development and mortality.Here, we applied finite element analysis to predict incubation temperatures for all embryos in five flatback sea turtle (Natator depressus) nests. To parameterise the models, we measured clutch size, nest depth, temperatures at several locations around nests, and the physical properties of beach sand, including density and moisture. Next, we simulated within-nest temperatures with an energy balance model that accounted for metabolic heat by applying an hourly heat flux, based on modelled embryonic metabolic rates, to each egg. Each model was validated by comparing predicted temperatures with observed temperatures at the base, centre and top of each clutch. On average, finite element models achieved good accuracy to within 0.4°C of observed data (mean error over the entire incubation period). By incorporating individual clutch size, nest depth and the metabolic contributions of embryos, our approach enhances the realism of temperature estimates for predicting the embryonic development of sea turtles, which is of increasing importance under rapid climate change. -
ECR Spotlight – Malindi Gammon
ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Malindi Gammon is an author on ‘ An application of finite element analysis predicts unique temperatures and fates for flatback sea turtle embryos’, published in JEB. Malindi conducted the research described in this article while a PhD student in Professor Nicki Mitchell's lab at The University of Western Australia School of Biological Sciences and Ocean's Institute, Perth, Australia. She is an ecologist in the lab of Dr Ian Davidson at The Cawthron Institute, Nelson, New Zealand, investigating ecology and ecophysiology. -
Pressure-induced circumferential and longitudinal deformations of tracheal tubes in the American cockroach
ABSTRACTInsects exchange gases through a complex internal network of tubes known as tracheae, which deliver oxygen directly to tissues and remove carbon dioxide. In some species, these tracheal tubes undergo active compression, periodically collapsing and reinflating to facilitate internal airflow. The mechanical behavior of the tracheal system is governed by its structural design, which in turn influences its physiological role in respiration. Despite the critical importance of tracheal material properties in insect respiratory function, there are relatively few published studies that characterize their uniaxial tensile behavior. In this study, we present new experimental methods for measuring the pressure-induced biaxial deformations of tracheal tubes isolated from the American cockroach (Periplaneta americana). To this end, an inflation–extension testing device was built to subject tracheae to increasing internal pressures (0–6 kPa) and axial displacements (0–0.2 mm). Local circumferential and longitudinal stretches were quantified using non-contact strain measurement techniques. In most cases, circumferential stretches increased nonlinearly with applied pressure at any axial displacements, whereas longitudinal stretches changed minimally. This behavior likely reflects the combined influence of structural anisotropy, mechanical coupling and geometric constraints. The observed deformations highlight the mechanical sophistication of insect tracheae. They underscore the importance of integrating geometry and microstructure to understand how these structures resist collapse, enable gas exchange and adapt to mechanical demands. -
Dehydration alters sprint speed capacity more than maximal endurance in a terrestrial lizard
ABSTRACTThe evolution of thermo-hydroregulation is determined by a cost–benefit balance, which in terrestrial ectotherms depends on the relationship between temperature, hydration status and maximal performance capacities. Earlier studies in amphibians uncovered deleterious effects of dehydration on a range of locomotor tasks and suggested that dehydration might further constrain the benefits of thermoregulation by decreasing tolerance to extreme temperatures. Hydric performance curves have been little investigated so far in dry-skin ectotherms, such as reptiles. Further, whether dehydration differently alters locomotor performance at low versus high temperatures in these organisms remains unresolved. Here, we manipulated drinking water availability over 10 days and quantified the hydric dependence of maximum running speed at different body temperatures as well as effects on endurance capacity in the lizard Zootoca vivipara. We further assessed whether performance decline could be explained by a loss of body condition, specifically hindlimb muscle loss. Lizards provided with limited drinking water declined significantly in condition and had much higher plasma osmolality, indicating sharp physiological dehydration. Despite that, we found only modest effects of dehydration on sprint speed, even at high body temperatures, and no obvious effects on endurance. Individual mass loss was non-linearly but weakly correlated with a decrease in endurance capacity. Sprint speed decreased with hindlimb muscle loss, and we found a slight reduction of the thermal performance breadth in the most dehydrated lizards. These results suggest that locomotor performance is primarily influenced by body temperature and secondarily by hydration state and only from a high dehydration threshold. -
Equivalent laws of pectoral fin propulsion parameters of cownose ray based on kinematic and hydrodynamic analysis
ABSTRACTBatoids achieve remarkable swimming efficiency through adaptive speed modulation. While previous studies have preliminarily linked pectoral fin kinematics to swimming speed in cownose rays (Rhinoptera javanica), the dynamic relationship between fin motion patterns and propulsive performance has remained unclear. By integrating kinematic analysis with hydrodynamic experiments, this study establishes a consistent framework that reveals their unique propulsion mechanism. Kinetically, we found that fin velocity exhibits a linear relationship with swimming speed via coordinated amplitude–frequency modulation. The Strouhal number (St) decreases with increasing speed, with most values falling within the optimal range of 0.2–0.4. A bio-inspired robot successfully replicated the figure-of-eight motion of biological pectoral fins. Hydrodynamic experiments demonstrated that the fins generate comparable instantaneous thrust during both upstroke and downstroke, with thrust in each half-stroke following a unimodal pattern – increasing to a peak before declining. A parameter equivalence law was identified: when the product of frequency and amplitude (fA) is held constant, different kinematic combinations yield consistent mean thrust, and thrust shows a significant positive correlation with fA. This confirms that the rays dynamically regulate swimming speed through fin velocity while maintaining high efficiency across conditions. These findings not only advance the understanding of cownose ray propulsion but also provide a theoretical basis for motion control in bio-inspired underwater robots.