Journal of Experimental Biology最新文献

Sympatric ectotherms belonging to the same guild often exhibit differences in thermal ecophysiology as a result of their evolutionary history or current ecological interactions. This study investigates the thermal biology and hydroregulation of two sympatric lizard species, Liolaemus riojanus and L. cuyanus, in the challenging environment of arid Monte Desert of Argentina. We examined field body temperatures (Tb), preferred temperatures (Tpref), thermoregulatory efficiency, critical thermal limits (CTMin, CTMax), panting temperature (Tpant), and total evaporative water loss (TEWL) under representative experimental temperatures. Despite similar field Tb and moderate thermoregulatory efficiency, significant interspecific differences emerged in laboratory traits. Liolaemus riojanus, the smaller species, exhibited a higher Tpref, a broader thermal tolerance (lower CTMin, higher CTMax), higher Tpant, and lower TEWL compared to L. cuyanus. Furthermore, L. riojanus showed reduced EWL at high experimental temperatures (40 °C), suggesting that species with higher thermal tolerance conserve water under warm conditions despite the higher surface area-to-volume ratio. Conversely, L. cuyanus displayed increased EWL with rising experimental temperatures, which is likely related to its relatively low CTMax and panting temperature, promoting water loss. These divergent physiological strategies likely contribute to thermal segregation in this harsh environment. Given the current trend for aridification and climate warming, understanding the interplay between thermal and hydric traits is crucial for predicting the persistence of these lizards under changing environmental conditions and to guide management measures.

Catecholamines may react with other molecules to produce catecholamine derivatives. For example, nitric oxide may induce nitration of dopamine to form 6-nitrodopamine (6-ND). The endogenous production of such a novel catecholamine has been demonstrated in the mammalian and reptilian cardiovascular system, and in vitro studies demonstrate that 6-ND relaxes pre-contracted aortic rings, and acts as a potent chronotropic agent. So far, however, the in vivo effects of 6-ND remain to be characterised on whole organisms. Using South American rattlesnakes (Crotalus durissus), we measured the endogenous production of 6-ND and other catecholamine derivatives in different tissues of the cardiovascular system and the intercostal muscle. We also used myography to measure the vascular reactivity of the mesenteric artery to 6-ND, and we utilized anesthetized individuals to measure hemodynamic responses to bolus injections of 6-ND (1 µmol×kg-1). Except for blood plasma, 6-ND was detected in all tissues studied, and the addition of L-NAME, a blocker of the nitric oxide synthesis, did not alter the production of 6-ND, indicating there are alternative biosynthetic pathways. The isolated mesenteric artery contracted in the presence of adrenaline, dopamine, noradrenaline, and 6-ND. We also observed a potentiation of the noradrenergic stimulation in the presence of 6-ND. Finally, injection of 6-ND elicited a small but significant reduction in the mesenteric conductance. It is likely that 6-ND per se exerts small effects on overall hemodynamics, but synergizes with noradrenaline and possibly other catecholamines to enhance cardiovascular regulation.

To counteract or to retreat presents a fundamental dilemma for biological organisms when facing adverse abiotic environmental conditions. In many cases, the predominant strategy animals adopt is to retreat. However, if counteraction is possible, and how the choice between counteraction and retreat is decided, are not clear. Here, we report that Drosophila larvae can actively counteract external mechanical pressure, inspired by Drosophila larval cleft-squeezing behaviour. We developed a behavioural paradigm to investigate the counteracting force of larvae in response to external pressures. Instead of retreating by crawling backward, a portion of Drosophila larvae could crawl forward and counteract against the external physical pressure. Under externally applied pressing forces of 25mN, 93.9% of forward peristaltic movements increased the counterforce, while 88.2% of backward peristaltic movements decreased it. The activeness in counteraction force was reflected by the longer inter-wave delay, more oscillation work and longer force wave period during consecutive forward peristaltic waves. As the external pressing force was increased from 25mN to 50mN, 75mN and 100mN, counteraction by forward peristalsis was less frequent, while retreat by backward peristalsis was more frequent when pressure is high. A reduction of the external pressure immediately following the counteracting forward peristalsis, which might serve as rewarding signal, could reinforce the counteraction and induce more ensuing forward peristalsis. The rewarding effect of reducing external pressure by forward crawling was much more than that by backward crawling. Our study sheds light on the intricate mechanisms underlying animal proactive responses to adverse abiotic environmental conditions.

Science is often claimed to be amid a reproducibility crisis, as evidenced by low replicability of many classic findings across multiple fields. Yet it is not clear how widespread this purported problem is. Physiological responses have potential for replicability issues because of laboratory-specific biases in animal maintenance as well as technically complex methodologies that are often undertaken using bespoke combinations of equipment. Here we take advantage of a cross-laboratory manipulative study on metabolic rate to assess the replicability of food restriction effects on metabolic scaling and level. Across seven skink species from the Egernia species complex and two universities, we found these responses to be extremely replicable. The slope of the interspecific metabolic scaling relationship was near one and animals reduced their mass-independent rates of energy use by an average of 32% in response to food restriction. This response was consistent across universities. Our study highlights that well designed and replicated studies with a large effect size can indeed be replicable and showcases the value of designing studies that allow tests of replicability to be incorporated explicitly. Such studies will be particularly valuable for treatment effects that generate a small effect size.

Hypoxia and hypercapnia often accompany seawater warming and interactively alter marine ectotherm performance, potentially threatening their populations. To detail mechanistic responses, we investigated whole-animal physiology alongside cellular homeostasis in a species expected to be relatively robust to their impacts, the oyster Ostrea edulis. Acute warming alone (W) and combined with hypercapnia and hypoxia (deadly trio, DT) started at 18°C, increasing stepwise by 2°C per 48 hours until critical temperatures (34 °C). Mortality onset at a lower temperature under DT than W but rates equalized by 34°C. DT-exposed oysters' hemolymph PO2 began 29% lower at 18°C, but by 34°C was only slightly lower than in W oysters. In both groups, resting metabolic rate (RMR) and heart rate rose with warming. Hemolymph PO2 was stable until 26°C, whence it declined. DT elicited a higher heart rate, which began to fall after ∼32°C, while heart rate in W-exposed oysters continued rising. Relative increases in branchial metabolite levels of alanine and fumarate, profiled via 1H-NMR spectroscopy, indicated greater contributions of anaerobic metabolism in DT- than W-exposed oysters. Gill tissue showed higher levels of the mitochondrial stabilizer sirtuin-5 alongside higher antioxidative capacity under DT than W-exposed oysters, before declining at temperatures beyond 30°C. Muscle intracellular pH, gill heat shock protein 70 and metabolic profiles appeared unaffected by DT compared to warming. Our results suggest that DT places an additional energetic burden on the oyster, lowering the critical temperature. Nevertheless, tolerance patterns indicate resilience to DT, which may require a re-balancing of passive tolerance mechanisms, especially a probable emphasis on metabolic depression.

Climate warming has many direct and downstream effects on animals. For example, warmer developmental temperatures can reduce insect melanism, which is related to thermoregulation, immunity, desiccation resistance, and life history. Increased temperature variation is also a feature of climate change, and it may have a larger impact on animals than warming. Here, we examined the combined effects of mean temperature and temperature variation on life history, heat tolerance, and melanism. We determined thermal plasticity using a factorial manipulation of mean temperature (20, 25, and 30℃) and daily temperature fluctuation (±0, 5, and 10℃) during development in the variable field cricket (Gryllus lineaticeps). We tested hypotheses comparing thermal plasticity due to (1) mean temperature vs. (2) temperature variation, (3) the interdependency of mean temperature and temperature variation in thermal plasticity (i.e., interactive effects on traits), and (4) whether life-history strategy (i.e., investment into dispersal vs. reproduction) influences thermal plasticity. Mean temperature had stronger effects on daily accumulated heat and on traits than temperature variation; yet, interactive effects were common, and their effect sizes were stronger than mean temperature alone for body mass and size, and reproductive investment. Warmer, more thermally variable environments of the future may be particularly costly. Flight-capable individuals differed in their responses to mean temperature and/or temperature variation regarding developmental rate, body size and mass, reproductive investment, and melanism. In sum, combined shifts in mean temperature and temperature variation strongly influence life-history strategy, heat tolerance, and coloration, all of which may be critical to animals' resilience in the face of climate change.

Predicting success is a common goal for ecologists and sports scientists, yet these disciplines rarely interact. Sports scientists often use tests of closed-skill or game performances, but these are often critiqued for their inherent uncertainties in predicting success. In contrast, ecologists embrace variance, measuring traits under controlled conditions to make probabilistic predictions of success. Integrating ecological perspectives could enhance team selection efficiency in youth sports. Here, we demonstrate this concept using territorial contests in crayfish. Like sports, individual traits in crayfish can be measured rapidly but do not perfectly predict contest outcome. First, we simulated populations of 100 male and 100 female crayfish that competed in 20 rounds of contests and estimated how many individuals must be selected to ensure the top 10% of performers are included. Selections were based on individual traits (body length, claw size and strength) and/or contest outcomes. When few contests have occurred, the top 10% of individuals were most efficiently selected on individual traits but increasingly more on contests as rounds progressed. Empirical data supported these theoretical simulations. We staged 10 rounds of contests among 27 male and 32 female Cherax destructor. After two rounds, ∼21 individuals were needed to capture the top 3; by round 10, ∼5 were required. Taken together, our study provides an initial but compelling demonstration of how ecological models can help improve talent identification strategies in sport. Such an adaptive selection framework efficiently narrows down selection of high-performing individuals under uncertainty and has the potential to be applied to reintroduction and translocation strategies in conservation.

Marine mammals possess specialized respiratory adaptations that enable efficient gas exchange and resilience to extreme pressures during diving, yet direct observation of lung mechanics under pressure has been logistically challenging. Electrical Impedance Tomography (EIT) measures real time changes in thoracic impedance, and provides continuous, regional maps of pulmonary air distribution. We validated EIT for estimating tidal volume (VT) in bottlenose dolphins (Tursiops spp.) and Cape fur seals (Arctocephalus pusillus) both on land and in water. EIT reliably tracked VT in both genera, showing strong within trial consistency, with between trial variability attributable to belt placement, body position, and electrode contact. EIT also generated dynamic functional images of regional ventilation, revealing spatial and temporal patterns of lung filling and emptying. These results demonstrate that EIT is the first non-invasive imaging method validated for marine mammals in seawater, representing a critical step toward visualizing lung function during diving.

The intertidal zone experiences significant fluctuations in temperature and pH, posing significant challenges to marine organisms. Perinereis aibuhitensis, a eurythermal and euryhaline polychaete inhabiting estuaries, where pH is often lower than in the open ocean and further reduced within sediments, has probably evolved robust adaptations to such stresses. We investigated its behavioral, physiological and metabolic responses under combined temperature (15°C, 20°C, 25°C) and seawater acidification (pH 5.5, 6.7, 8.0) conditions. Perinereis aibuhitensis exhibited stable behavioral performance and metabolic homeostasis under control conditions (20°C, pH 8.0). It maintained burrowing activity and activated physiological and metabolic regulation at pH 6.7. However, its motion significantly declined with failed behavioral regulation under pH 5.5: radial undulation duration decreased by 97.63% and pumping volume by 97.97%. Energy was reallocated toward antioxidant defense and maintenance of basic physiological functions, reflected in downregulation of the γ-aminobutyric acid (GABA) metabolic pathway alongside upregulation of ABC transporters and arachidonic acid metabolism. At 25°C, combined warming and acidification disrupted energy allocation under pH 5.5. This disruption was accompanied by enhanced motion, which further constrained energy allocation, leading to significant oxidative damage (malondialdehyde content increased by 94.54%) and concurrently impairing tryptophan metabolism, glycerophospholipid metabolism and ABC transporter function, with the entire cascade ultimately collapsing its adaptive mechanisms. This demonstrates that severe acidification, especially under warming, compromises bioturbation and metabolic stability in P. aibuhitensis, with potential negative impacts on polychaete communities and their vital ecological functions in intertidal ecosystems. Our findings provide critical insights for predicting climate change impacts on marine infauna.

Environmental signals exert influences not only on the current generation, but also extend to subsequent generations, even when these signals no longer persist. These transgenerational effects can be mediated through several mechanisms, including epigenetic inheritance and composition of the gut microbiome. In this study, we investigated the contribution of the microbiome to diet-induced transgenerational effects on reproductive dormancy. Multiple strains of Drosophila simulans were subjected to a shift from a sugar-rich to a sugar-poor diet and the impact of this diet switch on dormancy was determined over multiple generations. Consistent with significant transgenerational effects, we observed a gradual reduction in dormancy incidence with an increasing number of generations exposed to the new, sugar-poor diet. Despite the variation in dormancy induced by the dietary shift, the microbiome composition remained largely stable. Consequently, we conclude that these transgenerational effects are not determined by changes in the bacterial microbiome composition.