Publications
Publications in reverse chronological order
2026
- Short-finned pilot whales modulate surfacing and breathing patterns more strongly in response to dives than in anticipationAshley M. Blawas, Jeanne M. Shearer, Andreas Fahlman, and 2 more authorsAmerican Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Jan 2026
Diving marine mammals must allocate time between respiring at the surface and foraging underwater. Previous studies of optimal diving theory have attempted to predict such patterns, but the amount of time divers must spend at the surface before and after dives of varying durations remains difficult to assess. Here, we examined the surfacing and breathing patterns of short-finned pilot whales (Globicephala macrorhynchus) from biologger data to examine their use of anticipatory versus reactive strategies. We used linear mixed-effects models to examine the effect of dive characteristics on surface interval (SI) durations and breathing rate. Pilot whales increased SI duration before dives of increasing duration and after dives of increasing activity. Instantaneous breathing rates (fRs) of pilot whales demonstrated little anticipation but rather a strong reactive pattern seen by the modulation of fR in response to the previous rather than upcoming dive. During typical SIs, fR was predicted by time since previous dive, duration of the previous dive, time until upcoming dive, and activity of the previous dive. Short-finned pilot whales in our study area exhibit both benthic and pelagic foraging, which may compel anticipation when prey capture is predictable and reaction when prey capture is difficult to predict. The observed surfacing and breathing patterns therefore likely reflect a balance of the needs for blood gas homeostasis, aerobic metabolism, and the variability of foraging opportunities. An improved understanding of how animals make decisions about diving is critical for informing predictions of how they will contend with changing ocean landscapes.
2025
- Daily energetic expenditure and energy consumption of short-finned pilot whalesWilliam T. Gough, Brijonnay C. Madrigal, Augusta Hollers, and 14 more authorsJournal of Experimental Biology, Nov 2025
Diving is one of the most important behaviors undertaken by marine mammals. Pilot whales (Globicephala spp.) are oceanic dolphins that regularly forage at extreme depths (∼600–1000 m) and maintain body sizes similar to beaked whales. They are also listed as data deficient, with little known about their population dynamics. To help fill this knowledge gap, we estimated their energetic demands through a combination of multiple data streams (e.g. unoccupied aerial systems photogrammetry, high-resolution accelerometry tag data, stomach content analysis and long-duration dive data from satellite tags) from short-finned pilot whales (Globicephala macrorhynchus) in Hawaiian waters. We estimated and compared pilot whale field metabolic rates from breathing frequency against a more granular cost of transport method developed from morphometrics and swimming kinematics, finding that these methods gave similar estimates of energetic expenditure during foraging dives. We then combined expenditure and intake estimates into an exploratory model of daily net energetic balance. Using an estimate of prey size derived from squid beaks collected from a stranded animal, we found that an average of 142±59.8 squid day−1 (52,000±21,800 squid year−1) is enough for an average adult short-finned pilot whale to reach a neutral net energetic balance. This species has an estimated population abundance of ∼8000 individuals in Hawaiian waters, suggesting that the population as a whole would require 416±175 million squid (at an average of 559±126 kJ squid−1) or approximately 88,000±37,000 tonnes of squid annually, assuming similar energetic requirements for each animal.
- Life in the slowest lane: Feeding allometry lowers metabolic rate scaling in the largest whalesAshley M. Blawas, Simone K. A. Videsen, David E. Cade, and 5 more authorsScience Advances, Aug 2025Publisher: American Association for the Advancement of Science
The hypothesized impacts of whale foraging on ocean productivity are ultimately defined by their metabolic rate, but determining energy expenditure for ocean giants remains challenging. The largest baleen whales use a high-drag lunge-feeding strategy that is hypothesized to come at a high energetic cost, thus requiring exceptional calorie intake. We used biologging tags to measure respiratory rates in foraging rorquals and demonstrate that their field metabolic rates are less than half that predicted by prey consumption estimates and by scaling predictions from smaller marine mammals. The relative cost of rorqual foraging decreases with increasing size as larger whales spend disproportionately longer time filtering prey from engulfed water. By decoupling active swimming and filtration, the largest rorquals forage with limited movement costs. The evolution of lunge feeding confers an energetic advantage that is unique among filter feeders and may have provided an evolutionary pathway to the largest body sizes.
- Role of low-impact-factor journals in conservation implementationJonathan J. Choi, Leo C. Gaskins, Joseph P. Morton, and 6 more authorsConservation Biology, Aug 2025
Academic review, promotion, and tenure processes place a premium on frequent publication in high-impact factor (IF) journals. However, conservation often relies on species-specific information that is unlikely to have the broad appeal needed for high-IF journals. Instead, this information is often distributed in low-IF, taxa- and region-specific journals. This suggests a potential mismatch between the incentives for academic researchers and the scientific needs of conservation implementation. To explore this mismatch, we looked at federal implementation of the United States Endangered Species Act (ESA), which requires the use of the “best available science” to list a species as endangered or threatened and thus receive powerful legal protections. In assessing the relationship between academic sources of this “best available science” and ESA implementation, we looked at the 13,292 sources (e.g., academic journals, books, reports, regulations, personal communications, etc.) cited by the second Obama administration (2012–2016) across all ESA listings. We compared the IFs of all 4836 journals that published peer-reviewed papers cited in these listings against their citation frequency in ESA listings to determine whether a journal’s IF varied in proportion with its contribution to federal conservation. Most of the peer-reviewed academic articles referenced in ESA listings came from low-IF or no-IF journals that tended to focus on specific taxa or regions. Although we support continued attention to cutting-edge, multidisciplinary science for its ability to chart new pathways and paradigms, our findings stress the need to value and fund the taxa- and region-specific science that underpins actionable conservation laws.
2024
- Genetic and molecular adaptationsAshley M Blawas, Jason A Somarelli, and Andreas FahlmanIn The Physiology of Dolphins, Aug 2024
The Physiology of Dolphins is a robust, up-to-date reference. It provides a collection of review chapters from leaders in the field of dolphin ecophysiology, making it essential for instructors, researchers, and graduate students interested in the physiological and anatomical adaptations that make life possible for these charismatic marine mammals. Showcasing recent technological developments, it covers the complete physiology of these marine mammals and includes information on the current threats for dolphins and whales from environmental pressures such as climate change, overfishing, pollution, and our increasing human presence in the ocean. This is an excellent reference providing easy-to-follow details of the latest available research methods and some of the newer technologies that are expanding the field of marine mammal physiology.
- Aerobic dive limit in short-finned pilot whales Globicephala macrorhynchus: an assessment of behavioral criteriaAshley M. Blawas, Lauren E. Miller, Jeanne M. Shearer, and 8 more authorsMarine Ecology Progress Series, Sep 2024
Aerobic dive limits (ADLs) are a useful paradigm for assessing marine mammal diving ability. Given the allometry of total body oxygen stores and metabolic rate, larger animals should have increased diving capacities and thus elevated ADLs. The short-finned pilot whale Globicephala macrorhynchus is a deep-diving species with pronounced sexual size dimorphism, and individuals are regularly found in size-mixed groups. Therefore, we asked how body size constrains dive durations in this species and whether behavioral ADL (bADL), estimated as the 95th percentile of dive duration, is a useful measure of physiological ADL. We analyzed 30169 dives from 45 animals tagged with satellite-linked recorders off Cape Hatteras, North Carolina, and Jacksonville, Florida, USA, and determined a species-level bADL of 18.8 min and individual bADLs ranging from 13.9 to 22.1 min. To assess the influence of size on bADL, we estimated the body lengths of 19 whales from dorsal fin measurements. Body length did not fully explain intraspecific bADL variation, but similar dive distributions and lower bADL variance between animals tagged together indicated a potential effect of group membership. Moreover, individuals in Cape Hatteras had a significantly lower median bADL than those in Jacksonville, suggesting location may influence dive durations. These results indicate the potential impact of social and location-specific factors on bADL estimates in a deep-diving, sexually dimorphic species.
- Passive acoustic surveys demonstrate high densities of sperm whales off the mid-Atlantic coast of the USA in winter and springOliver Boisseau, Doug Nowacek, D. Ann Pabst, and 6 more authorsMarine Environmental Research, Oct 2024
Oceans are increasingly crowded by anthropogenic activities yet the impact on Outer Continental Shelf (OCS) marine life remains largely unquantified. The MAPS (Marine Mammal Acoustic and Spatial Ecology) study of 2019 included passive acoustic and visual vessel surveys over the Mid-Atlantic OCS of the USA to address data gaps in winter/spring for deep-diving cetaceans, including sperm whales. Echolocation clicks were used to derive slant ranges to sperm whales for design- and model-based density estimates. Although more survey effort was realised in the spring, high densities of whales were identified in both winter and spring (10.46 and 8.89 per 1000 km2 respectively). The spring model-based abundance estimate of 1587 whales (CI 946–2663) was considered the most representative figure, in part due to lower coefficients of variation. Modelling suggested that high densities of whales were associated with warm core rings, eddies and edges. As OCS waters provide an important foraging habitat for North Atlantic sperm whales, appropriate mitigation is required to ensure commercial pressures to develop offshore energy do not negatively affect this endangered species.
2023
- Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammalsRebecca S. He, Stacy De Ruiter, Tristan Westover, and 8 more authorsPhysiological Reports, Oct 2023
While basal metabolic rate (BMR) scales proportionally with body mass (Mb), it remains unclear whether the relationship differs between mammals from aquatic and terrestrial habitats. We hypothesized that differences in BMR allometry would be reflected in similar differences in scaling of O2 delivery pathways through the cardiorespiratory system. We performed a comparative analysis of BMR across 63 mammalian species (20 aquatic, 43 terrestrial) with a Mb range from 10 kg to 5318 kg. Our results revealed elevated BMRs in small (>10 kg and <100 kg) aquatic mammals compared to small terrestrial mammals. The results demonstrated that minute ventilation, that is, tidal volume (VT)·breathing frequency (fR), as well as cardiac output, that is, stroke volume·heart rate, do not differ between the two habitats. We found that the “aquatic breathing strategy”, characterized by higher VT and lower fR resulting in a more effective gas exchange, and by elevated blood hemoglobin concentrations resulting in a higher volume of O2 for the same volume of blood, supported elevated metabolic requirements in aquatic mammals. The results from this study provide a possible explanation of how differences in gas exchange may serve energy demands in aquatic versus terrestrial mammals.
- Cardiorespiratory coupling in the bottlenose dolphin (Tursiops truncatus)A. Fahlman, J. C. Mcknight, A. M. Blawas, and 3 more authorsFrontiers in Physiology, Sep 2023
Introduction: The bottlenose dolphin (Tursiops truncatus) is an intermittent breather, where the breath begins with an exhalation followed by inhalation and an extended inter-breath interval ranging from 10 to 40 s. Breathing has been shown to alter both the instantaneous heart rate (ifH) and stroke volume (iSV) in the bottlenose dolphin, with a transitory ventilatory tachycardia following the breath, and an exponential decrease to a stable ifH around 40 beats • min−1 during the inter-breath period. As the total breath duration in the dolphin is around 1 s, it is not possible to assess the contribution of exhalation and inhalation to these changes in cardiac function during normal breathing. Methods: In the current study, we evaluated the ifH response by separating expiration and inspiration of a breath, which allowed us to distinguish their respective contribution to the changes in ifH. We studied 3 individual male bottlenose dolphins trained to hold their breath between the different respiratory phases (expiration and inhalation). Results: Our data show that inspiration causes an increase in ifH, while expiration appears to result in a decrease in ifH. Discussion: These data provide improved understanding of the cardiorespiratory coupling in dolphins, and show how both exhalation and inhalation alters ifH.
- The Impact of Gulf Stream Frontal Eddies on Ecology and Biogeochemistry near Cape HatterasPatrick Clifton Gray, Jessica Gronniger, Ivan Sayvelev, and 13 more authorsFeb 2023
Ocean physics and biology can interact in myriad and complex ways. Eddies, features found at many scales in the ocean, can drive substantial changes in physical and biogeochemical fields with major implications for marine ecosystems. Mesoscale eddies are challenging to model and difficult to observe synoptically at sea due to their fine-scale variability yet broad extent. In this work we observed a frontal eddy just north of Cape Hatteras via an intensive hydrographic, biogeochemical, and optical sampling campaign. Frontal eddies occur in western boundary currents around the globe and there are major gaps in our understanding of their ecosystem impacts. In the Gulf Stream, frontal eddies have been studied in the South Atlantic Bight, where they are generally assumed to shear apart passing Cape Hatteras. However, we found that the observed frontal eddy had different physical properties and phytoplankton community composition from adjacent water masses, in addition to continued cyclonic rotation. In this work we first synthesize the overall ecological impacts of frontal eddies in a simple conceptual model. This conceptual model led to the hypothesis that frontal eddies could be well timed to supply zooplankton to secondary consumers off Cape Hatteras where there is a notably high concentration and diversity of top predators. Towards testing this hypothesis and our conceptual model we report on the biogeochemical state of this particular eddy connecting physical and biological dynamics, analyze how it differs from Gulf Stream and shelf waters even in “death”, and refine our initial model with this new data.
- Surface and diving metabolic rates, and dynamic aerobic dive limits (dADL) in near- and off-shore bottlenose dolphins, Tursiops spp., indicate that deep diving is energetically cheapAndreas Fahlman, Austin S. Allen, Ashley Blawas, and 8 more authorsMarine Mammal Science, Feb 2023
High-resolution dive depth and acceleration recordings from nearshore (Sarasota Bay, dive depth < 30 m), and offshore (Bermuda) bottlenose dolphins (Tursiops spp.) were used to estimate the diving metabolic rate (DMR) and the locomotor metabolic rate (LMR, L O2/min) during three phases of diving (descent, bottom, and ascent). For shallow dives (depth ≤ 30 m), we found no differences between the two ecotypes in the LMR during diving, nor during the postdive shallow interval between dives. For intermediate (30 m < depth ≤ 100 m) and deep dives (depth > 100 m), the LMR was significantly higher during ascent than during descent and the bottom phase by 59% and 9%, respectively. In addition, the rate of change in depth during descent and ascent (meters/second) increased with maximal dive depth. The dynamic aerobic dive limit (dADL) was calculated from the estimated DMR and the estimated predive O2 stores. For the Bermuda dolphins, the dADL decreased with dive depth, and was 18.7, 15.4, and 11.1 min for shallow, intermediate, and deep dives, respectively. These results provide a useful approach to understand the complex nature of physiological interactions between aerobic metabolism, energy use, and diving capacity.
2022
- Dynamic body acceleration as a proxy to predict the cost of locomotion in bottlenose dolphinsAustin S. Allen, Andrew J. Read, K. Alex Shorter, and 4 more authorsJournal of Experimental Biology, Feb 2022
Estimates of the energetic costs of locomotion (COL) at different activity levels are necessary to answer fundamental eco-physiological questions and to understand the impacts of anthropogenic disturbance to marine mammals. We combined estimates of energetic costs derived from breath-by-breath respirometry with measurements of overall dynamic body acceleration (ODBA) from biologging tags to validate ODBA as a proxy for COL in trained common bottlenose dolphins (Tursiops truncatus). We measured resting metabolic rate (RMR); mean individual RMR was 0.71–1.42 times that of a similarly sized terrestrial mammal and agreed with past measurements that used breath-by-breath and flow-through respirometry. We also measured energy expenditure during submerged swim trials, at primarily moderate exercise levels. We subtracted RMR to obtain COL, and normalized COL by body size to incorporate individual swimming efficiencies. We found both mass-specific energy expenditure and mass-specific COL were linearly related with ODBA. Measurements of activity level and cost of transport (the energy required to move a given distance) improve understanding of the COL in marine mammals. The strength of the correlation between ODBA and COL varied among individuals, but the overall relationship can be used at a broad scale to estimate the energetic costs of disturbance and daily locomotion costs to build energy budgets, and investigate the costs of diving in free-ranging animals where bio-logging data are available. We propose that a similar approach could be applied to other cetacean species.
2021
- Scaling of heart rate with breathing frequency and body mass in cetaceansAshley M. Blawas, Douglas P. Nowacek, Julie Rocho-Levine, and 2 more authorsPhilosophical Transactions of the Royal Society B: Biological Sciences, Aug 2021
Plasticity in the cardiac function of a marine mammal facilitates rapid adjustments to the contrasting metabolic demands of breathing at the surface and diving during an extended apnea. By matching their heart rate (fH) to their immediate physiological needs, a marine mammal can improve its metabolic efficiency and maximize the proportion of time spent underwater. Respiratory sinus arrhythmia (RSA) is a known modulation of fH that is driven by respiration and has been suggested to increase cardiorespiratory efficiency. To investigate the presence of RSA in cetaceans and the relationship between fH, breathing rate (fR) and body mass (Mb), we measured simultaneous fH and fR in five cetacean species in human care. We found that a higher fR was associated with a higher mean instantaneous fH (ifH) and minimum ifH of the RSA. By contrast, fH scaled inversely with Mb such that larger animals had lower mean and minimum ifHs of the RSA. There was a significant allometric relationship between maximum ifH of the RSA and Mb, but not fR, which may indicate that this parameter is set by physical laws and not adjusted dynamically with physiological needs. RSA was significantly affected by fR and was greatly reduced with small increases in fR. Ultimately, these data show that surface fHs of cetaceans are complex and the fH patterns we observed are controlled by several factors. We suggest the importance of considering RSA when interpreting fH measurements and particularly how fR may drive fH changes that are important for efficient gas exchange.
- An integrated comparative physiology and molecular approach pinpoints mediators of breath-hold capacity in dolphinsAshley M Blawas, Kathryn E Ware, Emma Schmaltz, and 10 more authorsEvolution, Medicine, and Public Health, Oct 2021
Ischemic events, such as ischemic heart disease and ischemic stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching tissues and organ systems, leading to cell and tissue death, and eventual organ failure. While humans are relatively intolerant to these ischemic events, other species, such as marine mammals, have evolved remarkable tolerance to chronic ischemia/reperfusion during diving. Here we capitalized on the unique adaptations of bottlenose dolphins (Tursiops truncatus) as a comparative model of ischemic stress and hypoxia tolerance to identify molecular features associated with breath-holding. Using RNA-Seq we observed time-dependent upregulation of the arachidonate 5-lipoxygenase (ALOX5) gene during breath-holding. Consistent with the RNA-Seq data, we also observed increased ALOX5 enzymatic activity in the serum of dolphins undergoing breath holds. ALOX5 has previously been shown to be activated during hypoxia in rodent models, and its metabolites, leukotrienes, induce vasoconstriction. The upregulation of ALOX5 occurred within the estimated aerobic dive limit of the species, suggesting that ALOX5 enzymatic activity may promote tolerance to ischemic stress through sustained vasoconstriction in dolphins during diving. These observations pinpoint a potential molecular mechanism by which dolphins, and perhaps other marine mammals, have adapted to the prolonged breath-holds associated with diving.
- Respiratory sinus arrhythmia and submersion bradycardia in bottlenose dolphins (Tursiops truncatus)Ashley M. Blawas, Douglas P. Nowacek, Austin S. Allen, and 2 more authorsJournal of Experimental Biology, Jan 2021
Among the many factors that influence the cardiovascular adjustments of marine mammals is the act of respiration at the surface, which facilitates rapid gas exchange and tissue re-perfusion between dives. We measured heart rate (fH) in six, adult male bottlenose dolphins (Tursiops truncatus) spontaneously breathing at the surface to quantify the relationship between respiration and fH, and compared this to fH during submerged breath-holds. We found that dolphins exhibit a pronounced respiratory sinus arrhythmia (RSA) during surface breathing resulting in a rapid increase in fH after a breath followed by a gradual decrease over the following 15-20 seconds to a steady fH that is maintained until the following breath. RSA resulted in a maximum instantaneous fH (ifH) of 87.4±13.6 beats min−1, a minimum ifH of 56.8±14.8 beats min−1, and the degree of RSA was positively correlated with the inter-breath interval (IBI). The minimum ifH during 2-minute, submerged breath-holds where dolphins exhibited submersion bradycardia (36.4±9.0 beats min−1) was lower than the minimum ifH observed during an average IBI, however during IBIs longer than 30 seconds, the minimum ifH (38.7±10.6 beats min−1) was not significantly different from that during 2-minute breath-holds. These results demonstrate that the fH patterns observed during submerged breath-holds are similar to those resulting from RSA during an extended IBI. Here we highlight the importance of RSA in influencing fH variability and emphasize the need to understand its relationship to submersion bradycardia.
2020
- Cardiorespiratory coupling in cetaceans; a physiological strategy to improve gas exchange?Andreas Fahlman, S. Miedler, L. Marti-Bonmati, and 6 more authorsJournal of Experimental Biology, Jul 2020
In the current study we used transthoracic echocardiography to measure stroke volume (SV), heart rate (fH), and cardiac output (CO) in adult bottlenose dolphins (Tursiops truncatus), a male beluga calf (Delphinapterus leucas, body mass [Mb] range: 151-175 kg), and an adult female false killer whale (Pseudorca crassidens, estimated Mb: 500-550 kg) housed in managed care. We also recorded continuous electrocardiogram (ECG) in the beluga, bottlenose dolphin, false killer whale, killer whale (Orcinus orca), and pilot whale (Globicephala macrorhynchus) to evaluate cardiorespiratory coupling while breathing spontaneously under voluntary control. The results show that cetaceans have a strong Respiratory Sinus Arrythmia (RSA), during which both fH and SV vary within the interbreath interval, making average values dependent on the breathing frequency (fR). The RSA-corrected fH was lower for all cetaceans compared to similarly sized terrestrial mammals breathing continuously. As compared with terrestrial mammals, the RSA-corrected SV and CO were either lower or the same for the dolphin and false killer whale, while both were elevated in the beluga. When plotting fR against fH for an inactive mammal, cetaceans had a greater cardiac response to changes in fR as compared with terrestrial mammals. We propose that these data indicate an important coupling between respiration and cardiac function that enhances gas exchange, and that this RSA is important to maximize gas exchange during surface intervals, similar to that reported in the elephant seal.
- Conditioned variation in heart rate during static breath-holds in the bottlenose dolphin (Tursiops truncatus)Andreas Fahlman, Bruno Cozzi, Mercy Manley, and 4 more authorsFrontiers in Physiology, Jul 2020
Previous reports suggested the existence of direct somatic motor control over the heart rate (fH) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2 storage management and also allow ventilation-perfusion matching for selective gas exchange, where O2 and CO2 can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid diving related gas bubble formation during repeated dives, and how stress interrupts this mechanism and causes excessive N2 exchange. To investigate the conditioned response, we measured the fH during a breath-hold in three bottlenose dolphins (Tursiops truncatus) when shown a visual signal to perform either a long (LONG) or short (SHORT) breath-hold, or during a spontaneous breath-hold without a signal (NS). The average fH (ifHstart), and the rate of change in fH (difH/dt) during the first 20 s of the breath-hold differed between breath-hold types. In addition, the minimum instantaneous fH (ifHmin), and the average instantaneous fH during the last 10 s (ifHend) also differed between breath-hold types. The difH/dt was greater, and the ifHstart, ifHmin, and ifHend were lower during a LONG as compared with either a SHORT, or an NS breath-hold (P < 0.05). Even though the NS breath-hold dives were longer in duration as compared with SHORT breath-hold dives, the difH/dt was greater and the ifHstart, ifHmin, and ifHend were lower during the latter (P < 0.05). In addition, when the dolphin determined the breath-hold duration (NS), the fH was more variable within and between individuals and trials, suggesting a conditioned capacity to adjust the fH response. These results suggest that dolphins have the capacity to selectively alter the fH-response during diving and provide evidence for significant cardiovascular plasticity in dolphins.
2017
- Effects of methyl and inorganic mercury exposure on genome homeostasis and mitochondrial function in Caenorhabditis elegansLauren H. Wyatt, Anthony L. Luz, Xiou Cao, and 5 more authorsDNA repair, Apr 2017
Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processes, like mitochondrial function. Proper mitochondrial function is important for cellular bioenergetics and immune signaling and function. Reported impacts of mercury on the nuclear genome (nDNA) are conflicting and inconclusive, and mitochondrial DNA (mtDNA) impacts are relatively unknown. In this study, we assessed genotoxic (mtDNA and nDNA), metabolic, and innate immune impacts of inorganic and organic mercury exposure in Caenorhabditis elegans. Genotoxic outcomes measured included DNA damage, DNA damage repair (nucleotide excision repair, NER; base excision repair, BER), and genomic copy number following MeHg and HgCl2 exposure alone and in combination with known DNA damage-inducing agents ultraviolet C radiation (UVC) and hydrogen peroxide (H2O2), which cause bulky DNA lesions and oxidative DNA damage, respectively. Following exposure to both MeHg and HgCl2, low-level DNA damage (∼0.25 lesions/10kb mtDNA and nDNA) was observed. Unexpectedly, a higher MeHg concentration reduced damage in both genomes compared to controls. However, this observation was likely the result of developmental delay. In co-exposure treatments, both mercury compounds increased initial DNA damage (mtDNA and nDNA) in combination with H2O2 exposure, but had no impact in combination with UVC exposure. Mercury exposure both increased and decreased DNA damage removal via BER. DNA repair after H2O2 exposure in mercury-exposed nematodes resulted in damage levels lower than measured in controls. Impacts to NER were not detected. mtDNA copy number was significantly decreased in the MeHg-UVC and MeHg-H2O2 co-exposure treatments. Mercury exposure had metabolic impacts (steady-state ATP levels) that differed between the compounds; HgCl2 exposure decreased these levels, while MeHg slightly increased levels or had no impact. Both mercury species reduced mRNA levels for immune signaling-related genes, but had mild or no effects on survival on pathogenic bacteria. Overall, mercury exposure disrupted mitochondrial endpoints in a mercury-compound dependent fashion.
2015
- Elucidating the links between endocrine disruptors and neurodevelopmentThaddeus T. Schug, Ashley M. Blawas, Kimberly Gray, and 2 more authorsEndocrinology, Jun 2015
Recent data indicate that approximately 12% of children in the United States are affected by neurodevelopmental disorders, including attention deficit hyperactivity disorder, learning disorders, intellectual disabilities, and autism spectrum disorders. Accumulating evidence indicates a multifactorial etiology for these disorders, with social, physical, genetic susceptibility, nutritional factors, and chemical toxicants acting together to influence risk. Exposure to endocrine-disrupting chemicals during the early stages of life can disrupt normal patterns of development and thus alter brain function and disease susceptibility later in life. This article highlights research efforts and pinpoints approaches that could shed light on the possible associations between environmental chemicals that act on the endocrine system and compromised neurodevelopmental outcomes.