John Eme

John Eme
California State University, San Marcos | CSUSM · Department of Biological Sciences

Doctor of Philosophy

About

65
Publications
10,976
Reads
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1,007
Citations
Introduction
Our research focuses on the cardiopulmonary system, development, energetics, thermal tolerance, and ecology of lower vertebrates (fish and reptiles) and their adaptations to environmental factors, particularly ambient oxygen level and temperature.
Additional affiliations
August 2015 - present
California State University, San Marcos
Position
  • Instructor
Description
  • BIOL 215 (Biostatistics): Fall 2015 (2 sections), Spring 2016 (2 sections); BIOL 353 (Comp Physiol): Spring 2016 (3 sections); BIOL 178 (Human Anat & Physiol): Fall 2015; GES 102 (Intro Biol): Fall 2015
August 2015 - May 2016
California State University, San Marcos
Position
  • Visiting Assistant Professor
August 2013 - July 2015
McMaster University
Position
  • PostDoc Position
Education
September 2005 - June 2010
August 2002 - May 2005
University of West Florida
Field of study
  • Biology
August 1996 - January 2000

Publications

Publications (65)
Article
Full-text available
Organismal temperature tolerance and metabolic responses are correlated to recent thermal history, but responses to thermal variability are less frequently assessed. There is great interest in whether organisms that experience greater thermal variability can gain metabolic or tolerance advantages through phenotypic plasticity. We compared thermal t...
Article
Allometric equations represent relationships between morphological/physiological traits and body mass Y = aMb, where Y is the trait, a is elevation, b is the exponent describing the shape of the line, and M is body mass. We measured visceral organ masses in hatchling alligators (Alligator mississippiensis) from five clutches from approximately 45 t...
Article
Lake whitefish (Coregonus clupeaformis) utilize overwintering embryonic development (up to 180 days), and such stenothermic, cold-water embryos may be particularly susceptible to thermal shifts. We incubated whitefish embryos in temperature treatments that were constant temperature (2.0 ± 0.1 °C, 5.0 ± 0.1 °C, and 8.0 ± 0.1 °C; mean ± SD) or variab...
Article
Full-text available
Crocodilians have complete anatomical separation between the ventricles, similar to birds and mammals, but retain the dual aortic arch system found in all non-avian reptiles. This cardiac anatomy allows surgical modification that prevents right-to-left (R-L) cardiac shunt. A R-L shunt is a bypass of the pulmonary circulation and recirculation of ox...
Article
Temperature is an important environmental factor that affects how organisms allocate metabolic resources to physiological processes. Laboratory experiments that determine absolute thermal limits for representative species are important for understanding how fishes are affected by climate change. Critical Thermal Methodology (CTM) and Chronic Lethal...
Article
Developmental hypoxia has been shown to result in significant changes in cardiovascular development of American alligators and common snapping turtles. These include similar effects on cardiac mass and aspects of cardiovascular function. However, given the distant phylogenetic relationship between crocodilians and chelonians, we hypothesized that s...
Article
Fish exhibit thermal tolerance and metabolism correlated to recent thermal history, and more studies should examine species’ responses to large fluctuations in daily temperatures. We compared thermal tolerance and metabolic responses between fish acclimated to constant temperatures and a large, daily thermal cycle of 10°C. Black Convict cichlid ( A...
Article
Temperature is a primary factor affecting species' ability to thrive in a particular ecological niche, but thermal conditions have changed dramatically in recent decades. Fishes shift their thermal tolerance range with a maximum and minimum temperature correlated to their recent thermal acclimation history, and species can show a reduced temperatur...
Article
Full-text available
Angiotensin II (ANG II) is a powerful vasoconstrictor of the renin–angiotensin system (RAS) that plays an important role in cardiovascular regulation in adult and developing vertebrates. Knowledge of ANG II’s contribution to developmental cardiovascular function comes from studies in fetal mammals and embryonic chickens. This is the first study to...
Article
Allometric equations represent relationships between a morphological size (e.g., organ size) or physiological rate (e.g., metabolic rate) and body mass using the equation Y=aM b , where Y is morphological size or physiological rate, a is elevation or y‐intercept, b is slope and M is animal body mass. Vertebrate organ growth relative to body mass va...
Article
Chronic hypoxic incubation is a common tool used to study developmental changes in reduced O2 conditions, and it has been useful for identifying phenotypically plastic periods during ontogeny in laboratory settings. Reptilian embryos can be subjected to natural hypoxia due to nesting strategy, and recent studies have been important in establishing...
Article
Lipids serve as energy sources, structural components, and signaling molecules during fish embryonic development, and utilization of lipids may vary with temperature. Embryonic energy utilization under different temperatures is an important area of research in light of the changing global climate. Therefore, we examined percent lipid content and fa...
Article
Full-text available
During embryonic development, environmental perturbations can affect organisms' developing phenotype, a process known as developmental plasticity. Resulting phenotypic changes can occur during discrete, critical windows of development. Critical windows are periods when developing embryos are most susceptible to these perturbations. We have previous...
Article
Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effe...
Article
Development of cardiovascular regulation in embryonic birds and reptiles has become an area of growing interest over the past 20 yrs. Embryonic cardiovascular control is predominantly dependent on humoral mechanisms across these vertebrate groups. This is evident in the absence of autonomic tone in many species of birds and reptiles, as well as ele...
Article
Phenotypic plasticity is the ability of an animal to modify its phenotype in response to the environment. Embryos may have critical windows during development when they are particularly plastic or susceptible to the environment. We examined whether there are critical windows during Lake whitefish ( Coregonus clupeaformis ) embryonic development whe...
Article
Temperature has pervasive effects on poikilotherm physiology, and embryos and newly hatched/born animals are especially vulnerable to temperature shifts. Lake whitefish ( Coregonus clupeaformis ) are a North American, freshwater lake species with lengthy (80–150 day, 2–8 °C) overwintering embryonic development. Stenothermic, cold‐water embryos may...
Article
Studies on embryonic and hatchling reptiles have revealed marked plasticity in morphology, metabolism and cardiovascular function following chronic hypoxic incubation. However, the long-term effects of chronic hypoxia have not yet been investigated in these animals. The aim of this study was to determine growth and postprandial O2 consumption (V̇O2...
Article
A reference staging series of 18 morphological stages of laboratory reared lake whitefish Coregonus clupeaformis is provided. The developmental processes of blastulation, gastrulation, neurulation as well as development of the eye, circulatory system, chromatophores and mouth are included and accompanied by detailed descriptions and live imaging. Q...
Article
Full-text available
Abstract Environmental conditions fluctuate dramatically in some reptilian nests. However, critical windows of environmental sensitivity for cardiovascular development have not been identified. Continuous developmental hypoxia has been shown to alter cardiovascular form and function in embryonic snapping turtles (Chelydra serpentina), and we used t...
Article
Full-text available
The timing, success and energetics of fish embryonic development are strongly influenced by temperature. However, it is unclear if there are developmental periods, or critical windows, when oxygen use, survival and hatchling phenotypic characteristics are particularly influenced by changes in the thermal environment. Therefore, we examined the effe...
Article
Full-text available
Adenosine is an endogenous nucleoside that acts via G-protein coupled receptors. In vertebrates, arterial or venous adenosine injection causes a rapid and large bradycardia through atrioventricular node block, a response mediated by adenosine receptors that inhibit adenylate cyclase and decrease cyclic AMP concentration. Chronic developmental hypox...
Conference Paper
Some reptilian embryos are naturally exposed to low levels of O2 and high levels of CO2. This phenomenon has provoked much research on the physiological effects of developmental hypoxia in reptiles and associated implications on survival. However, notably less attention has been given to the effects of hypercapnia. In this study, we investigated th...
Article
Some reptilian embryos are naturally exposed to low levels of O 2 and high levels of CO 2 . This phenomenon has provoked much research on the physiological effects of developmental hypoxia in reptiles and associated implications on survival. However, notably less attention has been given to the effects of hypercapnia. In this study, we investigated...
Article
Osteoderms are small bones found in the dermal layer of sauropsid scales, form an integral part of integumental armour and may participate in thermoregulation. Whether growth of osteoderms parallels that of the whole animal has not yet been ascertained. We studied histomorphometry of cervical osteoderms of juvenile female American alligator ( Allig...
Data
This short dartfish movie is a supplementary addition to the Marine Ecology Progress Series publication, Dartfish use teredinid tunnels in fallen mangrove wood as a low-tide refuge. Many pieces of large woody debris (LWD) in the intertidal zone of mature mangrove forests are tunnelled by bivalves of the family Teredinidae. At low tide, dartfish wer...
Article
Full-text available
The considerable quantities of dead wood in the intertidal zone of mature mangrove forests are tunnelled by bivalves of the family Teredinidae. When the surface of heavily tunnelled wood is broken open, cryptofauna are able to use tunnels as refuges. In this study, the exploitation of this niche during low tide by the dartfish, Parioglossus interru...
Article
Full-text available
Environmental conditions play a major role in shaping reptilian embryonic development, but studies addressing the impact of interactions between chronic and acute environmental stressors on embryonic systems are lacking. In the present study, we investigated thermal dependence of cholinergic and adrenergic cardiovascular tone in embryonic American...
Article
Full-text available
Reptile embryos tolerate large decreases in the concentration of ambient oxygen. However, we do not fully understand the mechanisms that underlie embryonic cardiovascular short or long-term responses to hypoxia in most species. We therefore measured cardiac growth and function in snapping turtle embryos incubated under normoxic (N21; 21% O2) or chr...
Article
Crocodilians have a suite of unique ventilatory features that differ from other reptiles. We examined mechanical aspects of the alligator ventilatory system including maximal lung volume, total static and dynamic pulmonary compliance (lung and body wall) and pressure‐volume hysteresis in juvenile alligators (58 g to 254 g) raised in normoxic enviro...
Article
Reptile embryos are basal amniotic vertebrate developmental models that tolerate severe chronic hypoxia. We measured heart rate (f H ) and arterial blood pressure (P m ) for normoxic (N21) and chronically hypoxic‐incubated (H10; 10% O 2 ) turtle embryos following pharmacological blockade, and we quantified heart tissue mRNA expression for genes usi...
Article
In response to chronic developmental stress, embryonic reptiles exhibit phenotypic plasticity resulting in morphological and physiological modifications. Utilizing chronic hypoxia, we investigated plasticity of cardiovascular regulatory maturation in two species, American alligator and common snapping turtle. Both exhibit phenotypic plasticity, res...
Article
Longitudinal growth rate (LGR) has been shown to correlate with calcified cartilage column height (CCC) in the growth plates of birds. In order to infer limb bone growth patterns in non‐avian dinosaurs, this correlation needs to be documented in crocodilians. We tested the LGR‐CCC correlation in femora of juvenile alligators raised for two years un...
Article
The cardiovascular (CV) system is the first operational organ system, and reptiles represent evolutionary intermediates between water‐breathing vertebrates and birds and mammals. Reptile eggs are subject to environmental stressors during development, including hypoxia, and we have shown that hypoxia impacts reptilian CV function and maturation. Usi...
Article
Regulatory mechanisms that alter cardiovascular function to meet convective transport demands are present in all adult vertebrates, from hagfish to reptiles to mammals and birds. Logical and rapidly expanding fields of inquiry are when do these systems become evident during an organism's life span and how are physical, regulatory and functional dev...
Article
Rockskippers (family Blenniidae) and mudskippers (family Gobiidae) are amphibious fishes common to tropical intertidal zones. While their emergence patterns differ, both groups spend considerable time on land where they are subject to desiccation. Using a gravimetric wind tunnel method we determined total and cutaneous resistance to evaporative wat...
Article
Hypoxia is a naturally occurring environmental challenge for embryonic reptiles, and this is the first study to investigate the impact of chronic hypoxia on the in ovo development of autonomic cardiovascular regulation and circulating catecholamine levels in a reptile. We measured heart rate (f(H)) and chorioallantoic arterial blood pressure (MAP)...
Article
Full-text available
Hypoxia is a naturally occurring environmental challenge for embryonic non-avian reptiles, and this study is the first to investigate the impact of chronic hypoxia on a possible chemoreflex loop in a developing non-avian reptile. We measured heart rate and blood pressure in normoxic and hypoxic-incubated (10% O(2)) American alligator embryos (Allig...
Article
Full-text available
All embryonic and fetal amniotes possess a ductus(i) arteriosus(i) that allows blood to bypass the pulmonary circulation and the non-functional lungs. The central hemodynamic of embryonic reptiles are unique, given the additional systemic aorta that allows pulmonary circulatory bypass, the left aorta (LAo). The LAo exits in the right ventricle or ‘...
Article
Full-text available
The functional and possible adaptive significance of non-avian reptiles' dual aortic arch system and the ability of all non-avian reptiles to perform central vascular cardiac shunts have been of great interest to comparative physiologists. The unique cardiac anatomy of crocodilians - a four-chambered heart with the dual aortic arch system - allows...
Article
Despite having a similar four‐chambered heart, crocodilians and birds differ widely in their aerobic capacity. We investigated whether this is due to differences in outflow tract design, which allows for cardiac shunting in crocodilians, but not in birds. We hypothesized that removal of cardiac shunt will improve aerobic capacity (VO 2 max) by forc...
Article
In contrast to mammals and birds, effects of exercise on bone microstructure in reptiles have received scant attention. We investigated the effects of long‐term exercise on a treadmill or in a flume on limb bones of the American alligator. Juvenile alligators were run or swum to exhaustion every other day for 17 months, and received fluorescent dye...
Article
The vertebrate cardiovascular (CV) system becomes operational early in development and must function and mature both anatomically and physiologically. Deviations in developmental environment create challenges that impact CV function and maturation. Reptilian embryos may be particularly impacted given features of development in egg‐laying species, s...
Article
1.Replicate thermal tolerance polygons were created using critical thermal methodology (CTM) and statistically compared.2.Reef-associated damselfish and cardinalfish displayed the smallest total and intrinsic polygon zones and equal upper and lower acquired tolerance zones within species.3.Two gobiids and a mullet species (resident and transient to...
Article
Full-text available
The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be 'metabolically inflexible' in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill traini...
Article
Exercise affects the vertebrate skeleton via biomechanical and biochemical stress. Exercise‐induced strains can elicit increased primary bone formation and/or secondary remodelling of limb bones. Exhaustive exercise results in high lactic acid loads, which may require buffering by bone mineral and thus influence bone remodelling. Cardiac shunting i...
Article
Over the past 30 years, cold events and disease have reduced much of the live Acropora cervicornis (Staghorn Coral) in Dry Tortugas National Park (DTNP), FL to fields of coral rubble. It is unclear how the resulting loss of three-dimensional reef structure has affected density and distribution of reef-dependent damselfishes. We compared densities o...
Article
Full-text available
We measured metabolic rates of six Indo-Pacific fishes from different thermal habitats at 26°C and after acute transfer to 32°C. Temperature–metabolism relationships were expressed as temperature quotients (Q10) and ranged from ~1.0 in tidepool-dwelling common (Bathygobius fuscus) and sandflat (Bathygobius sp.) gobies to 2.65 and 2.29 in reef-assoc...
Article
Reptilian cardiac shunting is hypothesized to confer a fitness advantage via physiological functions including inducing hypometabolism, aiding recovery from metabolic acidosis and facilitating digestion. Elimination of cardiac shunt has not previously been shown to reduce fitness. Crocodilians possess a unique reptilian cardiac anatomy (fully‐divid...
Article
1.Distribution and reproduction of marine tropical fishes accidentally introduced along the United States’ east coast and Gulf of Mexico are likely limited by low winter temperatures.2.Mean minimum acclimation temperature, minimum feeding cessation temperature and critical thermal minima for eight Indo-Pacific damselfishes (family: Pomacentridae) w...
Article
The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be 'metabolically inflexible' in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill traini...
Article
Full-text available
Air-breathing and non air-breathing gobiids inhabiting mangal tidepools on Pulau Hoga, Sulawesi, Indonesia, displayed differing types and degrees of behavioral and physiological adaptations to mitigate daily thermal and oxic stress. Non air-breathing Dusky Frillfin Goby, Bathygobius fuscus, and an undescribed sandflat goby species, Bathygobius sp.,...

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