Scientific Program : Plenary Abstracts

The Local Organizing Committee of the International Congress of Comparative Physiology and Biochemistry 2019 is actively working to organize an exciting meeting in Ottawa!

 

PLENARY TALKS with Abstracts

 
Torpor during development and after fire: implications for the evolution of mammalian endothermy and the survival of catastrophic events
Fritz Geiser1, Clare Stawski1,2, Chris B. Wacker1, Julia Nowack1,3
1 University of New England, Australia, 2 Norwegian University of Science & Technology, Norway, 3 John Moores University, UK
 
The asteroid strike causing global wildfires at the Cretaceous-Paleogene (K-Pg) boundary ~65 Million years ago resulted in the demise of dinosaurs and many other organisms. While it is generally accepted that small ectotherms probably survived the post-impact winter that lasted for months because of their low metabolic rate (MR) and low food requirements, it is unknown how the small quadrupedal endothermic mammalian ancestors that were present at this time managed to do so. However, it is highly unlikely that a strictly homeothermic small terrestrial mammal with a constant high body temperature (Tb), high MR and consequently high food requirements would have had a chance.  It instead has been proposed that these small ancestral mammals must have been capable of using torpor for energy conservation (i.e. were heterothermic). Torpor is characterised by substantial falls of MR and Tb, permitting small mammals to survive without food for up to a year. This hypothesis is supported by new evidence on a substantial increase of torpor use after fires and the further enhancement of torpor by charcoal/ash substrates in anticipation of prolonged detrimental conditions. Moreover, even at the beginning of the evolution of endothermy, heterothermy likely played a key role in the transition from ectothermy to endothermy. Our review will address current hypotheses and discuss the theoretical possibilities considering these and other new data with regard to two crucial evolutionary events: (i) the role of heterothermy in the evolution of avian and mammalian endothermy and (ii) the role of heterothermy in mammalian survival at the K-Pg boundary.
 
The heart of the world’s oldest vertebrate, the Greenland shark
Holly Shiels
University of Manchester, UK
 
The life span of the Greenland shark (Somniosus  microcephalus) is at least 272 years and may be as long as 500 years. The finding that they live in the deep, dark Arctic waters for hundreds of years has captured the imagination of the world and the attention of scientists. How does an animal born in Shakespeare’s time still patrol the deep today? This extreme longevity is particularly interesting with respect to the heart, because heart disease is synonymous with aging in humans.  What structures do their hearts have that permit this extreme longevity? Does the heart underlie the ability of this shark to live so long?  This lecture will explore recent work on the Greenland shark heart including analysis of fibrosis, atherosclerosis, mitochondrial dysfunction and regeneration.  These findings will be discussed in relation to the idea of chronological age versus ‘biological’ age.
 
Inter-individual variation as a window into physiological mechanisms and their evolution
Patricia Schulte
University of British Columbia, Canada

Natural populations exhibit substantial and repeatable inter-individual variation in many physiological and behavioral traits. Animal physiologists have often treated this variation as a “nuisance variable” that simply contributes noise to experimental studies.  However, inter-individual variation is an important resource that can provide insight into physiological mechanisms and their evolution. Here, I use studies from my laboratory to illustrate this point. For example, Fundulus heteroclitus is a species of small fish found in marshes and estuaries along the Atlantic coast of North America. Northern and southern subspecies differ in important physiological traits including metabolic rate, thermal tolerance, hypoxia tolerance, and salinity tolerance. By examining inter-individual variation in these traits in hybrid populations, we have been able to identify important candidate genes that contribute to this variation. For example, variation in the tight junction protein tricellulin is associated with to variation in salinity tolerance, and variation in a monocarboxylate transporter is associated with variation in metabolic rate. The northern and southern subspecies also differ in their thermal plasticity, with the northern subspecies exhibiting compensation of metabolic processes at low temperatures, while this response is absent in the southern subspecies. In the northern subspecies, this plasticity is associated with changes in mitochondrial membrane composition and the activity of electron transport chain components. This inter-individual variation in whole-organism traits and underlying physiological mechanisms likely represent adaptations to a changing environment, and also provides the substrate on which natural selection can act in the face of future environmental change.

Naked mole-rats: Blind, naked, and feeling no pain
Thomas Park
University of Illinois at Chicago, USA

Naked mole-rats have received attention in the past because of their incredible longevity, with lifetimes greater than 30 years, and their unusual, insect-like social organization. They are also very unusual, even among subterranean mammals because they live in large colonies where many individuals must share a limited, underground air supply characterized by chronically low oxygen and high carbon dioxide. We have identified several profound neural and metabolic adaptations in this species related to surviving in an environment that would be deadly to other mammals. These adaptations include intrinsic brain tolerance to hypoxia and the ability to enter a low-energy suspended animation state. They also show a blunted response to the pain associated with tissue acidosis (e.g. from high concentrations of carbon dioxide) as well as inflammation, and they are completely insensitive to carbon dioxide-induced pulmonary edema. Some of the mechanisms associated with these traits include the ability to use fructose for aerobic glycolysis and the lack of the neurotransmitter Substance P in peripheral pain nerves. Fully understanding the mechanisms of these extreme adaptations could be a boon for combating a variety of human disorders involving brain hypoxia and pain.  

Straighten up and fly right: Physiological mechanisms for long-distance dispersal in flies​
Michael Dickinson
California Institute of Technology, Pasadena, USA
 
Most experiments on the behavior of the fruit fly, Drosophila melanogaster, have been performed within confined laboratory chambers, yet the natural history of these animals involves dispersal that takes place over much larger spatial scales. Recently, my laboratory has performed a series of release-and-recapture experiments that demonstrate flies can navigate over ~10 km of open desert in just a few hours without the possibility of feeding along the way. Such excursions are only possible if flies actively maintain a constant compass heading. In this talk, I discuss a hierarchy of mechanisms that enable flies to maintain a stable course in the face of external and internal perturbations. By exploiting new experimental methods and modern genetics, my lab is attempting to identify the neurobiological and biomechanics specializations that underlie the flight capabilities of flies and other insects. Collectively, this new research provides insight into ancient sensory-motor modules that have helped make insects the most successful group of animals in the history of life.