Towards a better understanding of the benefits and risks of country food consumption using the case of walruses in Nunavik (Northern Quebec, Canada).

Food insecurity affects Inuit communities. One solution is to consume locally harvested foods, named country foods. However, some country foods are not eaten as often as before, and pressures including contaminants and environmental changes threaten the health of Arctic fauna, thus its suitability for local consumption. By combining Inuit Knowledge with laboratory data, our study assessed the benefits and risks of walrus consumption by Inuit in Nunavik, Québec, Canada. It aimed to increase understanding of: 1) the hunt of healthy Atlantic walruses (Odobenus rosmarus rosmarus); 2) the safe preparation of walruses; 3) the nutritional benefits and risks of consuming walruses. To do so, we interviewed 34 hunters and Elders from Nunavik. Levels of mercury, omega-3 polyunsaturated fatty acids and selenium were evaluated from locally harvested walruses. Through the Nunavik Trichinellosis Prevention Program, a total of 755 Atlantic walrus samples, collected between 1994 and 2013, were tested for Trichinella nativa. Information on botulism was reviewed. While interviews informed on how to select healthy walruses and prepare them for consumption, laboratory analyses revealed that walruses had elevated levels of omega-3 fatty acids and selenium but low levels of mercury compared to some other wildlife. Only 3% of the 755 walruses were infected with T. nativa. Most walruses' infections were found within individuals from the South East Hudson Bay stock, where Inuit have thus decided to stop hunting since mid-2000s. Finally, although the number of outbreaks of trichinellosis related to the consumption of walruses has significantly reduced in Nunavik, botulism could continue to be an issue when igunaq (i.e. aged walrus) is not properly prepared. With the support of the Nunavik Trichinellosis Prevention Program and transmission of Inuit knowledge on igunaq preparation, the consumption of Atlantic walruses has the potential to help address issues related to food insecurity in Nunavik in the future.

Evidence of degradation of hair corticosterone in museum specimens.

Researchers increasingly rely on non-invasive physiological indices, such as glucocorticoid (GC) levels, to interpret how vertebrates respond to changes in their environment. Recently, hair GCs have been of particular interest, because they are presumed stable over long periods of storage, which may facilitate the study of large-scale spatial and temporal patterns of stress in mammals. In the current study, we evaluated the stability of hair corticosterone levels in museum specimens, and the potential effects of different museum curation treatments. Using deer mouse (Peromyscus maniculatus) specimens collected from Vancouver Island (11 sites, 82 individuals) over 76 years, we found that specimens collected earlier in the 20th century had lower hair corticosterone than more recently collected specimens. These results suggest that hair hormone levels may not be stable over decades of storage time. We then subjected hair samples collected from white-footed mouse (Peromyscus leucopus, n = 36) to 3 different museum curation treatments, and found that borax lowered hair corticosterone levels relative to control samples, but air drying samples, or treating them with turpentine had no effect. Our results present a source of concern for the use of museum specimens for hair hormone analysis, and for studying long term trends in glucocorticoid levels.

50 years of comparative biochemistry: The legacy of Peter Hochachka.

Peter Hochachka was an early pioneer in the field of comparative biochemistry. He passed away in 2002 after 4 decades of research in the discipline. To celebrate his contributions and to coincide with what would have been his 80th birthday, a group of his former students organized a symposium that ran as a satellite to the 2017 Canadian Society of Zoologists annual meeting in Winnipeg, Manitoba (Canada). This Special Issue of CBP brings together manuscripts from symposium attendees and other authors who recognize the role Peter played in the evolution of the discipline. In this article, the symposium organizers and guest editors look back on his career, celebrating his many contributions to research, acknowledging his role in training of generations of graduate students and post-doctoral fellows in comparative biochemistry and physiology.

Dinosaurs, dragons, and dwarfs: the evolution of maximal body size.

Among local faunas, the maximum body size and taxonomic affiliation of the top terrestrial vertebrate vary greatly. Does this variation reflect how food requirements differ between trophic levels (herbivores vs. carnivores) and with taxonomic affiliation (mammals and birds vs. reptiles)? We gathered data on the body size and food requirements of the top terrestrial herbivores and carnivores, over the past 65,000 years, from oceanic islands and continents. The body mass of the top species was found to increase with increasing land area, with a slope similar to that of the relation between body mass and home range area, suggesting that maximum body size is determined by the number of home ranges that can fit into a given land area. For a given land area, the body size of the top species decreased in the sequence: ectothermic herbivore > endothermic herbivore > ectothermic carnivore > endothermic carnivore. When we converted body mass to food requirements, the food consumption of a top herbivore was about 8 times that of a top carnivore, in accord with the factor expected from the trophic pyramid. Although top ectotherms were heavier than top endotherms at a given trophic level, lower metabolic rates per gram of body mass in ectotherms resulted in endotherms and ectotherms having the same food consumption. These patterns explain the size of the largest-ever extinct mammal, but the size of the largest dinosaurs exceeds that predicted from land areas and remains unexplained.

Physiological and biochemical correlates of brood size and energy expenditure in tree swallows.

Intra-population variation in many fitness-related traits (e.g. clutch size) is often attributed to variation in individual parental quality. One possible component of quality is the level at which each individual can expend energy while provisioning dependent young. We used breeding tree swallows (Tachycineta bicolor) to test whether adults with large, natural-sized broods and/or nestlings in good nutritional condition had relatively high daily energy expenditures (DEEs). Adults with high DEEs were predicted to have large internal organs and high metabolic capacities. We first measured the growth rate of nestlings in natural broods of five, six and seven over a 4-day period and then measured parental DEE using doubly labelled water. Adults were then dissected for analyses of body composition and to determine maximum enzyme activities in the pectoral muscle. Although the total mass gain of large broods was greater than that of small broods, parental DEE was independent of brood size. We hypothesize that adults matched their clutch size (and consequently, brood size) to their individual foraging efficiencies. When statistically controlling for the effects of brood size, in one of two years there was a positive correlation between DEE and brood mass. This suggests that among individuals rearing the same-sized broods there were reproductive benefits of a relatively high DEE. There was no correlation between either brood size or DEE and the mass of any internal organ or the metabolic capacity of the pectoral muscle.

Effect of brood size manipulation on offspring physiology: an experiment with passerine birds.

The environment experienced during ontogeny has a significant impact on the physiological condition of offspring. This, in turn, forecasts survival probabilities and future reproductive potential. Despite the prominent role that the concept of condition plays in evolutionary studies, the physiological and biochemical characters that define it remain relatively unexplored. In this study, we quantified the impact of brood size manipulations on the physiology and biochemistry of nestling tree swallows (Tachycineta bicolor) shortly before they fledged. Over two breeding seasons, we either increased or decreased the number of individuals in a brood by a single nestling. Every 2-4 days, we determined the resting rate of oxygen consumption [V(O(2))] of individuals in each brood. Growth was followed until 16 days of age, at which time, to look for potential trade-offs in energy allocation, we measured total lipid mass, skeletal muscle and organ mass, indices of blood oxygen-carrying capacity and the activities of key metabolic enzymes in various tissues. Surprisingly, there was a minimal response of most characters to brood manipulation, suggesting that physiological and biochemical development is relatively invariant except perhaps under extreme conditions. Individuals reared in artificially enlarged broods, however, had a significantly lower body mass, body-size-adjusted [V(O(2))], gizzard mass and total lipid mass. These individuals also had decreased activity of cardiac 3-hydroxyacyl CoA dehydrogenase, suggesting a decreased capacity for oxidation of fatty acids. How these characters affect survival or the future adult phenotype remains unknown.

Allometric scaling of RNA, DNA, and enzyme levels: an intraspecific study.

The activities of oxidative and glycolytic enzymes show body size-dependent relationships across a wide variety of taxa; however, the mechanistic basis remains unknown. We sampled white epaxial muscle from rainbow trout (Oncorhynchus mykiss) spanning a 100-fold range in body mass. We measured activities of enzymes from aerobic and anaerobic metabolic pathways, RNA [total RNA and mRNA, pyruvate kinase (PK), citrate synthase (CS), and MyoD mRNA], and total DNA. Total RNA and DNA showed a biphasic relationship with body size, with a break point occurring after fish reached 1 yr of age. In contrast, total RNA/total DNA was constant across the entire size range. Neither CS activity nor CS mRNA levels scaled with body mass. PK activity and PK mRNA levels increased in parallel in yearling fish only (r(2) = 0.91, P < 0.01). This suggests that although PK expression is transcriptionally regulated in yearlings, the molecular mechanisms regulating expression change with growth and age. This was supported by a positive correlation between MyoD and PK mRNA levels (r(2) = 0.17, P < 0.05).

Interindividual variability in body composition and resting oxygen consumption rate in breeding tree swallows, Tachycineta bicolor.

Basal metabolic rate is one of the most widely measured physiological traits. Previous studies on lab mice and field-caught lizards suggest that individuals with relatively high basal metabolic rates or standard metabolic rates have relatively large masses of metabolically active tissues (e.g., heart, kidney, liver). As these are energetically expensive organs, there may be variability between breeding seasons dependent on, for example, availability of prey and capacity for energy intake. We present data from breeding tree swallows (Tachycineta bicolor) collected over two successive seasons. There was no difference between years in resting oxygen consumption rates, although there were significant interannual differences in the masses of all organs and tissues except the pectoralis. Interindividual differences in the masses of the kidney and small intestine explained 21% of the variation in oxygen consumption rates. Although individuals with relatively high resting oxygen consumption rates had relatively large, metabolically active kidneys, they had relatively small intestines and pectoral muscles. This is in contrast to all previous studies on mammals and to the single interspecific study of birds. Oxygen consumption rate also correlated positively with hematocrit. Our results suggest that assumptions of consistent positive relationships between resting oxygen consumption rate and organ masses cannot be extended intraspecifically for birds.