Migration

Why do we track animals using satellite tags

Common amount vertebrates, multiple reasons, physiological challenges, benefits outweigh costs

Why migrate

Food availability, water availability, change in weather, overcrowded habitat, increase survival, physiological maintenance.

Time to migrate

Lunar cycle, photoperiod, temperature change, hormone cycling, Decrease in food and water availability

Explain this figure

Associated with cost of locomotion, direct comparison with locomotion costs

Explain the periodic maintenance of killer whale migration

Resident killer whales in antarctica to brazil where the whales change color over the years. The warm water uses energy to change their skin which wont have much effect on their metabolic budget

How to prepare for migration

Increase energy stores (fat lvl increases), Build muscle mass (to maintain constant speed), change in preference for metabolic fuels (diets to support flight), change in morphology & size of gut and critical organs to reduce overall weight & get ride of things you dont need to fly.

Phenotypic flexibility of the bird gut during migration

Changes in digestive system when preparing for flight

Pre-migratory expansion

Hyperphagia phase: Bird eats massive amounts of food to build fat and protein stores

organ growth: Liver, pancreas and intestines increase in size

cellular changes: Hypertrophy and hyperplasia of intestinal epithelial cells to maximize nutrient uptake

In-flight atrophy

During migration

Energy saving: Gut atrophies (expensive to maintain) to reduce metabolic costs

Weight reduction: decrease in gut mass reduces weight of animal (cot)

-Structural shrinkage: Villi length, intestinal diameter and luman width decrease

-Muscular adjustments: Atrophy of submucosa and circular muscle layers= reduced function

Stopover rebuilding (refueling)

Rapid recovery: At stopover sites, gut quickly regrows and digestive enzymes are produced

Microbiome shifts: Gut bacteria remodel rapidly depending on local food sources encountered.

How do changes in organ masses of red knots during refueling relate to the purpose of migration

LDM: Lean dry mass

Explain this image

Muscle hypertrophy of red knots independent of photoperiod and aligns with departure date

How does brain size relate to migration

Brain is expensive to maintain, brain size of migratory birds is smaller than resident birds to reduce energetic costs and developmental costs

Explain the gut microbiome of migrating birds

Community of microorgansims like bacteria, fungi and viruses along with genetic material that live in specific spaces

What is the purpose of gut microbiome in migrating birds

Breakdown complex carbohydrates that gut enzymes cannot digest and produces short chain fatty acids, essential vitamins and protects intestinal lining from bacteria

Explain this image

The remodeling of gut microbiome and long distance flying. Demonstrates 4 groups of bacteria. The DNA/RNA sequence in gut as birds migrate. Gut bacteria absorb nutrients, breakdown carbs, fibres and fattya acids. As more traveling occurs, theres an increase in gut bacteria

What happens when antibiotics are given to migratory birds

The bacteria would die causing no nutrient absorption therefore leading to weight loss in birds

Impact of changes to microbiome during migration

1. Compositional shifts and flight mode

2. Functional adaptation to energetic demands

3. transient nature of stopovers

4. Vulnerabilityes: pathogens and dysbiosis

Explain compositional shifts

Active flight causes shifts in microbial ecosystem reflecting the high-stress conditions

Resilient strains

Explain function adaptation to energetic demands

Changes in microbial composition correlate w migratory conditioning and fat accumulation

Enhance lipid and nutrient abs, immune modulation(long distance travel is immunilogically challenging the shift establishes a defensive barrier against foreign pathogen)

Explain the transient nature of stopovers

Cinsumption of local organisms result in immediate exposure to new microorganisms

env microbes redefine the birds internal profile

Explain vulnerabilities when flying

Combination of extreme physiological stressm starvation during flight, changing diets

Dysbiosis (micrbial imbalance): leading to opportunity for pathogenic bacteria

Refueling during migration

MR of birds during migration is 10 to 15x that of resting, comes from extra-musc adipose reserves, migrant birds can mobilize transport and oxidize lipids more than 10x the max rate in mammals

Explain the stops during migration

Migrants accumular large lipid reserves by eating seasonally abundant amphipods buried in mudflats

EOA AND DPA important energy sources and enhance performance, increase endurance exercise capacity

How to enhance performance

Incorporation of dietary n-3 PUFA in membrane phospholipids

Change in membrane fluidity, alters local molecular env of key membrane proteins - CPT, NA/K+ATPase and Ca/Mg ATPase which increases function/rate of rxn and muscle function

Function of CPT

enzyme involved in oxidation of long chain fats to generate ATP via mitochondria

Na/K ATPase and Ca/Mg ATPase function

Ion pumps that maintain electrical chemical gradients in cells. critical to muscle function

Explain the natural doping by binding of n3 fatty acids to PPARa and b

N3 FA activate specific nuclear receptors which lead to increase in expression of proteins involved in oxidation and transport of fatty acids.

Increases in metabolic function and efficiency

What does binding to PPAR cause

Mitochondiral and perxisomal proliferation

Stimulation of gene expression for key proteins of lipid metabolism

Breakdwon FA, increases amount of protein needed to make ATP

Define PPAR

Peroxisome proliferator activated receptors