Biological Rhythms & Energy Balance Flashcards
Why synchronise activities to the earth’s rhythms?
- better food supply
- avoiding predators
- avoiding competitors
- better environmental conditions
- avoiding harsh conditions
- finding mates or a breeding place
- raising young successfully
- enhance survival and reproduction
Types of biological rhythms
1. circadian
2. circatidal
3. circalunar
4. circannual
5. what do these rhythms persist in the absence of?
- revolution of Earth - 24 hours (period length: entrained) - 22-26hrs (period length: free-running)
- tides - 12.4 hours (period length: entrained) - 11-14hrs (period length: free-running)
- phases of moon - 29.5 days (period length: entrained) - 26-32 days (period length: free-running)
- seasons of the year - 365.25 days (period length: entrained) - 330-400 days (period length: free-running)
- these rhythms persist in the absence of the geophysical cues with which they are synchronised (entrained)
Daily activity patterns
1. diurnal?
2. nocturnal?
3. crepuscular?
4. what have animals evolved to restrict?
5. what does temporal variation in behaviour reflects?
6. what varies over time?
- active during the day
- active during the night
- active during dusk and dawn
- animals have evolved to restrict many of their behaviours to specific temporal niches
- temporal variation in behaviour reflects temporal variation in underlying physiology
- endocrine secretion varies over time
Pineal gland
- size of pea
- ‘pinea’ (lat.) = ‘pine cone’
- located between hemispheres
- produces melatonin
- regulation of endogenous rhythms
Melatonin & Diurnal Rhythms
1. what does it regulate?
2. diurnal secretion rhythm?
3. what is secretion dependent on?
- regulates biological rhythms (e.g. sleep/wake cycles)
- diurnal secretion rhythm (high at night, low during the day)
- secretion dependent on light
Artificial & abnormal light exposure
1. blue light exposure
2. jet lag
- blue wavelengths interfere with melatonin production leading to disruption of circadian rhythm
- melatonin cycle remains aligned with the original time zone, but the external environment shifts to the new location -> delayed or advanced melatonin secretion relative to the local time (-> difficulties falling asleep / staying awake)
Circannual & Seasonal Rhythms
1. many of what have been described?
2. what are most of the seasonal changes in behaviour correlated with?
3. 2 types?
- many annual cycles of hormone-behaviour interactions have been described
- most of the seasonal changes in behaviour are correlated with seasonal changes in reproductive function
- 2 types:
(1) those that exhibit endogenous circannual cycles that are entrained, or synchronized, by photoperiodic cues (e.g. deer, sheep)
(2) those that fail to exhibit endogenous circannual cycles in the absence of photoperiodic cues (e.g. many rodents)
Seasonal Rhythms in Syrian hamsters
March to October = higher reproductive status
From Jan to Mid June - “Spontaneous” testicular regeneration
From Mid June to January - Pineal-induced testicular degeneration
(Fürtbauer et al., 2014, PNEC)
Reproductive seasonality
1. what is it a strategy to manage?
2. what are there seasonal fluctuations of?
3. what are energetically demanding activities timed with?
- strategy to manage an annual energy budget
- seasonal fluctuations in the quality of the environment
- energetically demanding activities are timed with favourable conditions, e.g. reproduction and food availability
Dissociated reproductive patterns - red-sided garter snake
1. production of gametes in red-sided garter snakes?
2. when is sperm produced?
3. androgens and their effect?
4. mating behaviour only in?
5. effect of removal of pineal gland?
- production of gametes and mating do not occur at the same time of the annual cycles in red-sided garter snakes
- sperm produced during summer and stored during 8-9 month winter torpor
- androgens during mating phase have no effect on mating behaviour
- mating behaviour only in snakes that experienced torpor
- removal of pineal gland eliminates mating behaviour
Pancreas
1. acinar cells
2. islet cells
- exocrine function (digestive enzymes)
- endocrine function (glucagon, insulin, somatostatin)
Islet cells:
1. alpha cells
2. beta cells
3. delta cells
- glucagon (raises blood sugar)
- insulin (lowers blood sugar)
- somatostatin (inhibits secretion of GH, glucagon and insulin)
C-peptide
1. what is it?
2. insulin essential for and what does it act as?
3. insulin production =?
4. during insulin synthesis?
5. C-peptide is excretes at what rate into urine, and in contrast to insulin, can be assessed from?
- a byproduct of insulin production released by the pancreas
- glucose absorption, utilization, and storage; acts as hormonal regulator of energy balance in the brain
- major component of energy metabolism and modulator of energetic condition
- C-peptide is cleaved from proinsulin and secreted on an equimolar (1:1) basis to insulin -> proxy for energy balance/nutritional status
- C-peptide is excreted at a consistent rate into urine and, in contrast to insulin, can be assessed from urine samples
Urinary C-peptide (UCP) in baboons
Does physical activity energy expenditure (PAEE) predict UCP?
1. what did most studies look into?
2. what did few studies use?
3. what does recent work show?
- most studies looked into the link between uCP and energy intake
- few studies used proxies of energy expenditure (travel time: Higham et al.,
2011; travel distance: Touitou et al., 2021;
monthly energy expenditure based on activity
budgets / energy constants: Lodge, 2012; mate
guarding: Girard-Buttoz et al., 2014) - recent work shows effect of physical activity on uCP (children: Huus et al., 2016; capuchins: Sacco et al., 2020)
(Morgan et al., 2023)
UCP & physical activity energy expenditure
1. what was tested?
2. what does physical activity affect?
3. implications for what?
- tested the effect of VeDBA on uCP
(use of UCP validated for baboons: Fürtbauer et al., 2020 Horm. Behav.) - physical activity affects uCP at short timescales
- implications for past and future studies using uCP as a proxy for energy balance
Thyroid hormones
- Triiodothyronine (T3)
- Thyroxine (T4)
- Calcitonin (regulates calcium
and phosphate levels in the
blood -> healthy bones) - protein, fat, and carbohydrate metabolism
- normal growth and development (together with GH)
- cardiovascular system (e.g. heart rate)
- reproductive system (fertility)
- nervous system (mental state)
- metabolic rate
-> biomarkers of energy allocation & growth
Effects of thyroid hormones
1. brain
2. eye
3. lungs
4. heart
5. liver
6. digestive system
7. reproductive system
8. musculoskeletal system and skin
- affects brain function and mood
- affects the function of the nerves and muscles
- affects breathing rate
- affects heart rate and function
- regulates liver function
- affects the rate at which energy is used and digestion
- affects functioning of the reproductive system
- affects growth and development
Non-invasive thyroid hormone measurements
What do thyroid hormone levels reliably trace?
energy availability, decreasing during periods of energy restriction and increasing when energy is abundant
Predictors of triiodothyronine (T3) in baboons
tested for commonly found effects on faecal T3
- Age
Age-related thyroid hormone level changes
1. evidence across?
2. reasons?
- evidence across species
- reasons not fully understood but include e.g. size and sensitivity of thyroid gland, reduced energy intake, etc…
Drivers of social aging
1. what is social aging?
2. (Siracusa et al., 2022) “Energetic deficiencies are expected to…”?
- age-related shifts in social behaviour (e.g. smaller social networks; social selectivity; fewer partners)
- “Energetic deficiencies are expected to restrict an individual’s movement and therefore their ability to socially engage or the likelihood of others coming into social contact, leading to reductions in the quality and quantity of social relationships.”
Energetic deficiencies & aging
1. what is old age characterised by?
2. what results in decline in energy availability?
3. (Manini, 2010) decrease in with increasing adult age?
- old age is characterised by changes in energy regulation
- decreased body mass, reduced energy intake and resting metabolic rate result in a decline in energy availability, and thus energy expenditure and activity levels
- decrease in all components of energy expenditure with increasing adult age
Age-dependent changes in locomotion primates
(Almeling et al., 2017; Rathke & Fischer, 2021; Hauser & Tyrrell, 1984)
what happens to locomotion with increasing adult age?
decrease in locomotion with increasing adult age
Energetic deficiencies as drivers of social aging - The problem
- (Siracusa et al., 2022) “Energetic deficiencies are expected to restrict…”?
BUT
- what poses major methodological challenges?
- formal tests of what are lacking?
- “Energetic deficiencies are expected to restrict an individual’s movement and therefore their ability to socially engage or the likelihood of others coming into social contact, leading to reductions in the quality and quantity of social relationships.”
- quantifying energetic condition, movement, and sociality in wild animals poses major methodological challenges
- formal tests of the ‘energetic deficiencies hypothesis’ (and sub-hypotheses) are lacking
Energetic deficiencies as drivers of social aging - Our approach
1. energetic deficiencies?
2. movement?
3. reductions in the quality and quantity of social relationships?
- age-dependent, endocrine proxy of energy metabolism (faecal T3)
- Broad- & fine-scale movement (GPS)
- Grooming & social proximity (accelerometers, GPS)
(Fürtbauer et al., 2024)
Broad- and fine-scale movement from GPS data
1. what 4 types of movement is measured?
- total distance travelled, step length, sinuosity, residence time
(Fürtbauer et al., 2024)
T3 & movement
1. what did T3 not predict?
2. what did T3 have a significant positive association with?
3. result?
- T3 did not predict total distance travelled, step length or sinuosity
- T3 significantly positively associated residence time
- individuals remain in the same area for longer when their energy availability is higher
(Fürtbauer et al., 2024)
Movement & Social opportunities
1. what are social opportunities?
2. what is residence time significantly positively associated with?
3. what does remaining in the same area for longer increase the likelihood of?
4. “…restrict an individual’s movement and therefore…” (Siracusa et al., 2022)
- social opportunities = frequency of coming into close physical proximity (2m) of others
- residence time significantly positively associated with social opportunities
- remaining in the same area for longer increases the likelihood of coming into social contact
- “… restrict an individual’s movement and therefore… the likelihood of others coming into social contact…” (Siracusa et al., 2022)
(Fürtbauer et al., 2024)
Movement & grooming
1. what do social opportunities predict?
2. what question arises?
- social opportunities predict grooming interactions
- Energetic cost associated with giving grooming?
(Fürtbauer et al., 2024)
Summary of results
1. lower energy availability ->
- lower energy availability -> shorter residence times -> less social
(Fürtbauer et al., 2024)
Discussion
1. why don’t find evidence for ‘restricted’ movement due to energetic deficiencies?
- longer residence times may incur higher energetic costs
lower-energy (i.e. older) individuals may use strategies to optimise energy expenditure
highly cohesive groups -> not moving would mean not keeping up…
