Adaptations to the warm

Question 1

Thermal tolerance in Antarctic marine ectotherms

What is a word for having a poor capacity to resist warming?

Answer 1

Stenothermal

Question 2

What can organisms do to survive current & predicted climate change?

Answer 2

1. Cope with the change within their existing phenotypic plasticity (physiological, developmental, epigenetic). This could include the expression and synthesis of heat shock proteins.

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2. Adapt to the changing conditions (genetic modification). This is a longer-term strategy, where genes that are either dormant or new become expressed – genetic modification.

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3. Migrate to sites with better conditions. Southernly species migrating into the North Sea. Not an option for Antarctic species
   (1. Example - Expression and synthesis of heat shock proteins,
4. Longer term strategy – an expression of dormant and unused genes or new genes –
5. Southerly species coming up into the north sea

Antarctic species – lack of space – more competition)

Question 3

Organisms can respond to environmental change in a wide range of ways

How do they vary in scale?

Answer 3

Vary in scale – classify from biochemical buffering, through physiological mechanisms and genetic adaptation to behavioral and ecological modification

• Molecular processes are within cells and are therefore quick to turn on.
• Gene expression is still quick ranging from seconds, minutes to months.
• Migration range changes scales dependant on the rate of change
• Gene transfer – 1 degree every 50 years – too fast for organisms to adapt

Question 4

Challenges for Antarctic marine ectotherms

Generation times

Answer 4

• Species with long generation times – phenotypic plasticity is essential
• Survival dictated by sufficient plasticity – predominately acclimation, to resist change for the necessary time.
• Antarctic species are at the end of the scale – therefore it is really important that they have some genotypic plasticity.
• Antarctic species end of scale – really important that they have some genotypic plasticity

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Question 5

How does the Rate of warming can have a big impact on acclimation and CTmax?

Answer 5

CTmax declines at lower rates of warming

Non-linear exponential regression analysis of broader literature data sets has allowed extrapolation of long-term thermal limits (>1yr) to be predicted at 3.3oC – only 3oC above long-term summer maxima

Important to remember that acclimation capacity varies with several factors such as physiological condition and season

Analysis of CTmax at different rates of warming is likely to give a better estimate of highest temperatures for long-term survival

Question 6

What is a •Warming allowance’?

Answer 6

• The buffer that a species or population has in its physiological capacity over current temperatures
• Both tropical and Antarctic marine species are less resistant to warming than those at intermediate latitudes as they are not exposed to the same rate of change. Tropical species, however, have the space to move.
• Species from less variable temperature environments have less phenotypic plasticity to respond to warming

Question 7

How do increased temperatures affect juveniles?

Answer 7

• Larvae and juveniles are less tolerant to temperature increases than adult stages (e.g. the gastropod Nucella emarginata). For the same temperature range you get a lot more mortalily than adults.
• May have a less developed oxygen delivery system (with a high partial pressure antarctic species have not has the evolutionary push for efficient oxygen uptake systems – change in partial pressure with heat.
• Increased temperature = increased growth, development and metabolic rate of juveniles to a critical threshold, causing an increase in energy and resource use. This may negatively impact development

Question 8

Describe the importance of warming rates on CTmax.

Answer 8

At a faster rate of warming Upper Thermal Limits (UTL) of organisms are higher than at slower rates of warming

More active species have higher UTLs than slow moving/sedentary organisms – this supports the oxygen limitation hypothesis as active species have a higher aerobic scope than sedentary species

Antarctic marine ectotherms are a good model for thermal sensitivity/resilience as they are stenothermal and have a poor ability to resist warming (could be due to absence of or a reduced capacity for a heat shock response)

Question 9

•To cope with stress, changes to “normal” environmental conditions will trigger biochemical responses to mitigate cell damage and counteract the environmental changes occurring.

What are these biochemical responses?

Answer 9

• The expression and overexpression of specific proteins at the molecular level is the only universal stress response found in all species.
• High temperatures and other stresses make it more difficult for proteins to form their proper structures and cause some already structured proteins to unfold - Heat Shock Proteins (HSPs) are induced rapidly at high levels to deal with this problem
• HSPs are highly conserved proteins which stabilise and refold proteins, preventing cytotoxic aggregations (can start to unravel at high temperatures)
• They are classified according to their molecular weight (kDA)

Question 10

HSP 7- - heat shock proteins

Answer 10

• HSP70 action has been described in response to a variety of stressors, with the classical activation of the inducible genes observed in response to highly elevated environmental temperatures
• Comprised of constitutive (heat shock cognate 70, HPC70), stress-inducible (HSP70’s) and glucose-regulated forms (GRP78, glucose-regulated protein 78)
• HSP70 up-regulation in response heat shock, has been observed in all organisms examined to date except Hydra oligactis, Euplotes focardii and several species of Antarctic notothenioid fish

Question 11

HSP70 gene family were cloned using PCR from 2 evolutionarily divergent Antarctic marine molluscs

Laternula elliptica – A sub-littoral burrowing bivalve

Nacella concinna – An intertidal gastropod found from the mid- shore to around 110m

What did this experiment tell us?

Answer 11

• •Results suggest that these ‘chaperone proteins’ form an essential part of the molluscs biochemical adaptation to low, stable temperatures
• •High constitutive levels of HSP gene family member may be a compensatory mechanism for coping with elevated protein damage at low temperatures
• Hence transcribing, translating and folding proteins is problematic in polar waters - cold denaturation is well documented
• Heat shock protiens srill in the genotype for protection from cold, will never be sequenced in enough volumne to protect from warm temperatures.