Basic Physiology

Question 1

How do marine organisms not only survive but become successful in some of the most challenging ecosystems?

Answer 1

• Physiology is the study of the function of animals and their constituent parts. A basic understanding of these functional processes allows us to study responses to environmental variability. What is it about these organisms that allow them to survive in their habitat.
• Reproductive success is part of the calculation for fitness and a key element in the theories of natural selection and evolution
• Behaviour, from mating to foraging and avoiding predation an understanding of behavioural patterns provides insights into the adaptive ecology of a species or taxa. To avoid predation, improve mating success with migrations ect.

Question 2

What are the potential challenges posed by of some of our familiar marine environments?

Examples; Deep-sea

Answer 2

• Pressure, overcome with biochemical and morphological adaptations
• Temperature – cold and hot!
• Finding food – finding mates - low densities
• Aphotic
• Anoxia

Question 3

What are the potential challenges posed by of some of our familiar marine environments? Examples; Open ocean

Answer 3

UV irradiation, plants with UV filtering chemicals

Finding food and avoiding being eaten

Question 4

What are the potential challenges posed by of some of our familiar marine environments? Examples; Estuaries

Answer 4

• influence of freshwater input
• Salinity
• Osmoregulatory adaptations
• Anoxia

Question 5

What will marine environments may exhibit variability in?

Answer 5

• Salinity
• pH
• Temperature
• Oxygen
• Irradiation
• Population size
• Food availability (prey abundance)
• Predator abundance

However, organisms in these environments may not find them to be challenging

As they exhibit varying degrees of adaptation over different time-scales.

External – abiotic characteristics

Ecology of animals also allow organisms to survive in different habitats

Question 6

What are the different types of extremophiles?

Answer 6

• Thermophiles - High temp over 45 degrees. (hydrothermal vents)
• Psychrophile (Cryophile) Low temperatures - sub 15 degrees. (Low temperatures)
• Halophile - salt loving 5x seawater (supersaline brine)
• We are most interested in highly fluctuating salinity - most literature on high altitude lakes.
• Barophile (Piezophile) High pressures (1100atm, 117 Mpa)

Question 7

Describe thermophiles

Answer 7

• Majority are Archaea
• Thrive at temperatures above 45oC
• Often found in geothermally heated regions
• deep-sea hydrothermal vents
• Contain enzymes that can function at high temperatures, and does not disrupt the folding mechanisms of the protein.
• Can be classified as OBLIGATE (require high temp) or FACULTATIVE (tolerant of high temperatures)
• Some require high temperatures for growth others can thrive over a range of temperatures

Question 8

Give an example of a eukaryotic thermophile?

Answer 8

Alvinella pompejana

• Deep-sea polychaete (up to 15cm)
• Only found at Pacific vents attached to smoker chimneys
• Thrive at temperatures up to 80oC
• One of the most heat tolerant complex organisms
• Live in thin-walled tubes
• Posterior end exposed to high temperatures
• Head and gills in 22oC
• Covered in white bacteria, provide food and protection from heat
• Huge temp variability over the length of the worm from inside the black smoker to the waters outside

Question 9

Describe psychropiles

Answer 9

• Majority are Bacteria or Archaea
• Capable of growth and reproduction at temperatures below 15oC
• Often found in high latitude waters and the deep oceans
• Utilise a range of metabolic pathways
• Maintenance of functional lipid membranes
• lipid cell membranes chemically resistant to the stiffening caused by extreme cold
• Create protein ‘antifreezes’ to keep their internal space liquid and protect their DNA
• Average temperature of the Antarctic sea is -1.8 degrees
• Overcome problems of lipids becoming stiff and inflexible

Question 10

Describe eukaryotic Psychrophiles.

Answer 10

• Antarctic water is very cold (1°C to -1.8°C) - slows larval development
• Antarctic krill, associated with ice edge
• Problems associated with ice – being frozen

Question 11

Describe halophiles

Answer 11

• Majority are Bacteria or Archaea
• Very high saline conditions
• Categorised as slight, moderate or extreme, by the extent of their halotolerance
• Expend energy to exclude salt from their cytoplasm to avoid protein aggregation
• prevent desiccation, through osmotic movement of water out of their cytoplasm,
• Specialised pigments for converting light to energy as they cannot fix CO2
• Conduct photosynthetic reactions with a red retinal pigment rather than chlorophyll
• Red pigment such as rhodopsin to create energy

Question 12

What is the term for existing in a broad range of salinities, and explain.

Answer 12

• Euryhaline
• Exist and can be found in a broad range of salinities,
• Carcinus meanus, Salmon – migrations, Eel
• Dessication, freezing, over-heating, Osmoregulation

Question 13

Under pressure: reproduction in deep-sea echinoids

Answer 13

• Echinus affinis – Young & Tyler 1993
• Seasonally reproducing, lives at bathyal depths (~2000m) in NE Atlantic
• Embryos developed more rapidly at 200atm than at 100atm
• At 0atm and 50atm fertilisation membranes formed and nuclei cleaved but cytoplasmic division was inhibited
• Low pressures may be as lethal for deep-sea embryos as high pressures are for shallow-water species
• Surface pressure embryos don’t develop / cleave
• Require high pressure for reproduction to work

Question 14

Talk about the generation of ATP in terms of what we need to know.

Answer 14

• Glucose is a fuel
• Glycolysis occurs in cytoplasm – no O2
• TCA cycle occurs in mitochondria – O2
• NADr (co-enzyme)donates electrons – oxidised
• More ATP molecules with O2
• The level of understanding that is required - oxygen is required as allows extra ATP to be produced.

Question 15

Uptake of oxygen - describe diffusion.

Answer 15

• Aerobic metabolism depends on the availability of oxygen to the tissues
• DIFFUSION – O2 molecules moving from high to low partial pressure (PO2)
  
  • Oxygen diffuses down a pressure gradient
• Rate of diffusion depends on PO2 gradients and tissue properties
• Diffusion coefficients and O2 demands dictate that the distance between metabolising tissues and respiratory surface can be no more than 1mm
  
  • Easy for a flatworm
• Oxygen rapidly bound after passing through the barrier in larger organisms.
• This transports the oxygen, but also maintains the gradient allowing oxygen to continue to diffuse.

Question 16

Describe circulatory systems.

Answer 16

• Increase capacity for O2 transport
• Rapidly remove O2 from respiratory surfaces – steep PO2 gradient

2 main systems:

• Both require muscular pumps

1. Open System - Large haemocoel
   
   • Contractile tubes and valved ostia
   • Arthropods and molluscs
2. Closed system – Arteries and veins
   
   • Muscular pulsing blood vessels (‘lateral’ hearts)
   • Annelids

Question 17

What are respiritory pigments?

Answer 17

Blood is primitively colourless and close in composition to seawater – gastropods and bivalves

• Respiratory pigments - specialised proteins capable of binding with O2
• Consist of proteins linked to a prosthetic group containing a metal
• Prosthetic groups can be porphyrins (haem) or polypeptides.

Question 18

Describe three respiritory pigments.

Answer 18

Haemcyanin

• Contains copper, carried in solution. Blue when oxygenated, colourless when deoxygenated
• Molluscs: chitons, cephalopods, gastropods, crabs and lobsters

Haemerythrin

• Contains Iron, always cellular. Non-porphyrin structure. Violet in colour
• Sipunculans, Polychaetes, Priapulans, Brachiopods

Haemoglobin

• Iron-porphyrin protein in solution or cellular. Red in colour
• Vertebrates, Echinoderms, Crustaceans: Daphnia and Artemia, Annelids; Arenicola, Spirorbids Nematodes: Ascaris

Question 19

What does the amount of O₂ carried depend on?

Answer 19

Amount of O2 carried depends on quantity of pigment and OXYGEN AFFINITY

Importance of O2 uptake relative to availability (ambient PO2)

Question 20

What is a P₅₀?

Answer 20

OXYGEN DISSOCIATION CURVES – P50 (half saturation value of pigment)

P50 values can vary with temperature, pH and PO2

Question 21

Describe how the enviroment affects the P50 values.

Answer 21

Pigment variability

Animals living in high ambient PO2 have high P50. Sabella, Loligo and Nephtys*

P50s can be low even at high PO2 when respiratory surfaces present a diffusion barrier. Decapods

P50s very low (<1) in low ambient PO2. Polluted or anoxic environments. Arenicola.

Question 22

Why does the bohr effect occur?

Answer 22

The Bohr Effect describes the relationship between the partial pressure of carbon dioxide and the oxygen affinity of the respiratory pigment haemoglobin (). An enzyme, carbonic anhydrase within the haemoglobin molecule converts most of the carbon dioxide into carbonic acid, which further dissociates into protons and hydrogen-carbonate ions, which decrease the pH of the blood outside the cell. Protons will bind to the surface amino acids on the protein and cause a shift in the structure towards a T-shape form. This creates an equilibrium between the concentration of protons and the structure of the protein. A shift towards the T-form will inhibit the proteins oxygen carrying capacity, decreasing the oxygen affinity of haemoglobin ().

Question 23

What P50 would be expected from the lug worm?

Answer 23

Arenicola – low P50; burrows in deoxygenated muds, irrigates burrow but not continuously so high-affinity pigments are advantageous as O2 store

Question 24

What do alrger organisms require for oxygen uptake?

Answer 24

• Size of respiratory surface is another limitation on oxygen uptake
• Increase in size, activity and evolution of protective and impermeable coverings requires VASCULARISED RESPIRATORY SURFACES
• Increase surface area by EVAGINATION
• ‘Gills’ in polycheates and arthropods, CTENIDIA in molluscs

Question 25

Describe the blood flow over the gills.

Answer 25

* Blood pumped through by heart in opposite direction to flow of water * Countercurrent flow is typical of gills (not Arenicola or cephalopods) * Water with lowest PO2 in contact with least oxygenated blood * Ventilation – assist O2 uptake * Lateral cilia on gill lamellae of bivalves increase water flow rates * Peristaltic movements in tubiculous polychaetes * Undulating appendages in crustaceans * Animals living in areas of low partial pressures maximise their capability of filling their oxygen demand, larger more vascularised gills occur. * Blood is pumped through the gills in the opposite direction of the gills, to allow the diffusion gradient to be maintained.

Question 26

What factors influence respiration?

Answer 26

* Activity * Feeding * Post-prandial response * Temperature * Oxygen concentration

Question 27

Describe activity as a factor in influencing respiration.

Answer 27

Movement involves the beating of cilia and contraction of muscles leading to increased rate of metabolism over the standard rate A mobile limpet consumes ~1.4x more O2 than an inactive one (3-4x for Palaemontes and estuarine shrimp)

Question 28

Describe feeding as a factor in influencing respiration.

Answer 28

Feeding * O2 consumption often increase immediately following a meal POST-PRANDIAL response referred to as a SPECIFIC DYNAMIC EFFECT (SDE) * Cost of processing food in the gut * Cost of degrading and excreting proteins * Cost of using raw materials to synthesise new tissues Bayne and Scullard (1977) Mytlius edulis * 25% increase in post-prandial O2 uptake. 80% to cost of filtering food and \<20% to cost of ammonia excretion

Question 29

Describe temperature as a facto influcing respiration.

Answer 29

* Invertebrates are POIKILOTHERMIC but those living in constant environments may not be true poikilotherms – so often referred to as ECTOTHERMIC * Respiration is generally increased by increasing ambient temperature and vice versa * Responses may not be lasting – ACCLIMATION * Allows for conservation of energy at high temperatures and maintenance of high level of ATP production at low temperatures * Can operate in reverse direction – NEGATIVE/REVERSE ACCLIMATION * Occurs in some limpets (Patella aspera) * Q10 index - Q10 indicates factor by which R is multiplied by for a 10oC increase. How much does respiration rates change for a 10 degree increase?

Question 30

Describe oxygen consumption as a factor influcing respiration.

Answer 30

Oxygen concentration (PO2) * Marine organisms often encounter low PO2 – pollution, air exposure at low tides, burrowing in anoxic sediments * REGULATORS – adjust ventilation and circulation rates to maintain fixed level of consumption * CONFORMERS – consumption alters in concert with environmental changes in PO2 * Pc = critical PO2 at which regulator becomes a conformer * Exposed to low PO2; adapted regulators with low Pc value i.e. fiddler crabs * PAYING THE OXYGEN DEBT – increased consumption following exposure to hypoxia or anoxia * Salinity * Involve activity, behavioural and physiological responses * Expected changes in O2 consumption – marine organisms often exhibit higher consumption at reduced salinities (25% sea water)

Question 31

What acclimation refer to?

Answer 31

Acclimation refers to a controlled one variable, and acclimatisation is to a range of variables.

Question 32

What requisites do marine species have for survival?

Answer 32

Obtain food, avoid becoming food & space to achieve first two.

Question 33

What diets require symbiotic gut bacteria?

Answer 33

Diet low in proteins/vitamins or high in complex carbohydrate polymers – require symbiotic gut bacteria Grazing animals have high levels of symbiotic gut bacteria to break down tough polymers

Question 34

What types of hunters are there?

Answer 34

3 broad types can be distinguished 1. Pursuit hunters i.e. squid 2. Searchers i.e. gastropods 3. Ambushers i.e. shrimp * 1 and 3 possess weapons of prey capture and immobilisation e.g. chelate appendages, sucker or hook-bearing arms and spines * Jaws associated with anterior gut – polychaete eversible pharynx 2 feed on sedentary prey – often protected by CaCO3, cellulose or chitin

Question 35

Describe grazing as a feeding type.

Answer 35

Mobile consumers of sessile prey Requires hard biting or rasping mouthparts such as the radula, Aristotle’s lantern…….. Major problem is high proportion of indigestible polymers Sea urchins have regions of the gut for culturing anaerobic fermenting bacteria – releasing fatty acids etc Molluscs have evolved cellulase enzymes - cellulose Wood feeders – Limnoria (isopod) Problem of scale – smaller animals require higher quality plant material Must break down the cell

Question 36

Describe deposit feeding as a feeding type.

Answer 36

* Often no specialist organ required - guts * Some groups have specialised lobes or tentacles around mouth with ciliary tracts * Problems with scarcity and poor quality of material in sediments * Deposit feeders often dependent on bacteria * Deposit feeders can be selective: \<5-10% of organic pool is available * May be reliant on living associates of detritus which merely provides vehicle for transport into gut * Selective feeders ingesting solely diatoms can achieve \>70% assimilation efficiency

Question 37

Descrieb susesion feeders as a feeding type.

Answer 37

* All posses some form of filter * Particle capture is largely size specific * Use of cilia to sort particles * Food passes to stomach in a food-laden mucus cord * pH of stomach lumen is acidic to reduce viscosity – intestine is alkaline * Mucociliary filter feeding * Style – rotating rod projecting into stomach winds the mucous cord * Lophophorates – mucous and faecal rod * Molluscs – crystaline style, a permanent feature composed of hyaline mucoprotein * Release amylases as tip dissolves in stomach

Question 38

What gills are Adapted for filter feeding and particle sorting?

Answer 38

Lamellibranch Gills - Adapted for filter feeding and particle sorting

Question 39

Talk about an enviromental effect on digestion.

Answer 39

* Cardium edule (Morton, 1970 JMBA) – tidal digestive rhythms * Crystaline style dissolved at low tide when animal is not feeding – reformed at high tide * Digestive diverticulum of bivalves * Absorption and intracellular digestion of material passed inward from stomach * The tidal cycle is having an effect on digestion at a cellular level.

Question 40

What is matabolism?

Answer 40

Metabolism - sum of total of all chemical reactions in an organism. 2 major metabolic pathways.

Question 41

Describe anabolism and catabolism.

Answer 41

Anabolism and catabolism- Net incorporation of nitrogen indicates anabolism through protein synthesis. Catabolism accompanied by release of chemical energy - ATP

Question 42

What can metabolic rate be affected by?

Answer 42

Metabolic rate can be affected by tissue growth & repair; osmotic internal work; locomotory external work; temperature; time of day; age; sex; mass; size

Question 43

Temperature classifications - initial classifications based on the stability of body temperatures

Answer 43

HOMEOTHERMS – regulate body temperature by producing heat and regulating loss POIKILOTHERMS – body temperature fluctuates with ambient inconsistencies required a new classification based on source of body heat ENDOTHERMS – generate body heat ECTOTHERMS – dependant on ambient heat

Question 44

Measuring metabolic rate - what are the different types of metabolic rates?

Answer 44

* BASAL METABOLIC RATE (BMR) – stable rate under conditions of minimum stress after halting of digestive and absorption processes. (stopping the effect of a post prandial repsonse) * STANDARD METABOLIC RATE – BMR at a given body temperature.Useful measures for baseline comparisons but little information of metabolic costs of activity * ACTIVE METABOLIC RATE – best describes metabolic behaviour; average rate of energy utilisation during ‘normal’ activities. Experiments use things like artificial swim tunnels. * METABOLIC FACTORIAL SCOPE – range of metabolic rates and animal is capable of * Ratio of maximum sustained metabolic rate to BMR or SMR under controlled rest * MFS is a dimensionless number * Increase of 10 -15 times with activity * Will change with fitness, age, sex. * Calculated with a simple ratio *

Question 45

Permeability and transport - explain membranes

Answer 45

Membranes * Occur at the surfaces of all animal cells * Compartmentalisation function * Act as barriers to free diffusion * Regulate net movement and hence concentrations of substances * Consist almost entirely of lipids and proteins Bi-layers: Polar hydrophilic heads and hydrophobic hydrocarbon tails (phospholipid membrane) Fluid mosaic model – globular proteins integrated with lipid bi-layer * Ion channels, membrane pumps etc

Question 46

Explain Osmosis

Answer 46

1. Movement of water down its concentration gradient 2. Produces a HYDROSTATIC pressure (HP) gradient 3. Rise in solution level until net flux reaches zero 4. This occurs when the HP of solution in compartment II is sufficient to force water molecules back through the semi-permeable membrane at the same rate as osmosis causes molecules to diffuse from I to II 5. Referred to as the OSMOTIC pressure (OP)

Question 47

Wjhat terms are applied to different solutions in osmosis?

Answer 47

* When two solutions exert equal OP they are said to be ISOSMOTIC * When one solution exerts less it is HYPOOSOMOTIC with respect to the other, vice versa becomes HYPEROSMOTIC * TONICITY – response of the cells or tissues immersed in the solution * ISOTONIC, HYPOTONIC and HYPERTONIC

Question 48

What are the different types of diffusion in osmosis?

Answer 48

1. Simple diffusion through bi-layer: Thermal energy of solute molecules allows them to enter lipid phase and cross the membrane. Must break hydrogen bonds with water and must dissolve in the lipid bi-layer. Lipid-water partition coefficient 2. Diffusion through membrane channels: Charged molecules (Na+, K+, Cl-) cannot simply diffuse through the lipid bi-layer. Selective permeability of membranes implies presence of water-filled channels \<1.0nm diameter. Very little surface area is required 3. Facilitated transport: Some solutes will exhibit saturation kinetics indicating a limiting step in the permeation process. Transport of permeating solute by carrier molecules that are free to diffuse. Number of carrier molecules and rate at which they cross the membrane will be finite. Rate of transport will reach a maximum when all carrier-molecules are occupied

Question 49

Permeability and transport -what is active transport?

Answer 49

Active Transport * Passive diffusion continues until solute concentrations reach equilibrium * However, most solutes across the membranes of living cells are not in equilibrium * Chemical energy (ATP) is expended to maintain concentrations

Question 50

Permeability and transport - what are membrane pumps?

Answer 50

* Na+ ions are actively transported at the same rate at which they leak in * Sodium pump – transport against a gradient (cytoplasm has [Na+] 1/10th of extracellular fluid) * Pumps are often very selective * ATP or other energy source required * Some pumps exchange one type of molecule or ion for another on the other side of the membrane * Na+ - K+ exchange pump * Important to move things against the concentration gradient * Cells not in equilibrium – one will be hypo and one hyper

Question 51

What is a term for producing a transmembrane current?

Answer 51

* Rheogenic – produce a transmembrane electric current. * 3Na+ - 2K+ Membrane Exchange Pump. * ATP – hydrolysis \> ATP + Pi

Question 52

What do osmoregualtion methods regulate?

Answer 52

Difference between optimal intra- and extracellular concentrations of ions Mechanisms to regulate differences between a) intra- and extracellular compartments, b) extracellular compartment and the external environment

Question 53

May be daily fluctuations but animals tend to be in an osmotic steady state over the long term Water enters as the animal feeds and drinks and leaves in urine, faeces and by evaporation What types of osmotic exchanges occur?

Answer 53

* Osmotic exchanges may be OBLIGATORY (in response to physical factors) or REGULATED (physiologically controlled to maintain homeostasis) * Regulated exchanges occur to compensate for obligatory exchange * Obligatory exchange is influenced by gradients in solute concentrations * Marine fish in hypertonic seawater loses water so needs to drink * Freshwater fish in hypotonic environment takes up water but loses salt. * In general the body fluids of marine invertebrates are close to seawater in both osmolarity and salt concentration. * Do not need to expend much energy regulating osmolarity of body fluids

Question 54

What is the difference in secretions between marine and freshwater fish?

Answer 54

Marine fish will drink as they are constantly secreting sodium and chloride ions and loosing water. They will produce concentrated urine to secrete the ions. Freshwater fish excrete copious amount of dilute urine to get rid of excess water, but never drink.