Marine Biology: Physiology of Marine Organisms

3 ways which organisms respond to environmental change

Acclimation, regulation, and conformance

Acclimation

Response to environmental change by establishing a new equilibrium (change to metabolic preference)

Regulation

Regulation of constancy despite environmental change (warm blooded)

Conformance

Internal state changes to match external environmental change (cold blooded)

How are poikilotherms conformers?

When temperature increases it results in increased metabolic rate and energy use

Is acclimation possible in poikilotherms?

Yes which can reduce the response of increasing metabolic activity with increasing seasonal temperature (thermal optimum). They are able to stabilize metabolic rate over a wide range of temperatures

Homeotherms

Able to maintain body temperature at a constant level, usually above that of the surrounding environment

When is heat loss a problem in Homeotherms?

Problem when maintaining high body temperatures

Insulation (Homeotherms)

Used by many invertebrates

Countercurrent Heat Exchange (Homeotherms)

Circulating blood in opposite directions while vessels are in contact to reduce heat loss

Where does countercurrent heat exchange occur in dolphins?

Occurs in dolphin limbs where the artery is surrounded by veinlets, which return the heat

What organisms use countercurrent heat exchange?

Dolphins, Tuna, and White Marlin

Heat Shock

Another way which temperature impacts marine organisms, which can disrupt membranes, and ultimately disrupt the transport of ions and other cell functions

2 adaptations to heat shock

Heat shock proteins and ubiquitin

Heat Shock Proteins

Formed during heat stress and work to prevent denaturation of protiens

Ubiquitin

Low molecular weight protein that binds to degraded proteins, then degraded by intracellular enzymes (tags)

Seasonal Temperature Extremes

Impacts both activity and reproductions. Effects are different at northern and southern limits of geographic range

How can freezing temperatures effect marine life?

Freezing temps can destroy cells as cytosol freezes

Adaptation for freezing temperatures

Some fish have glycoproteins and glycopeptides functioning as antifreeze binding to ice crystals to prevent further growth

Leatherback Sea Turtles

Poikilotherms where cold water can lead to cold stunning of turtles. Females come to tropical beaches to nest monthly. Feeds mainly on jellyfish.

Leatherback Sea Turtles and Heat Loss

Heat loss occurs because of latitudinal distributions. Even though they are poikilotherms, their body temp is 10 degrees celsius above temp. Maintains same swimming speed in warm and cold water

Leatherback Sea Turtles and Countercurrent Heat Exchange

Found in their extremities where there are intertwined arteries and veins at the roots of all four limbs. This heats muscles in the extremities and the core body keeps heat through insulation

What is the problem with osmosis?

If salt content differs on either side of the membrane, osmotic pressure is created, and water moves towards higher salt content

What is the problem with diffusion?

Diffusion makes it challenging for organisms to regulate the concentrations of physiologically important ions

Does diffusion and osmosis occur simultaneously?

Yes

Which species does ion regulation the best?

Crustacea ion regulates the best

When is ion regulation accomplished?

Accomplished when isolation of body from seawater is possible so exchange and regulation localized

Ion regulation

Cells exchange ions through channels between cells and circulatory system and or tissue fluids

Osmolytes

Organic substitute for inorganic ions (Na, K, Ca) allows regulation of cell volume and maintenance of inorganic ion concentrations

Can organisms create their own osmolytes?

Yes. When an organism has a higher salinity, organisms create their own osmolytes for these ions which allow for change of the gradient associated with osmosis

3 examples of osmolytes

Free amino acids, urea, and glycerol/mannitol/sucrose

Free Amino Acids

An osmolyte used by many invertebrates, bacteria, and hagfish. Use uncharged amino acids that have little effect on protein function (alanine, taurine)

Urea

An osmolyte which is used by sharks and coelacanths

Glycerol, Mannitol, and Sucrose

An osmolyte used by seaweeks and unicellular algae

Do fish need constant osmotic salinity regulation?

Yes bony fishes do because their body are osmotically more dilute that surrounding seawater so the fish must drink a lot of seawater and exchange excess salts across gills, not just by urine

Need for oxygen in marine organisms

This increases efficiency of production of ATP which is an energy source in cells

3 mechanisms for uptake of oxygen

Diffusion, feathery gills and blood pigments

Feathery gills

High surface area to absorb oxygen; mammals have lungs with enormous surface area to take up oxygen

Blood pigments

Substances that greatly increase blood’s capacity for transporting oxygen

What are the 4 blood pigments?

Hemocyanin, hemerythrin, chlorocruorin, and hemoglobin

Hemocyanin

Copper containing protein found in molluscs and arthropods

Hemerythrin

Iron-containing protein, found in various worms

Chlorocruorin

Iron-containing protein, found in some worms

Hemoglobin

Protein unit with iron-bearing ring (heme) found in molluscs, arthropods, various worms

3 basic ways marine animals form an image

Pinhole camera, lenses, and curved reflector

Pinhole camera

In nautilus where light enters through a tiny hole and rays directly hit retina. Hole acts as pinhole camera allowing inverted images to form in back of eye

Disadvantage of pinhole camera

Allows vision only in high light

Lenses

Some marine animals use a lens or series of lenses, to focus light gathered by the eye. A brain or some other part of nervous system must then integrate all images

What marine organisms have lenses?

Fishes, squids, annelid worms, and arthropods

Marine lenses

More dense toward the center. Fish have muscles that move lense forward and backward to adjust focus.

Curved reflector

In scallops where light first passes through crude lens, then through two retina and reflects from a curved mirror like layer detected on return by retina