OEB 130 Lecture 9-10 (Respiration + Swimbladder)

Midterm 2

Air vs water as a media to breathe

1. Air is much easier to access O2 supply

2. Enables high metabolic rates of mammals and birds

Oxygen solubility trend with temperature

O2 solubility decerases with increased temperature & salinity

• freshwater likely more O2 available

Why is efficient uptake vital to fish?

because of low O2 water solubility

Gills are the site of

oxygen uptake and carbon dioxide release

• Blood enters the gills directly after leaving the heart

Gill tissue also contains

specialized cell types, including chloride cells which help maintain fish blood osmotic balance

What do chloride cells?

help maintain fish blood osmotic balance

• similar to kidney function

How can fish remove 80 - 90% of O2 available from water?

1. Short diffusion distance at gill site

2. Large surface area for diffusion at gill site

3. Counter current exchange of gases at gill site

4. Large volume of water passes over gills

% of O2 that fish remove from water vs humans from air

Fish remove 80-90% of O2 passing through gills

Humans remove ~25% of O2 from air before exhalation

diagram of Actinopterygii gills

Gill surface area trends

Fast swimming fish have large gill surface areas (up to 50x more than sedantary “goosefish”)

Inactive fish have low gill surface ares

diagram of shark gills

How do fish move water over the gills? Using what pumps?

Use 1) a buccal pump and 2) an opercular pump

1. Fill mouth cavity (open mouth, expand volume of mouth, expand volume of gill chamber with operculum closed)

2. Fill gill cavity (close mouth, squeeze mouth cavity, expand gill cavity, with operculum closed

3. Expel water from gill cavity (squeeze mouth and gill cavities, open operculum)

4. Reset for next cycl

obligate air breathers and why?

Requires gulps of air to survive

• Water near the surface is more highly oxygenated, and aquatic respiration here could have led to air breathing

• eg. arapima

Anatomical Air Respiration Structure

• Air bubbles in the intestine of a catfish

• Vascularized gut in some catfish absorbs oxygen when air is swallowed

Physostomous swimbladders

modified respiratory organs into swim bladders (ie. Holostei in gar and bowfin)

“walking catfish” have developed

Suprabranchial organ support air breathing

“Labyrinth” fishes have

an accessory labyrinth-like air-breathing organ above the gills

• labyrinth organ

• ie. climbing perch

Labyrinth fish belongs to ___ group

percomorph anabantoid

anabantoid fishes

Air respiration in anabantoid fishes with a labyrinth accessory respiratory organ

Air respiration in lungfishes

Air respiration in Polypterus

recoil aspiration

Two basic physiological principles that you need to understand the swimbladder:

1. Countercurrent exchange

2. The effect of lactic acid on Hemoglobin

Why are fish denser than water?

Because they are made of Bone (2.0 as dense), Muscle (1.05), Cartilage (1.1)

Relative density aka

specific gravity

Relative density / specific gravity is…

the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material

Problem of fish density

Most fish are denser than water, and tend to sink unless they have some way of compensation

How can fish fight their density problem?

Fish can compensate by:

1. Reducing overall body density

2. Generating lift forces when swimming (like an airplane, covered in the locomotion lectures)

How do sharks fight density issue?

Reduce tissue density with special oils like squalene

How do deep-sea fish fight density issue

Reduce tissue density with thin and light bones; watery tissues.

What is squalene?

Oil with very low density that is present in shark livers

Broad phylogenetic patterns of Cyclostomes/Agnatha density

• no gas bladder or lung:

  • individuals are negatively buoyant, and no way to avoid this problem

Broad phylogenetic patterns of Chondrichthyes density

• no gas bladder or lung

• calcified cartilaginous skeleton

• lots of low density oils in the liver

• use fins and body to generate lift during locomotion

Broad phylogenetic patterns of Ray-finned fishes (+Sarcopterygii) density

• gas bladder (=swimbladder) or lung

• living on the bottom – no need for weight reduction

• reduced ossification in many deep-sea fishes

• and increased water content in body tissues

• Also use fins and body to generate lift during locomotion

What is the swimbladder? What is it also called?

aka gas bladder

• a gas inclusion in the body cavity important for buoyancy

Sacropterygii have duct to the lungs on what side?

Ventral duct from the esophagus into the lungs

Ray-finned fishes have duct to the lungs on what side?

Dorsal duct from the esophagus into the lungs

Swimbladder evolution

derived in evolution from ancestral lungs, and serves an important buoyancy function in fishes. It can also be respiratory.

How many chambers do swimbladders have?

commonly between 1-2

What is the swimbladder covered in? Why?

often covered by a thick fibrous coating of connective tissue, and can have a layer of guanine crystals that make it relatively impervious to gas leakage

Facts bout the swimbladder

• Swimbladders have many different shapes and sizes in fishes

• Swimbladders can have muscles attached to them too which can be used to make sounds

• Swimbladder can have air-filled connections to the ear which improves hearing

• The swimbladder can be secondarily vascularized and used as a respiratory organ also (remember air-breathing fishes!)

What is the gas in the swimbladder composed of?

• ~70+ % oxygen, although this varies quite a bit , ~ 20% nitrogen, and a little CO2

Physostomous means what? What fish? What does it look like?

“stomous” = having a “mouth” or opening of some kind

• Filled with gas using the pneumatic duct (has an opening into the esophagus)

ie. soft-rayed teleosts--herrings, salmonids, catfishes, cyprinids, eels, (Otocephala, Elopomorpha), etc.

Physoclistous means what? What fish?

• Filled with gas from the blood/circulatory system

ie. spiny-rayed teleosts—Neoteleost fishes: Acanthopterygii, sunfishes, perch, most marine fishes

Phylogeny of physostomous and physoclistous

What do you know about benthic fishes and swimbladders

No swimbladder at all, would be physoclistous

What problems does having a gas bladder introduce?

1. stability

2. how to adjust the volume (esp. changing depth)

• volume should decrease as they go down

stability-maneuverability tradeoff

• Need constant fin action to maintain posture

• Negatively buoyant; CB below CM

• Very effective at maneuvering and controlling position

Swim bladder and noises

• Swimbladders can make noises

• The posterior duct is used to expel gas from the swimbladder

Why is there a stability problem? What is it the tradeoff called?

• Because of the relative locations of the swimbladder compared to the denser issues, most actinopterygian fish are somewhat unstable in the water

• stability-maneuverability tradeoff

What do you know about hemoglobin?

• can bind 4 oxygen

• BUT in presence of acid, hemoglobin changes shape and oxygens will leave

What is the oval used for?

Gas Reabsorption region taking O2 from dorsal aorta

What is the Rete Mirabale? What does it mean?

“wonderful net”

• Counter current exchange allows gas in the swimbladder to stay there and not diffuse out

• makes the leaving blood acid which causes O2 to dissociate and diffuse down its concentration gradient into the swimbladder

Counter-current exchange allows

1. “isolation” of a region

2. Enhanced exchange of ions, thermal energy, etc. by maintaining an exchange gradient

What does changing the acidity of blood alter?

alters Hb subunit conformation and hence alters the binding properties of oxygen

• Increasing acidity of blood reduces the affinity for Oxygen

• Hb usually binds 4O2

Physoclistous diagram

Physostomous diagram

Counter current exchange diagram