Aquatic respiration of Aquatic respiration of vertebrates and vertebrates and

physiological implications physiological implications of aquatic respirationof aquatic respiration

Nandana

By: Nandana Nayana KumaraUniversity of KelaniyaSri LankaStudent # BS/A002/066

1/7/20071/7/2007 22

Aquatic vertebrates rely on following Aquatic vertebrates rely on following surfaces for gas exchange,surfaces for gas exchange,

Cutaneous body surfaceCutaneous body surface External filamentous gillsExternal filamentous gills Internal lamellar gillsInternal lamellar gills

1/7/20071/7/2007 33

Cutaneous respirationCutaneous respiration

Ex- eels, some catfish, bullheads, some Ex- eels, some catfish, bullheads, some fish larvae, Salamanders (ex-siren), frogs fish larvae, Salamanders (ex-siren), frogs

1/7/20071/7/2007 44

Significance of cutaneous Significance of cutaneous respiration is determined by,respiration is determined by,

Favorable ratio of body mass Favorable ratio of body mass to surface area to surface area (folding of skin-ex hellbender (folding of skin-ex hellbender salamander, Telmatobius, salamander, Telmatobius, cylindrical ones has less cylindrical ones has less surface/volume)surface/volume)

Thickness of the skinThickness of the skin Proximity of capillaries to the Proximity of capillaries to the

surfacesurface Whether the circulatory system Whether the circulatory system

is well developed or notis well developed or not Body movements- prevent Body movements- prevent

boundary layer of low DOboundary layer of low DO

1/7/20071/7/2007 55

Using external filamentous gills,Using external filamentous gills,

Present in few vertebrates, usually during Present in few vertebrates, usually during periods of increased activity and Operiods of increased activity and O22 demand. demand.

E.g.- E.g.- Elasmobranch embryos have filamentous gills Elasmobranch embryos have filamentous gills

that extend from their internal gill chamber into that extend from their internal gill chamber into the surrounding albuminous fluid.the surrounding albuminous fluid.

Adult male lung fish has filamentous gills on their Adult male lung fish has filamentous gills on their pelvic fins at the time of nest building. pelvic fins at the time of nest building.

Many aquatic salamandersMany aquatic salamanders

1/7/20071/7/2007 66

Using external……cont’dUsing external……cont’d

Some cat fish, sturgeons, paddlefish and Some cat fish, sturgeons, paddlefish and climbing perch have filaments of vascular climbing perch have filaments of vascular epithelium in their branchial chambers for gas epithelium in their branchial chambers for gas exchanging when they air breath. exchanging when they air breath.

Male African ‘Hairy frog’ develops numerous Male African ‘Hairy frog’ develops numerous highly vascularized filaments of skin during the highly vascularized filaments of skin during the breeding season.breeding season.

Larval amphibians (tadpoles) have external gills, Larval amphibians (tadpoles) have external gills, (in some they disappear when they (in some they disappear when they metamorphose and in others it’s not)metamorphose and in others it’s not)

Adult Adult NecturusNecturus (mud puppy) (mud puppy)

1/7/20071/7/2007 77

1/7/20071/7/2007 88

Using internal lamellar gills,Using internal lamellar gills,

Most fish rely on internal lamellar gills for Most fish rely on internal lamellar gills for respirationrespiration

1/7/20071/7/2007 99

CyclostomesCyclostomes (lamprey and hag fish)(lamprey and hag fish)

They have 6-14 They have 6-14 pairs of gill pairs of gill pouches that pouches that extend from the extend from the pharynx.pharynx.

1/7/20071/7/2007 1010

ElasmobranchElasmobranch and and TeleostTeleost fish fish

They have a They have a considerably considerably more elaborate more elaborate gill structure than gill structure than do cyclostomes.do cyclostomes.

1/7/20071/7/2007 1111

Thin epithelial Thin epithelial cell layers of cell layers of lamellae are lamellae are separated by separated by pillar cellspillar cells, which , which have have extensionsextensions that contact that contact adjacent pillar adjacent pillar cells and cells and surround the surround the capillaries. capillaries.

1/7/20071/7/2007 1212

Active fish tend Active fish tend to have more to have more gill filaments gill filaments and more and more secondary secondary lamellae than lamellae than do sluggish fish do sluggish fish and air and air breathing fish. breathing fish.

1/7/20071/7/2007 1313

Gill surface area is Gill surface area is highly correlated highly correlated with body mass. with body mass.

Slope is usually Slope is usually about 0.7-0.8about 0.7-0.8

Intercept varies for Intercept varies for different taxadifferent taxa

1/7/20071/7/2007 1414

Diffusion path lengthDiffusion path length

The diffusion path length between water and The diffusion path length between water and lamellar blood is also significant in determining lamellar blood is also significant in determining the rate of oxygen exchange, since influx is the rate of oxygen exchange, since influx is inversely proportional to diffusion path length. inversely proportional to diffusion path length.

As a result, path length is quite low in both As a result, path length is quite low in both active fish and sluggish fish. active fish and sluggish fish.

Laminar boundary layer due to water flow over Laminar boundary layer due to water flow over the gill tissue and mucus layers also reduce the the gill tissue and mucus layers also reduce the gas exchange. gas exchange.

1/7/20071/7/2007 1515

Types of gill ventilationTypes of gill ventilation

Buccal-opercular Buccal-opercular pumpingpumping In teleost fish, a In teleost fish, a

complex coordination complex coordination of expansion and of expansion and contraction of buccal contraction of buccal and opercular and opercular chambers maintains chambers maintains anan almost continuousalmost continuous one-way flow of water one-way flow of water over the gillsover the gills. .

1/7/20071/7/2007 1616

Ram ventilationRam ventilation Elasmobranchs draw water into the buccal cavity by Elasmobranchs draw water into the buccal cavity by

negative pressure and then force the water through negative pressure and then force the water through the gill filaments to the outside. This type of the gill filaments to the outside. This type of forced forced ventilation is called as ram ventilationventilation is called as ram ventilation..

Also Also many active fish use ram ventilationmany active fish use ram ventilation as an as an

alternative means of gill ventilation. These alternative means of gill ventilation. These active fish active fish swim with their mouth open, and water is forced over swim with their mouth open, and water is forced over the gillsthe gills without buccal or opercular pumping. without buccal or opercular pumping.

The energy for water flow over the gills is derived from The energy for water flow over the gills is derived from the swimming muscles, rather than the buccal and the swimming muscles, rather than the buccal and opercular muscles.opercular muscles.

1/7/20071/7/2007 1717

Many fish utilize buccal opercular pumping Many fish utilize buccal opercular pumping when stationary or swimming slowly and when stationary or swimming slowly and use ram ventilation at higher swimming use ram ventilation at higher swimming speeds; there is a transition stage speeds; there is a transition stage between these two methods. between these two methods.

Many active fish (e.g. Tuna) can’t maintain Many active fish (e.g. Tuna) can’t maintain sufficient gill ventilation by buccal-sufficient gill ventilation by buccal-opercular pumping and suffocate if forced opercular pumping and suffocate if forced to stop swimming.to stop swimming.

1/7/20071/7/2007 1818

The rate of water flow over the gills is The rate of water flow over the gills is related to the body size, the metabolic related to the body size, the metabolic demand, and the extent of Odemand, and the extent of O22 extraction extraction from the water. from the water.

1/7/20071/7/2007 1919

Blood flow through the gill lamellae is Blood flow through the gill lamellae is generally in a generally in a countercurrent directioncountercurrent direction to the water flow because this provides a to the water flow because this provides a high efficiency of Ohigh efficiency of O22 exchange from water exchange from water to blood, if the rates of gill water flow and to blood, if the rates of gill water flow and blood flow are suitably maintained. blood flow are suitably maintained.

The The optimal ventilation/perfusion ratiooptimal ventilation/perfusion ratio is is about 10 to 20 because water has a lower about 10 to 20 because water has a lower OO22 carrying capacity than blood. carrying capacity than blood.

1/7/20071/7/2007 2020

OO22 extraction efficiency (E) of extraction efficiency (E) of gillsgills

Percentage of OPercentage of O22 removed from the removed from the incurrent water flow, relative to the incurrent water flow, relative to the incurrent Oincurrent O22 content content

E= 100(PE= 100(PiiOO22- PeO- PeO22) /P) /PiiOO22

Where, PiOWhere, PiO22 is the incurrent PO is the incurrent PO22 and and PeOPeO22 is the excurrent PO is the excurrent PO22

Values for fish gills are typically 20-60%, Values for fish gills are typically 20-60%, and a similar range is found for and a similar range is found for invertebrates. invertebrates.

1/7/20071/7/2007 2121

Gill water flow is determined by, Gill water flow is determined by, • resistance to water flow resistance to water flow • pressure gradient across gillspressure gradient across gills

The effect of gill resistance is much The effect of gill resistance is much greater due to high surface area of the greater due to high surface area of the lamellae and narrow interlamellar spaces. lamellae and narrow interlamellar spaces.

So, gill water flow is primarily determined So, gill water flow is primarily determined by the gill resistance. by the gill resistance.

1/7/20071/7/2007 2222

Anatomical dead spaceAnatomical dead space

Not all the water flowing through the gills is Not all the water flowing through the gills is available for gas exchange. available for gas exchange.

Some water flows out between the ends of Some water flows out between the ends of the gill lamellae form adjacent gill arches. the gill lamellae form adjacent gill arches. This fraction of gill water flow is called as This fraction of gill water flow is called as the the anatomical dead spaceanatomical dead space. .

1/7/20071/7/2007 2323

Physiological dead spacePhysiological dead space

Not all the water flowing between the lamellae is Not all the water flowing between the lamellae is necessarily involved in gas exchange. necessarily involved in gas exchange.

A A wide spacing of lamellaewide spacing of lamellae, exceeding 2× the , exceeding 2× the water boundary layer thickness, allows the water boundary layer thickness, allows the central stream of water to pass through the gills central stream of water to pass through the gills without exchanging any Owithout exchanging any O22; this is called ; this is called Physiological dead space Physiological dead space

Another source of dead space is a Another source of dead space is a nonoptimal nonoptimal ventilation/perfusion ratioventilation/perfusion ratio (V (VWW/V/Vbb).).

1/7/20071/7/2007 2424

1/7/20071/7/2007 2525

Fick’s law of diffusionFick’s law of diffusion VOVO22=DA (C=DA (C22-C-C11)/x)/xWhere,Where, VOVO22 is the oxygen consumption rate (mlO is the oxygen consumption rate (mlO22/min)/min) D is the diffusion coefficient (constant)D is the diffusion coefficient (constant) A is the diffusion areaA is the diffusion area (C2-C1)/x is the concentration gradient(C2-C1)/x is the concentration gradient

For a particular species For a particular species A is increased only due to a A is increased only due to a chronic increased demand of Ochronic increased demand of O22. For example the . For example the lengths of external gill filaments are increased in some lengths of external gill filaments are increased in some amphibians in response to hypoxia. amphibians in response to hypoxia.

So the most appropriate way to increase oxygen uptake So the most appropriate way to increase oxygen uptake at instant increased demand is increasing the at instant increased demand is increasing the concentration gradient. Many fish increase this by concentration gradient. Many fish increase this by increasing both rate and stroke volumeincreasing both rate and stroke volume. .

1/7/20071/7/2007 2626

Regulation of respiration in Regulation of respiration in aquatic vertebratesaquatic vertebrates

Matching of respiratory ventilation with the metabolic Matching of respiratory ventilation with the metabolic demand requires a regulatory system. demand requires a regulatory system.

A respiratory system generally has,A respiratory system generally has,• Pacemaker neuronsPacemaker neurons – spontaneous activity, produce – spontaneous activity, produce

basic respiratory cyclebasic respiratory cycle• Respiratory regulatory systemsRespiratory regulatory systems with sensory detectors with sensory detectors

and a motor effector systemand a motor effector system A sensory system monitoring the decline in blood or A sensory system monitoring the decline in blood or

branchial pObranchial pO22 rather than pCO rather than pCO22 would be most would be most appropriate for aquatic animals because the pCOappropriate for aquatic animals because the pCO22 increase only slightly due to its high solubility. increase only slightly due to its high solubility.

In fish pOIn fish pO22 receptors are usually in the buccal cavity, receptors are usually in the buccal cavity, gills, opercular cavity, arterial blood vessels, venous gills, opercular cavity, arterial blood vessels, venous vessels or brain.vessels or brain.

1/7/20071/7/2007 2727

Many stimuli other than pOMany stimuli other than pO22 and pCO and pCO22 influence influence the respiratory rhythm, e.g., stretch of the the respiratory rhythm, e.g., stretch of the branchial cavity, osmotic stress, mechanical branchial cavity, osmotic stress, mechanical stress, chemical stimuli, temperature etc stress, chemical stimuli, temperature etc

Temperature has two important influences on Temperature has two important influences on respiration. respiration.

An increase in temperature An increase in temperature lowers the oxygen lowers the oxygen content of the watercontent of the water and at the same time and at the same time increases the metabolic rate because of higher increases the metabolic rate because of higher body temperaturebody temperature; both effects increase the ; both effects increase the respiratory demand. respiratory demand.

1/7/20071/7/2007 2828

Physiological implications of Physiological implications of aquatic respiration aquatic respiration

1/7/20071/7/2007 2929

The physiological properties of water determine The physiological properties of water determine many aspects of the design and functioning of many aspects of the design and functioning of aquatic gas exchange systems. aquatic gas exchange systems.

Water is dense and viscous, with a low OWater is dense and viscous, with a low O22 availability. availability.

The water flow over a gill is unidirectional to The water flow over a gill is unidirectional to avoid the energy cost of reversing the water avoid the energy cost of reversing the water flow. flow.

This one way flow of water makes it This one way flow of water makes it mechanically practical to have a countercurrent mechanically practical to have a countercurrent flow of blood and this can greatly increase the flow of blood and this can greatly increase the physiological efficiency of gas exchange. physiological efficiency of gas exchange.

1/7/20071/7/2007 3030

The flow of water over the respiratory The flow of water over the respiratory surface should be about 20 times more surface should be about 20 times more than the blood flow through the respiratory than the blood flow through the respiratory surface. surface.

There is a high metabolic cost to aquatic There is a high metabolic cost to aquatic respiration because water is a dense, respiration because water is a dense, viscous fluid.viscous fluid.

1/7/20071/7/2007 3131

The low OThe low O22 content of water (relative to content of water (relative to air) and high cost of ventilation generally air) and high cost of ventilation generally limits aquatic animals to having a low limits aquatic animals to having a low metabolic rate. metabolic rate.

The high heat capacity of water generally The high heat capacity of water generally precludes thermoregulation by aquatic precludes thermoregulation by aquatic animals because the metabolic heat is animals because the metabolic heat is rapidly dissipated into the water ventilated rapidly dissipated into the water ventilated through the gills. through the gills.

1/7/20071/7/2007 3232

Thank you for your attention