Respiratory System of Fish Fish : A limbless cold blooded vertebrate animal with gills and fins living wholly in water.

Fish is a high protein , low fat food that provides a range of health benefits. Respiration : Respiration is the biochemical process common to all in which the cell of an organism obtain energy by combining oxygen and glucose resulting in the release of carbon di oxide , water and ATP.

Cell respiration formula :

푪ퟔ푯ퟏퟐ퐎ퟔ + ퟔ푶ퟐ = ퟔ퐂퐎ퟐ + ퟔ퐇ퟐ퐎 + 퐀퐓퐏 Respiratory System : The respiratory system is a biological system consisting of specific organs and structure used for gas exchange in animals.This gas exchange is also called breathing or extarnel respiration. In most fish respiration takes place through gills.Lung fish however posses one or two lungs.The lybrinth fish have developed a special organ that allows them to take advantage of the oxygen of the air , but is not a true lung.

Fish use the process known as countercurrent flow , in which water and blood flow in opposite directions across the gills, maximizing the diffusion of oxygen.

Importance of respiration :  The importance of respiratory system is critical , organism can endure many days without food and sometimes a few without water , but cannot survive for more than a few minutes if respiration ceases.

 It is important because it produces energy that is essential for normal functioning of the body.Respiration provide cells with oxygen and expel toxic carbon di oxide. Difference between terrestrial and aquatic respiration Aquatic respiration Terrestrial respiration  Respiration is through  Respiration is through gills. lungs.  Diffusion of oxygen is less  Air contains more oxygen in water so organism will so organism will not have have to spend more energy to spend more energy  They have leatherly hard  They have a soft slippery or spiny skin. skin Respiratory Mechanism in Fishes ❑ At The Beginning Operculam is Closed and Mouth is Opened By The Action of Elevator Muscle.

❑ Water is Thus Enter Into The Mouth.

❑ The Buccal and Opercular Cavities Begin to Reduce and water Pass Through the Gills and Excreate out ❑ Blood Pumped By Heart Enter The Gills ❑ The Afferent Branchial Arteries Come From The Ventral Aorta. ❑ It Carries Carbon Dioxde Rich Blood From Heart to Gill ❑ The Efferent Branchial Arteries Open Into Dorsal Aorta ❑ It Carries Oxigenated Blood From Gill to The Body ❑ Fish Take Oxygen-Rich Water and Pump it To Gills

❑ When Water Passes Gill Filaments, Blood inside The Capillary Network Picks Up The Dissolved Oxygen.

❑ The Oxygen Then Transported All Over The Body.

❑ While Picking Up Oxygen, Carbon Dioxide Then Removed From The Body Through The Gills. ❑ Haemoglobin is The Main Funtional Unit Of Blood For Exchanging Or Transporting Oxygen

❑ Oxygen Enter The Blood Through a Method Known as Counter Current Mechansm.

❑ Carbon Dioxide Transfer From Blood to Water. TYPES OF RESPIRATION Respiration can be divided into two major types- External respiration Internal Respiration External respiration

 Respiration is a physiological process by which organisms exchange gases specially intake of oxygen and release of carbon dioxide, with the environment. This process is known as external respiration.  In this process gaseous exchange oxygen and carbon dioxide taking place between blood and water or air through the medium of respiratory organs. Internal Respiration

 Internal Respiration is also known as cellular respiration means the oxidization of complex organic substances carbohydrates or fats within cells and tissues for Cabon dioxide and water with relesse of energy.  It is the essential for transfer of gases between blood and tissues of cells of the body. Respiratory organs  The primary respiratory organs of fish's are gills and lungs-  Gills- Gills is the paired respiratory organ of fish by which oxygen in extracted from water flowing over surfaces within or attached to the walls of the pharynx.  In most fish respiration takes place through gills.  These organs located on the sides of the head, are made of gill filaments, feathery structures that provide a large surface for gas exchange. Structure of gill  Gill is structured by –  Gill slits  Pseudobranch  Gill raker  Gill Filaments

• Primary gill lamellae

• Secondary lamellae  Branchial glands  Mucous glands  Chloride Cells Gill slits

 Gill slits are individual opening to gills  There are six or seven pairs of gills in cartilaginous fishes.  In bony fishes there are four pairs of gills.  Gill slits of bony fish are covered by operculum. Pseudobranch

 Pseudobranch is an accessory or spurious gill as on the inner surface of the operculum in various fishes.  It is usually small.  Some times it completely hidden beneath the epithelium.  It supplies highly oxygenated blood to the optic choroid and retina.  It helps in metabolic gas exchange of retina and filling of gas bladder. Gill Raker

 Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch.  It occurs in two rows on the inner margin of each gill orch. Gill filamats

 One of the threadlike processes forming the respiratory surface of a gill.  There are two types of gill filament- primary secondary lamellae. Function of Filament

 Both type of lamellae are used to increase the amount of oxygen intake of the blood.  Contain huge amount of capillaries and are the sites where the exchange of oxygen from the water and Carbon dioxide from the blood. Branchia gland

 These are specialized cells of the epithelium.  They are glandular in nature and perform different function I normal and experimental conditions.  The most common specialized branchial gland are the mucous glands and acidophilic granular cells. Mucous glands

 These gland cells are unicellular.  Typical goblet cell .  They secrete mucus which is glycoproteins both acidic and neutral. Chloride cells

 These cells contain granules, which take acidic stain hence called acidophilic.  They are provided with a large number of mitochondria. There are three general variation in gills found in Fishes-

 Pouched gills  Septal gills  Opercular gills Function of Gills

 Gills are tissue that are like short threads, protein structeres called filaments. These filaments have many function including the – ❑Transfer of ions and waters ❑As well as the exchange of oxygen, carbon dioxide, acids and ammonia. ❑Gills can also be used in excretion of nitrogens water in the form of ammonia regulation of salts in the body. LUNG  Lung is each of the pair of organs which air is drawn so that oxygen can pass into the blood and carbon dioxide be removed.  Which all fish have gills one fish also has lung. The lungfish can survive when its water habited dries up from seasonal drought.  Lung fish have both lungs and gills, and can breath both under the sea and land.  Lung fish is a unique animal.  The “Dipnoi” commonly known as lung fish. Function of lungs

The main function of the lungs is the process o gas exchange called respiration. In respiration, oxygen from incoming air enters the blood, and carbon dioxide a waste gas from the metabolism, leaves the blood.

Accessory Or Extrabranchial Respiration In Fishes ▪ Mainly fishes are gill breathers. Under exceptional environmental condition when branchial respiration is insufficient, they are adopted to aerial respiration. ▪ But in other case fishes use accessory respiratory organ to increase the availability of oxygen. ▪ The usage of accessory respiratory organ prevent death during aestivation. ▪ Mostly air-breathing organs are present in fresh water fishes. The Commonest Air-Breathing Structures Found Among Fishes ➢ Skin ➢ Branchial Epithelium Or Branchial Diverticulam ➢ Pharyngeal Epithelium Or Pharyngeal Diverticulam ➢ Air-Filled Branchial Chamber ➢ Gas bladder And Lung ➢ Intestine Cutaneous Respiration By Skin

Simplest Form of Aerial Respiration. In this case the skin is thin, moist, glandular and richly vascular. The embryos and larvae of many fishes breathe by skin, until gills become functional. Acipenser and some catfishes, the highly vascular opercular fold serve as an accessory respiratory structure. Eg:Anguilla , Periophthalmus , Boleophthalmus. ACIPENCER Anguilla Periophthalmus Boleophthalmus Bucco-Pharyngeal Respiration

➢ Buccal and pharyngeal epithelia are richly vascular that they may serve as a respiratory surface for gas exchange.

➢ Fish may keep its branchial chamber water filled, while going out of water, gill respiration to continue. ➢ Eg :Periophthalmus,Monopterus,Electrophorus Periophthalmus Monopterus Electrophorus Pulmonary Respiration By Gas Bladder

Gas bladder is one of the characteristic feature of the true fishes. It is also regarded as swim bladder or air bladder. Also helps in sound production, sound perception, fat storage. It is an important hydrostatic organ which contains a gas secreting complex, is composed of a gas gland covered with blood vessels.

Thegas bladder of some teleostsplayimportantrolein air- breathing. ( eg: Erythrinus,Gymnarch) Gas bladder Gas bladder Functions of Gas bladder

✓ Sound production • Hydrodynamic : Sound produced as a result of swimming movements particularlywhile rapidchanges in directionor velocityoccurs. • Stridulatory: Sound produced by rubbing of teeth, fin, spines and bones. Eg:Grunts. • By gas bladder: Sound produced by vibrations of striated muscle which originatesfrom dorsal body wall. ✓ Sound reception ✓ Hydrostatic organ Respiration Through Air Reservoirs

➢ In a number of fishes accessory respiratory organs are air sacs or air reservoirs. ➢ They contain specialized air storage to exchange gas. ➢ This functions through extension or outpushing of the branchial chamber, buccal cavity, pharynx, stomach or intestine The commonest type of air reservoirs ❖ Labyrinthine organs ❖ Branchial air tubes ❖ Intestinal air reservoirs Labyrinthine organs These are rosette-like concentric plates of tissue present in the suprabranchial chamber. Respiration takes place when fishes gulp air. Mainly it located one on each side above the gills.

AIR MOUTH PHARYNX AIR CHAMER

OUT SIDE LABYRINTHIN ORGAN BRANCHIAL CHAMBER

Eg: Anabas , Osphronemus, Macropodus , Betta Labyrinthine organs in fishes

Anabas Osphronemus Branchial Air Tubes

➢ It is a long lung like air tubes ➢ The tube situated one on each side of the vertebral column. ➢ They are extension of the branchial chamber and extentend middle of tail. It provides a respiratory surface for gas exchange.

 AIR MOUTH PHARYNX BRANCHIAL CHAMBER

OUT SIDE GILLS BRANCHIAL AIR TUBE

Eg : Heteropneustes Heteropneustes Intestinal Air Reservoirs

➢ Unusual method of air breathing ,specialized vascular pouch present in intestine Eg: Cobitidae,Doras

➢ Rectum is used as an air reservoirs Eg: Cat Fish Callichthys CALLICHTHYS Factors Affecting Respiratory system of Fish  Respiratory system is one of the fundamental needs of a Fish.  The Factors are- ▪ Effects of temperature ▪ Effects of Oxygen content ▪ Effects of Carbon dioxide ▪ Effects of Respirable mateials Adaptation of Air breathing in fish

 Fishes are modified in a Varity of way for the purpose of air breathing.  There are 2 conditions are responsible for such modifications  Oxygen deficiency in the environment  A higher metabolic activity of fish Structural different from lung

 The gills are covered with thik film of mucus which enhances the diffusion of gases as in spiny eels

 Inner surface of gill chambers and operculum is folded and highly vascularised as in mudskippers 2 kinds of modification are seen in fishes for air breathing Those structure which does not involve gas bladder. Those in which gas bladder, gill and lung are used for air breathing . Ram Ventilation

 The production of respiratory flow in some fish in which the mouth is opened during swimming, Such that water flows through the mouth and across the gill.