General Characters and Examples - Pisces

PISCES GENERAL ACCOUNT 

• They have streamlined body to cut the water 💦 current.

• They are Poiklothermal or Cold blooded animals.

• They lack the capacity to regulate their body temperature.

• Heart is two-chambered (one auricle and one ventricle). 

• Pisces are divided into  Chondrichthyes and  Osteichthyes

Chondrichthyes

• They are marine animals with streamlined body and have cartilaginous endoskeleton.

• Mouth is located ventrally. 

• Notochord is persistent throughout life. 

• Gill slits are separate and without operculum (gill cover). 

• The skin is tough, containing minute placoid scales. Teeth are modified placoid scales which are backwardly directed. 

• Their jaws are very powerful. These animals are predaceous. 

• Due to the absence of air bladder,  they have to swim constantly to avoid sinking.

• Some of them have electric organs for example Torpedo and some possess poison sting for example Trygon.  

• Sexes are separate. In males pelvic fins bear claspers. 

• They have internal fertilisation and many of them are viviparous.

Example of Chondrichthyes

1.Scoliodon 

• It is commonly called as Dog 🐕 fish.

• Body of Scoliodon is spindle shape and divided into head trunk and tail.

• Body of scoliodon is dorsoventrally compressed and form  snout. It has head , nostril and eyes.

• Body of Scoliodon has lateral fin which include two pectoral and two pelvic fin. 

• It also has an unpaired median fin that include first and second dorsal fin.

• The  tail is heterocercal type.

• Body of scoliodon is covered by the exoskeleton made up of placoid scale which is backward directed.

• Type of Dentition is homodont  and polyphyodont.

• In males Scoliodon,pelvic fins bear claspers. 

• They have cloacal between the  two pelvic fins.

2.Pristis 

• It is commonly called as Saw fish.

• It has flattened body with wing like pectoral fins.

• Mouth and gills are located ventrally and eyes are located dorsally .

• It has a long rostral saw which covers 20 to 30% of body length.

• Saw is widest at the base and comprises 20 to 30  long and sharp teeth. Except Saw teeth , it has additional row of teeth.

• It is ovoviviparous and fertilisation is internal.

• It has large triangular pectoral fin on head. It has two dorsal fin found before the pelvic fin.A  large caudal fin with distinct lobe is present.

• Body is covered by special scales called dermal denticles.

• According to IUCN, sawfish has been included in endangered species.

3.Carcharodon

• It is commonly called as Great white shark.

• It has large bulky body like blunt torpedo. 

• It has conical snout with  large pectoral fin and dorsal fin with crescent shape tail. 

• They are good hunters with strong muscle 💪 with good eye  👁️ sight and strong sense of  smell.

• It has complex circulatory system which store heat generated during swimming by muscles.

• White shark are generally solely but some can swim in pairs.

• Fertilisation is internal. Male insert it's clasper into cloacal of female.

• Reproduction is viviparous because fertilized eggs are retained in body of female for development .

• Body is covered by Placoid  tooth shape scales.

• Sharks have no swim bladder therefore it keep to swim constantly to avoid sinking.

 4.Trygon

• It is commonly called as Sting ray.

• It has kite shape flat  body. Mouth is ventral and rectangular.

• Tail is whip like and long.It terminate into caudal fin at last.

• Head has no rostellum. Pectoral fin are fused with the head.

• Spiracles are present behind the eyes on dorsal side.

• Five pairs gill slits are present on ventral  side for respiration.

• Fertilisation is internal. Male has clasper near pelvic fin and  insert into cloacal of female.

• Reproduction is viviparous because fertilized eggs are retained in body of female for development.

• Body is covered by Placoid  tooth shape scales.

• Trygon  have no air bladder  and operculum. It need  to swim constantly to avoid sinking in absence of air bladder.

• It has a poisonous sting at the base of tail. Sting is a modification of dorsal fin.

5 .Torpedo

• It is commonly called as Electric ray.

• Torpedo has a thick flabby body with. Strong tail.

• Dorsal fin is large round and angular shape. 

• It has an oval  pectoral disc with straight edge.

• Torpedo have small spiracles with small knob.

• Five pairs gill slits are present on under side on disc.

• Torpedo has a  short thick tail With skin fold.

• It has a triangular caudal fin with blunt corner.

• Torpedo  have no air bladder  and operculum. It need  to swim constantly to avoid sinking in absence of air bladder.

• Fertilisation is internal. Male has clasper near pelvic fin and  insert into cloacal of female.

• Reproduction is ovoviviparous because fertilized eggs are retained in body of female for development .

• Body is covered by Placoid  tooth shape scales.

• Electric organ of Torpedo are modified muscle tissue located at the base of pectoral fin. It use these organ to generate the electricity for defence , capturing prey and  to find sensory location.

Osteichthyes

• It includes both marine and fresh water fishes with bony endoskeleton. 

• Their body is streamlined. Mouth is mostly terminal.

• They have four pairs of gills which are covered by an operculum on each side. 

• Skin is covered with cycloid/ctenoid scales. 

• Air bladder is present which regulates buoyancy. 

• Heart is two- chambered (one auricle and one ventricle). 

• They are cold-blooded animals. 

• Sexes are separate. Fertilisation is usually external. They are mostly oviparous and development is direct.

Example of Osteichthyes:  1.Exocoetus 

• It is commonly known as flying fish .

• It has streamlined body to counter the water current.

• It's formed tail  has two lobe. Lower lobe is longer than upper lobe. 

• It has wing like pectoral fin to glide up to more than five hundred feet 

• It has enlarged Pelvic fin therefore called as four wing flying fish.

• Mouth is wide with both teeth and jaws.

• Head is blunt with slopping forehead in front of eyes.

• Fertilisation is external. Male and female release sperm and egg🥚 in water same time.

• Reproduction is oviparous because fertilized eggs are developed into larva called fry .

• Body is covered by cycloid scale with blue and silver white in color on upper and lower side of body respectively.

• It  have  air bladder  and operculum. It maintain buoyancy  to swim constantly due to  presence of air bladder.

2. Hippocampus   

• It is commonly called as Sea Horse and bent horse in Greek.

• Sea horse has horse like head , tubular snout and toothless mouth.

• Tai is prehensile , used to grasp the corals and sea grasses.

• Eyes of Hippocampus are able to move independently to each other.

• Sea horse can change the color to warn the predator through the camouflage.

• It has a cup like depression on the top of head called crown which is unique for sea horse.

• Male sea horse has pouch  on the stomach to carry egg.

• It is found in marine  warm and temperate countries around the corals and sea grasses.

• It uses its dorsal fin to swim rapidly and used its pectoral fin to steer. Caudal fin is absent.

• During mating , female sea horse deposit approx 1500 eggs into male pouch and male show parental care.

3.Labeo

• It is found in fresh water and called as Rohu.

• It has a streamlined elongated body with thick middle and tapering head and tail.

• It has cycloid scale with moderate size.

• It has paired pectoral fin, dorsal fin, ventral fin,  anal fin, caudal fin.

• Mouth is terminal with thick lips 

• Rohu has large eyes without eyelids with transparent cornea.

• It has a pair nostril infront of eyes.

• Large operculum or gill cover is present to cover the gills.

• It has a four pairs of gills slits.

• Skeleton and vertebral column is Bony.

4. Catla

• It is found in fresh water and called as Katla.

• It has a short  body, laterally compressed with  large head

• It has cycloid scale on body but head is devoid of scales.

• It has paired pectoral fin, dorsal fin, anal fin, forked caudal fin.

• Mouth is wide witj prominent lower jaw.

• Catla has large eyes 👀 and visible under the head.

• It has completed lateral line with approx 40 scales.

• Large operculum or gill cover is present to cover the gills.

• It has a three row of pharyngeal teeth with define pattern.

• During Breeding season, male develop  a tough pectoral fin and female develop a pink genital opening on abdomen.

5. Clarias 

• It is commonly called as Magur and  found in fresh water.

• It has a slender  and elongated body. Head is flat with broad mouth.

• The skin is devoid of scales.

• Dorsal and anal  fin is long and without spines.

• Four pairs of Barbles are present around the mouth.

• Pectoral fin is strong and large with the skin.

• It's gill arches are modified into large accessory breathing organ.

• Large operculum or gill cover is present to cover the gills.

• Villiform teeth are present in form of patches on jaws and palate.

6. Betta

• It is commonly called fighting fish and domesticated in aquarium.

• It has a stream line body to swim smoothly.

• The skin is composed  of overlapping scales.

• Beta fish is diurnal, carnivorous and territorial.

• Male individual has well developed feathers.

• These fishes are excellent swimmers and jumpers.

• Life span of Betta fish is 3 to 5 years.

• Male Betta fish build bubble nest.