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Kingdom:Animalia

Phylum:Chordata

Subphylum:Vertebrata

Infraphylum:Gnathostomata

Superclass: Osteichthyes

The Class OsteichthyesThe Class Osteichthyes

• (Greek, Osteon = bone, ichthyes = (Greek, Osteon = bone, ichthyes = fish).fish).

•     The bony fish are the most diverse The bony fish are the most diverse class of vertebrates.  They comprise class of vertebrates.  They comprise more than 95% of all fish and 50% of more than 95% of all fish and 50% of all species of vertebrates.all species of vertebrates.

• consists of the bony fishes and is the consists of the bony fishes and is the largest class of vertebrates, largest class of vertebrates,

• with over 24,000 species. with over 24,000 species.

•Bony fish skeleton is made of bone, which is an important characteristic.

•operculum –a flap on each side of the head that covers the gills. The movements of these flaps allow the fish to breathe without moving.

• Bony fishes range Bony fishes range in size from the in size from the very small very small Philippine Goby Philippine Goby Mugilogobius Mugilogobius parvusparvus ,(topmost) ,(topmost) which is only about which is only about 10 mm long, to the 10 mm long, to the ocean sunfish ocean sunfish Mola Mola molamola, which can , which can grow up to 4 m in grow up to 4 m in length and 1500kg length and 1500kg in weight (bottom). in weight (bottom).

• As well as many As well as many vertebrae for vertebrae for structural support structural support and calcium and calcium storage, the bony storage, the bony fishes have special fishes have special adaptations to adaptations to control their control their buoyancy. A special buoyancy. A special organ called the organ called the swim bladder acts as a gas-filled chamber to control their depth in the water.

THE BONY FISH

• Another prominent feature of the Another prominent feature of the bony fishes is the bony fishes is the operculumoperculum. This . This constitutes the lateral fleshy grooves constitutes the lateral fleshy grooves on the fish that cover the chambers on the fish that cover the chambers housing the housing the gills. The operculum allows the fish to breathe (even if it is not swimming) by moving water currents over the gills. Other features include paired fins, dermal scales in the skin (in most species) and numerous vertebrae.

Major Sub-groups in the Major Sub-groups in the PhylumPhylum

There are two subclasses of There are two subclasses of Osteichthyes: Osteichthyes:

• ACTINOPTERYGII- ray-finned fish ACTINOPTERYGII- ray-finned fish

• SARCOPTERYGII- lobe-finned fish SARCOPTERYGII- lobe-finned fish

• 1.1.

ACTINOPTERYGII ACTINOPTERYGII

• The ray-finned fishesThe ray-finned fishes

• are very diverse and successful, are very diverse and successful, especially the teleosts, and can be especially the teleosts, and can be found in nearly all aquatic found in nearly all aquatic environments.environments.

•are oviviparous and lay many thousands of tiny eggs at one time, which are then fertilized externally.

ACTINOPTERYGII- infraclassACTINOPTERYGII- infraclass

• Most chondrostean species lived during Most chondrostean species lived during the late the late Palaeozoic. There are only two . There are only two chondrostean lineages that survive today, chondrostean lineages that survive today, the paddlefish of Canada and China and the paddlefish of Canada and China and the sturgeons of Europe, Asia and Canada.the sturgeons of Europe, Asia and Canada.

• Both lineages have secondarily lost a Both lineages have secondarily lost a number of their actinopterygian number of their actinopterygian characters: characters:

• scales lost on most of the body, scales lost on most of the body, • cartilaginous skeleton, cartilaginous skeleton, • shark-like, heterocercal tail, shark-like, heterocercal tail, • rostrum extending past the mouth, which rostrum extending past the mouth, which

forms the paddle of the paddlefish. forms the paddle of the paddlefish.

PADDLE FISH

LAKE STURGEON

• The holosteans arose in the The holosteans arose in the Permian. .

• They succeeded the Chondrosteans as They succeeded the Chondrosteans as the dominant fishes in the middle of the the dominant fishes in the middle of the Mesozoic. Even fewer holosteans than . Even fewer holosteans than chondrosteans survive today. These chondrosteans survive today. These include the bowfin include the bowfin AmiaAmia of eastern of eastern Canada, and seven species of garpikes Canada, and seven species of garpikes ((LepisosteusLepisosteus and and AtractosteusAtractosteus) from ) from North and Central America. North and Central America.

• share with other primitive fishes a share with other primitive fishes a mixture of characteristics of mixture of characteristics of teleosts and and sharks

Longnose Gar

Bow fin

• Holosteans have more advanced jaws Holosteans have more advanced jaws than the chondrosteans. The posterior than the chondrosteans. The posterior end of the maxilla is free, which allows end of the maxilla is free, which allows it to swing forward, stretching the fold it to swing forward, stretching the fold of skin. Instead of snapping the mouth of skin. Instead of snapping the mouth shut, the fish produces a powerful shut, the fish produces a powerful sucton. Jaws are shorter and better sucton. Jaws are shorter and better supported and the scales tend to lose supported and the scales tend to lose their shiny ganoid covering. From the their shiny ganoid covering. From the Jurassic onwards, the holosteans onwards, the holosteans dominated the world oceans, but, they dominated the world oceans, but, they became rare in the became rare in the Cretaceous and and are now largely extinct. are now largely extinct.

• The numbers of teleost species far exceed those of The numbers of teleost species far exceed those of any other fish group, as 96% of living fishes are any other fish group, as 96% of living fishes are teleosts. They are the most successful fish group teleosts. They are the most successful fish group since their radiation in the since their radiation in the Cretaceous. Teleosts have . Teleosts have been found to survive in freezing Antarctic waters, in been found to survive in freezing Antarctic waters, in hot springs (up to 44 oC), in alkaline lakes, in acid hot springs (up to 44 oC), in alkaline lakes, in acid streams, in the deep sea and in shallow rivers.streams, in the deep sea and in shallow rivers.

• By the end of the Cretaceous, teleosts had become By the end of the Cretaceous, teleosts had become the dominant fishes in both the oceans and in the dominant fishes in both the oceans and in freshwater habitats. Teleosts are characterized by a freshwater habitats. Teleosts are characterized by a fully movable maxilla and premaxilla (which form the fully movable maxilla and premaxilla (which form the biting surface of the upper jaw); the movable upper biting surface of the upper jaw); the movable upper jaw makes it possible for teleosts to protrude their jaw makes it possible for teleosts to protrude their jaws when opening the mouth. Teleosts are also jaws when opening the mouth. Teleosts are also distinguished by having fully distinguished by having fully homocercalhomocercal (symmetrical) tails.(symmetrical) tails.

• Teleosts include eels, catfish, tarpon, tuna, halibut, Teleosts include eels, catfish, tarpon, tuna, halibut, flounder, trout, cod, herring, salmon, and many other flounder, trout, cod, herring, salmon, and many other fishes.fishes.

2.

SARCOPTERYGIISARCOPTERYGII

• The lobe-finned bony fishes. The The lobe-finned bony fishes. The sarcopteryians are a very ancient sarcopteryians are a very ancient subclasses of fishes with three orders: subclasses of fishes with three orders: RHIPIDISTIA, , ACTINISTIA, and , and DIPNOI. . All sarcopterygians are viviparous, i.e. All sarcopterygians are viviparous, i.e. they give birth to one or two highly they give birth to one or two highly developed young at one time. developed young at one time.

1.1.

• The rhipidistians are a The rhipidistians are a mixed group of lobe-mixed group of lobe-finned fishes that form finned fishes that form outgroups ('ancestors') outgroups ('ancestors') to the two main living to the two main living groups, the Actinistia groups, the Actinistia and the Dipnoi. and the Dipnoi. Rhipistians also include Rhipistians also include ancestors of the ancestors of the tetrapods. These fish tetrapods. These fish groups - such as the groups - such as the porolepiform porolepiform HoloptychiusHoloptychius and the and the osteolepiform osteolepiform EusthenopteronEusthenopteron, were , were restricted in time mainly restricted in time mainly to the Devonian, with a to the Devonian, with a few survivors into the few survivors into the Carboniferous. .

The tristichopterid 'rhipidistian' Eusthenopteron

•Rhipidistian characters that ally Rhipidistian characters that ally them with tetrapods are seen them with tetrapods are seen in the arrangement of the in the arrangement of the bones in the skull and in their bones in the skull and in their lobe fins - many details of the lobe fins - many details of the skeleton of the pectoral and skeleton of the pectoral and pelvic fins match fairly closely pelvic fins match fairly closely the bones in the forelimb and the bones in the forelimb and hindlimb of tetrapods. hindlimb of tetrapods.

2.2.

• The coelacanths arose in the The coelacanths arose in the Devonian. . They are characterized by their three-They are characterized by their three-lobed tail: the tail is symmetrical, with a lobed tail: the tail is symmetrical, with a curved upper and lower section, and a curved upper and lower section, and a longer, projecting, rather lobed middle longer, projecting, rather lobed middle portion. Famously, the coelacanths were portion. Famously, the coelacanths were thought to have gone extinct in the thought to have gone extinct in the Cretaceous, when the laast fossils are Cretaceous, when the laast fossils are found. But then in 1938, a living (or found. But then in 1938, a living (or recently dead) specimen of a 2-metre-recently dead) specimen of a 2-metre-long coelacanth was fished up in the long coelacanth was fished up in the Indian Ocean, off East Africa. Since 1938, Indian Ocean, off East Africa. Since 1938, as many as 200 specimens of the living as many as 200 specimens of the living coelacanth, coelacanth, LatimeriaLatimeria, have been found, , have been found, some of them now off Indonesia. some of them now off Indonesia.

A specimen of the living A specimen of the living coelacanth coelacanth LatimeriaLatimeria

3.3.

• The lungfishes also arose in The lungfishes also arose in the the Devonian, when forms , when forms such as such as DipterusDipterus were were important predators. Since important predators. Since the Devonian, lungfishes the Devonian, lungfishes evolved specialized tooth evolved specialized tooth plates, and other plates, and other characters, so they had characters, so they had most of their modern most of their modern features by the Permian. features by the Permian. Today there are three Today there are three species of lungfishes, living species of lungfishes, living in Australia, souther Africa, in Australia, souther Africa, and South America. and South America. Lungfishes do indeed have Lungfishes do indeed have lungs, as do all the other lungs, as do all the other sacropterygians. Indeed, sacropterygians. Indeed, lungs were probably present lungs were probably present in most basal osteichthyans, in most basal osteichthyans, and they have simply been and they have simply been lost subsequently in the lost subsequently in the actinopterygians. actinopterygians.

BIOLOGY•All bony fish possess gills. For the majority

this is their sole or main means of Respiration. Lungfish and other osteichthyan species, are capable of respiration through lungs or vascularized swim bladders. Other species can respire through their skin, intestines, and/or stomach

•ectothermic – cold-blooded•They can be any type of heterotroph:

omnivore, carnivore, herbivore, or detrivore.

•Some bony fish are hermaphrodites, and a number of species exhibit parthenogenesis

• Fertilization is usually external, but can be internal. Development is usually oviparous (egg-laying) but can be ovoviviparous, or viviparous.

1.1. Primitive fishes date back to the Primitive fishes date back to the Cambrian period, about 550 million Cambrian period, about 550 million years ago. These jawless fishes lived years ago. These jawless fishes lived relatively unchanged over the relatively unchanged over the following 100 million years.following 100 million years.

2.2. The Devonian period, about 360 to The Devonian period, about 360 to 400 million years ago, is known as 400 million years ago, is known as the "Age of Fishes", because of the the "Age of Fishes", because of the abundance and diversity of fishes abundance and diversity of fishes that appeared during this period.that appeared during this period.

• In the Devonian, fishes began to develop jaws and paired fins. All four living classes of fishes and the three subclasses of Osteichthyes were established by the mid-Devonian.

• Bony fishes continued to evolve after the Devonian period.

• Most modern orders of bony fishes probably evolved during the Triassic period, about 200 million years ago.

• Today, the Actinoptergians are the dominant vertebrates in the oceans and in freshwater systems.

• The Devonian sarcopterygians included The Devonian sarcopterygians included lungfishes and coelacanths, both groups lungfishes and coelacanths, both groups still surviving. But modern lungfishes still surviving. But modern lungfishes and coelacanths are a modest remnant and coelacanths are a modest remnant of once-diverse groups, and they are of once-diverse groups, and they are often called 'living fossils'. The other often called 'living fossils'. The other Devonian sarcipterygians are often Devonian sarcipterygians are often grouped loosely as the 'rhipidistians', a grouped loosely as the 'rhipidistians', a paraphyletic ('incomplete') group that paraphyletic ('incomplete') group that includes forms such as the includes forms such as the osteoelpiforms, tristichopterids and osteoelpiforms, tristichopterids and panderichthyids, that lie on the line of panderichthyids, that lie on the line of ancestry to the tetrapods. ancestry to the tetrapods.

• Early actinopterygians, such as the Devonian Early actinopterygians, such as the Devonian CheirolepisCheirolepis, had heavy bony scales over the , had heavy bony scales over the whole body, and large bony plates over the head whole body, and large bony plates over the head region. The jaws operated as a simple hinge, region. The jaws operated as a simple hinge, with modest movements of other skull bones to with modest movements of other skull bones to widen the gape. Late actinopterygians had more widen the gape. Late actinopterygians had more complex jaw apparatuses that allowed them to complex jaw apparatuses that allowed them to project the jaws forward and to use suction in project the jaws forward and to use suction in feeding. This perhaps was one of the keys to the feeding. This perhaps was one of the keys to the success of the teleosts, which arose in the success of the teleosts, which arose in the Triassic or Jurassic, but radiated dramatically in Triassic or Jurassic, but radiated dramatically in the Cretaceous and Tertiary. the Cretaceous and Tertiary.

• Fossil species from all sub-groups -the Fossil species from all sub-groups -the Chondrosteans, the , the Holosteans, the , the Teleosteans, , Rhipidistia, , Actinistia, and , and Dipnoi- have been - have been identified. identified.

Lionfish

Blackeye goby

DID YOU KNOW????

•The largest bony fish ever was Leedsichthys

•The ocean sunfish is the largest bony fish in the world

•while the longest is oarfish

•The smallest fish is Philippine goby

...FIN.....FIN..

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