The living fossils: coelacanth

Celeste ThomasCeleste ThomasDepartment of biodiversity and conservation biologyDepartment of biodiversity and conservation biology

University of the western capeUniversity of the western capePrivate bag x17Private bag x17Bellville 7535Bellville 7535

2324851@uwc.ac.za

The coelacanth classification are as follows.The coelacanth classification are as follows. Kingdom: animalia Kingdom: animalia Phylum : chordate Phylum : chordate Class : sarcoterygii Class : sarcoterygii Order : coelacathiformesOrder : coelacathiformes Family : latimeriidae Family : latimeriidae Genus : Genus : latimerialatimeria

http:// en.wikipedia.org/wiki/coelacanthhttp:// en.wikipedia.org/wiki/coelacanth

The living vertebrates consists mainly of two groups in the modern The living vertebrates consists mainly of two groups in the modern classification.classification.

The Gnasthostomata and the jawless Agnatha are divided into two The Gnasthostomata and the jawless Agnatha are divided into two groups cartilaginous chondrithyes and bony Osteichthyes.groups cartilaginous chondrithyes and bony Osteichthyes.

The actinopterygii and sarcpoterygii are the two main groups of the The actinopterygii and sarcpoterygii are the two main groups of the bony vertebrates.bony vertebrates.

The latter comprises of three groups the coelacanth, lungfishes and The latter comprises of three groups the coelacanth, lungfishes and the four-limbed tetrapods.the four-limbed tetrapods.

The sarcopterygii is applied to a group comprising the coelacanth The sarcopterygii is applied to a group comprising the coelacanth and the lungfishes.and the lungfishes.

A modern scientist J L B Smith thus believed that four-legged land A modern scientist J L B Smith thus believed that four-legged land dwellers evolved from the extinct groups like the coelacanth.dwellers evolved from the extinct groups like the coelacanth.

However, although the coelacanth share characteristics with early land However, although the coelacanth share characteristics with early land dwellers the lungfishes shared more.dwellers the lungfishes shared more.

Thus few scientist believe that the coelacanth is the missing link.Thus few scientist believe that the coelacanth is the missing link. The research that has been done showed that the coelacanth latimeria The research that has been done showed that the coelacanth latimeria

chalumnae has not radically evolved from the way coelacanths chalumnae has not radically evolved from the way coelacanths appeared millions of years ago.appeared millions of years ago.

Thus by studying latimeria chlumnae is studying an ancient fossil that is Thus by studying latimeria chlumnae is studying an ancient fossil that is alive. alive.

The Crossopterygii and Dipnoi were the only vertebrates orders between The Crossopterygii and Dipnoi were the only vertebrates orders between Devonian period and recent times.Devonian period and recent times.

The choanichthyes is made up by crosspterygii and dipnoi.The choanichthyes is made up by crosspterygii and dipnoi. The rhipidistia and coelacanthini are two suborders included in The rhipidistia and coelacanthini are two suborders included in

crossopterygii.crossopterygii. The rhipistians however, became extinct in early Permian.The rhipistians however, became extinct in early Permian. Even though the rhipidistians became extinct in the early Permian, they Even though the rhipidistians became extinct in the early Permian, they

were important because they gave rise to the tetrapods as well as to the were important because they gave rise to the tetrapods as well as to the coelacanths.coelacanths.

The lungfishes were derived from the primitive rhisidistians or from their The lungfishes were derived from the primitive rhisidistians or from their common ancestral group. common ancestral group.

In the middle Devonian were the coelacanth already well defined.In the middle Devonian were the coelacanth already well defined. http://links.jstor.org/sici=0.014-3820(195203)

Thus the coelacanths studied by scientist since 1839 were only Thus the coelacanths studied by scientist since 1839 were only through their fossils.through their fossils.

The fossil fish Coelacanthus granulatus were found by Louis Agassiz.The fossil fish Coelacanthus granulatus were found by Louis Agassiz. Over the next century scientists had found fossils of dozens of species Over the next century scientists had found fossils of dozens of species

of coelacanth. of coelacanth. 400 million years ago was the appearance of the earliest fossils, while 400 million years ago was the appearance of the earliest fossils, while

the most recent were 70 million years ago.the most recent were 70 million years ago. Thus according to the fossils record coelacanths disappeared Thus according to the fossils record coelacanths disappeared

completely.completely.

Although only two representatives present, as a group the Although only two representatives present, as a group the coelacanths were once successful. coelacanths were once successful.

These species left abundant fossil record from Devonian to the These species left abundant fossil record from Devonian to the cretaceous period.cretaceous period.

The coelacanth have been known to remain unchanged for millions The coelacanth have been known to remain unchanged for millions of years. of years.

Macropoma a extinct genus of crustaceous resembled the living Macropoma a extinct genus of crustaceous resembled the living specie.specie.

http://en.wikipedia.org/wiki/Coelacanth#Biological_characteristcs

Marjorie courtenary-latimer were first person that discovered the Marjorie courtenary-latimer were first person that discovered the specimen in 1938 in coastal waters of South African.specimen in 1938 in coastal waters of South African.

The coelacanth were not particularly successful in total numbers of The coelacanth were not particularly successful in total numbers of distinct genera even in spit of their long history.distinct genera even in spit of their long history.

http://en.wikipedia.org/wiki/Coelacanth#Biological_characteristcs

The diversity of these fishes reached a peak in Triassic, only with 11 The diversity of these fishes reached a peak in Triassic, only with 11 genera of this period.genera of this period.

The Devonian coelacanth has been found in marine formations suggesting The Devonian coelacanth has been found in marine formations suggesting marine origin. marine origin.

Thus negative evidence were available that showed coelacanth deserted Thus negative evidence were available that showed coelacanth deserted marine environment by missippian. marine environment by missippian.

The carboniferous and Permian coelacanths occurred in freshwater The carboniferous and Permian coelacanths occurred in freshwater sediments and Triassic genera were about 60% marine.sediments and Triassic genera were about 60% marine.

The lungfishes were equally well defined group.The lungfishes were equally well defined group. They arose in early Devonian having same total number of genera like They arose in early Devonian having same total number of genera like

coelacanthini.( http://links.jstor.org/sici=0.014-3820(195203)coelacanthini.( http://links.jstor.org/sici=0.014-3820(195203)

Major unique features are present that distinguishes among the Major unique features are present that distinguishes among the coelacanth and other fishes.coelacanth and other fishes.

This involves aspects like external forms, skeleton anatomy etc.This involves aspects like external forms, skeleton anatomy etc. The feature in the coelacanth in particular being the extra tail the The feature in the coelacanth in particular being the extra tail the

epicaudal.epicaudal. The fins of coelacanth are also different instead of 1 dorsal fins they have The fins of coelacanth are also different instead of 1 dorsal fins they have

2. 2. Dentricales are present which aids in protection.Dentricales are present which aids in protection.

http://www.pds.org/gbh/nova/fishhttp://www.pds.org/gbh/nova/fish

The skeleton of the coelacanth was also different from modern fishes.The skeleton of the coelacanth was also different from modern fishes. The skeleton were made mostly of cartilage.The skeleton were made mostly of cartilage. A notochord, which are fibrous, elasticity are usually thick walled in A notochord, which are fibrous, elasticity are usually thick walled in

coelacanth.coelacanth. Thus most creatures with backbones, have vertebrae which replaces their Thus most creatures with backbones, have vertebrae which replaces their

notochord.notochord.

The head region of the coelacanth is also a mystery.The head region of the coelacanth is also a mystery. It is occupied by 6 small holes , two near each eye and two towards the tip It is occupied by 6 small holes , two near each eye and two towards the tip

of the snout.of the snout. This identification was never observed in coelacanth fossils.This identification was never observed in coelacanth fossils. These strange holes led to a space in the coelacanths head in which this These strange holes led to a space in the coelacanths head in which this

cavity had never been seen in a living fish.cavity had never been seen in a living fish. The six holes were an outer opening of a tube filled with jelly-like The six holes were an outer opening of a tube filled with jelly-like

substances. substances. The rostral organ are formed together by the tube and cavity .The rostral organ are formed together by the tube and cavity . Thus this organ has unique functions which are not observed in modern Thus this organ has unique functions which are not observed in modern

fishes.fishes.

The eye features of the coelacanth is normally large which is attached The eye features of the coelacanth is normally large which is attached to the optic nerves.to the optic nerves.

The presence of color rods assist the coelacanth in vision.The presence of color rods assist the coelacanth in vision. The brain is quit small and occupies about 1.5 percent of the braincase The brain is quit small and occupies about 1.5 percent of the braincase

in mature individuals it differs in the pups.in mature individuals it differs in the pups. The gills of the coelacanth normally indicates that they found in depth The gills of the coelacanth normally indicates that they found in depth

of 500-800m. (of 500-800m. (http://www.pbs.org/wgbh/nova/fish/anatomy.html)

The coelacanth has unique ways of swimming and gliding through the The coelacanth has unique ways of swimming and gliding through the water.water.

Their lobed pectoral and pelvic fin move similar to the way a son moves Their lobed pectoral and pelvic fin move similar to the way a son moves his arms.his arms.

In spite of thickness of fins they quit flexible.In spite of thickness of fins they quit flexible. When swimming pairs lobed fins move the way horses legs do when When swimming pairs lobed fins move the way horses legs do when

trots.trots. A intentional fin locomotion is thus unique to the coelacanthA intentional fin locomotion is thus unique to the coelacanth. .

The coelacanth rests close to the bottom of the ocean bed.The coelacanth rests close to the bottom of the ocean bed. Its fins are used for many functions like balance and steering as it swims.Its fins are used for many functions like balance and steering as it swims. To escape its prey the fish uses its large thick, caudal fin.To escape its prey the fish uses its large thick, caudal fin. The coelacanth thus has limited energy, it only swims fast enough to escape The coelacanth thus has limited energy, it only swims fast enough to escape

its predator.its predator.

The coelacanth are usually opportunistic feeders, hunting on cuttlefish, The coelacanth are usually opportunistic feeders, hunting on cuttlefish, squids etcsquids etc They are known to be nocturnal with unique feeding habits. They are known to be nocturnal with unique feeding habits. Instead of hunting in packs they usually hunt alone.Instead of hunting in packs they usually hunt alone. They usually allowed themselves to be steered by the water currents.They usually allowed themselves to be steered by the water currents. This type of hunting displayed by the coelacanth is called drift hunting. This type of hunting displayed by the coelacanth is called drift hunting.

The coelacanth in its natural habitat are distinguish from one another The coelacanth in its natural habitat are distinguish from one another by having white marks present on their body.by having white marks present on their body.

They usually assist in camouflaging the fish.They usually assist in camouflaging the fish. During late hours of the night are these fishes usually active, During late hours of the night are these fishes usually active,

performing all sorts tricks. performing all sorts tricks.

The coelacanth are indeed declared as an endangered species.The coelacanth are indeed declared as an endangered species. Many programmes are available, like the CITES for eg that decides what Many programmes are available, like the CITES for eg that decides what

needs to be done with a captured coelacanth.needs to be done with a captured coelacanth.

Blaxter, J.H.S, Marshall N.B, Bone Q 1995. Biology of fishes. Chapman Blaxter, J.H.S, Marshall N.B, Bone Q 1995. Biology of fishes. Chapman and Hall, New York. pp323. ISBN 04127411407.and Hall, New York. pp323. ISBN 04127411407.

Rogers, B 1986 Looking at vertebrates. Longman,USA.PP189. ISBN 0-Rogers, B 1986 Looking at vertebrates. Longman,USA.PP189. ISBN 0-58245086-1.58245086-1.

Pough,FH, Heiser J.B, and Mcfarland W.N 1989 Vertebrate life. Pough,FH, Heiser J.B, and Mcfarland W.N 1989 Vertebrate life. Macmillan Publishing, New York.Macmillan Publishing, New York.

Walker, S.M (2002) Fossil fish found live. INC./ Minneapolis,USA.pp 64. Walker, S.M (2002) Fossil fish found live. INC./ Minneapolis,USA.pp 64. ISBN 1-57505-5368 ISBN 1-57505-5368