CLASS OSTEICHTYES, SUBLASS SARCOPTERYGII
Lungfishes and coelocanths
By Laura Jean Edwin
- characterized by having at least some bones in their skeleton and or scales, an operculum covering the gill openings and lungs or a swim bladder.
- members of the subclass sarcopterygii have lobe(muscular) associated with their fins and usually use lungs in gas exchange.
One group of Sarcopterygii is the lungfishes:
- only genera survived today and all are found in regions where seasonal droughts are common.
- when freshwater lakes and rivers begin to stagnate and dry, these fishes use lungs to breathe air.
- they survive stagnation by breathing air, but normally use gills and cannot withstand total drying.
- they have completely lost the use of gills for gas exchange and can survive when rivers or lakes completely dry.
- when a lake and river has nearly dried these lungfishes burrow into the mud.
- they keep a narrow pathway open by bubbling air to the surface.
- lungfishes may remain in aestivation for six months or more (aestivation is a dormant state that helps an animal withstand hot, dry periods.
- when it rains again and dills the lakes and riverbeds, lungfishes emerge from their burrows to feed and reproduce.
The second group of sarcopterygii are coelacanths:
- the most recent fossils of coelacanths are over 70 million years old.
- 1938, people fishing in deep water off the coast of South Africa brought up fishes that were identified as coelacanths.
- 1997, coelacanths specimen was also claimed in a North Sulawesei, Indonesia fish market. The weight of the specimen was approximately 30 kg. However the length was about 1.3m TL.
- the condition on capture " the fish was still alive when the net was hauled in, and remained alive for several hours.
- In 1998, second specimen of coelacanth was also fount at the same place and this was milestone event.
- The weight of this specimen was about29.9 kg. And it was believed to be a female with three ovarian eggs , each approximately 3cm in diameter.
- However, latimeria is probably the closest living fish relative of terrestrial verterbrates.
- Ancient coelacanths lived in freshwater lakes and rivers, thus the ancestors of Latimeria must have moved from freshwater habitats to the deep sea.
" A third group of sarcopterygians are entirely extinct. They are believed to have been the ancestors of ancient amphibians.