Biodiversity and Interrelationships of Teleostean Fish at the DNA Level
Of the approximate 62,000 vertebrate species, about a half are fishes. "Medium-sized" groups such as cyclostomes (lampreys and hagfishes) and cartilaginous fish (sharks and rays) contain several hundreds of species each. Very small groups including "living fossils" have only a couple (the coelacanths) to several (sturgeons) species. Others, the vast majority of species belong to teleosts. Teleostean fishes are typical advanced bony fish characterized by well developed bones, light and smooth scales, and the symmetric fan-like caudal fin support.
Teleostean fish accounts for over 30,000 species, and form the most diverged vertebrate group with about 320 million years of evolutionary history. They live in almost everywhere of aquatic environment: a small stream from a Hymalayan glacier, abyssal bottom of thousands of meters, under the Antarctic ice, among tropical reefs, and even in underground water. Taking number of species as a criterium, teleostean fish is the most prosperous vertebrate group on the earth.
Teleostean fishes concern deeply with human activities. They are important resources in economy, industry and culture. Fish materials for sushi, for example, are almost exclusively teleostean fish. Also, when you imagine fish, it may be bream, flatfish, mackerel, skipjack, rockfish, cod, medaka, saury, salmon, ayu-fish, carp, sardine, eel, and so on and on... They are teleostean fish.
Resolving interrelationships among them and delineating the biodiversity of them, we can see their physiological and ecological characteristics in an evolutionary sense. The knowledge about fish biodiversity is helpful to see how to get the biggest yield keeping their stocks stable.
Recent advancement in molecular genetics enabled us to study evolutionary changes at the DNA level. In my laboratory studies on differentiation and interrelationships among local populations and species have been done or are now ongoing in Pacific cod, Japanese flounder, mackerels, etc.
