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Monday, July 25, 2011

The Beauty Of Zebrafish - Danio Rerio

Beauty Of Animals | The Beauty Of Zebrafish - Danio Rerio | Zebrafish The zebrafish, Danio rerio, is a tropical freshwater fish belonging to the minnow family (Cyprinidae) of order Cypriniformes. It is a popular aquarium fish, frequently sold under the trade name zebra danio, and is an important vertebrate model organism in scientific research. The fish is named for the five uniform, pigmented, horizontal blue stripes on the side of the body, all of which extend to the end of the caudal fin. Its shape is fusiform and laterally compressed, with its mouth directed upwards. Males are torpedo-shaped and have gold stripes between the blue stripes; females have a larger, whitish belly and have silver stripes instead of gold.
Adult females will exhibit a small genital papilla in front of the anal fin origin. The zebrafish can grow to 6.4 centimetres (2.5 in), although it is uncommon for them to grow past 4 cm in captivity. Life-span in captivity is around 2–3 years, although in ideal conditions, may extend to 5 years.The approximate generation time for the Danio is 3–4 months. A male must be present for ovulation and spawning to occur. 
Females are able to spawn at intervals of 2–3 days, laying hundreds of eggs in each clutch. Upon release, embryonic development begins; absent sperm, growth stops after the first few cell divisions. Fertilized eggs almost immediately become transparent, a characteristic that makes D. rerio a convenient research model species.Development progresses rapidly.
Precursors to all major organs appear within 36 hours of fertilization. Hatching takes place 48–72 hours after fertilization, depending on the embryo's internal conditions and the external temperature, ideally 28.5 °C (83.3 °F). Swimming and feeding behavior begin about 36 hours later. The sex of juveniles cannot be distinguished except by dissection, and sex determinants are not clearly understood.Recently, transgenic zebrafish have become commercially available that express green fluorescent protein, red fluorescent protein, and yellow fluorescent protein. They are tradenamed GloFish. Other cultivated varieties include golden, sandy, longfin and leopard.
The leopard danio, previously known as Danio frankei, is a spotted colour morph of the zebrafish caused by a pigment mutation. Xanthistic forms of both the zebra and leopard pattern, along with long-finned subspecies, have been obtained via selective breeding programs for the aquarium trade.

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