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公斑馬魚 Male Zebrafish-05-Best | by 阿鶴
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公斑馬魚 Male Zebrafish-05-Best

Acknowledgement :

Thanks for the "Lin Li-Yih Lab"* supplied the zebrafish.

* Lin Li-Yih Lab, The Department of Life Science, The National Taiwan Normal University, ROC.

................................................................................................................................The following descriptions of zebrafish quote from wikipedia website (URL: en.wikipedia.org/wiki/Zebrafish). All Rights are belonging to "Wikipedia website".

 

Zebrafish:

 

1.Introduce: The zebrafish, Danio rerio, is a tropical freshwater fish belonging to the minnow family (Cyprinidae). It is a popular aquarium fish, frequently sold under the trade name zebra danio, and is an important vertebrate model organism in scientific research.

 

2.Distribution: The zebrafish is native to the streams of the southeastern Himalayan region., including the countries Pakistan, Bangladesh, Nepal, and Myanmar. It arose in the Ganges region in Eastern India. It commonly inhabits streams, canals, ditches, ponds, and slow-moving to stagnant water bodies, including rice fields. Zebrafish have been introduced to parts of the United States, presumably by deliberate release or by escape from fish farms. They have also been sighted in Colombia.

 

3.Description: 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 can be described as 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 centimetres in captivity.

The approximate generation time for the Danio is 3–4 months. It has been observed that there must be a male present in order for ovulation and spawning of eggs to occur. Females are able to spawn as often as 2–3 days with hundreds of eggs being laid in each clutch. Upon release from the mother, developmental steps will be made, however without the presence of sperm growth will stop after the first few embryonic cleavages. Fertilized eggs will almost immediately become transparent, which is an important characteristic yielding D. rerio as a convenient research model. Development rapidly progresses, with precursors to all major organs appearing within 36 hours of fertilization. Hatching will take place anywhere from 48–72 hours post-fertilization, depending on the internal conditions of the embryo itself and the external temperature (ideally 28.5 °C). Swimming and feeding behavior are observed to occur approximately 72 hours post-fertilization. The sex of juvenile zebrafish cannot be distinguished except by dissection, and the genetic sex determinants are not clearly understood. The range of life-span for a zebrafish in captivity is around 2–3 years, although in ideal conditions, they may live up to 5 years. The zebrafish is omnivorous, and it primarily eats zooplankton, insects, and phytoplankton. It can eat a variety of foods if its main sources are not readily available.

 

4.Model organism for development and genetics: Zebrafish chromatophores, shown here mediating background adaptation, are studied by scientists D. rerio are a common and useful model organism for studies of vertebrate development and gene function. They may supplement higher vertebrate models, such as rats and mice. Pioneering work of George Streisinger at the University of Oregon established the zebrafish as a model organism; its importance was consolidated by large scale forward genetic screens (commonly referred to as the Tübingen/Boston screens). The scholarly journal Development devoted an issue to research using the fish in celebration of this landmark. An online database of zebrafish genetic, genomic, and developmental information, the Zebrafish Information Network (ZFIN), has been established. D. rerio is one of the few species of fish to have been flown into space.

A Zebrafish Pigment Mutant. The mutant called bleached blond was produced by insertional mutagenesis. The embryos in the picture are four days old. At the top is a wild-type embryo, below is the mutant. The mutant lacks black pigment in the melanocytes because it fails to synthesise melanin properly.

Research with D. rerio has allowed advances in the fields of developmental biology, oncology, toxicology, reproductive studies, teratology, genetics, neurobiology, environmental sciences, stem cell and regenerative medicine, and evolutionary theory. Perhaps its greatest advantages for use in the laboratory as a model system come from its now sequenced genetic code, well understood, easily observable and testable developmental behaviors, and the availability of well-characterized mutants. Zebrafish embryonic development provides advantages over other vertebrate model organisms as well. Although the overall generation time of zebrafish is comparable to that of mice, zebrafish embryos develop rapidly, progressing from eggs to larvae in under three days. The embryos are large, robust, and transparent and develop externally to the mother, characteristics which all facilitate experimental manipulation and observation. Their nearly constant size during early development facilitates simple staining techniques, and drugs may be administered by adding directly to the tank. Unfertilized eggs can be made to divide, and the two-celled embryo fused into a single cell, creating a fully homozygous embryo.

See link for pigmentation mutants of D rerio: www.nature.com/hdy/journal/v97/n3/fig_tab/6800867f5.html#...

A common reverse genetics technique is to reduce gene expression or modify splicing in zebrafish using Morpholino antisense technology. Morpholino oligonucleotides are stable, synthetic macromolecules that contain the same bases as DNA or RNA; by binding to complementary RNA sequences, they reduce the expression of specific genes. The journal Genesis devoted an issue to research using Morpholino oligos, mostly in D. rerio. Morpholino oligonucleotides can be injected into one cell of a zebrafish embryo after the 32-cell stage, producing an organism in which gene expression is reduced in only the cells descended from the injected cell. However, cells in the early embryo (www.flickr.com/photos/chenhowen/sets/72157618669794787/

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Taken on August 15, 2007