Once it is hatched, the larvae measures about 3mm in length. This, however, has been shown to largely depend on the thickness of the chorion (in which the embryo resides) as well as the muscular activity of the embryo.ĭepending on these factors, hatching of some embryo may be delayed. Hatching occurs between 48 and 72 hours after fertilization. This prepares the offspring for hatching. In these two stages, structures of the organism develop further with the head and tail becoming more pronounced and visible. This is followed by two other phases namely, segmentation and the pharyngula stage before hatching. Whereas blastulation occurs between 2 and 5 hours after fertilization, gastrulation occurs between 5 and 10 hours following fertilization. The next stage of development is known as gastrulation and results in the production of three germ layers and thus the body plan of the organism. This is the form of the embryo resembling a hollow ball and contains many layers of cells that surround a cavity known as the blastocele. The cleavage phase in which cell division is experienced produces the blastula. This may take between 40 minutes and 2 hours.ĭuring this phase, cell division may result in between 16 and 64 cells as the embryo moves to the next phase. Fertilization is followed by egg division in the cleavage phase.
This may occur immediately as the eggs are released (and fertilized) or within a period of 72 hours. Zygotes are formed once the eggs are fertilized. The unfertilized eggs do not develop beyond the first few cleavage phases. Although they are non-adhesive and tend to be released on un-prepared substrate, the eggs of Zebrafish have been shown to be activated by water even in cases where they are not fertilized by male sperm. The eggs, about 0.7mm in diameter, are released on a substrate where they become activated and start undergoing developmental steps. Given that eggs are released to be fertilized externally, the production of this many eggs allows for many offspring to survive through the development process before they reach adulthood even as some die in the process. The following are some of the main stages of the lifecycle of a Zebrafish:Ī female Zebrafish can produce as many as several hundreds of eggs per spawning. This has been shown to be the case with performance and trainability of the organism as they age. As they age, Zebrafish have been shown to portray a declining exercise capacity similar to mammals. On average Zebrafish have a lifespan of three and a half years (3.5years). A soft dorsal fin with between 30 and 32 branched rays.A striped anal fin with between 10 and 12 branched rays.Some of the other anatomical features of Zebrafish include: Females (adult) have a small genital papilla located in front of the anal fin.Males also have a golden appearance on their pelvic and ventral fin.Whereas the female Zebrafish tend to be larger in size with a rounded belly (whitish in color) male Zebrafish are more slender with a golden appearance on their belly.The difference between male and female Zebrafish: Gold xanthophores - Gives the pale yellow color of the dorsal and belly part of the fish.
The dark blue melanophores - Responsible for the blue stripes.Some of the pigments that give Zebrafish their color include: Moreover, the upper (dorsal) part and belly part may appear pale yellow in color causing some Zebrafish to appear more golden. These include the rostal (nasal) barbels that extend to the orbit's anterior margin and the long maxillary barbels on either side of the mouth that act as taste buds and are also used to search for food.Īlthough Zebrafish are generally silvery white in color, they have about 5 horizontal lines (blue in color) on either side of their body extending to the caudal fin.
ZEBRA FISH SKIN
Zebrafish also have two pairs of skin sensory appendages known as barbels. They lack oral teeth (on their jaws) but Zebrafish have teeth attached to their fifth brachial arch consisting of a dentine layer, an enamel coating as well as a pulp core. In addition to a moderately elongated body that gives them the classic fish shape, Zebrafish have a mouth that forms slightly upwards and a dorsally compressed head. Zebrafish Characteristics (Appearance and Morphology)Īs already mentioned, Zebrafish are small fish that measure about 6 cm in length on average.
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