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A. Morula and B. cross section of a blastula displaying the blastocoel and blastoderm of early animal embryonic development. Blastulation is the stage in early animal embryonic development that produces the blastula. In mammalian development, the blastula develops into the blastocyst with a differentiated inner cell mass and an outer trophectoderm.
Coregonus is a diverse genus of fish in the salmon family ().The Coregonus species are known as whitefishes.The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate.
The morula then develops by cavitation to become the blastocyst, or in many other animals the blastula. Cell differentiation then further commits the morula's cells into two types: trophectoderm cells that surround the lumen and the inner mass of cells (the embryoblast). The inner cell mass is at the origin of embryonic stem cells. [15]
The blastocoel further expands and the inner cell mass becomes positioned on one side of the trophoblast cells forming a mammalian blastula, called a blastocyst. The axis formed by the inner cell mass and the blastocoel is the first axis of symmetry of mammalian embryo and determines its attachment point to the uterus.
Lake whitefish are found throughout much of Canada and parts of the northern United States, including all of the Great Lakes. The lake whitefish is sometimes referred to as a "humpback" fish due to the small size of the head in relation to the length of the body. [3] [a] It is a valuable commercial fish, and also occasionally taken by sport ...
The Alaska whitefish (Coregonus nelsonii) is a species of whitefish in the family Salmonidae. It is found in parts of northwestern North America, where it occurs only in small and large rivers, and rarely in lakes. The maximum length recorded for this species is 56.0 cm (22.0 in).
There is much variation among the European whitefish forms, but in general they have a tapered body, a slightly protruding upper jaw and a fleshy dorsal fin that is typical of the salmon family. The snout is short and tapered, a fact that distinguishes this species from the two other North European Coregonus species, vendace ( Coregonus albula ...
The ocean whitefish has a sturdy, quadrangular body with a relatively deep head which has a steep profile and a small mouth extending to the front of the eye. There is a fleshy ridge along the centreline of the body in front of the dorsal fin. The gill cover has a short blunt spine while the preoperculum is serrated.