Embryonic Development of the Heart In Mosquito Fish Gambusia affinis (Baird & Girard)

A. Al-Rawi, A.H.; Al-Mukhtar, K.A.K.; B. Alwan, J.

	Embryonic Development of the Heart In Mosquito Fish Gambusia affinis (Baird & Girard)
Baghdad Science Journal
Article 1, Volume 1, Issue 1, 2004, Pages 38-47
Authors
A.H. A. Al-Rawi; K.A.K. Al-Mukhtar; j. B. Alwan
Abstract
first sign ؛ه' heart development in mosquito fish starts in an embryo of 0.6 mm. long. It appears as ١٦٧٢١ thiekenings in the splanchnic mesodermal p^es loeated on bouth sides of the ventral median line ofthe embryo under the foregut. l-'rom these two thitckenings a group of loose cells are detached. These cells represent the heart primordium which develops into the endocardial tube. The endocardial tube appears to be surrounded by the two thickened plates of splanchnic mesoderm. These go to form a heart tube with a double-layered wall. The heart chambers will differentiate in a antero-posterior direction; starting with the bulbus arteriosus then the ventricle followed by the atrium and lastly the sinus venosus. The embryo of7 mm. long shows that the heart chambers are arranged on a bent line. This bent continues and the heart chambers will occupy the perieardial cavity. In the new born larva the bulbus arteriosus assumes an anterior position, the ventricle has the dorsal, the atrium has the ventral, and the sinus venosus has the posterior position. With the development, the ventricle and the atrium interchange in their positions. This interchange occures as a result of a rotary motion of 180؛ in a clockwise direction. As a result the ventricle occupies a ventral position and the atrium occupies . a dorsal position. Thus the heart takes its final shape as that in the adult fish.

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