Vol. 2, Issue 5 (2017)
The nature and causes of cyclomorphosis in some species of Brachionus - Brachionus falcatus and Brachionus forficula
Author(s): Nasrullah Ahad, RJ Rao
Abstract: In the present study zooplankton samples were collected from Tighra Reservoir Gwalior. They were classified and measured under microscope with the magnification power of 10X. 15X. Form variation of two Brachionus species viz. Brachionus falcatus and Brachionus forficula was studied for a period of six months. In both the species the body size and the size of spines were decreased from May 2012 to October 2012. In Brachionus forficula the total length in the month of May was 0.255 mm which was decreased to 0.121 mm in the October, the length of postero-lateral spine decreased from 0.105 mm to 0.053 mm and the antero-lateral spine length also decreased from 0.030 mm to 0.053 mm in respective months. In Brachionus falcatus total length decreased from 0.435 mm in May to 0.277 mm in October and among the spines, the length of antero-intermediate spine decreased from 0.105 mm in May to 0.060 mm in October, the length of antero-lateral spine decreased from 0.030 mm to 0.015 mm and the length of postero-lateral spine also decreased in respective months from 0.180 mm to 0.112 mm. It is concluded that the temperature is the most important factor responsible for the cyclomorphosis. With increasing temperature the density of water decreases hence the size of body and spines of both spines increases which let them float in the less dense water.
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