Cyclomorphosis of fresh water rotifers from wetlands of contrasting ecological feature – seasonal analysis
By: Subhasri Middya, Susanta Kumar Chakraborty
Key Words: Cyclomorphosis, Rotifera, Wetland, Phenotypic plasticity.
J. Bio. Env. Sci. 8(5), 155-163, May 2016.
Cyclomorphosis, an interesting biological phenomenon involves the alteration of different of morphs in time. Various eco-biological parameters including temperature, Dissolved Oxygen, pH, alkalinity, turbidity and nutrients (total phosphate phosphorus and total nitrogen) along with meteorological changes may have a role in inducing this survival strategy of phylum Rotifera. The primary aim of this study is to test the hypothesis that the morphological variations of various species of Rotifers occur due to environmental oscillations pertaining to different seasons of a year in different contrasting ecoregions. This manifestation of phenotypic plasticity in two different species of rotifers (Brachionus sp. and Keratella sp.) was studied from three wetlands having contrasting ecological features over a period of one year. Simultaneous recording of physico-chemical parameters and computing their relationships with the density of cyclomorphic forms were also done. Cyclomorphic forms of Brachionus sp. were found mostly during summer season while that of Keratella sp. species occurred during late monsoon and winter season. Rooted aquatic macrophytes were observed to display inverse relationship with the abundance of cyclomorphic forms of Brachionus sp. Recording of proportion of body length and posterior spine length in Keratella sp. revealed the appearance of longest
posterior spine length during winter and the development of posterior spines tended to become smaller in eutrophicated water body. We concluded that high temperature, availability of nutrients and turbulence of water triggered the cyclomorphic or polymorphic development of various species of Rotifers.