Malaysian Applied Biology Journal

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Malays. Appl. Biol. (2008) 37(2): 29–33



1 Laboratory of Protozoology, Dept. of Biology, Shahrekord University, Shahrekord 88186, PO B 115, Iran
2 Faculty of Medical Sciences, Shahrekord


Laboratory experiments were done to determine the effects of photoperiod and temperature on Didinium nasutum encystment. The cyst production in this freshwater ciliate was relatively independent of photoperiodic regimes (LL, LD or DD) at high temperatures (24-14oC). When temperature decreased down to 3oC, regardless of light conditions, population of the Didinium nasutum gradually started to form cyst so that after 72 hours nearly all observed individuals had transformed into cysts, even though there was still a fraction that never became encysted. The rate of the cyst production in DD (shortest daylength) was fastest, slow in LD and slowest in LL (longest daylength) conditions. This study suggests that temperature is a more critical cue than daylength in the cyst production of Didinium nasutum.

Key words: Encystment, freshwater ciliate, photoperiod, temperature, Didinium nasutum


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