Excystment of the oligotrich ciliate Strombidium conicum

Abstract

Cysts of an oligotrich ciliate were isolated from sediment samples collected in Onagawa Bay on the northeastern Pacific coast of Japan and incubated under laboratory culture conditions. Successful excystment occurred regularly and the excysted cells Tvere identified as Strombidium conicum. The cyst of S. conicum has a papuliferes form and is enveloped by a double-layered wall, rigid inner and membranous outer layers. The excysted cells showed a distinctive conical shape with welldeveloped trichltes and a ventral kinety restricted to the posterior e n d . The effects on excystment of temperature, light intensity, oxygen concentration, bacteria, a n d storage in the dark and at cold temperatures a r e reported. Among these variables, temperature is likely to b e the principal factor controlling excystment.