부유성 섬모충 Strombidium capitatum의 시스트형성과 수중 개체군 동태와의 관계

Abstract

Cysts of an oligotrich ciliate were isolated from natural sediment samples collected in Masan Bay from October 2005 to November 2006 and incubated under laboratory culture conditions. Excysted vegetative cells were observed after protargol staining and scanning microscopy and were identified as Strombidium capitatum based on the morphological characteristics. Cysts of S. capitatum have a spherical shape, with a papula and cyst wall ornamented with spines. Cyst size was ca. 60 µm in total length and ca. 50 µm in width. Seasonal changes in the vegetative population and sedimentation of newly formed cysts were investigated in situ. Planktonic vegetative cells were abundant during the intermediate season (spring and autumn) when the water temperature was around 15 ℃ while the cells were not detected in summer. Mass encystment occurred in October and November 2006, when the vegetative population flourished in fall peak, while minor encystment during the spring peak time. These results indicate that S. capitatum is an adapted species in low to moderate temperature and aestivates during the warm period in summer.