Occurrence and significance of resting cysts in a hyaline tintinnid, Helicostomella subulata (Ehre.) Jorgensen

Abstract

The hyaline tintinnid Helicostomella subulata (Ehre.) Jorgensen, a dominant member of the summer-fall microzooplankton community in Bedford Basin, Nova Scotia, was cultured in the laboratory over 10 months, on a diet of microflagellates. The cultures produced resting cysts in ≈2 months, although the culture conditions (temperature, light, food type and concentration) had not been altered. The field population also produced cysts contemporaneously. The laboratory-produced cysts excysted in 8 to 10 wk at the same uniform environmental conditions under which they were produced. Field-collected cysts, and those produced in the laboratory, excysted at warmer temperature after spending a period of time in simulated winter conditions. The cyst formation provides a mechanisms for repopulation of the species in the inshore areas after unfavorable winter conditions.