Morphological features and viability of calcareous dinoflagellate cyst, Scrippsiella trochoidea, in benthic environment

Abstract

Recently, two morphotypes of Scrippsiella trochoidea cyst, one typical type with short calcareous spines (spiny-type cyst) and another transparent type without the calcareous spines (naked-type cyst), were detected in natural surface sediments.). Shin et al. (2013) reported that the naked-type cysts represent a morphological response to the acidic environment of sediments caused by biogeochemical processes related to the degradation of organic matter under oxic and anoxic conditions in the hypoxic zone of eutrophic areas. In this study, we estimated the change in the abundances of spiny- and naked-type cysts exposed to natural sediments, and additionally examined the morphological features and germination capability of the two cyst morphotypes isolated from faecal pellets of the polychaete Capitella sp. produced in a restricted habitat. The decreases in the abundances of the two morphotype cyst exposed to natural sediments were observed for 30 days, and the destruction of calcareous spines and the thin organic wall were observed in both spiny- and naked-type cysts after passage through the gut of Capitellasp.. This seemed to occur rapidly for naked-type cysts. In addition, the germination of both spiny- and naked-type cysts isolated from faecal pellets on day 2 of harvesting was significantly reduced and subsequently completely abolished, in contrast to previous findings from ingestion studies. Our results indicate tnts.). Shin et al. (2013) reported that the naked-type cysts represent a morphological response to the acidic environment of sediments caused by biogeochemical processes related to the degradation of organic matter under oxic and anoxic conditions in the hypoxic zone of eutrophic areas. In this study, we estimated the change in the abundances of spiny- and naked-type cysts exposed to natural sediments, and additionally examined the morphological features and germination capability of the two cyst morphotypes isolated from faecal pellets of the polychaete Capitella sp. produced in a restricted habitat. The decreases in the abundances of the two morphotype cyst exposed to natural sediments were observed for 30 days, and the destruction of calcareous spines and the thin organic wall were observed in both spiny- and naked-type cysts after passage through the gut of Capitellasp.. This seemed to occur rapidly for naked-type cysts. In addition, the germination of both spiny- and naked-type cysts isolated from faecal pellets on day 2 of harvesting was significantly reduced and subsequently completely abolished, in contrast to previous findings from ingestion studies. Our results indicate t