Morphological features and viability of Scrippsiella trochoidea cysts isolated from fecal pellets of the polychaete Capitella sp.

• Two cyst morphotypes of Scrippsiella trochoidea, spiny- and artificially induced naked-type, were consumed by Capitella sp.
• Morphological destruction of the two cyst morphotypes isolated from fecal pellets was observed.
• The germination was significantly reduced and subsequently completely abolished.

To investigate the impact of grazing by the polychaete Capitella sp. on the two cyst morphotypes of Scrippsiella trochoidea, the typical morphotype with short calcareous spines (spiny-type cyst) and artificially induced the transparent type without calcareous spines (naked-type cyst), we examined the morphological features and germination capability of the two cyst morphotypes isolated from fecal pellets of the polychaete Capitella sp. produced in a restricted habitat. The morphological destruction was observed in both spiny- and naked type cysts after passage through the gut of Capitella sp., and this seemed to occur rapidly for naked-type cysts. In addition, the germination of both spiny- and naked-type cysts isolated from fecal pellets on day 2 of harvesting was significantly reduced and subsequently completely abolished, in contrast to previous findings from ingestion studies. Our results indicate that continual grazing by Capitella sp. within a restricted habitat can compromise the survival of S. trochoidea cysts.