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

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. To investigate the impact of grazing by the polychaete Capitella sp. on the two morphotype cysts of S. trochoidea, we 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 destruction of calcareous spines and the thin organic wall were 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 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 that continual grazing by Capitella sp. within a restricted habitat can compromise the survival of S. trochoidea cysts.nts. To investigate the impact of grazing by the polychaete Capitella sp. on the two morphotype cysts of S. trochoidea, we 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 destruction of calcareous spines and the thin organic wall were 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 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 that continual grazing by Capitella sp. within a restricted habitat can compromise the survival of S. trochoidea cysts.