Acontia and mesentery nematocysts of the sea anemone Metridium senile (Linnaeus, 1761) (Cnidaria: Anthozoa)


  • Carina Östman Animal Development and Genetics, Evolutionary Biology Centre, Uppsala University
  • Jens Roat Kultima Uppsala University
  • Carsten Roat Department of Ecology, Environment and Geology, Umeå University
  • Karl Rundblom Uppsala University



cnidae, SEM, acontia, mesenterial filaments


Acontia and mesentery nematocysts of Metridium senile (Linnaeus, 1761) are described from interference- contrast light micrographs (LMs) and scanning electron micrographs (SEMs). The acontia have 2 nematocyst categories grouped into small, medium and large size-classes, including 5 types: of these, large b-mastigophores and large p-amas- tigophores are the largest and most abundant. Mesenterial tissues, characterised by small p-mastigophores and medium p-amastigophores, have 3 nematocyst categories grouped as small and medium, including 6 types. Attention is given to nematocyst maturation, especially to the differentiation of the shaft into proximal and main regions as helical folding of the shaft wall proceeds. Groups of differentiating nematoblasts occur along acontia, and near the junction between acontia and mesenterial filaments. Nematoblasts are sparsely found throughout mesenterial tissues.


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How to Cite

Östman C, Roat Kultima J, Roat C, Rundblom K. Acontia and mesentery nematocysts of the sea anemone Metridium senile (Linnaeus, 1761) (Cnidaria: Anthozoa). Sci. mar. [Internet]. 2010Sep.30 [cited 2024Apr.20];74(3):483-97. Available from: