Illustrated Glossary of Sea Anemone Anatomy - Entire Body Cross Sections

This page features illustrations, photographs, and microscope slides of cross sections through the column of anemones. In these sections it is possible to see the actinopharynx, siphonoglyphs, mesenteries, retractor muscles, and parietal muscles.

Idealized cross-sections of a sea anemone, left one at the level of the actinopharynx, right nearer the base. In the latter cross-section, the numeral 1 indicates primary mesenteries, of which there are six pairs; the numeral 2 indicates secondary mesenteries, of which there are six pairs; and the numeral 3 indicates tertiary mesenteries, of which there are 12 pairs. Polyps of some species have fewer cycles of mesenteries and some have many more. In the former cross-section, three cycles of mesenteries are also represented. The primary mesenteries are complete (they connect to the actinopharynx) whereas the secondary and tertiary mesenteries are incomplete (they do not connect to the actinopharynx). The number of cycles of complete mesenteries is a character of systematic importance - in some actiniarians mesenteries of several cycles are complete. Note that two diametrically opposite pairs of primary mesenteries connect to the siphonoglyphs; the retractor muscles of these directive mesenteries lie on the outer side of the mesenteries whereas the retractor muscles of all other mesentery pairs (the non-directive mesenteries) face one another. (Adapted from Hyman, 1940)

Sicyonis ingolfi. Diagram of the arrangement of the sterile mesenteries.
Limnactina laevis. Transverse section of a specimen with 10 perfect mesenteries.
Stoichactis digitata. Cross section at the level of the actinopharynx showing the arrangement of the mesenteries. a: Actinopharynx.
Edwarsia Adenensis. Cross section in the region of the gametogenic tissue.
Microscope slide of Corynactis carnea from Dr. Oskar Carlgren at the level of the actinopharynx.
Microscope slide of Phymanthus strandesi from Dr. Oskar Carlgren showing gametogenic tissue.

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