Control of Cnida Discharge: III. Spirocysts are Regulated by Three Classes of Chemoreceptors

Spirocysts are two to three times more abundant than nematocysts in the feeding tentacles of acontiate sea anemones. Despite their prevalence, little experimental work has been done on the discharge of spirocysts because of the difficulty in detecting and counting them after they have discharged. To circumvent this problem, we have developed a simple, reliable, enzyme-linked lectin sorbent assay (ELLSA) for quantifying discharged spirocysts. With this method, we have shown that the discharge of spirocysts, like that of mastigophore nematocysts, is chemosensitized in a dose-dependent manner by three classes of low molecular weight substances, typified by N-acetylneuraminic acid (NANA), glycine, and certain heterocyclic amino compounds, such as proline and histamine. We also show that spirocysts exhibit considerable agonist-specific variation in the dose-responses of discharge, suggesting the existence of multiple populations of spirocyst-bearing cnidocyte/supporting cell complexes (CSCCs). Our findings call into question commonly held views regarding the respective roles of spirocysts and mastigophore nematocysts in the retention of captured prey.