Glen M. Watson, Ph.D and Patricia Mire, Ph.D
Sea anemones including Haliplanella luciae (shown above) are highly successful marine predators of swimming zooplankton. Prey are captured by discharging cnidae (stinging capsules including spirocysts and nematocysts) that evert tubules into contact with the prey organism. Depending on the type of cnida discharged, the tubule adheres to the surface of the prey or penetrates its integument in order to inject potent venoms. (The picture to the right shows discharged nematocysts as imaged using phase-contrast microscopy. Notice the spines that decorate the everted tubules).
For a single prey organism that swims into contact with the tentacles of the anemone, literally hundreds to thousands of cnidae discharge to ensure that the prey is successfully captured. In order to be successful, anemones must not waste cnidae. Each cnida can discharge only once.
Consequently, it comes as no surprise that discharge is carefully regulated. Such regulation involves chemoreceptors that bind specific prey-derived compounds and mechanoreceptors. Known chemoreceptors include those that bind N-acetylated sugars including N-acetylneuraminic acid (NANA) and amino compounds including glycine and proline. Sugars such as NANA are common components of glycoproteins found in mucus coverings of organisms, or glycoproteins or glycolipids found in the plasma membranes of cells. N-acetylated sugars constitute a useful chemical marker that signals to the anemone that a prey organism might be nearby. Amino compounds are found in the hemolymph of planktonic crustaceans. Mechanoreceptors involved in regulating discharge include touch receptors that respond to any object that contacts the tentacle epithelium and hair bundle mechanoreceptors that respond to vibrations in the vicinity of the tentacles.
Our research efforts focus on the hair bundle mechanoreceptors and their interaction with the chemoreceptors. To learn more about the mechanoreceptors, click this link...
Department of Biology