Underwater Grossology – Part 2

Last week we began our investigation of all things gross in Life Sciences as a tribute to Pacific Science Center’s current exhibit: Grossology – The (Impolite) Science of the Human Body. Continuing our discussion of underwater grossology this week, we present the ubiquitous sea anemone.

Sea anemones, unlike sea cucumbers, don’t have a mouth at one end and an anus at the other. Instead, food goes in and waste comes out the same orifice after being digested in the gastrovascular cavity. Pacific Science Center’s staff often uses this fact as a hook to start conversations.

However, when you actually watch a sea anemone go through the process it is not particularly messy or gross. The anemone’s digestive enzymes are quite powerful and what little undigested material they eject is usually pretty harmless looking.

What can appear fairly unattractive are anemones at low tide, or during our weekly tide pool “backflush.” Because anemones have no internal structure, they lose their normal posture without the support of water, and either sink or hang from their substrate. You may notice that they collapse their tentacles inward, trapping as much water as they can in their body cavity. The water they retain is important to get them through till the waves return. So please don’t poke anemones at low tide. That would be too gross – and very unkind!