Creature Feature: Acoel

Now go over them again. You may think we are featuring the bubble coral or it’s resident shrimp but no, we are highlighting those brown specks you see on those bubble corals. If you are surprised to know those are living organisms by themselves, don’t worry. You are probably just as shocked as we are. For the past n years that we have been diving, we have always thought there is a species of bubble coral that is characterized by brown speckles.

It was only recently, thanks to our friends from Mangrove Eco Resort, that we realized that those specks are a kind of flatworm, more specifically the acoel flatworm (waminoa sp). They are also commonly referred to as “rust-brown flatworm” or “acoel”. Of late, they have been classified to be much simpler than the flatworms. Like flatworms, acoels don’t have circulatory or respiratory systems. Acoels don’t have an excretory system. They have a mouth but they don’t have a gut to process the food nor an anus to excrete waste. Instead, what happens is that the food simply goes straight to digestive cells. They really are one of the simplest animals around.

As you already know by now, these flatworms normally attach themselves to bubble corals. When they don’t hang out with bubble corals, you may find them living between grains of sediment, swimming around as plankton, or crawling on algae and other organisms. They feed on edible bits and pieces trapped in the mucus produced by the host animals they attach to. An acoel infestation on corals may hinder penetration of sunlight which is needed for the photosynthetic activity of resident algae, which in turn helps the coral remove waste, and generate raw materials to make proteins, fats, carbohydrates and produce calcium carbonate.

Have you also been fooled by this creature like us? Tag a friend who still thinks there is such a thing as brown-spotted bubble coral.

Next time you think you know a creature, think again.