As divers we enjoy our time on the reefs, we love to talk about it and show everyone the awesome underwater shots we took. On the Two Fish Divers Sanur Facebook page we try to post a reef fact every month, sometimes about the reef we see, and sometimes from greater depths. Because isn’t it amazing that we know less about our own oceans, than we know about space?! There is so much to discover! In this blog you’ll find our latest reef fact posts.
Sponges
Sponges make up a large part of the reef and if you’ve ever dived with us around Bali you’ve probably seen a lot of different sponges around. Usually we call these sponges ‘corals’, but did you know this is not actually coral?
Sponges are one of the most primitive animals existing today, they don’t contain a nervous system, digestive or sensory system. Sponges have many pores in their body that are used to filter food out of the water. Some sponges are symbiotic with algae or bacteria (similar to corals), if they have this symbiosis they make up to 3x more oxygen than it requires and they produce more nutrients than required. In some habitats these symbiotic sponges are therefore a very significant food and oxygen source.
Barrel sponge on the reef
Anemones
Everybody knows anemones; either from the Disney movie Nemo, from snorkelling or from scuba diving. But do you know what an anemone is? Is it coral, is it a plant or is it an animal?
Anemones are animals, and are related to jellyfish. Most anemones have a base that attaches to a hard surface, but some float freely or burrow into the sand. Tentacles surround their mouth; they can actively catch prey and bring the prey to their mouth. The tentacles contain specialized toxin cells (nematoxysts) that can paralyze prey. They eat crabs, molluscs and small fish.
Anemones often live in symbiosis with other animals, some anemones live on the shell of hermit crabs, but a more famous example is the anemone fish (clownfish). Anemone fish live in between the anemone’s tentacles providing safety for them and their eggs. In return anemone fish clean the anemones from parasites and defend the anemone from predators.
Why the anemone fish is able to live in between the stinging environment of the anemone’s tentacles is not completely known yet.
Anemone fish with an anemone
Hydroids
Did you ever experience that nasty sting during a dive? Not by a jellyfish but by something that looked like a plant? Guess again, highly likely that you haven’t been stung by a plant but by an animal!
Stinging hydroids are large colonies of animals. These stinging hydroids anchor on rocks, kelp leaves and shipwrecks. The animals in the colony all have their own specific function and cannot live individually. Most of the individuals are specialized in feeding (gastrozooids).
The main reason these hydroids sting is because they use it to catch prey, next to that it has a defensive function. The speed at which the toxin is injected into the prey’s skin is one of the fastest cellular in responses in nature; the toxin is injected within three milliseconds of contact with the prey!
How to prevent hydroid stings? Take the PADI Peak Performance Buoyancy specialty course and learn how to control your buoyancy during your dive and stay away from these stinging hydroids!
A stinging hydroid
What would you like to learn about? Or do you have a cool reef fact? Let us know, comment below!
