Cephalopods are a group of mobile molluscs that include 800 living species. Cephalopods are exclusively marine animals. They have a bilaterally symmetrical body, with a prominent head, and a set of arms or tentacles that are modified foot. All of them are carnivorous. Cephalopods have advanced vision, can detect gravity with statocysts, and have a variety of chemical sense organs.
Squid are seen frequently over the reef, under the surface of the water. There are over 300 species of squid, but the most common one is the bigfin reef squid (Sepioteuthis lessoniana). Their body is covered with chromatophores which enable it to change colour to suit the surroundings making it a master of camouflage. When swimming they do not look like the classic squid, a body with tentacles, as they use their tentacles for propulsion through the water. Squid are carnivorous. They also use their tentacles for feeding, drawing food into their mouth. Their large eyes, and their horizontal formation in the water can identify them. Their mouth contains a powerful beak used to kill and tear prey. They have an incredible sense of taste – maybe 1000 times better than humans!
Giant Squid – less commonly seen!! Giant squid can reach up to 13m, have the largest penis of all mobile animals relative to their body size! Giant squid have eyes as big as basketballs!
Octopus (Common Reef Octopus Octopus vulgaris) can be seen on most reefs, but they are masters at camouflage so are hard to spot hiding in-between rocks and holes. Octopi have eight tentacles, two eyes and three hearts!! Their mouth is at the centre point of its tentacles. As octopi have no skeleton, they can easily hide in odd shapes holes on the reef and squeeze into tight spaces. Octopi are able to change colour and skin texture rapidly and dramatically, either for hiding from predators or to protect their territory. Octopi are carnivorous, feeding on crabs, worms and other molluscs. They move around the reef either my crawling or swimming, but by far the fastest way travel is by of jet propulsion, expelling water from the body as jets. They are considered the most intelligent of all invertebrates. If captured it can escape by losing an arm and regrow it later. If threatened they will release a cloud of purple-black ink. Female octopuses lay eggs. Once the eggs are hatched both the male and female die shortly after, they live between 12 – 18 months