Octopus & Squid

Bobtail and Pygmy squids are related, sharing the ability to produce a type of carbohydrate-bsed glue from cells in the skin. Bobtails make use of the glue to stick sand to their body when under threat. Pygmy Squid use it to stick themselves to something so they can save energy swimming. These tiny squid only live around 10 weeks.

Bobtail Squid have a special organ housing symbiotic bioluminescent bacteria.

In spite of being called squid, they are more closely related to cuttlefish.

Cuttlefish have tubular bodies that are usually relatively wide. They are characterised by having a rigid aragonite compartmentalised "bone" that they use to regulate their bouyancy. Their eyes are unique in being shaped like a "W". They have eight arms, two of which are long and retracted, but can be rapidly shot out to capture prey.

Cuttlefish, particularly the smaller species are frequently seen on reefs.

One species, the Flambouyant Cuttlefish (Metasepia pfefferi) is almost entirely benthic. Its body contains the same lethal toxin as in the bite of Blue-Ringed Octopus. Walking slowly along the bottom, it often pulses its warning purple & yellow colouration while in search of shrimps, crabs and fish. If ian individual chances on an area with commensal gobies, it can clear out all the shrimps and gobies in a short space of time. As they become older, they seem to become more sedantary hiding half-buried in sediment, adopting a camouflage colour and surface structure. The hunting strategy is then as an ambush predator. (pers.obs.)

Like cuttlefish, squid have eight arms, two of which are long and retracted, being used for hunting. Their "skeleton" comprises a rod-like pen made of chitin. Unlike cuttlefish, the are negatively bouyant and have tp They are not typical reef-dwellers.

Sepioteuthis lessoniana is seen close to reefs in sea-grass beds even during the day, where they can often be observed laying their white, sausage-shaped egg-masses.

Other species are seen mostly at night where the hunt above the reefs. A range of their extraordinary postures are shown in the images.

Octopus have 4 pairs of arms, of which one pair is often used for "walking". Reef octopus are all bottom dwelling, relying on camouflage and hiding in tight crevices for protection. They only swim when under extreme duress. Some species have developed the ability to hold shells around their soft bodies as protection. The Coconut Octopus is the most well know of these.

Some species, e.g. Octopus cynaeus hunt actively on the reef during the day. Mimic Octopus and the Wonderpus hide just below the surface of the sand/sediment, suggesting that they may be camouflage preditors as well as active hunters. The Wonderpus is seen more often late afternoons. Much is written about these two species. One photograph shows a true defensive posture and colouring in the Wonderpus as a a ribbon eel swims over the Wonderpus.

Night is a time to see many octopus hunting over the reefs, across seagrass beds, sand and sediment. With luck, octopus paralarvae can be seen just after settling down from the plankton.

One Abdopus species, the Algae Octopus and an undescribed Octopus sp. which is very "hairy" are the two octopus have hair-like skin flaps. Both seem to be active in the afternoon. Neither are seen often, but their camouflage is very good. As can be seen from the images of the Hairy Octopus, sand is trapped between the hairs adding the effectiveness of the camouflage. The photographed individual was seen gently "bouncing" across a sandy area. The bounce was achieved by the octopus swimming just over the sand surface with one leg hanging down below and pushing it up from the sand every few centimeters.

The four species of Blue-Ringed Octopus (Hapalochlaena) and the Mototi Octopus (Amphioctopus mototi) produce a tetrodotoxin that is absorbed through the skin even if the skin is not punctured. There is no known antidote.

A good article on Blue-Ring Octopus is here.