Among our favourite seafood, "sotong" or squids and cuttlefishes are commonly seen on some of our shores.
These delightful creatures are delicious to observe, with their colour changes and busy behaviour.
What are squids and cuttlefish? They are not fish! These animals are molluscs (Phylum Molusca) like snails, slugs and clams. They belong to the subgroup of molluscs called cephalopods (Class Cephalopoda) which include octopuses.
Compared to their more sedate cousins the slugs and snails, squids and cuttlefishes are fast-moving predators that hunt speedy prey like fish. They may also hunt snails and clams, crabs and prawns. Most have a horny bird-like beak to rip up prey.
Jet-propelled molluscs: Squids and cuttlefish squirt a jet of water out of a funnel to zoom off in the opposite direction. They can move in any direction, but move fastest backwards.
Squids tend to be more streamlined than cuttlefish. Squids are among the fastest aquatic invertebrates, some can reach speeds of up to 40km/hr. A cuttlefish can also hover or swim slowly by undulating the fins along the sides of its body. A squid does not have this all-round fin. Instead, the fin is limited to a triangular flap at the tip of the body, which acts as stabilisers.This ball-shaped squid, however, is not very streamlined. It reminds me of Dumbo the Flying elephant, with its pair of large fins around a fat body. It is sometimes seen on Changi, usually burying itself in sand when disturbed.
Lightweight shell: Relying on speed, squids and cuttlefish do not have a thick, heavy outer shell. Their shells are reduced to lightweight internal bones. In squids, the bone is thin and pencil-like. In cuttlefish, these are flat surfboards riddled with tiny gas-filled chambers. By controlling the amount of gas in the cuttlebone, the cuttlefish can control its bouyancy. The cuttlebone is often seen on the beach among the flotsam. Cuttlebones are sold in pet shops as a source of calcium for caged birds.
Armed and Dangerous: Squids and cuttlefish have eight arms. These arms are short and stout, with suckers along their entire length. Some have toothed suckers and hooks for an even better grip.
In addition to the eight arms, squids and cuttlefish also have a pair of tentacles. These may be twice as long as the arms, are thinner and have spoon-shaped tips. Only the tips have suckers. A squid or cuttlefish uses these two longer tentacles to grab prey. These tentacles shoot out and retract in an eye blink, bringing the prey within the grasp of the eight shorter arms which firmly grip the prey for the killing bite with its sharp beak.This tiny squid is common on our shores but often missed. In the photo on the left, you can see the two tentacles extended beyond the arms. And in the photo on the right, the little squid has caught a tiny shrimp!
Disappearing Ink: When alarmed, squids and cuttlefish may squirt a cloud of 'ink'. The ink may contain substances that affect the senses of other sea creatures. The inky clouded water also allows it to make a getaway. Sometimes, mucous is also released that 'holds' the ink into a shape that distracts the predator.Colourful Talk: Squids and cuttlefish can rapidly change colours to hide from predators and prey by matching their surroundings. The colour changes are achieved by contracting and expanding special 'pockets' of colour in their bodies.These colour changes are also used to communicate with each other, for example during courtship. In some species, males and females display different colours and patterns.
Eggs are laid in capsules, attached to hard objects and surfaces; or inserted into crevices and other hiding places. In the phots below are eggs found on seaweed and on sponges.
Some cuttlefish incorporate ink into the capsules, making them black.Squids usually mate only once in their life and die soon after mating and laying eggs. Cuttlefish don't produce as many eggs as squids.
People everywhere enjoy eating squids and cuttlefish. In Asia, they may be eaten freshly cooked, or they may be dried. They are also made into candied snacks. In the past, cuttlefish ink, called 'sepia', was used for writing and painting.
Squids also have a role in human medical applications. Squids have gigantic nerve cells that are relatively easy to study. Much of what we know about our own nervous system is based on studies of squid nerve cells. Several Nobel prizes were based on such studies! The squid's efficient jet propulsion system is also inspiring designs for better underwater vehicles.
None of our squids or cuttlefishes are listed among the endangered animals of Singapore. However, like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors and over-collection can also affect local populations.
Sotong stupid? Locally, the word 'sotong' is often used to describe someone who is clueless. But obviously, squids and cuttlefishes are quite smart. So it's not certain why this came about.
Links to more
More photos of our squids and cuttlefishes on wildsingapore flickr