29 April 2018

Stealthy sotong and awesome octopuses of Singapore's seagrass meadows

A squid with a glue gun on its butt is commonly seen in Singapore! Our seagrass meadows are  indeed home to fascinating squids, cuttlefishes and octopuses.
Slender seagrass octopus
The Slender seagrass octopus is hardly bigger than a sea star
but is commonly seen on Changi and other Northern shores.
Here's a glimpse at what you can see, if you look carefully. Most are only active at night, and many can change their colours and patterns to blend in with their surroundings.


Many different kinds of 'sotong' or squids and cuttlefish find shelter among the seagrass meadows. They are not fish! They belong to the same group as snails and clams. Unlike them, squids and cuttlefishes are jet-propelled predators. Squids and cuttlefish squirt a jet of water to zoom off in the opposite direction. They can move in any direction, but move fastest backwards.
Glittering cuttlefish (Sepiella inermis)
Glittering cuttlefish
Relying on speed, squids and cuttlefish do not have a thick, heavy outer shell. Their shells are reduced to lightweight bones inside the body. In squids, the bone is thin and narrow. In cuttlefish, the bone is a  flat surfboard riddled with tiny gas-filled chambers. By controlling the amount of gas in the cuttlebone, the cuttlefish can control its buoyancy.
Cuttlebone - internal skeleton of a cuttlefish
Cuttlebones are often seen washed up on the shore.
Cuttlebones are sold in pet shops as a source of calcium for caged birds.
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.
Curvespine cuttlefish (Sepia recurvirostra) inking
Curvespine cuttlefish
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.
Glittering cuttlefish (Sepiella inermis)
The Pygmy squid has a glue gun on its butt. This is how it lurks among the meadows, with its butt stuck on a seagrass blade while its deadly tentacles are ready to snatch nearby prey. It can catch and eat shrimps half as big as itself! This tiny creature doesn't get any bigger than about 1cm long.
Oil-slicked Tanah Merah: Pygmy squid (Idiosepius sp.) eating a shrimp
Bobtail or bottletail squids are generally rather spherical with a pair of rounded fins that make them look a little like an aquatic version of Dumbo the Flying Elephant!
Bobtail or Bottletail squid (Sepiolida)
Bobtail or bottletail squid
Squids and cuttlefishes lay egg capsules. Some egg capsules look like small tear-drop shaped capsules joined together in a 'string' attached to a firm structure or surface such as a tubeworm's tube or sea fans.
Cephalopod egg capsules on tube worm
Egg capsules attached to a tubeworm tube.
The capsules are black but become transparent just before the babies emerge as miniatures of the adults.
Cephalopod egg capsules
Attached to a sea fan.
There are also octopuses among our seagrass meadows. Many are well hidden in empty shells and litter on our shores.
Big-head seagrass octopus
Big-head seagrass octopus hiding in a pot.
An octopus searches for prey mostly at night, spreading out its eight long arms to feel into crevices for crabs, prawns, snails, clams and other such morsels. The highly flexible arms have strong suckers to grip objects so that the octopus can slowly 'creep' over the surface as it stealthily investigates all hiding places (octopuses use jet propulsion when they are in a bigger hurry). The arms also have numerous receptors sensitive to taste and touch.
Big-head seagrass octopus with eggs
This Big-head seagrass octopus appears to be carrying strings of eggs.
The arms are joined together near the head with webbing. An octopus uses this webbing like a net. For example, to envelope a little mound of rubble where some small titbit might be hiding. When the prey attempts to escape, it is literally surrounded by octopus! Prey is killed with a bite of its sharp, hard beak. It is often then hauled back to the octopus' den for a leisurely meal.
Slender seagrass octopus
Slender seagrass octopus

Don't touch the octopus!

Octopuses bite! Although octopuses have a hard beak, they don't chew their food. Digestive juices are injected into the prey which soften the tissues. Some can inject a toxin with their beaks. The tiny Blue-ringed octopus (Hapalochaena maculosa) - which has a toxin deadly to humans - is recorded for Singapore, but not commonly seen. Still, it is best to avoid touching any kind of octopus. Especially small ones.

Where can I see these animals in Singapore?

They are most common in seagrass meadows on our Northern shores, e.g., Changi, Pasir Ris. One of the best ways is to join intertidal walks by NParks at Chek Jawa, Pulau Ubin. Or check out these opportunities to explore our shores through walks, or during volunteer work for our shores.

Here's more about Singapore's seagrass meadows and how you can visit them and make a difference for them.

Learn more about Singapore's squids and cuttlefishes and octopuses on the wild fact sheets on wildsingapore.

This article is written for Celebrating Singapore Shores as part of International Year of the Reef 2018.

Celebrating Singapore shores for IYOR 2018 logo

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