Cuttlefish

Introduction

Cuttlefish are members of the Phylum Mollusca, Class Cephalopoda,, Order Sepioidea, Family Sepiidae. In Australia, there are 3 genera comprising approximately 26 species although the taxonomy and biology are poorly known. The largest species, Sepia apama,(giant cuttle) is one of the commonest species and can attain a length of 80 cm.

They have 4 pairs of arms and 1 pair of tentacles all equipped with suckers. The tentacles are clubbed on the end and can be withdrawn into special pockets at the base of the tentacles on the side of the head. The body is flattened and the arms are generally short and the head robust with prominent eyes.

Feeding

All cuttlefish are active carnivores feeding on fish, prawns and other, often large animals. The animal tends to be an ambush hunter hiding in rocks or seaweed and they have an excellent ability to change colour to suit their surroundings. They grasp their prey with the tentacles which are shot forward when the prey is within reach. The prey is killed by the beak and the radular teeth rasp flesh off the larger animals.

Movement

Cuttlefish possess a characteristic calcareous sepion or cuttle which is porous, finely laminated and is found dorsally in the animal just under the skin. It is the primary buoyancy organ of the animal and the spaces between the layers within the sepion contain liquid and gas (largely nitrogen). By varying the amount of gas and liquid the degree of buoyancy can be altered as the animal changes its depth position. Thus it doesn’t need to expend extra energy swimming up or down. Each species possesses a characteristic sepion shape which can be used to identify the different species present in a given region.

Cuttlefish move by jet propulsion and because of their neutral buoyancy, can hover in one position indefinitely with the help of the fins on the sides of their bodies.

Reproduction

The males of many cuttlefish species have a specially modified arm(hectocotylised) which transfers sperm from the penis to the mantle cavity of the female.This special arm is located on the left ventral side and has reduced sucker size and special folds to help hold the sperm. In the giant cuttlefish (Sepia apama) mating occurs in July/August in coastal N.S.W. where animals gather in large numbers on the bottom where they lay their eggs. After laying their eggs the animals die and their bodies are often fed upon by dolphins and fish which leave their tooth marks in the sepion. The mutilated bodies and sepions are washed ashore.

ACKNOWLEDGEMENTS: MOLLUSCA THE SOUTHERN SYNTHESIS PART A CSIRO PUBLISHING 1998

Students holding a dead giant cuttlefish that washed up on a rock platform in August, 2005 after it had finished mating in the waters off Long Reef.