THE OCTOPUS FILE
British octopods are intelligent, very flexible and bad news for crabs, says Paul Naylor
The lesser or curled octopus (pictured), which has only one row of suckers along each arm and a maximum arm span of about 70cm, occurs all around the UK. The common octopus is more of a warmwater dweller, and the Channel is the northern extent of its range. It has double rows of suckers and can reach 3m from armtip to armtip.
The female octopus lays her eggs in large bunches which hang down from the ceiling of rock crevices. She stays to guard them until they hatch, hosing them with water from her funnel to keep them clean and aerated. The devoted mother barely feeds during this vigil, and dies soon after it is completed.
Octopods mate in pairs but, while they don't simply shed spawn into the sea water like many marine animals, their coupling is hardly an intimate affair. The timid lovers seem to keep as far apart as possible and the male caresses the female with an outstretched arm before inserting packages of sperm into her egg ducts. One of the male's arms is specially adapted for this purpose.
The bag-like body of the octopus contains no skeletal support similar to the cuttlebone of its relative, the cuttlefish. The body can thus be moulded into virtually any shape and squeezed through the tiniest crevice in an attempt to catch prey or evade a predator such as a conger eel, cod or sea mammal.
Octopods (that is the plural!) have highly developed brains. They can learn to recognise different shapes by sight or touch and even navigate through a maze to gain food offered as a reward. The correct solutions will then be remembered for several weeks. Of more practical value, they learn fast not to attack hermit crabs that carry stinging anemones.
Crabs, which form a large part of the octopus's diet, are enveloped by the arms, pierced with sharp jaws and killed by injected poison. Digestive enzymes are pumped in and the resulting crab "soup" is sucked out. Empty crab carcasses or heaps of crab parts often indicate that there is an octopus lair