GIFTS FROM THE SEA: OCTOPUS

Thursday, September 8, 2011

OCTOPUS

THE OCTOPUS IS A CEPHALOPOD MOLLUSC OF THE ORDER OCTOPUSES. THEY HAVE TWO EYES AND FOUR PAIR OF ARMS, AND LIKE OTHER CEPHALOPODS THE ARE BILATERALLY SYMMETRIC. AN OCTOPUS HAS A HARD BEAK, WITH ITS MOUTH AT THE CENTER POINT OF THE ARMS. OCTOPUSES HAVE NO INTERNAL OR EXTERNAL SKELETON ALLOWING THEM TO SQUEEZE THROUGH TIGHT PLACES. OCTOPUSES ARE AMONG THE MOST INTELLIGENT AND BEHAVIORALLY FLEXIBLE OF ALL INVERTEBRATES. THERE ARE OVER 300 RECOGNIZED OCTOPUS SPECIES, WHICH IS OVER ONE-THIRD OF THE TOTAL NUMBER OF KNOWN CEPHALOPOD SPECIES.

THE COMMON OCTOPUS

OCTOPUSES HAVE THREE HEARTS. TWO BRANCHIAL HEARTS PUMP BLOOD THROUGH EACH OF THE TWO GILLS, WHILE THE THIRD PUMPS BLOOD THROUGH THE BODY. OCTOPUS BLOOD CONTAINS THE COPPER-RICH PROTEIN HEMOCYANIN FOR TRANSPORTING OXYGEN. THEY ARE HIGHLY INTELLIGENT, LIKELY MORE SO THAN ANY OTHER ORDER OF INVERTEBRATES. THEY ALSO HAVE A HIGHLY COMPLEX NERVOUS SYSTEM, ONLY PART OF WHICH IS LOCALIZED IN ITS BRAIN. TWO-THIRDS OF THE OCTOPUSES NEURONS ARE FOUND IN THE NERVE CORD OF ITS ARMS. IN LABORATORY EXPERIMENTS, OCTOPUSES CAN BE READILY TRAINED TO DISTINGUISH BETWEEN DIFFERENT SHAPES AND PATTERNS.

GREATER BLUE-RINGED OCTOPUS

OCTOPUSES HAVE A RELATIVELY SHORT LIFE EXPECTANCY, AND AND SOME SPECIES LIVE FOR AS LITTLE AS SIX MONTHS. LARGER SPECIES, SUCH AS THE NORTH PACIFIC GIANT OCTOPUS, MAY LIVE FOR UP TO FIVE YEARS UNDER SUITABLE CIRCUMSTANCES. REPRODUCTION IS ALSO THE CAUSE OF DEATH, THE MALES CAN LIVE ONLY A FEW MONTHS AFTER MATING, AFTER PUTTING HIS PACKET OF SPERM INTO THE FEMALES MANTLE THEY DIE WITHIN A FEW MONTHS. FEMALES DIE SHORTLY AFTER THERE EGGS HATCH. THEY HAVE ENDOCRINE SECRETIONS FROM THE TWO OPTIC GLANDS THAT CAUSES THEIR DEATH.

COMMON OCTOPUS

HUMANS EAT OCTOPUS IN MANY CULTURES. OCTOPUS IS COMMON IN JAPANESE COOKING. IN KOREA SOME SMALL SPECIES ARE SOMETIMES EATEN ALIVE AS A NOVELTY FOOD. A LIVE OCTOPUS IS USUALLY SLICED UP AND IS EATEN WHILE STILL SQUIRMING. OCTOPUS IS EATEN REGULARLY IN HAWAII.

OCTOPUSES MOVE ABOUT BY CRAWLING OR SWIMMING. THEIR MAIN MEANS OF SLOW TRAVEL IS CRAWLING, WITH SOME SWIMMING. FOR A FASTER TRAVEL, THEY CRAWL, AND WALK ON THEIR ARMS. OCTOPUSES SWIM BY EXPELLING A JET OF WATER FROM A CONTRACTILE MANTLE, AND THEY SWIM HEADFIRST, WITH ARMS TRAILING BEHIND.