Despite its great length, the Giant Squid is not particularly heavy in weight compared to its chief predator -- the Sperm Whale -- due to the majority of its length being accounted for by its eight arms and two tentacles. Weights of recovered specimens have been measured in hundreds, not thousands, of pounds. Though an adult has never been seen alive, post-larval juveniles have been discovered in surface waters off New Zealand, And there are plans to capture more such juveniles and maintain them in a aquarium in an attempt to learn more about the creature's biology and habits.
The reproductive cycle of the Giant Squid is still a great mystery, but what has been learned so far is both bizzare and fascinating; male Giant Squid are equipped with a prehensile spermataphore depositing tube of over three feet in length, which extends from inside the animal's mantle and apparently is used to inject sperm containing packets into the female squid's arms- how exactly the sperm then is tranferred to the egg mass is still a matter of much debate; but the recent recovery in Tasmania of a female specimen having a small subsidiary tendril attached to the base of each of its eight arms could be a vital clue in the solution of this enigma.
The Giant Squid possesses the largest eye of any living creature, over one foot (30cm) in diameter; and its arms are equipped with hundreds of suction cups in total; each is mounted on an individual "stalk" and equipped around its circumference with a ring af sharp teeth to aid the creature in capturing its prey by firmly attaching itself to it both by suction and perforation. The size of these suction cups can vary from 1-2 inchs in diameter (2-4cm), and it is not uncommon to find their circular scars on the head area of Sperm Whales that have fed upon Giant Squid. The only other known predator of the giant squid is the Sleeper shark, found off Antarctica.
One of the more unusual aspects of the Giant Squid (as well as some other species of large squid) is their reliance upon the light weight of ammonia in relation to seawater to maintain neutral buoyancy in their natural environment, as -- unlike fish -- they lack a gas-filled swim bladder to accomplish this function...instead using vast numbers of tiny "statocysts" -- ammonia filled cellular structures -- throughout their bodies. This makes the Giant Squid unfit for human consumption, although Sperm Whales seem to be attracted by its taste.
Tales of giant squid have been common among mariners since ancient times, and may have led to the Norwegian legend of the kraken, a tentacled sea monster as large as an island capable of engulfing and sinking any ship.
Recently a possibly even more massive squid, the little known colossal squid Mesonychoteuthis hamiltoni, has been described in more detail due to a new specimen being found. It is an inhabitant of Antarctic waters, and unlike the Giant squid, relies upon both claw-like hooks and suction cups on its arms and tentacles to capture prey. Although its body may be of greater size than the Giant Squid, its tendrils appear to be considerably shorter in length; it also leaves scars on the heads of Sperm Whales as they feed upon it.