~ Adaptations ~

Body size

We can think of nearly every aspect of Architeuthis anatomy and physiology in terms of adaptations. Foremost is the animal's size. Is there a reason why Architeuthis dux grows so much larger than other squid? Animal size generally is closely related to the size and abundance of food items as well as the nutritional value of the food eaten. Larger animals must eat more food than smaller ones. As a rule, the rate of metabolism decreases as animals increase in size. What this means is that per kilogram, larger animals eat less than smaller ones, even though they must eat more food. We call this an inverse relationship.

The cost of being large is the greater quantity of food required to sustain an animal. For some animals, one benefit to being large is the ability to feed on bigger items of food. Still, it is not yet clear how the monstrous size of Architeuthis is an adaptation to a specific diet. Does it feed primarily on large, not giant, squid? Does it feed on fish in a size range that is too large for other squid? A trip into the realm of Architeuthis may unravel the answers to these questions. Another very important aspect of large body size and fast growth rate is that giant squid are able to outgrow rapidly the large number of predators to which they are initially exposed. Even at half-size, giant squid will have outgrown all potential predators except sperm whales.

Visual System

Architeuthis is equipped with the largest eyes in the animal kingdom. A number of vertebrate animals are larger than Architeuthis, yet none have eyes of comparable size. At 25 cm in diameter, the eyes of Architeuthis are the size of a human head! Cephalopods are visual animals and are distinguished among invertebrates for their highly complex visual system.

The visual systems of cephalopods and vertebrates are an example of convergent evolution. This means both groups of animals see alike, but their ability to see evolved separately in each group. In fact, if we compare squid eyes to our own, we find remarkable similarity in the anatomy. Squid and people both have eyes with single lenses, pupils, irises and retinas. We can only guess at the light sensing capabilities of an eye with such an enormous retina.

Long tentacles

Far longer than the arms, the tentacles seem impossibly long to manage with enough accuracy to snag prey at distances in excess of 10 meters. Are we to assume they are like other squid, propelling sucker-laden tentacles with quick bursts of speed, not unlike the tongue flick of a frog? Or do they use them with stealth, sneaking the tentacles within close range of their prey? Without any direct observations of their feeding, it is best to assume they behave like other squid by snatching prey with quick bursts of tentacular speed.