There is no doubt that stories about octopi can set the imagination racing. Roger Klocek, in an article in Aquaticus, the journal of the Shedd Aquarium, Chicago, calls them the most interesting animals alive. He pulled together some astonishing facts. For instance, there is good evidence that an octopus with an arm span of more than 50 metres did exist, up to a few centuries ago anyway. These days the biggest is the giant Pacific octopus, a cool-water species, that reaches 10 metres in arm span, quite large enough if you encounter one during a dive!

Tropical species tend to be short lived; about a year, while even the giant Pacific beast normally lives only 3 years, but up to 5 years in really cold waters (who'd want to?). Monster octopi must live in icebergs to enhance their longevity.

Like squids, octopi die after mating. Optic glands behind the eyes extinguish irreversibly the feeding response in octopi when they are ready to mate. Connoisseurs take note that mating is achieved via the male's third arm on his right side. Makes one feel inadequate, sort of.

The females are enviable in their stoicism. A female octopus can store the packet of sperm passed by a male's "third arm" for up to 10 months until her eggs are ripe, when she punctures the packet, fertilizes the eggs and then secretes a protective membrane over them. Depositing the eggs in a nest takes one to 15 days, depending on the species. She may tend to them for one to over five months, although they may not hatch until later: two months later in the case of the giant Pacific octopus.

What happens after hatching? As divers, we only see adult octopi lurking around crevices and holes in rocks. How do they get there? Does the storkfish bring them or what? Baby octopi do not turn up in plankton sampling nets. Scientists do not know why. Maybe octopi did not have a planktonic phase in their life, that is a period of drifting or swimming in the upper layers of the sea.

You need to breed them to solve this riddle and it is surprising that octopi have in the past, only been bred once in captivity. The early life history of octopi was recently the subject of a short article in the scientific journal, Nature. The research was about the second successful breeding of an octopus, (Octopus vulgaris), which is found in northern temperate seas and a million seafood restaurants. It has a life span of 12 to 18 months from egg to seafood omelete!

The researchers found that, on hatching, Octopus vulgaris looks like a round snuff bottle, the short neck being its tiny arms, which have only three suckers on each. The whole thing is 3mm long. These miniature snuff bottles jet around backwards in the water as part of the plankton for 47 to 54 days (this is at 21 degrees C), while their arms grow proportionally longer and their speed gets slower. Then they settle on the bottom. By day 60, they have grown to 125 times their weight at hatching. However, they are still only 9mm long, so it's no wonder they are hard to spot. Their jetting capability must be good enough to keep them out of plankton nets, and so to have kept their planktonic life a secret until now.

Jay Maclean is a marine biologist and artist living in Manila and Anilao, Philippines.