This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Most octopuses take the million-to-one-odds strategy when it comes to reproduction. They lay thousands—if not tens or hundreds of thousands—of tiny eggs. Out of these hatch bitty proto-octopuses, which drift around with other plankton and paralarvae, at the mercy of currents and anything hungrier and larger than they are (which can even include their siblings).
Most members of these large broods are destined to perish at an early age. But if an average of one male and one female from each group survive long enough to mature into full-grown adults and mate, then a population can remain stable.
Some octopus species, however, take a different approach to producing productive offspring. Instead of innumerable eggs they might lay just dozens. These eggs, however, are quite a bit larger. And from these egg casings spring forth not helpless short-armed paralarvae, but fully formed, fully mobile juvenile octopuses.
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One species that engages in this tactic is the deep-seaBathypolypus arcticus, sometimes called the spoonarm octopus (thanks to the curly tips of its arms). This species of octopus lives in the northern North Atlantic. They prefer a seafloor life some 200 to 600 meters below the surface, where they can live from three to possibly six years (a near record old age in octopus terms). But these are hardly deep-sea monsters—the adults weigh an average of just 45 grams.
In the 1990s a team of researchers collected a sampling of these octopuses to study in the lab. Kept in conditions similar to their deep-sea habitats—at a chilly 7 degrees Celsius—the octopuses mated, laid eggs and young hatched.
The males seem to contribute just a couple large sperm packets (called spermatophores). And the females brooded their big eggs for more than a year. When the young emerged, they weighed roughly 0.2 to 0.3 grams—far smaller than the adults, but much larger than hatchlings of most other species.
The (relatively large) offspring from this species skips the hazardous drifting planktonic phase altogether. Once they hatch, they are ready to begin a relatively grown-up life on the seafloor. In fact, researchers have captured video of these new hatchlings literally walking away from their egg casings.
Video courtesy of Wood, J.B., E. Kenchington, and R.K. O'Dor. Malacologia, 39(1-2): 11-19
Illustration courtesy of Ivan Phillipsen
