Like their adult parents, they're sensitive to water pH and temperature and all of that jazz. But unlike grown octopuses in captivity, the babies almost always die of starvation. Often just within a few days of hatching.
We humans have tried feeding them: frozen shrimp bits, wriggling brine shrimp, amphipods, larval crustaceans, crustacean arms and who knows what else. But nothing seems to whet their appetite. And within a few days, almost all of them go (tiny, empty) belly up.
Which is sad.
But it is also a big problem for science. Most octopus researchers rely on wild-caught octopuses, which have questionable life histories—a bit of an issue if you're trying to do standardized science. If researchers could rear octo-subjects from eggs in a controlled environment over a known time period, ceph science could advance in just about every realm (intelligence, evolution, genetics). And to accomplish that, researchers would probably be willing to wait on their invertebrates hand and head-foot (sorry, Latin cephalopod joke).
In the wild, young octopuses can be ravenous eaters. After hatching, they take with them a few days' worth of snacks in the form of their yolk casing. But after they suck down that nutritious smoothie, they are on their own to find—and digest—food.
And eat they do. Some can double in weight each week, notes octopus researcher James Wood. So what the heck are these hungry little critters eating in the open ocean that we can't seem to cater to them in captivity?
A team of researchers has taken a first step in investigating this hiccup in cephalopod science. "Knowledge about developmental biology and digestive physiology…is insufficient and even zero in some species," the group wrote in a new paper, published earlier this month in SpringerPlus: Biomedical and Life Sciences. So they went straight for the stomach.
The Mexico-based team collected a female two-spot octopus (Octopus bimaculatus) off the coast of Baja California that laid—and then cared for—a brood of eggs in captivity. After just 33 days of incubation, the egg-ensconced larval octopuses had started developing a digestive system. Step one: check.
Upon hatching (day 61), the biggest organ in these octopuses' bodies was the digestive gland. They also had a stomach, esophagus and all of the other "organs involved in the ingestion and digestion of food," including salivary glands, the researchers noted. Step two, three, four: check, check, check.
So what is keeping these little guys from (figuratively) salivating over lab food?
Slight differences were found between hatchling digestive systems and those of fully grown octopuses. The babies didn't have all of the types of stomach cells that adults possess, and the membrane around the wee ones' digestive gland was still maturing.
But these findings don't yet explain what we could do differently to keep hatchling octopuses well fed so that they survived in captivity. The next steps will be to further examine some of these physiological differences—and also to more closely observe hatchling feeding behavior in the wild.
In the meantime, anyone willing to try Goldfish?
To learn more about the all of the quirks of octopuses different stages, dig into Octopus! The Most Mysterious Creature In the Sea.