Most squid live relatively short lives before they release a massive number of eggs and die. The vampire squid has a different strategy, Danna Staaf reports for KQED Science. Researchers were recently surprised to find that female vampire squid go through cycles where they spawn and then rest.
One long-lived female apparently experienced at least 38 and possibly as many as 100 separate spawning events with rest periods of at least a month between, the research team, led by Henk-Jan Hoving, report in Current Biology. Staaf writes:
Out of 27 adult females, Hoving and his colleagues found that 20 had “resting ovaries” without any ripe or developing eggs inside. However, all had proof of previous spawning.
As in humans, developing eggs are surrounded by a group of cells called a follicle. After a mature egg is released, the follicle is slowly resorbed by the ovary. The resorption process in vampire squid is so slow, in fact, that the scientists could read each animal’s reproductive history in its ovaries.
The cycles can continue for three to eight years, the researchers concluded. And this finding isn’t the only thing that’s surprising about vampire squid.
The deep red or inky black, milky-eyed apparition from the deep sea bears the scientific name, Vampyrotheuthis infernalis literally meaning "vampire squid from hell." Yet although the odd creature sports rows of spines that hide beneath cloak-like webbing spread from arm to arm, the "teeth" are fleshy, not pointy. It doesn’t feed on blood and it isn’t even a squid.
Perhaps scientists were hasty in naming the creature. The vampire squid is related to squid and octopuses, but it’s comes from a more ancient branch off the cephalopod family tree. Many aspects of how the creature lived remained mysterious for decades after their discovery in 1903 because they spend their time in dark, chilly water 2,000 to 3,000 feet or more below the surface. Instead of seeking out prey, as their fearsome appearance might suggest, the cephalopods use two long yellow tentacles to eat the best form of food that makes it to those depths: detritus. RR Helm writes for Deep Sea News:
It turns out, vampire squid use these tentacles like fishing lines, but they’re not catching living prey, they’re catching ‘snow’. Vampire squid scoop up sinking ocean gunk, known as marine snow, with their thin yellow tentacles, and then suck it off these appendages (like licking your fingers). This gunk includes bits of algae, dead animals, poo and bacteria from the ocean above.
That diet of detritus may be why vampire squid have such a slow reproductive strategy, Hoving and his colleagues suggest in the new study. Since their diet isn’t as rich as the fish, crabs, shrimp and even squid other cephalopods enjoy, vampire squid can’t afford to squander their energy on a massive spawning event. Instead they patiently let one egg ripen at a time. The cold water of their ocean home may also keep their metabolisms slow and allow them to live long enough for the strategy to pay off.
Plus, down in the oxygen-poor depths, few predators can survive for long. So the vampire squid and their babies are relatively safe. Their parenting may not look like much compared to human child care, but vampire squid seem to have hit upon a good way to help their offspring survive.