A record breaking commitment to parenting: Graneledone boreopacifica
Across the animal kingdom it is possible to find examples of committed parents, such as emperor penguins, which spend an impressive 2 months constantly brooding their eggs, and elephants, which gestate for 20 to 21 months before giving birth. Some parents invest in the wellbeing of their offspring before their arrival; clownfish fathers will care for fertilised eggs until they hatch by cleaning them and ensuring a consistent flow of well-oxygenated water. Others spend longer caring for their young after birth; sea otter mothers spend 6-8 months teaching their pups how to dive, hunt for food, and break through the tough shells of their prey.
Octopuses are semelparous, reproducing only once before death. In the case of males, this often means dying within a couple of months after passing their spermatophore (a package of sperm) to a mate. Once a female has laid her eggs, she is fully invested in protecting them from predators and keeping them well oxygenated, passing away shortly after they hatch. Shallow water octopuses tend to only live for a couple of years, so typically spend 1-3 months brooding their eggs. In the deep sea these processes tend to take a lot longer, with Graneledone boreopacifica being a perfect example.
Graneladone boreopacifica mothers have been found to exhibit the longest period of egg brooding seen anywhere in the animal kingdom, totalling at over 4 years! This was a discovery made off the coast of central California, USA, in the Monterey Submarine Canyon by the Monterey Bay Aquarium Research Institute (MBARI). Using ROVs to explore a rocky substrate almost a mile into the canyon, they identified an individual G. boreopacifica, which they continued to observe caring for her eggs for over 4 years.
Octopuses in shallow water typically lay thousands of eggs, which is a necessary investment as the majority of those that hatch will not survive to adulthood. In the case of G. boreopacifica, it was observed the mother to brood about 160 eggs, a much smaller clutch size than octopuses usually have. This smaller clutch size and longer brooding time lead to octopus hatchlings that are much more equipped, since they are much larger and better equipped for hunting and surviving on their own.
The long term maternal investment of G. boreopacifica is especially impressive, as she will not leave her eggs at all during their development, not even to hunt. She spends over 4 years continually covering her eggs with oxygenated seawater and attentively pushing away potential predators such as crabs and shrimps. As she continues to care for them, her eggs grow larger, but at her own expense. Towards the end of the brooding period, she loses weight and becomes pale, becoming weaker as her offspring grow stronger.
Octopuses have evolved to make the ultimate sacrifice for their offspring, with mothers spending their last days prioritising the future success of their hatchlings, never to see the outcome. In the case of G. boreopacifica, the extreme investment is exhausting, but has been worthwhile for the species as a whole; they are one of the most common octopus species in the depths of the Northeastern Pacific. By brooding eggs for long enough that they hatch as miniature adults that are already 5cm in length rather than as helpless tentacled plankton, they begin life with an invaluable headstart.
Maternal investment in the survival of offspring is not uncommon. Many mothers throughout the animal kingdom spend months, or even years, caring for and raising their young, devoting time and energy to their success, something human parents can relate to as well. While octopuses don’t get the opportunity to watch their offspring grow up, their commitment to the next generation is admirable, especially in the case of G. boreopacifica, who truly selflessly commit themselves to their eggs for years.
To learn more about MBARI’s discovery, watch their video: