These cephalopods are also known as the smooth-skinned octopus due to their unblemished mantle. The Pearl octopus and its relatives are deep-sea invertebrates, typically found more than 650 ft below the ocean waves, and they can live even deeper. Some individuals, however, have been found in water as shallow as 230 ft and, more recently, nearly 50 ft deep, accessible via scuba diving. Otherwise, remote operating vehicles are required to study them alive in the wild.
Unlike other octopus species that exhibit defining features such as flaps of skin over the eyes or Dumbo ear-like fins across the mantle, the Pearl octopus and its relatives are smooth-skinned. There are just over two dozen Pearl or smooth-skinned octopus species, and their classification has a tumultuous history. New information could help shed light on these mysterious invertebrates of the Abyss.
In general, a Pearl octopus is orange to red in color, with big eyes and eight arms equipped with paired sets of about 100 suction cups per arm. They have some webbing between their arms that reaches about a quarter of the way down their length. The animal's mantle averages about 6 inches long, with females slightly larger than their male counterparts. Males have a specialized arm for transferring sperm to the female's mantle cavity. Similar to many octopus species, both parents perish after mating.
These invertebrates display unique behavior among all known octopus species. At the depths where these cephalopods live, the water temperature is near freezing. Typically, the colder the environment, the longer it takes for eggs to develop. Warmer temperatures often expedite the development process. It's believed that a mother Pearl octopus uses this phenomenon to promote faster development of her own eggs.
Pearl octopus mothers gather in huge groups, the largest known gatherings of any octopus species. There may be thousands of mothers all seeking out the warmer waters of deep ocean hydrothermal springs. Unlike hydrothermal vents that spew cloudy heated water far above the ocean's floor, hydrothermal springs simply have heated water that seeps out from cracks in the ocean sediment. The Pearl octopus mothers gather in droves around these ocean bottom fissures, where the temperature is warmer. Here, egg development that may have taken 5 to 10 years takes just under two, meaning the eggs are far less susceptible to predation. Plus, the mother octopus remains with her spawn the entire time, splaying her arms in a defensive posture.
Predators to the Pearl octopus include skates and other large fish such as Rockfish and Dogfish, sea lions and fur seals, as well as beluga whales. In turn, the invertebrates eat crabs and other crustaceans, as well as small fish. A mother Pearl octopus doesn't eat while she protects her brood, and shortly after they've matured, she'll die. However, her body contributes to the organic cycle around the hydrothermal spring, so these habitats tend to be full of life.
