Monterey Bay Aquarium Research Institute

These observations are a reminder of the diversity of amazing animals thriving deep underwater. The deep sea is closer than you think. The choices we make in our everyday lives can safeguard the future for deep-sea animals and ecosystems.

This Grimpoteuthis octopus propels itself through the water using the rhythmic movement of its large fins and webbed arms. Those ear-like fins have earned this group the nickname "dumbo octopuses." Typically found on or near the deep seafloor, dumbo octopuses use finger-like cirri lining their arms to help detect and capture small crustaceans, worms, and other prey.

The dandelion siphonophore (Dromalia alexandri) is one of several species in the family Rhodaliidae. These siphonophores are typically found just above the seafloor, where the water is rich in food. They use long, sticky tentacles to anchor themselves in place while other tiny tentacles grab any food drifting in the currents.⁠ ⁠ The flurries surrounding this delightful deep-sea drifter, known as marine snow, are constantly falling from the ocean's surface down to the deep sea. This mixture is made up of dead bodies, poop, and snot. The dead bodies are the remains of microscopic algae and animals that live in shallow waters but sink to the depths after they die. The poop consists of fecal pellets from small, shrimp-like animals such as copepods or krill. Much of the snot is debris from gelatinous animals called larvaceans, which filter and consume marine snow using mucous nets.⁠ This steady stream of organic matter helps sustain a remarkable community of animals living far below the ocean's surface.

The octopus squid (Octopoteuthis deletron) is unusual among squids. Most squids have eight arms and two long tentacles, making a total of 10 appendages. As young Octopoteuthis mature into adults, their two feeding tentacles are reabsorbed into their bodies.⁠ ⁠ While exploring the midwater, we often encounter octopus squid in a distinctive posture: large fins spread wide, and arms with twinkling tips curled above the head. Light-producing organs called photophores flash with bioluminescence at the end of each arm.⁠ ⁠ Octopoteuthis can change color, a behavior common in cephalopods that live in shallow waters but relatively rare among deep-dwelling species. We have documented an astonishing array of colorful and complex body patterns in octopus squid, including patches, stripes, and various postures. However, we have yet to decipher the code hidden within these markings.

Market squid (Doryteuthis opalescens) are common along the central coast of California, especially in the spring and fall when they migrate into the shallow waters of Monterey Bay to spawn. These sprightly squid use their two longer tentacles to catch prey, which include crustaceans like krill, small fishes, and other juvenile squids. They grow quickly and can reach up to 28 centimeters (11 inches) long. ⁠ ⁠ These squid have long been one of California's most important commercial fisheries, supporting coastal communities and generating tens of millions of dollars in revenue. However, cyclical changes in ocean conditions can affect the productivity of California waters, making squid abundant in some years and difficult to find in others.

At first glance, many species of these little red jellies look nearly identical, making them surprisingly difficult to identify. By collecting data over decades and carefully analyzing their shape and form, MBARI scientists are helping untangle the diversity of life in the deep sea. Every observation brings us closer to understanding the remarkable animals that thrive beneath the ocean's surface.

Animals like the long-armed jewel squid are a reminder that the deep sea still holds countless mysteries. By exploring and documenting life in the deep, scientists can better understand the biodiversity and ecosystems that shape our ocean world.

Like other cephalopods, glass squids (family Cranchiidae) are covered in tiny pigment sacs called chromatophores. They often keep their chromatophores closed, so their skin is basically see-through. This invisibility cloak hides them from both predators and prey.⁠ ⁠ When the glass squid’s cover is blown, they expand their chromatophores to darken their appearance. Some may fill their body cavity with ink instead, presumably to blend into the darkness. And when danger still looms, a glass squid may squirt ink into the water and jet away. A ghostly shroud of ink creates a distraction so the squid can escape.⁠ ⁠ More than 60 species of glass squids live in deep twilight waters around the world. Some are little more than 10 centimeters (four inches) long, but others are giants. In fact, the largest of all squids—the colossal squid (Mesonychoteuthis hamiltoni), nearly 10 meters (33 feet) long and weighing up to 495 kilograms (1,091 pounds)—belongs to the family Cranchiidae. We typically see smaller glass squids about 30 centimeters (12 inches) long, likely because the larger ones are faster swimmers that can easily elude our slow-moving submersibles.

Red disk jellies (Poralia rufescens) are found worldwide and grow to about 25 centimeters (nearly 10 inches). They live deep below the sea surface to thousands of meters and are usually seen floating near the seafloor, where prey accumulates as a result of ocean currents. They use those trailing tentacles to catch their next meal, often smaller jellies or arrow worms.

Grimpoteuthis octopuses use the movement of their large fins and arms to propel themselves through the water. They are affectionately called the "dumbo" octopuses because of those flapping fins. This group of octopuses is typically found on or near the deep seafloor, where they use finger-like cirri on their arms to catch small crustaceans, worms, and other prey items.⁠ ⁠ The seafloor squish next to this cutie pie cephalopod is a sea pig (Scotoplanes sp.). Sea pigs are one of the most commonly sighted animals on the deep seafloor off Monterey Bay. Unlike most sea cucumbers, which have stumpy tube feet tucked beneath their bodies, sea pigs use their long, stilt-like tube feet to suspend their bodies above the soft mud.

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This adorable baby is the eryoneicus larval stage of a deep-sea lobster. These fuzzy globs of cute float and feed in the water column until they're ready to change into juvenile lobsters and settle on the seafloor. During this stage, they are covered with thousands of tiny hairs, which they eventually lose as they develop into adults. This larva is about five centimeters (two inches) long. You're welcome. 😍