Marine Biology - Marine Mammals: Cephalopods, Crustaceans, & Other Shellfish

Acorn Barnacle

Barnacles, somewhat surprisingly, are crustaceans (like crabs, lobsters, krill, etc.). Unlike most crustaceans, however, adult barnacles are sessile - they can't move. After a short phase spent as planktonic larvae, barnacles settle, attach to a hard substrate, and never move again. The Acorn Barnacle is one species in a large group of species with the same common name that do not have stalks and instead attach their shells directly to the substrate. Gooseneck Barnacles are a common example of the stalked variety. Acorn Barnacles live along rocky shores throughout the north Atlantic and north Pacific oceans.

Cephalopods, Crustaceans, & Other Shellfish

Cephalopods, crustaceans and other shellfish play important roles in maintaining healthy ocean systems. Cephalopods like the southern blue-ringed octopus and the vampire squid look other-worldly, while Atlantic blue crab and American lobster are the focus of major fishing industries.

Spanish Dancer

Reaching sizes of at least 16 inches (40 cm), the Spanish Dancer is the largest nudibranch and one of the largest sea slugs on the planet. Like most nudibranchs, the Spanish Dancer is brightly colored and does not blend in well with its surroundings. This bright coloration, similar to that of the poison dart frogs and many other species, serves as a warning to potential predators that the Spanish Dancer does not taste good and may even make a predator sick.

American Horseshoe Crab

The American Horseshoe Crab is not a true crab and is not even a crustacean at all. In fact, this species is more closely related to spiders and scorpions than to crabs, shrimps, and lobsters. As a broader group, horseshoe crabs have been around for at least 450 million years, making them one of the oldest lineages of animals alive today. Horseshoe crabs were roaming the seafloor more than 200 million years before dinosaurs existed!

American Lobster

The American Lobster (also known as the Maine Lobster) is a large-bodied, clawed lobster that supports a large, lucrative fishery throughout its range. This species is closely related to the European Lobster but only distantly related to the spiny lobsters of the Caribbean and California, all of which are also commercially targeted species.

Antarctic Krill

The Antarctic Krill is an extremely common, pelagic crustacean native to the waters surrounding Antarctica and is one of the most important prey species near the bottom of Southern Ocean food webs. It can form dense aggregations, and scientists believe the total combined biomass of this species to be as much as several hundred million metric tonnes - more than that of all humans. Several species of Southern Ocean foragers and predators specialize on Antarctic Krill as one of their primary food sources.

Argentine Shortfin Squid

The Argentine Shortfin Squid is a common species off the coasts of Brazil and Argentina and is the target of one of the largest fisheries in the world. This species is relatively small, with a mantle (= body) length of only about one foot (30 cm) or less and tentacle length of another 9 inches (22 cm). It forms extremely dense aggregations, however, and is captured in fisheries by the ton.

Atlantic Blue Crab

The Atlantic Blue Crab (also known as the Chesapeake Blue Crab) is a common species along the east coast of the United States and in the Gulf of Mexico and lives as far south as Argentina. It is named for its blue color (in life) and is a favorite seafood species throughout its range. This species is the target of one of the largest U.S. crab fisheries outside of Alaska. When cooked, Atlantic Blue Crabs are bright red.

Blue King Crab

The Blue King Crab is the largest king crab species and one of the largest crustaceans. In the past, this species supported a large fishery, worth millions of dollars, but numbers have been reduced to the point that commercial fishers no longer target the Blue King Crab directly. It lives on soft bottom habitats throughout the Bering Sea and adjacent waters. Along with true crabs, prawns, and lobsters, the king crabs are decapods; they have ten legs. Blue King Crabs are covered with a spiny exoskeleton that provides them some protection from potential predators, but at different stages of its lifecycle, the species is preyed upon by fishes, octopuses, and other predators.

Caribbean Reef Octopus

The Caribbean Reef Octopus is an absolute master of disguise and one of the most intelligent known invertebrates. Individuals of this species can completely change their color from one moment to the next using specialized color cells called chromatophores. In doing so, they often perfectly blend with their surroundings, even when settled on a surface with multiple colors. They also have such amazing control of their skin and muscles that they can match the texture of their surroundings as well. A camouflaged Caribbean Reef Octopus can be nearly impossible to see.

Caribbean Spiny Lobster

The Caribbean Spiny Lobster is one of the largest crustaceans on coral reefs and seagrass beds in the Caribbean Sea and adjacent waters and is one of the most valuable fishery resources for every country throughout its range. Along with true crabs, prawns, and other lobsters, the Caribbean Spiny Lobster is a decapod; it has ten legs. It is covered with a spiny exoskeleton that provides it some protection from potential predators, but it remains the favorite prey of many species, including Nurse Sharks and Nassau Groupers.

Chambered Nautilus

The Chambered Nautilus is one of six species of nautilus, the only cephalopods (squids, octopuses, and relatives) that have external shells. Like in most shelled animals, this species can retract completely into its shell when threatened. The Chambered Nautilus lives in deep waters of the open ocean and is one of very few species of shelled invertebrates that live in the water column instead of in contact with the seafloor or reef surface. The animal only lives in the outermost chamber of the shell. The other chambers are filled with gas that helps the Chambered Nautilus remain neutrally buoyant, giving it the ability to hover in the water.

Colorful Hermit Crab

The Colorful Hermit Crab is a large hermit crab that lives along both coasts of South America. Like all hermit crabs, an individual of this species carries around a heavy shell that it uses for protection. It does not build this shell, however. Instead, it scavenges an empty snail shell from a variety of species and carries the shell with its tail and abdomen. As the Colorful Hermit Crab ages, it must find new, larger shells that can accommodate its growing body.

Colossal Squid

The Colossal Squid is a massive squid that lives in the deep sea surrounding Antarctica, and it is the holder of multiple records. Not only is it the largest invertebrate on Earth, it also has the largest eyes of any animal, larger even than those of the great whales. Human knowledge of the Colossal Squid is based on very few specimens that have been captured in deep-sea fisheries and on beaks that have been found in the stomachs of this species' most significant predator, the Sperm Whale [link]. With such limited opportunities for study, it is difficult to characterize the biology and ecology of such a rare species, even one as large as the Colossal Squid.

Southern Blue-Ringed Octopus

The four species of blue-ringed octopuses are small predators that live in tide pools and shallow rocky reefs throughout the western Pacific and Indian oceans. They reach lengths (including the arms) of only 8-10 inches (20-25 cm) and are named for the bright blue circles that they display on their bodies and arms.

Common Limpet

The Common Limpet is an herbivorous marine snail that lives along the rocky shores of Western Europe. As they live in the intertidal zone (the area along the shore between the high tide and low tide sea levels), these limpets are extremely well adapted to an amphibious life. The thick, conical shell and strong, muscular foot combine to offer the Common Limpet a formidable defense against predators both in and out of the water. Large crabs and sea stars are potential predators underwater and birds are a primary threat above. However, the shell is shaped in such a way that it is difficult to grasp and it is thick enough to be difficult to break. It also perfectly covers the entire soft part of the body.

Flamingo Tongue

The Flamingo Tongue is a small marine snail that lives on coral reefs in the western Atlantic Ocean. This species is very colorful, with bright pink or orange coloration and black spots. Interestingly, these colors are not associated with the shell, which is somewhat drab. Instead, the color comes from the snail's soft tissue, which is almost always wrapped around the entire outside of the shell.

Geoduck

The Geoduck (pronounced "gooey duck") is a large clam native to the west coast of North America. Unlike the Giant Clam, which is almost all shell, the Geoduck has a small shell compared to the soft part of its body, which it cannot retract into the shell. The shell rarely grows larger than about 8 inches (20 cm), but the soft body can be over 3.3 feet (~1 m) long. Geoducks burrow deep into soft, muddy or sandy sediments, and this long "neck" is actually the siphon that the clam uses to bring clean seawater down to the deeply buried shell. They are the largest of all burrowing clams.

Giant Triton

The Giant Triton is a very large marine snail that can reach sizes of one and a half feet long (0.5 m). This species is also known as Triton's Trumpet, named for the son (Triton) of the Greek god of the sea (Poseidon) and the fact that the shell can be used to make trumpet-like sounds.

Humboldt Squid

The Humboldt Squid is a large squid that lives throughout the eastern Pacific Ocean. It is named after an explorer who visited that region at the turn of the 18th and 19th centuries and is also often called the Jumbo Squid, as a result of its size. This species is the largest of the flying squids, with mantles (= bodies) at least four feet (1.2 m) long and tentacles at least another couple of feet. It can reach weights of over 110 pounds (50 kg), and is one of the most common large predators throughout its range.

Peacock Mantis Shrimp

The Peacock Mantis Shrimp is a brightly colored crustacean that lives on Indo-Pacific coral reefs and associated sand flats. Its common name reflects the brilliant greens and blues that adorn the male's exoskeleton (shell).

Queen Conch

The Queen Conch is a large marine snail that lives in the Caribbean Sea and adjacent waters and is one of the most valuable fishery resources for every country throughout its range. Reaching its maximum length of approximately one foot (30 cm) in three to five years, the Queen Conch spends its growth resources thickening its shell, rather than increasing its size, for the remainder of its life.

Red King Crab

The Red King Crab is one of the largest and most valuable king crab species and is the target of a large fishery throughout the Bering Sea and adjacent areas. It lives on soft bottom habitats from the shallows down to depths of at least 600 feet (180 m). Along with true crabs, prawns, and lobsters, the king crabs are decapods; they have ten legs. Red King Crabs are covered with a spiny exoskeleton that provides them some protection from potential predators, but at different stages of its lifecycle, the species is preyed upon by fishes, octopuses, and some marine mammals. Red King Crabs are also known to be occasionally cannibalistic.

Dumbo Octopuses

The name dumbo octopus refers not just to one species but to an entire genus of deep-sea umbrella octopuses, noted for their fins that resemble Dumbo the elephant's ears (of Disney fame). There are at least 15 species of dumbo octopuses, and like all umbrella octopuses, their arms are connected by a web of skin, causing them to resemble umbrellas when their arms are spread apart.

Striped Pyjama Squid

The striped pyjama squid is one of the few known poisonous cephalopods (squid, octopus, cuttlefish, and nautilus) that roam the seafloor of the Indo-Pacific Oceans, along with the flamboyant cuttlefish and the southern blue-ringed octopus. Scientists believe that the striped pyjama squid's distinctive black stripes give away its venomous nature to potential predators, but small glands under the body are responsible for releasing the toxic slime that is dangerous to passersby.

Vampire Squid

Though it resembles both, the Vampire Squid is neither a squid nor an octopus. It is a unique animal that has been separated by scientists into its own group. Like many of its relatives, the Vampire Squid has eight arms and two tentacles. It does not suck or drink blood, and instead gets its common name from its dark color and the skin that connects the arms, resembling a cape. This species lives in the nearly completely dark waters of the mesopelagic zone.

Tiger Prawn

Tiger Prawns are large-bodied prawns that are native to the Indo-West Pacific Ocean but have established invasive populations in other areas, including in the Gulf of Mexico. Tiger Prawns get their common name from the stripes that cover their shell. This species is a highly valuable seafood species, is targeted widely by commercial fishers throughout its range, and is grown in aquaculture farms all over the world. Along with true crabs, lobsters, and other prawns, the Tiger Prawn is a decapod; it has ten legs, and it is covered with a spiny exoskeleton that provides it some protection from potential predators.

White Shrimp

White Shrimp are short-lived prawns with ranges that include the Gulf of Mexico and the eastern coast of the United States from Florida to New York. This species is the largest prawn in its range, reaching lengths of nearly 8 inches (20 cm), and is one of the more highly sought seafood species wherever it lives. It therefore supports a highly lucrative fishery in the Gulf of Mexico and in the southeast United States. Along with true crabs, lobsters, and other prawns, the White Shrimp is a decapod; it has ten legs, and it is covered with a spiny exoskeleton that provides it some protection from potential predators.