Nautilids, Octopods, Cuttlefishes, Squids, and Relatives: Cephalopoda

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NAUTILIDS, OCTOPODS, CUTTLEFISHES, SQUIDS, AND RELATIVES: Cephalopoda

LONGFIN INSHORE SQUID (Loligo pealeii): SPECIES ACCOUNTS
PEARLY NAUTILUS (Nautilus pompilius): SPECIES ACCOUNTS
COMMON OCTOPUS (Octopus vulgaris): SPECIES ACCOUNTS
VAMPIRE SQUID (Vampyroteuthis infernalis): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

The bodies of all cephalopods (SEF-oh-lo-pahd) remain firm thanks to a system of muscles that maintain fluid pressure inside. Their bodies are more or less divided into three regions: the armlike tentacles surrounding the mouth; the head that has a pair of large, distinctive eyes, one on each side; and the body, or mantle, sometimes with a pair of fins on the sides. Some species, like nautiluses, have sixty tentacles arranged in two rings around the mouth, while others have a single ring of eight tentacles. Of these species, some have a pair of additional tentaclelike appendages and appear as though they have ten tentacles. The head has beaklike mouthparts and a scraping or drilllike radula (RAE-jeh-leh). The radula is a tonguelike organ covered with rows of very hard teeth. Inside the head is a highly complex brain. Inside the head and mantle of cephalopods is a highly developed nervous system, although it is less developed in the nautiluses.

The mantles of the smallest adult cephalopods measure only 0.23 to 0.31 inches (6 to 8 millimeters) in length, while the mantle length of giant squids (Architeuthis may reach 71 inches (1.8 meters). These giants are believed to weigh up to 661.3 pounds (300 kilograms). Several kinds of squid and at least two species of octopuses grow larger than an adult human.

Many cephalopods have the ability to change their colors rapidly. They do this with several different kinds of color-producing organs in their skin that are controlled by the nervous system. Together these organs can create different colors and patterns in an instant. Some species have light-producing organs. These organs either produce blue green light by mixing chemicals together or rely on special bacteria that live inside chambers associated with the ink sac. The ink sac produces a thick inky fluid that is squirted into the water and helps them to hide from predators.

GEOGRAPHIC RANGE

Cephalopods are found in all of the world's oceans.

HABITAT

Cephalopods are found in tide pools, on sea bottoms, and swimming in open water. They live at depths of 16,400 feet (5,000 meters) or more.

DIET

Most cephalopods prey on fishes, crustaceans, and mollusks, including other cephalopods. However, nautiluses and their relatives scavenge dead animals.

BEHAVIOR AND REPRODUCTION

Cephalopods have large brains, well-developed eyes, and complex behaviors. Some species, such as octopuses, lead solitary lives, while others, like cuttlefish, live in small to very large groups called schools. Some cuttlefishes or squids get together only to find a mate and reproduce. Many species live at depths of 1,310 to 3,280 feet (400 to 1,000 meters) during the day and swim closer to the surface at night to feed, but the activity patterns of most are unknown. Most cephalopods do not guard or defend territories. Some species will change their colors as a means of camouflage or to startle predators. Many squids and octopuses have special glands for making a defensive inklike fluid that is squirted in the water to confuse their enemies.

Both males and females are required for reproduction, but the mating behaviors of most cephalopods remain unknown. Although nautiluses reproduce many times throughout their lives, most cephalopods do so only once. The time for reproduction in these species may be either very brief or extended over a long period of time. In some species, the male simply grabs the female and places a packet of sperm in a specific place on or inside her body. Others engage in elaborate courtship behaviors that involve lots of touching just before they mate.

Depending on the species, females produce dozens to hundreds of thousands of eggs at a time. One or more layers of a special, protective coating surround each egg. The eggs are usually laid in masses, either on the ocean bottom, in between rocks, or inside seashells, while others release them into the open water. Only some kinds of octopuses and squids care for their eggs until they hatch.

The eggs take a few days to several months to hatch. The hatchlings of some species look and live like the adults and simply grow larger as they develop. Others look nothing like the adults and spend the early part of their lives as plankton. Planktonic plants, animals, and other organisms live in open water and float about on ocean currents. Eventually, the young planktonic cephalopods settle to the ocean bottom, where they develop to more closely resemble the adults in both form and habit.

CEPHALOPODS AND PEOPLE

For hundreds of years, cephalopods have appeared in the art and literature of many human cultures around the world. Today they are sometimes featured in science fiction books and films as "sea monsters." Stories of giant squids washed up on the beach or captured in fishing nets sometimes dominate the news.

In 2000, about 4.0 million tons (3.6 million metric tons) of cephalopods were harvested, equaling about 4.2% of the world's total marine catch. Around the world, many people consider carefully prepared squids, cuttlefishes, and octopuses as tasty meals. Fishermen commonly use cephalopods as bait to catch very desirable species of marine fish for the dinner table.

DEEP-SEA BATTLES

It has long been known that sperm whales eat giant squids. Whalers would find parts of these enormous cephalopods in the bellies of their catch, especially the tentacles and their beaklike mouthparts. The bodies of the whales sometimes bore the sucker patterns inflicted by the long tentacles of the squid. Win or lose, these battle scars prove that giant squids certainly do not go down without a fight.

Cephalopods are of unusual interest to scientists because they have well-developed brains and eyes, but they do not have backbones. They represent one of the most highly developed of all animals but are not related to fishes, birds, mammals, or other animals with backbones. The nerve tissues of giant squids have helped scientists to understand the basic functioning of the human nervous system. In fact, the study of cephalopod bodies is helping medical doctors to understand other aspects of human bodies.

Sometimes octopuses are considered pests because they enter traps set to capture mollusks such as whelks or lobsters. Once inside, they eat the catch. On rare occasions, cephalopods can be directly harmful to humans. Their bites, especially those of some octopuses, are painful to divers and sometimes deadly because of their toxic secretions. Schools of the large Humboldt squid have been known to attack scuba divers and fishermen who have fallen into the water.

CONSERVATION STATUS

No species of cephalopods are considered threatened or endangered.

LONGFIN INSHORE SQUID (Loligo pealeii): SPECIES ACCOUNTS

Physical characteristics: The mantle is of variable color with brown, red, purplish, and yellow speckles. It is cylinder-shaped, tapered toward the rear, and measures about 17 inches (430 millimeters) long, and 3.62 inches (92 millimeters) wide. The head has a large pair of eyes that are covered by a clear membrane. The eight tentacles are about half the length of the mantle, while the pair of tentaclelike appendages is about two-thirds its length. The triangular fins on each side of the rear end are each about half the length of the mantle.

Geographic range: This species is found in the Western Atlantic continental shelf and upper slope waters from Nova Scotia to Venezuela, including the Gulf of Mexico and the Caribbean Sea.

Habitat: They live near the ocean surface and in shallow waters in summer, but move to depths of 92 to 1,200 feet (28 to 366 meters) in winter. Adults live on the ocean bottom during the day and swim toward the surface at night.

Diet: They eat crustaceans, fishes, and other squids.

Behavior and reproduction: They migrate north and closer to the shore in summer to reproduce, returning to deeper, more southerly water in fall and winter.

Females lay their eggs in jelly-covered, fingerlike strands attached to solid surfaces at depths down to 820 feet (250 meters). The strands are often bunched together in large masses and are called "sea mops." The hatchlings do not resemble the adults and are planktonic.

Longfin inshore squid and people: They are harvested as food for humans and are also used as study animals by scientists looking at animal behavior and the workings of the nervous system.

Conservation status: The longfin inshore squid is not considered threatened or endangered. ∎

PEARLY NAUTILUS (Nautilus pompilius): SPECIES ACCOUNTS

Physical characteristics: The pearly nautilus lives inside a coiled, snaillike shell that has a distinctive flame-striped color pattern. The shell is divided internally into a series of chambers.

Geographic range: This species is found in the Indo-West Pacific.

Habitat: They prefer to live in habitats with a hard ocean bottom, especially among coral reefs. They swim down to depths of about 2,460 feet (750 meters).

Diet: The nautilus eats bottom-dwelling animals, as well as dead or decaying animal flesh.

Behavior and reproduction: They are active mostly at night.

Like other nautiluses, they reproduce repeatedly throughout their adult lives. Females protect their eggs by covering them with irregular shaped coverings. The egg mass is then attached to hard surfaces.

Pearly nautiluses and people: This species is harvested for food. Collectors also value their shells.

Conservation status: The pearly nautilus is not considered threatened or endangered. ∎

COMMON OCTOPUS (Octopus vulgaris): SPECIES ACCOUNTS

Physical characteristics: The mantle plus the longest tentacle is about 120 inches (3 meters) long. The ball-shaped mantle is variable in color but usually reddish brown. The skin is smooth but may temporarily have bumps of different sizes and shapes. The thick, armlike tentacles are four times the length of the mantle and have two alternating rows of suckers. The head is nearly as wide as the mantle and has a pair of distinctive eyes.

Geographic range: They are found worldwide in both cool and warm waters.

Habitat: They live on the ocean bottom among rocks, coral reefs, and seagrass beds, from the seashore down to depths of 656 feet (200 meters).

Diet: They eat mostly crabs, lobsters, clams, and snails.

Behavior and reproduction: These animals appear to be quite intelligent, and their complex behaviors are well-known to scientists.

Adults reproduce twice a year, in spring and fall. Females lay between 120,000 and 400,000 eggs in strings and deposit them among rocks and corals in shallow waters. The hatchlings are planktonic.

Common octopuses and people: They are harvested as food and are used as study animals by scientists interested in animal behavior.

Conservation status: The common octopus is not considered threatened or endangered. ∎

VAMPIRE SQUID (Vampyroteuthis infernalis): SPECIES ACCOUNTS

Physical characteristics: This squid's skin has many light-producing organs. There are large, circular light-producing organs just behind the fins on the mantle. The tentaclelike arms are covered by tiny, hairlike structures called cirri (SIH-ree). The arms have suckers only on the outer halves.

Geographic range: This species is found in all cool and warm water oceans.

Habitat: Vampire squids live in open waters at depths of 1,965 to 4,920 feet (600 to 1,500 meters).

Diet: They probably eat jellylike animals carried about on ocean currents.

Behavior and reproduction: These fast-swimming animals resemble an umbrella or a bell shape as they move through the water with their webbed arms extended forward. They create complex flashing displays with their light-producing organs.

Vampire squids and people: This species is commonly seen on television programs featuring deep-sea animals.

They hatch with one pair of fins, but then develop a second pair closer to the front of the body. For a short period the vampire squid has two pairs of fins. The first pair soon disappears. Except for the fins, young vampire squid resemble the adults.

Conservation status: The vampire squid is not considered threatened or endangered. ∎