Corals & Other Invertebrates

The American oyster is a well-known species found in the Chesapeake Bay and other eastern North American coastal waterways. In the past, this species was so widespread and produced such enormous reefs that it was known to pose a navigational risk in some locations. Sadly, overfishing, pollution, and physical harm in the past have caused certain populations of American oysters to drop to just 1% of their former abundance.

The blue glaucus, a species of vividly colored sea slug (nudibranch), is found in temperate and tropical waters all over the Atlantic, Pacific, and Indian Oceans. It is also known as the blue dragon, sea swallow, or blue angel. This species of nudibranch, like the majority of them, absorbs poisonous substances or stinging cells from its food into its own skin. The blue glaucus has a protection mechanism against predation thanks to its aptitude.

The bluebottle, also known as the Indo-Pacific Man of War, is a siphonophore, a group of tiny, specialized polyps that cooperate as colonies rather than a jellyfish. The blue, gas-filled sac (pneumatophore) that floats on the surface of the water makes the bluebottle easy to identify. Strong winds in the Southern Hemisphere's summertime transport bluebottles to Australia's coasts, where tens of thousands of bluebottle stings are reported annually.

The deep fjords of southern Chile and maybe other deep benthic habitats in southern South America are home to the Chilean basket star, a type of brittle star. Every hair-like appendage on this species, like all basket stars, originates from five central arms that regularly divide into the basket form that gives the group its popular name. This species possesses five-part symmetry, like all basket stars.

The Christmas Tree Worms are so-called because of their spindly, fir-tree-like appearance. Their festive-looking crowns protrude from their otherwise tube-like body, which is made up of radioles (hair-like) appendages that radiate from the worm's spines. These appendages are used to catch dinner in the water, which is typically microscopic plants and animals.

The cockscomb cup coral is a true stony coral that lives in deep seas and cold-water fjords rather than shallow tropical coral reefs. This species, like all corals, is related to anemones, jellyfish, and other animals in the Phylum Cnidaria. Cockscomb cup corals and other deep-water corals, unlike shallow-water corals, do not get their food from symbiotic algae living inside their cells. Instead, they are filter feeders that get all of their energy from picking individual plankton from deep-sea currents.

Acanthaster planci, the crown-of-thorns starfish, is a large starfish that feeds on hard, or stony, coral polyps. The venomous thorn-like spines that cover the upper surface of the crown-of-thorns starfish are named after the biblical crown of thorns. It is one of the world's largest starfish. Crown-of-thorns Starfish populations fluctuate between times of high densities and times of low densities. This species is not used by humans, but scientists consider it a species of concern - not because its numbers are too low, but because locally high populations can threaten other species.

The cushion star, like all sea stars, moves on a system of tube feet that are powered by a hydraulic system controlled by the main body. They are known to feed on corals, sedentary animals, and decaying organic matter. They feed by inverting their entire stomach through the mouth and digesting soft tissue from a coral's skeleton or clam meat right in the open environment, sucking down the available nutrients. Cushion stars reproduce by broadcast spawning, which involves several females releasing eggs and several males releasing sperm into the water column above the sand at the same time. This method increases the likelihood of successfully fertilised eggs and that fertilised eggs will not be eaten by egg predators near the reef.

The eccentric sand dollar is a small species (only a few inches across) that lives off the west coast of North America, from Alaska to Baja California. Despite being completely flat, these sand dollars are frequently seen buried in the sand on an edge, with half of their bodies buried and half sticking out into the water. Eccentric sand dollars, like most sand dollars, are filter feeders, and they snag crustacean larva, plankton, and other tiny prey with the small spines that cover their bodies. The food is slowly passed from spine to spine until it reaches the mouth at the bottom of the body's middle.

The edible sea cucumber, like most sea cucumbers, is a scavenger. It crawls along soft bottoms near coral reefs and seagrass beds, consuming sand and mud along the way. It separates and digests any plant or animal matter before passing through the sand, leaving a clean sand trail behind. The edible sea cucumber feeds all day and night, only sleeping occasionally. This species reproduces by broadcast spawning, in which females release eggs and males release sperm into the water column simultaneously. This method increases the likelihood of successfully fertilised eggs and that fertilised eggs will not be eaten by egg predators on the reef surface.

Elkhorn coral structures are actually colonies of genetically identical animals coexisting. These colonies are hermaphroditic, meaning that each animal produces both eggs and sperm, and they can reproduce both sexually and asexually. Elkhorn corals release bundles of eggs and sperm that float to the surface, break apart, and mix during the few days surrounding full moons in the fall. Because sperm cannot fertilise eggs from the same colony, several colonies release their gametes simultaneously, a process known as broadcast spawning. The fertilised egg hatches quickly, and the baby coral spends a few days in the water column before landing on the reef and starting a new colony. Elkhorn coral colonies can reproduce by fragmentation as well (asexually). When a storm or other disturbance rips a colony apart, each piece can reattach to the reef surface and begin growing again.

Felimare cantabrica, like all nudibranchs, is hermaphroditic, meaning that each individual produces both eggs and sperm. Individuals cannot fertilise their own eggs, so pairs must still mate. They reproduce by internal fertilisation and laying eggs on the reef surface or other hard substrates. Long strings of eggs are frequently spiral shaped. Neither parent looks after or protects the eggs. Little is known about the conservation status of Felimare cantabrica, like most small marine invertebrates, but this species has a relatively small home range. As a result, any significant changes to the rocky reef ecosystems in its range, as well as general threats to the marine environment, could jeopardise the survival of this naturally rare species.

Cerata are the bright orange, white-tipped structures that run along the dorsal surface of the flameback and increase the skin's surface area. Because this nudibranch absorbs oxygen through its skin, a larger surface area aids respiration. The cerata also increase the number of defence cells stored by the flameback from its prey. The flameback, like all nudibranchs, is hermaphroditic, meaning that each individual produces both eggs and sperm. Individuals cannot fertilise their own eggs, so pairs must still mate. They reproduce by internal fertilisation and laying eggs on the reef surface or other hard substrates. Long strings of eggs are frequently spiral shaped. Neither parent looks after or protects the eggs.

This jellyfish drifts around for a long time, slowly pulsing its bell. The mouth-arm openings in the jellyfish's numerous short, club-like appendages allow it to trap and feed on prey. Zooplankton and other jellyfish are the Fried Egg Jellyfish's primary prey. These appendages are typically deep purple in colour, and while stingers are present, the sting has little effect on humans. Its sting is so mild that the tentacles will sometimes shelter small fish in the open ocean. Cotylorhiza tuberculata is a species of Fried Egg Jellyfish that is most commonly found in the Mediterranean Sea. Another is Phacellophora camtschatica, a larger jellyfish found all over the world.

Sponges are one of the Earth's oldest and most primitive animal groups. Sponges have been around for over 500 million years. Sponge cells serve no specific function. Each individual cell in a sponge can transform to perform the function of any other cell in the body. Because of this lack of specialisation, sponges, like all other animals, lack tissues. In fact, a sponge that has been destroyed in a blender can reform itself in a laboratory setting as the cells swim back together and take on the form and job required for recovery. Giant barrel sponges eat by filtering water through their body walls, trapping food particles and excreting waste into the inner bowl.

This predatory anemone feeds on fish, crustaceans, and other invertebrates that get too close to its tentacles. Stinging cells cover the tentacles, paralysing their prey. After capturing a small fish or other prey, the anemone quickly wraps it in as many tentacles as possible. It then efficiently transports the prey to its mouth, which is located in the centre of its disc. Though no anemonefishes are native to the Caribbean, the giant Caribbean sea anemone is known to house some symbiotic animal species. Juvenile cardinalfishes, cleaner shrimps, and crabs have all been observed using giant Caribbean sea anemones as a habitat.

Giant carpet anemones, like most corals and several other anemones, feed in a variety of ways. The majority of their energy comes from symbiotic algae living within their cells, which provide the anemones with excess energy produced by photosynthesis (the conversion of carbon dioxide into food/energy using sunlight). In exchange, the algae have a safe place to live and the nutrients they need to photosynthesize. The giant carpet anemone gets those nutrients by eating fish or invertebrates that it captures with stinging cells on the ends of its tentacles and passes to its mouth near the centre of its body.

The largest known giant clam specimen was over four and a half feet (1.3 m) wide and weighed around 550 pounds (250 kg). The shell accounts for the vast majority of a giant clam's mass, with the soft parts accounting for only about 10% of its weight. Giant clams, like most corals, some anemones, and other reef organisms, feed in a variety of ways. The majority of their energy comes from symbiotic algae living within their cells, which provide the clams with excess energy produced by photosynthesis (the conversion of carbon dioxide into food/energy using sunlight). In exchange, the algae have a safe place to live and the nutrients they need to photosynthesize.

Because the giant kelp is not a plant, it lacks roots. Instead, it gets all of its nutrients from the water and is attached to the rocky bottom by a structure called a holdfast. The giant kelp, like plants, harvests the sun's energy via photosynthesis and does not feed on other organisms. This species is one of the world's fastest growing, and under ideal conditions, it has been known to grow up to two feet (60 cm) in a single day. Once a giant kelp reaches the sea surface, it grows horizontally, forming large mats that shade the water column and sea floor below.

Giant Pyrosomes are bioluminescent (light emitting), hence the common name, which is derived from the Greek words for fire ("pyro") and body ("soma"). The light emitted by Giant Pyrosomes is particularly bright and long-lasting, making it a sight to behold. Because individual tunicates can reproduce through cloning, the colony can regenerate injured parts or continue to grow after being split up. A colony can theoretically live forever, shrinking and growing based on available food and physical disturbance unless all individual clones are killed at the same time. Individual clones are hermaphrodites, meaning they produce both eggs and sperm. Individuals are likely to engage in sexual reproduction when two colonies meet in the open ocean.

This species produces large, circular structures with diameters of more than 6 feet (nearly 2 m). Despite their size, only the outer few millimeters are alive tissue, with the rest being a calcium carbonate skeleton. Grooved brain coral structures grow only a few millimeters per year and can live for hundreds of years. Each structure is actually a colony of genetically identical animals coexisting. These animals reproduce sexually and are hermaphroditic (each individual produces both eggs and sperm). Sperm are released into the water column and are captured by other organisms that filter feed. Instead of being consumed, sperm are used to fertilize eggs within the colony.

Shallow-water populations are known to have symbiotic algae living within their cells, providing the corals with excess energy produced by photosynthesis (the conversion of carbon dioxide into food/energy using sunlight). Nearly all shallow-water coral species, as well as several other groups of reef invertebrates, have symbiotic relationships with these algae. However, because there is insufficient sunlight to perform photosynthesis on deep reefs, ivory bush corals obtain all of their energy by filter feeding individual plankton from the water that flows along deep-sea currents.

The lion's mane jellyfish is easily identified in the open ocean, where it prefers to float. Some individuals can rival the size of the blue whale, the world's largest animal, with tentacles up to 120 feet long. The majority of lion's mane jellyfish live in the Arctic and North Pacific Oceans, from Alaska to Washington. The lion mane gets its name from its'mane' of long, hair-like tentacles hanging from the underside of its bell-shaped body. The mouth is located on the underside of the bell and is surrounded by tentacles divided into eight clusters of up to 150 tentacles each. These tentacles are armed with nematocysts that contain poison and stun prey when they are engulfed.

This species builds massive structures that can span several meters. Despite their size, only the outer few millimeters are alive tissue, with the rest being a calcium carbonate skeleton. Lobe coral structures grow only a few centimeters per year and can live for hundreds of years. Each structure is actually a colony of genetically identical animals coexisting. Several colonies grow together in some areas to form a nearly continuous stretch of lobe corals that can be tens of meters (or more) long. Lobe corals, unlike many other coral species, are either male or female. They reproduce by broadcast spawning, in which several individuals simultaneously release their eggs or sperm into the water column.

The lophelia coral builds structures that provide habitat for a variety of invertebrates and fishes wherever it lives. Some lophelia coral reefs can stretch for miles and rise to at least 100 feet (30 meters) above the seafloor. This size of Lophelia coral reef could be tens of thousands of years old. Individual lophelia colonies are extremely slow growing and can live for over 1000 years. This species is typically found at depths of about 3300 feet (1000 meters), but it has been observed or collected at depths of nearly 10,000 feet (3000 m).

Though the moon jelly can be found throughout the epipelagic zone, it is most commonly found near the coast and in upwelling areas, where its prey is more abundant. Because this species is not a strong swimmer, it is frequently found on beaches after strong storms or high tides. Moon jellies, like other jellies, are a favorite prey of some open ocean predators, such as the ocean sunfish and the leatherback turtle. They have very little nutritional value, so predators that specialize in them must consume hundreds and hundreds of these jellies to maintain their energy levels.

Purple sea urchins, for example, are important prey for sea otters and sea stars on the Pacific seafloor. Humans consume Pacific purple sea urchins. The meat inside, known as "uni" in Japanese, is considered a sushi delicacy, with demand increasing in recent years. Because of their increasingly aggressive feeding behavior, Pacific purple sea urchins are at least partially to blame for the deforestation of Northern California's kelp forests. Marine heatwaves have caused kelp forest declines and contributed to the rise of "urchin barrens," or large swaths of seafloor overrun by kelp-feasting Pacific purple sea urchins and other species.

The Portuguese man o' war is a predator. It stings and paralyzes small fish, pelagic crustaceans, and other invertebrates with its feeding tentacles. Some individuals have feeding tentacles that are up to 160 feet (50 meters) long! These tentacles have a strong sting and are used to defend against predators. Few species consume the Portuguese man o' war, but some predators that specialize in stinging, gelatinous invertebrates (e.g., loggerhead sea turtles and ocean sunfish) have been observed eating this and other siphonophores.

The sea wasp hunts small fish and pelagic invertebrates such as swimming crabs and prawns using these stinging cells. Cnidocytes are also the source of the potent sting, and stories of sea wasp deaths almost always involve a person being wrapped in multiple tentacles, with stings covering much of the body. Because the genus Chironex contains numerous cryptic species, the exact range of the sea wasp is unknown. It is especially common off Australia's northern coast, where beachgoers are frequently stung, prompting the tourism industry to launch a massive campaign to install nets off of major swimming areas to keep the sea wasps out.

Though this species spends most of its time crawling along the reef surface, when threatened, it will swim, violently flapping its external gills and other appendages and flashing its brightest warning colors. This behavior resembled that of a flamenco dancer to some observers, earning the Spanish dancer its common name. Spanish dancers are specialized predators that prefer to eat sponges and concentrate compounds found in their prey to provide chemical defense for themselves and their eggs. Spanish dancers, like other nudibranchs, are hermaphrodites; all individuals are both male and female. Individuals, on the other hand, cannot self-fertilize and must always have a mate. Once the eggs are laid on the reef, neither parent takes care of them.