Coral Reef Anemones

Sea Anemones are a group of marine predators related to corals and jellyfish. They are classified within the Cnidaria phylum and often look like large, floating sea flowers. A great majority of these creatures live out their lives attached to a rock through a basal disc at the bottom of their bodies. They have a very simple digestive system, in which they capture prey through the mouth, digest it, and then excrete waste through the same opening. Most sea anemones are venomous users of nematocysts, like jellyfish.

Sea Anemones have a complex internal anatomy consisting of a number of unusual features. Their incomplete digestive system is one such feature for which they have adapted a unique response to. The anemone nerve system is also unusual, in that sea anemones do not appear to have any specialized organs for sense – no eyes, touch-sensitive cells or the ability to smell. Unlike other cnidarians, most sea anemones do not spend a portion of their life in a medusa stage where they freely swim and float about until finding an appropriate place to attach themselves to. They will stay attached to the same spot until conditions force them to move.

These particular cnidarians can reproduce both sexually and asexually. In sexual reproduction, males release sperm in the water and, thus, stimulate females into releasing eggs, and fertilization occurs in the open water between the two individuals. The resulting fertilized egg then turned into a planula that grows into a single polyp that then attaches itself to a nearby rock. In asexual reproduction, sea anemones can bud extra individuals, reproduce by binary fission, or through regeneration of lacerated parts of the pedal disc. Large enough parts cut off of a sea anemone will regenerate into a new individual.

The sea anemone features an oral disk that it uses to capture and eat prey. Because the anemone is largely immobile, it will attach itself to a rock and wait for unsuspecting prey to travel too close. When this happens, the venomous nematocysts will discharge, rendering the prey helpless as the anemone consumes it. It is not uncommon for sea anemones to foster symbiotic relationships with certain fish, algae and crustaceans, some of which are responsible for bringing food sources to the anemone. Some algae directly provide oxygen and glycerol to the organism.

Tube Anemone

The tube anemone is a large species widespread across the Mediterranean, around the coast of Africa and around Papua New Guinea. The species is known by many names, all of them referring to one aspect or another of the animal’s appearance or behavior – it is often called the tube-dwelling anemone, the colored tube anemone or the burrowing anemone. The creature is not a true anemone in fact, having numerous features that distinguish it from true anemones.

These creatures come in all the colors of the rainbow, usually in combinations of fluorescent colors. They are also quite large, reaching over 20 cm in diameter, with two different sets of tentacles (one of the features that sets tis creature apart from true anemones that have only one type of tentacles) – shorter labial tentacles used for the manipulation of the prey in the center of the disc and longer feeding tentacles used for capturing prey towards the edges around 30 cm in length. The two types of tentacles are usually of different colors. The lower part of the tube anemone consists of a soft, cylindrical body that end in a strong and pointed foot that is used by the anemone to burrow into the substrate (unlike true anemones, these creatures do not attach themselves to the substrate). The body is surrounded by a protective tube built by releasing special, venomous threads that connect to form hard and resistant woven tissue. When the anemone feels threatened, it can either use its venomous tentacles to sting the attacker or it can withdraw into the tube completely and it can also dig a hole in the sandy substrate with its foot and disappear in it.

Tube anemones are nocturnal and carnivorous. Unlike true anemones, these tube-dwelling creatures do not rely on photosynthesis byproducts as sources of energy, obtaining nutrients exclusively from the prey such as small shrimps, crustaceans and small fish that they catch in the water column.

Very little is known about the proliferation of tube anemones, but what seems to be sure is that fertilization takes place externally, with male and female individuals releasing their gametes into the water and all small or young individuals are born male and some of them become female after a certain age or when they reach a certain size. They are very long-lived, many tube anemone individuals reaching 100 years of age, maybe even more.

Sebae Anemone

Also known as the leathery sea anemone, the purple tip, blue tip or the long tentacle anemone, the sebae is among the largest anemone species dwelling the Indo-Pacific region. Widespread in the coastal areas around Africa to Australia, Polynesia and the Red Sea, these creatures prefer the shallow waters in reef areas not deeper than 40 m where they can cling to corals.

The oral disc of the anemones is flared and can grow to a diameter of 50 cm. The number of the tentacles is usually a multiple of six, but not more than 800. They are long, usually around 15 cm and they end in a rounded, colorful tip. The tentacles are arranged around a central oral cavity and are usually grey, greenish, violet or tan, they have white, wart-like dots, but they otherwise have smooth texture and leathery appearance. Sebae anemones can also be of uniform light grey color as well. The animal gets its coloring from the zooxanthellae algae that live inside its tissues, but the algae are not the only life forms that sebae anemones live in symbiosis with – the large disc and the long tentacles provide home for over 15 different species including fish and shrimps. However, this anemone species uses advanced techniques to deter animals that are harmful or dangerous – the tentacles have cells called nematocysts that secrete venom, making the sting of the anemone painful.

These anemones, like most other species of true anemones, use two feeding methods: they extract food particles and capture tiny prey such as miniature shrimps and other crustaceans from the water column with the help of the tentacles and they also use the waste produced by the photosynthetic zooxanthellae algae inside them. The mouth in the center opens only when the animal is feeding – when it is not hungry and searching the water column for food, the mouth is sealed.

These anemones have two reproduction methods as well: they can either multiply asexually, by means of a fissuring into two separate individuals (a process called scissiparity) and sexually. When the latter method is chosen, the male and the female release their respective gametes into the water simultaneously. Fertilization occurs externally, the fertilized eggs soon hatching into larvae that grow to form new sebae anemone individuals.

Rock Flower Anemone

The rock flower anemone is the most spectacular and the most colorful out of all anemone species. Common across the Caribbean and in the West Indies, this flower-like animal often called the beaded or the red beaded anemone not only adds spots of color to the sandy substrate, but further enriches the chromatic spectrum of the coral reefs as well.

Flower anemones are not big, the flat disc usually measures around 15 cm when the animal is fully developed. The first feature that meets the eye when looking at the rock flower anemone is how colorful it is. The basal disk with the mouth of the animal in the center is usually cream-colored or tan, with red and greyish stripes. The short tentacles – there are usually 200 of them on a full-grown disk – come in multiple colors, from brown, yellow, purple, green to red and green and they are arranged concentrically from the mouth toward the edges. The column comes with bright red suckers that capture debris for camouflage. The tentacles also have stinging cells that the anemone uses to protect itself, but only as a last resort – these flower anemones are known to be very peaceful, trying to withdraw into the substrate or into crevices when they feel threatened and using the stinging cells only when nothing else helps. Rocky flower anemones provide home to numerous other species such as zooxanthellae algae, copepods and various fish and snail species. Though these anemones spend most of their time anchored to the substrate or to corals with their base, they are mobile to a certain extent, able to move slowly around if they need to.

Like many other anemone species, rock flower anemones feed primarily on the waste produced by the zooxanthellae algae that live in their tissues. The algae photosynthesize and as a byproduct of the process they eliminate carbohydrates and oxygen used by the anemone. The animal also pursues food actively, capturing tiny food particles that swim by in the water column.

These anemones have a very long reproductive cycle, mating occurring once a year or once every two years. They reproduce sexually – the males release their sperm into the water, but fertilization takes place internally, in the female’s body. When the juvenile rock flower anemone individuals are released from the female’s body, they settle immediately in the vicinity of the mother.

Ritteri Anemone

The Ritteri anemone, also known as the magnificent sea anemone, is a spectacular species living in the shallow waters of the Indo-Pacific region. It prefers areas where the substrate is hard and sunlight is plentiful, so it is very rarely found in waters deeper than 20 m.

The Ritteri anemone is large, having a flared oral disc that usually measures 20-50 cm in diameter, but can grow to around 1 meter. The base, the tentacles and the oral cavity of the magnificent anemone are of the same color, usually cream or white, but the tentacles can be of any color from white and green to blue, pink and orange. The tentacles are long, usually measuring 6-8 cm and they are distributed in concentric circles. The tentacles end in finger-like tips that are often of a different, brighter color than the rest of the tentacle. Magnificent anemones are not peaceful, but they live in symbiosis not only with algae, but with numerous larger species such as shrimps and fish, especially colorful species such as clownfish or anemonefish that have bodies covered in a special mucus that protects the fish against the stinging toxin released by its host. When the anemone feels threatened, its tentacles are almost completely withdrawn into the base, but it may also choose to defend itself by stinging the attacker with its tentacles. Though they live on the substrate attached to a suitable spot, they are also able to move, following ideal food and light conditions.

These anemones have not one, but two highly efficient feeding methods, used simultaneously: they use their tentacles to capture prey such as juvenile fish and small invertebrates and they also use the microscopic zooxanthellae algae that live in symbiosis with them to obtain nutrients from the byproducts of the photosynthesis carried out by the algae such as carbohydrates and glucose.

Like many other anemone species, magnificent sea anemone can reproduce sexually as well as asexually. Sexual proliferation takes place by means of spawning – the males and females release their gametes into the water at the same time, fertilization occurring externally, in the water, then the fertilized eggs hatching into tiny larvae that float until they are sufficiently developed to settle. Asexual reproduction takes place via scissiparity – the Ritteri anemone divides itself starting from the mouth or from the foot to form two individuals.

Carpet Anemone

The carpet anemone is a family of marine animals that includes some of the most beautifully colored, but also some of the deadliest creatures of the sea. The members of the family all live in tropical waters, most of them in the shallow waters of the Indo-Pacific.

Carpet anemones are large, many of them growing to a diameter of over 3 feet. They have very short stalks, an aspect that gives them their carpet-like appearance. The tentacles vary in coloring – they can be any hue from bright blue and purple to green, cream and tan. The foot that fastens the anemone to the substrate is usually whitish or cream-colored, with colorful warts. These anemones are fragile and very sensitive to being touched and, therefore, they protect themselves using various methods. When threatened, one of the members of the family, Haddon’s anemone first tries to bury itself in the sand and uses its stinging tentacles only when burying proves ineffective. Other types of carpet anemones are unable to bury themselves, so they protect themselves with the help of the nematocysts at the tip of their tentacles that secrete a potent neurotoxin – dangerous not only for marine predators, but to humans as well. Though venomous, carpet anemones live in peaceful symbiosis with over ten other animal species that find shelter and protection among the stinging tentacles. The species that anemones live in symbiosis with include many different anemonefish that secrete a special kind of mucus to protect their skin against the stinging nematocysts of the host animal.

These large and sensitive creatures obtain their food from various sources. The microscopic zooxanthellae algae that live inside the anemones photosynthesize and during the process they produce waste materials that are valuable sources of energy for the host anemone. The anemone also uses its stinging tentacles to paralyze and capture small fish, shrimps and crabs that swim by. Sometimes they feed on the snails that come close enough to the tentacles.

Carpet anemones can reproduce both sexually and asexually. Many anemones are hermaphrodites that are able to produce eggs as well as sperm. Fertilization takes place externally, after the fluids are released into the water. During asexual reproduction, the creature divides itself into smaller pieces, each of which develop into new carpet anemone individuals.

Bubble Tip Anemone

Entacmaea quadricolor, commonly known as the bubble tip anemone, is a beautiful predatory creature that lives attached to the substrate in the shallow waters of the Indo-Pacific region. These anemones prefer coral reef habitats, where they live in colonies or alone. They often become the preferred habitat for other species as well – anemones are known to live in symbiotic relationships not only with zooxanthellae algae, which help them get food, but also with small fish and crustaceans.

Entacmaea quadricolor individuals relatively small, the maximum diameter they can grow to being around 30 cm. The bubble tip is a sessile species, living fixed to the substrate with a strong foot, but like most anemone species, bubble tips can detach themselves from the substrate if it is absolutely necessary for survival. Out of the foot grow the tentacles at the end of which spherical or pear-shaped bubbles appear right under the tip. The bubble comes in various colors, from brown and pink to green, blue and purple. The number of the tentacles (and with the tentacles, the number of the bubble tips) keeps growing as the anemone ages – young individuals have only about 20 tentacles, while older ones might have hundreds of them!

These creatures are unable to move, and therefore they get the nutrients they need by filtering the water column and by using the help provided by microscopic algae and other species that live in, on and around them. During the filter-feeding process, the anemone uses its tentacles to snatch tiny food particles from the water. It also feeds on the debris it scrapes off the body of another of its symbionts, the anemonefish that is given shelter among the long, often stingy tentacles of the anemone. Another example of the symbiotic relationships the anemone engages into is with the microscopic algae that reside in the digestive tract – the algae find in the anemone the exposure to solar rays that they need for photosynthesis and the anemone is provided with oxygen, glucose, alanine and other nutrients that are the by-products of the photosynthesis.

Bubble tips can reproduce both sexually and asexually. This means that they can proliferate by cloning and they are also known to be spawners. The males and the females release their reproductive fluids into the water, and then fertilization happens in the water column, followed by the development of the free-floating larvae. Floating continues until the larva finds a suitable place to settle and to start growing into a beautiful bubble tip anemone.

Whale in Ocean