Symbiosis is the interaction between two different organisms living in close association.
Symbiotic relationships are an important component of life in the ocean. In such relationships, plants or animals of different species may be dependent on one another for survival. They may share habitats or lifestyles or interact in a specific way to benefit from the presence of another organism.
When two organisms are in a symbiotic relationship, sometimes both organisms benefit (mutualism) and other times one organism may benefit while another is unaffected (commensalism). If one of the organisms is completely dependent on the other, it is called an obligate relationship; if the relationship is preferred, but not dependent, it is a facultative relationship. And, not all symbioses are positive for both organisms: in a parasitic relationship, one member benefits while the “host” is harmed…
image: Hermit crabs are often found inhabiting shells decorated with anemones or other sessile animals, which offer added protection and camouflage. Image courtesy of NOAA Okeanos Explorer Program, 2013 Northeast U.S. Canyons Expedition.
Bolocera tuediae is large sea anemone that can grow up to 300mm across tentacles. This large and distinctive anemone is capable of shedding its tentacles, pinching them off by muscular action, hence the groove at their bases. The reason for this is unknown.
Generally distributed throughout the north Atlantic, north to the Arctic Circle and east to north America, this species is recorded from all coasts of Britain but rare in south.
The specimen shown is 25 cm in diameter. It was photographed in St.Abbs, Eyemouth, Scotland, UK.
(Nature category) - An over/under water split level image of beautiful crimson red waratah anemones in a rock pool at low tide in Australia. What I really love about over/under photographs is that it gives the underwater element a sense of place. For the viewer it marries the underwater environment with our own familiar world. It links the unknown with the known.
Two red Anthomastus octocoral (a large one and small one), a squat lobster (Munidopsis sp.), an unidentified species of anemone, and several shrimp on a rocky outcrop, deep sea, from the Gulf of Mexico 2012 Expedition.
Image courtesy of the NOAA Okeanos Explorer Program.
The hydrothermal chimneys and wildlife around the vents called Soria Moria are located roughly 2,300 feet (700 meter) below the surface, about 60 miles (100 km) east of Jan Mayen, a remote Norwegian volcanic island in the Arctic Ocean.
This alien-looking creature is known as Nematostella vectensis, or the starlet sea anemone. Like other anemones, starlets start life as free-swimming larvae. They then settle into an appropriately mucky spot on the seafloor and metamorphose into their adult polyp form, seen here.
Anemones lack brains, but the section of the larvae containing the sensory organs actually becomes the bulbous root end of the adult, while the other side sprouts delicate tentacles and transforms into a filter-feeding mouth.
Researchers have now found that the “head genes” of N. vectensis, though held in what eventually becomes the animal’s “foot,” correspond to the head genes found in the actual heads of higher animals. Humans and other brainy beasts share a common, brainless, ancestor with sea anemones that lived 600 million to 700 million years ago. The findings were released Feb. 20, 2013 in the journal PLOS Biology.
A sea anemone and hermit crab share a snail shell, providing a wonderful example of mutualism. The anemone (like all cnidarians) has stinging cells that help protect the crab from predators; and benefits from having a free ride around the seafloor habitat, as well as receiving scraps from the crab’s feeding activities. When the crab outgrows its borrowed shell, it finds a larger vacant shell… and brings the anemone along to share its new home.
Image courtesy of NOAA Okeanos Explorer Program, INDEX-SATAL 2010.
Cup corals (Desmophyllum) grow around an anemone on a mud-covered ledge. During the Deepwater Canyons 2013 expedition, scientists collected cup coral specimens to help them understand the factors that influence the distribution of this species and perhaps even solve the mystery of differences observed between the deep and shallow populations.
Also known as the tentacle shedding anemone, the pom-pom anemone is a species of sea anemone found in deep water in the north east Pacific. Like other anemones the pom-pom anemone is a carnivore and will attempt to eat any small animals unfortunate enough to swim into its tentacles. Pom-pom anemones are also fed on by sea spiders who steal tentacles from it. Although it usually lives a sessile lifestyle, the pom-pom anemone does not attach its self to a substrate and it can roll itself up like a rug and drift with the current like a tumbleweed, stopping when it reaches a solid object.
Also known as the giant plumose anemone, the white-plumed anemone is a species of sea anemone found throughout the western seaboard of North America. Like most anemones, the giant plumose anemone is a carnivore and feeds on small invertebrates and zooplankton that swim into their stinging nematocysts. White-plumed anemones have very long lifespans (with individuals living up to 100 years) and can grow fairly large and as such have few predators, although nudibranchs and large starfish have been observed feeding on them.
The numerous young are seen on the pedal disk are derived from eggs fertilized in the digestive cavity. The motile larvae, after swimming out of the mouth, migrate down to the disk and becomes installed there until they become little anemones ready to move and be able to feed themselves.
(Photo and caption: Brocken Inaglory, via: wikimedia)
A fundamental question in the evolution of animal body plans, is where did the head come from? In animals with a clear axis of right-left symmetry, the bilaterians, the head is where the brain is, at the anterior pole of the body.
Little is known about the possible ancestor of bilaterians. Fortunately their sister group from that same progenitor, the cnidarians, can be studied in parallel today to give some clues. Cnidarians are creatures like jellyfish, hydra, and sea anemone which possess rudimentary nerve nets, but no clear brain. They all have just a single orifice to the external world, which basically does it all.
In a recent paper published in PLOS Biology, researchers from the University of Bergen in Norway compared gene expression patterns in sea anemone (Nematostella vectensis, Nv) with that from a variety of bilaterian animals. They found that the head-forming region of bilaterians is actually derived from the aboral, the opposite-oral, side of the ancestral body plan…
Also known as the proliferating or small green anemone, the brooding sea anemone is a species of sea anemone endemic to the north-eastern Pacific. This species is unique as it is protogynic hermaphrodite, meaning it starts its life as a female and when it reaches a certain size it develops testes and lives as a proper hermaphrodite for the rest of its life. This species gets the name “brooding” as its young will remain within its mother’s gastrovacular cavity during early development. Like most cnidarians this anemone is a suspension feeder, disabling any prey that happens to stumble upon its tentacles.