Pretty Sea Anemone - a photo on Flickriver

Pretty Sea Anemone

            Photographed at a dive site called Far Garden, Sharm el Sheikh, Egypt.

Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger prey and also lack a medusa stage. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra.

A sea anemone is a polyp attached at the bottom to the surface beneath it by an adhesive foot, called a basal disc, with a column shaped body ending in an oral disc. Most are from 1.8 to 3 centimetres (0.71 to 1.2 in) in diameter, but anemones as small as 4 millimetres (0.16 in) or as large as nearly 2 metres (6.6 ft) are known. They can have anywhere from a few tens to a few hundred tentacles.

A few species are pelagic, and are not attached to the bottom; instead they have a gas chamber within the pedal disc, allowing them to float upside down in the water.

The mouth is in the middle of the oral disc surrounded by tentacles armed with many cnidocytes, which are cells that function as a defense and as a means to capture prey. Cnidocytes contain nematocyst, capsule-like organelles capable of everting, giving phylum Cnidaria its name. The cnidae that sting are called nematocysts. Each nematocyst contains a small vesicle filled with toxins (actinoporins), an inner filament, and an external sensory hair. When the hair is touched it mechanically triggers the cell explosion, a harpoon-like structure which attaches to organisms that trigger it, and injects a dose of venom in the flesh of the aggressor or prey. This gives the anemone its characteristic sticky feeling. The sea anemone eats small fish and shrimp.

The venom is a mix of toxins, including neurotoxins, which paralyzes the prey and allows it to be moved to the mouth for digestion inside the gastrovascular cavity. Actinoporins have been reported as highly toxic to fish and crustaceans, which are the natural prey of sea anemones. In addition to their role in predation, it has been suggested that actinoporins could act, when released in water, as repellents against potential predators[citation needed]. Anemonefish (clownfish), small banded fish in various colors, are not affected by their host anemone's sting and shelter themselves from predators within its tentacles.

The internal anatomy of anemones is quite complex.

Taken in: مصر / جنوب سيناء (show map)

Taken on: September 28, 2012

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Pretty Sea Anemone

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Sets appears in: • Scuba Diving

Groups appears in: • Underwater Magic • Diving more » • All Animals • Scuba Diving • Sharm • Nature Photography • Scuba • Underwater • Animal Planet • Nature Heals the Soul • PADI Diving Society • Red Sea • Underwater Macro • *Animal Photography* • Underwater Beauty • Sharm El Sheikh - Egypt • Underwater Photos (Scuba, Free Diving) • Scuba Diving Photography • Underwater Photography - Scuba • RED SEA LOVERS • uk diving - on holiday • Any kind of wildlife/nature « less

Camera: Fujifilm FinePix F100fd, f/9.0, 1/60 sec, 6.4mm, ISO 320 (more info) (hide info)

Camera:	Fujifilm FinePix F100fd
Aperture:	f/9.0
Exposure Time:	0.017 sec (1/60)
Focal Length:	6.4mm
ISO:	320
Exposure Bias:	0 EV
Flash:	On, Fired
Exposure Program:	Program AE
Exposure Mode:	Auto
Metering Mode:	Multi-segment
White Balance:	Auto
Color Space:	sRGB
Software:	Adobe Photoshop CS6 (Windows)
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