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Sea anemone  

From Wikipedia, the free encyclopedia


Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria. They are named for the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia.  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.


Many sea anemones form symbiotic relationships with single-celled dinoflagellates, whetherzooxanthellae or zoochlorellae, that live within their cells.


The global trade in marine ornamentals for aquariums is rapidly expanding, and threatens sea anemone populations as the trade depends on collection from the wild, and the animals grow and reproduce relatively slowly.


Anemones  : 

Anatomy :


A sea anemone is a sessile 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 cm (0.71 to 1.18 in) in diameter, but anemones as small as 4 mm (0.16 in) or as large as nearly 2 m (6.6 ft) are known.[3] They can have 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, also the anus of the sea anemone, is in the middle of the oral disc surrounded by tentacles armed with many cnidocytes, cells that are both defensive and used to capture prey. Cnidocytes contain stinging nematocysts, capsule-like organelles capable of everting suddenly, giving the phylum Cnidaria its name.[5] Each nematocyst contains a small venom vesicle filled with actinotoxins, an inner filament, and an external sensory hair. A touch to the hair mechanically triggers a cell explosion, which launches a harpoon-like structure that attaches to the organism that triggered 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, that paralyzes the prey so the anemone can move it to the mouth for digestion inside the gastrovascular cavity. Actinotoxins are highly toxic to prey species of fish andcrustaceans. However, Amphiprioninae (clownfish), small banded fish in various colors, are not affected by their host anemone's sting and shelter themselves from predators among its tentacles.[6] Several other species have similar adaptions and are also unaffected (see Symbiotic relationships). Most sea anemones are harmless to humans, but a few highly toxic species (notably Actinodendron, Phyllodiscus and Stichodactyla) have caused severe injuries and are potentially lethal.


The internal anatomy of anemones is quite complex.

Sea Anemone Anatomy.
1. Tentacles 2. Mouth 3. Retracting muscles 4. Gonads 5. Acontial filaments 6. Pedal disk 7. Ostium 8. Coelenteron 9. Sphincter muscle 10. Mesentery 11. Column 12. Pharynx

Digestive system :


A gastrovascular cavity (which functions as a stomach) with a single opening to the outside is both a mouth andanus. Waste and undigested matter is excreted through this opening, which can be described as an incomplete gut. The mouth is typically slit-like in shape, and bears a groove at one or both ends. The groove, termed asiphonophore, is ciliated, and helps to circulate water through the gastrovascular cavity.[4] Some anemones feed on small particles, which are caught with the aid of a mucus secretion and moving currents that are set up by the tentacles. Most sea anemones are predacious, immobilizing their prey with the aid of their nematocysts.


The mouth opens into a flattened pharynx. This consists of an in-folding of the body wall, and is therefore lined by the animal's epidermis. The pharynx typically runs for about two-thirds the length of the body before opening into the gastrovascular cavity that fills the remainder of the body.


The gastrovascular cavity itself is divided into a number of chambers by mesenteries radiating inwards from the body wall. Some of the mesenteries form complete partitions with a free edge at the base of the pharynx, where they connect, but others reach only partway across. The mesenteries are usually found in multiples of twelve, and are symmetrically arranged around the central pharynx. They have stomach lining on both sides, separated by a thin layer of mesoglea, and includes filaments of tissue specialised for secreting digestive enzymes. In some species, these filaments extend below the lower margin of the mesentery, hanging free in the gastrovascular cavity as acontial filaments.

Nerve system : 


A primitive nervous system, without centralization, coordinates the processes involved in maintaining homeostasis, as well as biochemical and physical responses to various stimuli. No specialized sense organs are present.


The muscles and nerves are much simpler than those of most other animals, although more specialised than in other cnidarians, such as corals. Cells in the outer layer (epidermis) and the inner layer (gastrodermis) have microfilaments that group into contractile fibers. These fibers are not true muscles because they are not freely suspended in the body cavity as they are in more developed animals. Longitudinal fibres are found in the tentacles and oral disc, and also within the mesenteries, where they can contract the whole length of the body. Circular fibers are found in the body wall and, in some species, around the oral disc, allowing the animal to retract its tentacles into a protective sphincter.


Since the anemone lacks a skeleton, the contractile cells pull against the gastrovascular cavity, which acts as a hydrostatic skeleton. The anemone stabilizes itself by shutting its mouth, which keeps the gastrovascular cavity at a constant volume, making it more rigid. Although generally sessile, sea anemones are capable of slow movements using their pedal disc, or of swimming, using either their tentacles or by flexing their bodies.



Lifecycle : 


Unlike other cnidarians, anemones (and other anthozoans) entirely lack the free-swimming medusalstage of their lifecycle; the polyp produces eggs and sperm, and the fertilized egg develops into aplanula that develops directly into another polyp.


Anemones tend to stay in the same spot until conditions become unsuitable (prolonged dryness, for example), or a predator attacks them. In that case, anemones can release themselves from the substrate and use flexing motions to swim to a new location. Most sea anemones attach temporarily to submerged objects; a few thrust themselves into the sand or live in burrows; a few are parasitic on other marine organisms,[8] and some have symbiotic relationships with hermit crabs.


The sexes in sea anemones are separate in some species, while other species are protandrichermaphrodites. The brooding anemone (Epiactis prolifera) is gynodioecious, starting life as a female and later becoming hermaphroditic, so that populations consist of females and hermpaphrodites, and all 


females are fertilized by hermaphrodites. The gonads are strips of tissue within the mesenteries. Bothsexual and asexual reproduction can occur. In sexual reproduction, males release sperm to stimulate females to release eggs, and fertilization occurs. Anemones eject eggs and sperm through the mouth. The fertilized egg develops into a planula, which settles and grows into a single polyp.


Anemones can also reproduce asexually, by budding or in some cases by binary fission, when the polyp separates into two halves. Some species can also reproduce by pedal laceration. In this process, a ring of material breaks off from the pedal disc at the base of the column which then fragments, the pieces regenerating into new individuals.  The sea anemone Aiptasia diaphana displays sexual plasticity. Thus asexually produced clones derived form a single founder individual can contain both male and female individuals (ramets).[  When eggs and sperm (gametes) are formed, they can produce zygotes derived from “selfing” (within the founding clone) or out-crossing, that then develop into swimming planula larvae.

The 49th plate from Ernst Haeckel's Kunstformen der Natur, 1904, showing various sea anemones classified as Actiniae

Striped colonial anemone

Brooding anemone (Epiactis prolifera) with developing young

Ecology :


The sea anemone has an oral disk, which the organism uses to capture prey. The anemone attaches to the substrate using the basal disk at its posterior end. Others also burrow into weaker objects. Some species attach to kelp while others are free-swimming.

Symbiotic relationships :


Further information: symbiosis


Although not plants and therefore incapable of photosynthesis themselves, many sea anemones form an important facultative symbiotic relationship with certain single-celled algae species that reside in the animals' gastrodermal cells. These algae may be either zooxanthellae, zoochlorellae or both. The sea anemone benefits from the products of the algae's photosynthesis, namely oxygen and food in the form of glycerol, glucose andalanine; the algae in turn are assured a reliable exposure to sunlight and protection from micro-feeders, which the sea anemones actively maintain. The algae also benefit by being protected by the sea anemone's stinging cells, nematocysts, reducing the likelihood of being eaten by herbivores.


Several species of fish and invertebrates live in symbiotic or commensal relationships with sea anemones, most famously the clownfish, but also certain cardinalfish (such as Banggai cardinalfish), juvenile threespot dascyllus,  Bucchich's (or anemone) goby, juvenile painted greenling,  various crabs (such as Inachus phalangium, Mithraculus cinctimanus and Neopetrolisthes), shrimp (such as certain Alpheus, Lebbeus, Periclimenes and Thor),  opossum shrimp (such as Heteromysis and Leptomysis),   and various marine snails.


Two of the more unusual relationships are those between certain anemones (such as Adamsia, Calliactis and Neoaiptasia) and hermit crabs or snails, and Bundeopsis or Triactis anemones and Lybia boxing crabs. In the former, the anemones live on the shell of the hermit crab or snail.  In the latter, the small anemones are carried in the claws of the boxing crab.



Actinoscyphia aurelia

Habitats :


Most species inhabit tropical reefs, although there are species adapted to relatively cold waters, intertidal reefs, and sand/kelp environments.


Exploitation  : 


The global trade of marine ornamentals has been a rapidly expanding industry involving numerous countries worldwide. In the early 1980s, the estimated value of imported marine fish and invertebrates was US$24–40 million annually.  Current estimates place that value at US$200–330 million,  with the United States accounting for 80% of the industry imports . Despite advances and the expansion ofaquaculture, postlarval capture and rearing, the majority of marine ornamentals are collected in the wild as adults or juveniles.


Anemones are susceptible to overexploitation due to their long lifespans, slower relative growth rates, and lower reproductive rates than their resident fish, which are also affected because they settle exclusively and are restricted to specific host sea anemones. The demand for these organisms is reflected in fishermen's catch records, which document the value they are paid per catch, and on average sea anemones were valued at five times the average value of anemonefish, and 10 times the value of the most abundant anemonefish, and in fact only made up 4.1% of the total value of the catch.


Aquarium fishing activities significantly impact the populations of anemones and anemonefish by drastically reducing the densities of each in exploited areas,  and could also negatively impact anemone shrimp, and any organisms obligately associated with sea anemones. Anemonefish can survive alone in captivity, as has been shown by multiple research efforts. 


In southern Italy and southwestern Spain, the anemone Anemonia sulcata is consumed as a delicacy.  The whole animal is marinated in vinegar, then coated in a tempura-like batter and deep-fried in olive oil. They are similar in appearance and texture to croquettes, but have an intense seafood taste.





Actinodendron sp.

Fossil record :


Most Actiniaria do not form hard parts that can be recognized as fossils, but a few do exist; Mackenzia, from the Middle Cambrian Burgess Shale of Canada, is the oldest fossil identified as a sea anemone.


Taxonomy  :


Rodriguez et al. proposed a new classification for the Actiniaria based on extensive DNA results.

Suborders and Superfamilies included in Actiniaria are:

- Suborder Anenthemonae  :

     -  Superfamily Edwardsioidea

    - Superfamily Actinernoidea

-Suborder Enthemonae :

     - Superfamily Actinostoloidea

     - Superfamily Actinioidea

    - Superfamily Metridioidea

The relationships of higher-level taxa in Carlgren’s  classification are re-interpreted as follows:

Carlgren taxon                                                                  Phylogenetic result


Protantheae                             Sister to Boloceroidaria 


Ptychodacteae                         Polyphyletic because its members are not recovered as sister                                                         taxa; clustered with members of former Endomyaria


Endocoelantheae                      Sister to athenarian family Edwardsiidae; together these                                                                clades are re-classified as suborder Anenthemonae 


Nynantheae                                Polyphyletic because of the relationship                                                                                             between Edwardsiidae and Endocoelantheae and because                                                           members of Protantheae and Ptychodacteae are recovered                                                           as sister to its members


Boloceroidaria                            Boloceroides mcmurrichi and Bunodeopsis nested among                                                           acontiate taxa; B. daphneae apart from other Actiniaria 


Athenaria                                    Polyphyletic: families formerly in this suborder distributed                                                             across tree as sister to former members of Endomyaria,                                                                 Acontiaria, and Endocoelantheae


Thenaria                                      Boloceroidaria, Protantheae, Ptychodacteae, and most                                                                   Athenaria nest within this group


Endomyaria                                Paraphyletic: includes Pychodacteae and some Athenaria


Mesomyaria                                Polyphyletic: one clade at base of Nynantheae, other lineages                                                       are associated with former members of Acontiaria


Acontiaria                                    Paraphyletic; includes several lineages formerly in                                                                          Mesomyaria and Athenaria, plus Boloceroidaria and                                                                      Protantheae



Guide for Keeping Anemones in a Reef Tank


courtesy to  Written by Katherine Barrington

Cultivating a reef tank can be quite a challenge because it requires you to maintain very specific water parameters. In order to keep all of your reef inhabitants healthy, you also need to follow strict feeding guidelines to keep your tank inhabitants from starving. One type of reef inhabitant that hobbyists often have difficulty with is the anemone.


Anemones require certain tank conditions including lighting, water flow and oxygen levels in order to thrive so if you are not able to provide these conditions, you may not be able to keep anemones in your tank. Below you will find a wealth of information about anemones in general as well as some detailed tips regarding their care. Before you attempt to add an anemone to your tank, read this guide so you will be more prepared for the challenge.


About Anemones :


Sea anemones belong to the order Actiniaria – there are four suborders and forty-six different families. These creatures can be described as terrestrial flowers, because that is what they look like with their waving fronds and floating appendages. The anemone is, however, a predatory animal that is related to corals and jellyfish. The basic anatomy of an anemone includes a polyp attached to the underside of a basal disc (an adhesive foot) – a column-shaped body extends from the disc and ends in an oral disc. You are probably familiar with sea anemones in relation to their symbiotic bond with clownfish.

Keeping anemones in a reef tank can be a challenge if you are not fully prepared. Read more to learn what is required to successfully keep anemones.

Most sea anemones grow between 1.5 and 3 centimeters in diameter but some are as small as 4 mm around. These creatures may exhibit anywhere from a few dozen to a few hundred tentacles. Sea anemones use an oral disc to capture their prey and they may attach either to substrate or by burrowing into a weaker object like kelp. Anemones are not photosynthetic organisms but they have a symbiotic relationship with certain photosynthetic organisms like single-celled green algae. These algae produce oxygen and glucose as a product of their synthesis, both of which are beneficial to the anemone.


Top Recommended Species:


As you’ve already learned, there are many different species of anemone out there. If you are thinking about adding an anemone or two to your tank, consider one of the species listed below:


  • Bulb Anemone (Entacmaea quadricolor) – The bulb anemone is one of the most commonly used anemones in the aquarium hobby. This species is named for the bulb-like tip at the end of each tentacle. These anemones typically have brown columns with green, brown, or bright orange tentacles. This species may reproduce asexually in the tank which makes it particularly interesting to keep.

  • Adhesive Anemone (Cryptodendrum adhaesivum) – This type of anemone is sometimes sold as the “pizza anemone” because it has rounded, ridged edges that resemble a pizza crust. The adhesive anemone is very unique in appearance but it does have a potent sting – it may not do much harm to humans, but it can be dangerous for certain tank inhabitants.

  • Beaded Anemone (Heteractis aurora) – The beaded anemone is named for the beadlike swellings along the length of its tentacles which may be brown, green, or purple in color. This species tends to burrow into sand or gravel instead of anchoring itself to hard substrate and it is a host for seven different anemonefishes. The beaded anemone is fairly easy to keep in the home aquarium as long as a thick bed of sand and adequate illumination are provided.

  • Corkscrew Anemone (Macrodactyla doreensis) – The corkscrew anemone has a dull orange or red column with several rows of small bumps running up its length. This species tends to prefer soft substrates, burying its base in sand or mud. When provided with a suitable habitat, the corkscrew anemone is a fairly hardy species.

Tank Requirements and Care : 


Though specific tank requirements will vary from one species of anemone to another, all species have several general requirements in common. The first is that the water quality of the tank should be very high – the water needs to be clean and free from accumulated debris. Sea anemones require high levels of dissolved oxygen and a stable pH between 8.1 and 8.3. The ideal temperature range for anemones is between 76 and 78°F and the salinity should remain at a stable specific gravity between 1.024 and 1.026. Levels of phosphate, ammonia and nitrite should be as close to 0 as possible and nitrate should be no more than 2 ppm.

Common Mistakes:


One of the most dangerous mistakes you can make in adding an anemone to your tank is to do so before the tank has properly matured. While it may only take a few weeks for a tank to cycle – that is, for the nitrogen cycle to become established, it takes longer for a tank to become mature. Only after a tank has been running for 12 months or more can it be considered “matured” in that it is less prone to changes in water parameters and the tank inhabitants have adapted to the tank environment. Anemones generally do not handle changes in water conditions well, so they need to be added to a very stable tank environment.


Another mistake aquarium hobbyists sometimes make is failing to feed their anemones at all. Some hobbyists maintain that anemones are able to get enough food from the water and from the algae growing in their tissues, but you may need to feed your anemones a few times a month to make sure they don’t starve. To accelerate the growth of your anemones, feed them once a week or more often. The ideal foods for anemones are protein-rich foods such as scallops, clams, shrimp and mussels.



Another important aspect of keeping a tank for anemones is achieving the ideal level of water movement and flow. Anemones require some degree of water flow because they absorb oxygen directly from the water and may also gather their food from the water. If the water in the tank does not move, the anemones will not have access to the oxygen and the food that they need to survive. Most species do well in tanks with low to moderate flow, but some species may be more tolerant of higher flow. Lighting is also very important for an anemone tank. As mentioned, anemones are not photosynthetic organisms themselves but they obtain essential nutrients from the photosynthetic algae growing in their tissues. This being the case, you should equip your tank with a full-spectrum light – ideally, one that is designed especially for marine and reef tanks.

Placing your anemone once you get it home can also be a challenge for aquarium hobbyists. Before you purchase an anemone, research the particular species to find out what location they prefer in the tank. Some species prefer to attach to a crevice in a rock while others bury themselves directly in the substrate. After placing your anemone, it is important that you do not touch it or feed it for one week – the anemone needs a rest period to adjust to the new tank. During this time you should not be alarmed if the anemone moves – it may be moving to a location it prefers.


Summary : 


 No matter what you choose to stock your reef tank with, you need to make sure you perform some basic research first to gain an understanding of these amazing creatures. Anemones in particular require very specific water parameters and if they are not met, they may fail to thrive or they might die completely. Waiting to add an anemone to your tank until it has matured is a good step, but you also need to be sure the tank itself is a good environment in terms of lighting, water quality and water flow. If all of these factors line up appropriately, you are more likely to succeed in keeping an anemone in your tank.

Anemones list : 


Most Anemones are sessile with a specialized foot used to anchor them in soft substrates or attach themselves to rocks and corals. Provide excellent water conditions, moderate to strong current, and intense lighting. Bits of shrimp or other meaty foods can be used to supplement their diet.

1-Rose Bulb Anemone

Entacmaea quadricolor 


Minimum Tank Size: 30 gallons

Care Level: Moderate

Temperament: Semi-aggressive

Reef Compatible: With Caution

Lighting: Moderate to High

Waterflow: Medium

Water Conditions: 72-78° F, pH 8.1-8.4, sg 1.023-1.025

Max. Size: 1'

Color Form: Red

Supplements: Iodine, Trace Elements

Origin: Fiji, Indonesia

Family: Actiniidae

The Rose Bubble Tip Anemone is a less common form of the Bubble Tip Anemone which is often referred to as the Four-colored, Bulb Tentacle, Bulb Tip, or Bulb Anemone. At rest, the enlarged tip at the end of the tentacles is a rose to red color.


The Bubble Tip Anemone is usually found in coral rubble, or in solid reefs. Its pedal disc is usually attached deep within dead coral. It stretches its tentacles to become sweeper tentacles when hungry. That is, the tentacles become elongated to capture a meal, then the tentacles shorten and the bubble tips return.


Handle this invertebrate, and all Anemones, with care. They can sting other Anemones, as well as Corals.


In order for the Rose Bubble Tip Anemone to keep its bright coloration and bulb tips, it needs strong illumination supplied by metal halides, or intense florescent lighting of at least 6 watts per gallon. They require an aquarium of at least 30 gallons, as they can grow up to 12" across in the aquarium. These anemones will typically remain compact and will gain bulb tips under intense lighting. If the lighting is insufficient, they will expand their bodies to great lengths to make the most of the available light. It should be kept with a Clownfish for best results. At times, the tentacles may appear stringy; this may be due to insufficient light or the need for food.


Its diet should include chopped fish, shrimp, or worms if a clownfish is not present.


Approximate Purchase Size: Small: 1" to 2" Medium: 2" to 5"



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