Aiptasia Biology

 

Kingdom: Animal, Phylum: Cnidaria, Class: Anthozoa, Zoantharia ^sC (=Hexacorallia), Order: Actinaria, Family: Aiptasiidae, Genus: Aiptasia

 

Physical Description: Called the "Pale Anemone" and “Glass Anemone”, it is a small anemone, with oral disk diameter of no more than about 2 cm and a height of 5 cm. It is dark brown to pale gray in color, has a slender column, and a mixture of a few long and many short tentacles. The mouth opens at one end of the coelenteron and marks the oral end.  The mouth is at the tip of a process, the manubrium that elevates it above the oral surface. The opposite pole is the aboral end.  The imaginary line connecting the oral and aboral poles is the axis of symmetry around which the radial symmetry of the body is organized.  The mouth is surrounded by one or more rings of up to 100 tentacles anchored toward the outer part of the oral surface.

Like all cnidarians, all aiptasia species exemplify the tissue level of organization and are composed of two cell layers: an epidermis and a gastrodermis. The two cell layers are cemented together by an acellular matrix known as mesoglea. Like other anthozoans (zooanthids, anemones, corals), the gastrovascular cavity of aiptasia sp. is partially subdivided by radially arranged septa containing string-like acontia and gonads along their inner edge. Symbiotic single celled dinoflagellate algae, xooxanthellae, are found within the gastrodermal cells. Both the acontia and epidermis harbor cnidocyte stinging cells capable of capturing and subduing small prey (zooplankton), stinging fish, killing or causing tissue regression in sessile invertebrates or corals and pack a lethal sting to larval fish and young seahorses. In low concentration, they are harmless to humans. In high concentration the acidic fluid of their stinging cells can cause irritation and sores on the skin. Unlike most cnidarians, aiptasia are extremely successful in generating or regenerating an entire animal from a single cell. It is this basic regenerative ability that makes the aiptasia anemone so difficult to control and it can completely colonize some coastal areas such as dock pilings. Aiptasia anemones are very wide spread and may also be found far out at sea completely coating anchor chains on weather stations. They situate their base deep inside depressions, holes and under rocks for protection from all forms of attack by predators. Any attack on this anemone stimlates spawning and ultimately releases thousands of Planula Larval stages to colonize or recolonize the area at a later date when conditions improve. The only effective removal method for long term success in the aquarium is the one predator that does not initiate spawning in this anemone - a nudibranch.

Reproduction is both sexual and asexual.  Asexual reproduction is referred to as basal (or pedal) laceration. During this laceration of the foot, small bits of tissue bud from the periphery of the anemone's radially arranged basal disk. Within the radial arrangement, the divisions of the basal area isolate these little “seeds” from the larger part of the anemone. Migration and division from the foot may take a few days to several weeks.  Within a week or two after completely separating from the foot the bud develops a mouth and small tentacles and begins to feed on its own. Basal laceration is a very easy and efficient method for the anemone to reproduce and leave behind many identical little clones that go unnoticed for some time.  Some of these clones will release and be distributed in the water column to colonize other locations.  Aiptasia sp. increase asexual reproductive basal lacerates during times of extreme stress such as low oxygen, decreased circulation, low  lighting situations (rock slides, new coastal construction, coral growth resulting in shading), attack by predators or exposure to chemicals.  Basal lacerations and Planula Larva from sexual reproduction may remain and disperse through the system for up to a year or more after what appears to be a successful attack on one anemone by a larger predator or man made chemical applications.  In sexual reproduction, oocyte sizes and gonad weights as well as asexual basal lacerations increase with more light and more feedings or nutrients.  However we should not assume that nutrient poor water or reduced fish feedings will slow the process any because aiptasia contain their own processor cells called xooxanthellae.

 

Xooxanthellae, the single celled dinoflagellate algae of the genus Symbiodinium are surrounded by a host derived membrane forming a vesicle known as the sybiosome.  The symbiosis is mutualistic.  The algae have access to nutrients (IE: N and P) which would otherwise be in very short supply. These compounds are produced as metabolic waste products of the host (IE: NH₄⁺). The host, in turn, receives photosynthetic products (mainly as glycerol) from the algae and in this has a reliable supply of carbohydrates to furnish it with energy.  The anemone gives the dinoflagellate a place to live which is high in minerals and in return the anemone is fed glycerol by the dinoflagellates. Glycerol is the backbone of triglycerides and phospholipids and is a good source of carbon and energy. These are important building blocks in animal biology. How about that; protein and carbohydrates in constant supply.  Using HPLC-EC (high pressure liquid chromatography) dopamine and serotonin (5-hydroxytryptamine, 5-HT) can be found in both tentacles and the whole animal. Dopamine affects the central nervous system, serotonin brain activity and balance. At this time it is unknown how these proteins react with chemicals used on the host anemone or its effect on corals in a closed system.  It is possible these compound the problems of the chemicals and is an additional contributor to the mystery death seen in some species of corals within days to weeks following the use of currently marketed and widely accepted chemical methods used against the host aiptasia. It is certain that nutrients are released and not exported from the system when aiptasia are attacked chemically or physically unless this is done in a separate container isolated from the main system.

 

In tanks with aiptasia, reproduction by sexual means as well as asexual lacerates results in settling of gametocytes and spreading of cells forming an intricate biofilm on the rocks. The dispersal of new aiptasia cells combined with the tissue level of organization means that a good target natural predator is eventually desired for complete aiptasia harvest. It is also helpful in the culture of Aiptasia anemones to know this. It may take some time for the small cells to become visible aiptasia, but given the time, they will. Successful Aiptasia culture is beneficial in the laboratory setting for study and rearing of Berghia nudibranchs. Many projects can be done with these two animals and if one is to provide extermination of the Aiptasia in a coral reef, understanding the creature we're after will help us be successful. In the case of medical research, this could still be another source for a cure.

 

Home | Aiptasia Intro | Aiptasia Culture