Enthemonae

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Enthemonae
Sea Loch Anemone.jpg
Protanthea simplex , Sound of Mull, Scotland
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Hexacorallia
Order: Actiniaria
Suborder: Enthemonae
Rodríguez & Daly, 2014
Superfamilies

See text

The Enthemonae is a suborder of sea anemones in the order Actiniaria. It comprises those sea anemones with typical arrangement of mesenteries for actiniarians. [1]

Contents

The Enthemonae is any member of the invertebrate suborder characterised by soft bodied, marine animals that look like flowers which primarily attach to hard or rigid surfaces, such as coral or rocks. An Enthemonae is a suborder of sea anemone of the order Actiniaria, which includes the overall majority of the actiniarians, which belong to the former groups of Protantheae, Ptychodacteae, and Nynantheae. [1]

Classification

It is seen that within the suborder of Enthemonae there are 46 families showing the large amount of diversity within the species. This diversity stems from the depth, heat and environment of the water they are growing in.

The differential feature between the 2 suborders of sea anemone; Enthemonae and Anenthemonae is that they are primarily characterised by having basilar muscles, mesoglea marginal sphincter and they lack acontia and arotinoids. [2] However, Enthemonae are seen to rarely lack these types of basilar muscles and sphincters causing the outer column to be smooth in texture.

Superfamilies

Within the Enthemonae suborder, there are 3 different superfamilies; Actinostoloidea, Actinoidea and Metridioidea, all superfamilies having other families within.

Actinostoloidea and Metridioidea is known for the rare phenomenon of brooding which is only seen in 57 species out of approximately 1100 within Actiniaria. These superfamilies which are predominately found in the Southern Ocean and therefore brood externally as well as having a combination of morphological features including 12 mesenteries and an oral disc similar to glandular sacs. [2] Whereas, the Actinoidea is a shallow water Enthemonae.

Superfamilies and families in the suborder Enthemonae include: [3]

Structure

The internal structure of a sea anemone Sea Anemone Structure.png
The internal structure of a sea anemone

Sea Anemones are solitary hexacoral polyps which in contrast to the majority of colonial forms have no skeleton. They are diploblastic animals, with a body that displays a wall consisting of 2 layers; the epidermis and the gastrodermis, separated by an extracellular mesoglea which contains many amebocytes. [4]

Body

The body is of a cylinder shape or a truncated cone shaped that contains the oral disk with a fringe of tentacles arranged in one to several configurations around the mouth opening. The basal body end in the majority of species extends into the pedal disk which serves with the purpose of an attachment to the substrate. [4]

Mouth

The slit in the mouth leads to a flattened tube known as the actinopharynx which is seen to extend into the gastrovascular cavity. These two slit like structures run along the end of the mouth to ensure that the water circulates through the gastrovascular cavity for the end goal of re-pumping it out. [4]

Gastrovascular Cavity

The gastrovascular cavity is lined by gastrodermis cells and divided by radical septa known as mesenteries, into both lateral chambers and the central part. There are incomplete and complete mesenteries that are located in pairs; the complete mesenteries have their internal edge in the upper part that attaches to the actinopharynx. Where in comparison, the incomplete ones fail to reach the actinopharynx therefore seeing them attach to the pedal or oral disc. [4]

Musculature

Musculature is the arrangement of muscles in a body or organism.

The simple body plan of actiniarians shows the high level of morphological convergence, where many of their morphological characteristics have been lost. This form of evolution which results in unrelated organisms independently producing similarities of form, usually because they become adapted to living in similar types of environment. [1]

Within Enthemonae, their marginal musculature has shown to be phylogenetically consistent revealing that on occasion these features have been lost several times over centuries. The enthemonae's feature of marginal musculature was lost in the Family Edwardsioidea and Family Actinoidea which stemmed from a reduction in total body size or a shift in habitat. [1]

Basilar muscles are characteristic of all enthemonae's and are lost a number of times within each sublineage. Despite this it is implied that the endodermal and mesogleal marginal muscles represent independent and alternative derivations of marginal musculature in order to optimise the marginal sphincter muscles on our trees. These arose as the mesogleal muscles, being transformed into an endodermal muscle in their lineage. This process has arisen around 3 times within the Hexacorillia, and in each case resulted in the development of these mesogleal muscles. [1]

Venom

Enthemonae produce venom dependent on the superfamily with vast molecular diversity which are classified according to pharmacological activity and amino acid sequence. However, the exact receptors they target are either unknown or incomplete. [5]

Venom system

All cnidarians lack a centralised venom system and in replace produce numerous venom tissues throughout the body, using 2 different cell types; nematocytes and ectodermal gland cells. [6]

Nematocysts are the main venom delivery tissue which are capsules containing an inverted tubule capsule of extremely powerful discharge. They are present in all cnidarians and produce highly complex venom filled organelles. [7] The most functional and common venom tissue within Enthemonae include tentacles which are used to capture prey, immobilise threats and used in digestion. [8]  

The other cell type is ectodermal gland cells which is responsible for producing a distinct collections of toxins. These toxins can be released in greater quantities due to the larger capacity of the gland in comparison to the nematocytes, which allows for the opportunity for the reach of the venom to extend.

In general, the venom of an Enthemonae are harmless to humans and in most cases only cause skin rashes and edema in the area of contact with the tentacles.

Venom Tissue

The venom that is found within these tissues are a complex combination of proteins, polypeptides and other non-protein based compounds. These components are grouped into 4 functional categories, [9] in the ‘Cytolytic peptide and protein toxins from sea anemones’.

Phospholipase A2

Degrades the membrane of the neurological and muscle cells which causes never damage and muscle inflammation.

Cytolysins

Causes cell lysis on the cell membrane.

Neurotoxins

Interact with the receptors causing an altered neural transmission through interacting with voltage-gated and ligated ion channels.

Non-protein compounds

Induce pain when there is an interaction with the venom. These can include purines and biogenic amines.

Enzymes

Due to Enthemonae not having a centralised gland system, it makes it difficult to distinguish between enzymes that play a generalised role and that of an envenomation role.

The PLA 2 catalyses the hydrolysis of the phospholipids into free fatty acids and lysophosholipids. This have been convergently recruited into the venom. [5]

Feeding and diet

Although they are flexible in the ways that they obtain their nutrition's, they are fundamentally predatory animals that use their venomous tentacles to catch prey. The dietary composition differentiates between the marine habitats that they are occupying. The mouth of the anemone can stretch as well in order to help capture their pray and ingest larger animals such as crabs, molluscs and even some species of small fish. [10]

Some Enthemonae also are considered to be opportunistic and omnivorous feeders that feed a large extent of their diet through organic detritus, which is caught with the acid of their mucus secretion. [5]

Habitat

It is part of a highly diverse order that successfully occupies marine habitats across all depths of the ocean, ranging from the tidal zone to more than 33,000 feet. There are 3 superfamilies and up to 48 family's within, thus making it one of the largest suborders of the sea anemones long side the Anenthemonae. The greatest range of Enthemonae are found in the warmer tropical areas of the ocean but there is still a number of superfamilies that inhabit the colder and deeper waters. [2]

Reproduction

All suborders of sea anemones can reproduce both sexually and asexually.

Sexual reproduction

The sexual reproduction is a simple and straightforward process involving the fertilisation of an egg which evolves into a planula further to a polyp then an adult, which results in full anemones being released from the mouth of the adult. [11]

The origin and the development of the germ cells in lower invertebrates originate from differentiated epithelial cells of the epidermis. This sees the simple reproductive system of sea anemones have no true gonads resulting in the accumulation of the sexual products at the mesenteries. [12]

The sex of the germ cells is not always easy to determine at the initial stages of the cell differentiation process. However, developing oocytes unlike male germ cells, the changes in their nuclei begin earlier, with neighbouring cells may significantly differ in size. [12]

Asexual reproduction

In comparison, there are multiple ways they can reproduce asexually including budding, fragmentation or by longitudinal or transverse binary fission. [13]

Budding

This occurs when fragments of the organism breaks off and develops into new individuals. Some stretch themselves along the base of the surface they are attached to and split across the middle resulting in two new enthemonae, this method is known as longitudinal fission.

Another method includes smaller pieces of tissue break off from the base forming tiny anemones, this is known as basal laceration.

Binary fission

Fission is often irregular and can be stimulated by changes in the ambient conditions, such as abrupt changes in temperature or illumination. The process involves separation of small, irregularly shaped fragments from the edge of the disk of the sessile or the slowly moving sea anemone. Here sees the fragments after separation develop new tentacles on the closures of then wounds. As a result, new offspring created through binary fission have an abnormal number of tentacles and an irregular arrangement of septa. [14]

Reproduction by autonomy of tentacles

The sphincters at the base of their tentacles can separate due to contractions of the circular muscles. The opening in the basal part of the separated tentacle is closed by a ‘tissue plug’, which then falls off with the onset of active cell proliferation and subsequent formation of the body of a new anemone. [15]

Symbiotic relationships

Green Algae

The immense ecological success of sea anemones, such as Enthemonae is due to the symbiotic relations between the hosts and the unicellular green algae. These algae's are photosynthetic and therefore the exchanges between the two are based on a nutritional exchange of the algae's bi products of oxygen and glucose. Then in response the anemone provides the algae with a safe harbour as well as provides them with a greater exposure to sunlight used for photosynthesis. [16]

Hermit Crabs

The Enthemonae and a young hermit crab will often develop a symbiotic relationship from a young stage. This involves the young hermit crab attaching the shell to the tentacles of the sea anemone, becoming partners for the duration of their life cycle. This process often results in the two organisms growing at roughly the same rate. [17]

The type of symbiotic relationship they develop is known as commensalism as the hermit crab is protected from predators from the venom inside the tentacles of the Enthemonae. The anemone spreads its long thin tentacles over the crab as well as extending the venomous tentacles further out as an additional layer of protection. [17]

In return the anemone gains a food sources from the excess tidbits that the hermit crab leaves behind, providing a steady flow of a food supply.

Phylogeny

Phylogeny of Sea Anemone.png

Actiniaria contains 2 subclasses known as Anenthemonae and Enthemonae, which exhibited within the following image has a number of superfamilies that are currently or still need to be explored.

Related Research Articles

<span class="mw-page-title-main">Anthozoa</span> Class of cnidarians without a medusa stage

Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.

Reef safe is a distinction used in the saltwater aquarium hobby to indicate that a fish or invertebrate is safe to add to a reef aquarium. There is no fish that is completely reef safe. Every fish that is commonly listed as reef safe are species that usually do not readily consume small fish or invertebrates. Fish listed as reef safe also do not bother fellow fish unless in some cases, for instance tangs, they do not get along with conspecifics and sometimes fish with similar color or body shape. Every fish has a personality, is different, and, in some cases, are opportunistic feeders. Tangs, which by most accounts are reef safe, may in adulthood eat some crustaceans shortly after they molt. Many larger predatory fish, for instance eels and pufferfish, will adapt very well to a reef tank and will be problem-free as long as they have sizable tank-mates and no crustaceans. Some aquarists have also had success in keeping smaller fish with predatory ones in reef tanks by adding the smaller fish at night, sometimes with newly rearranged rockwork.

<span class="mw-page-title-main">Octocorallia</span> Class of Anthozoa with 8-fold symmetry

Octocorallia is a class of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians within three orders: Alcyonacea, Helioporacea, and Pennatulacea. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries. As with all Cnidarians these organisms have a complex life cycle including a motile phase when they are considered plankton and later characteristic sessile phase.

<i>Corynactis californica</i> Species of sea anemone

Corynactis californica is a brightly colored colonial anthozoan corallimorph. Unlike the Atlantic true sea anemone, Actinia fragacea, that bears the same common name, strawberry anemone, this species is a member of the order Corallimorpharia, and is the only member found in the North American West Coast. Other common names include club-tipped anemone and strawberry corallimorpharian. The anemone can live up to at least 50 meters deep on vertical rock walls, and at the bottom of kelp forests. It is known to carpet the bottom of some areas, like Campbell River in British Columbia, and Monterey Bay in California.

<i>Anemonia sulcata</i> Species of sea anemone

Anemonia sulcata, or Mediterranean snakelocks sea anemone, is a species of sea anemone in the family Actiniidae from the Mediterranean Sea. Whether A. sulcata should be recognized as a synonym of A. viridis remains a matter of dispute.

<span class="mw-page-title-main">Sea anemone</span> Marine animals of the order Actiniaria

Sea anemones are a group of predatory marine invertebrates constituting the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.

<i>Bolocera tuediae</i> Species of sea anemone

Bolocera tuediae, commonly known as the deeplet sea anemone, is a sea anemone found in the sublittoral zone of the North Sea. It was first discovered near Bewick, England by Johnston in 1832. It is distinguished by its large, hexamerous size and shedding of tentacles. The nematocysts of the anemone can have dangerous effects, including the rupturing of human blood cells. The deeplet sea anemone was observed to have a symbiotic relationship with shrimp, as they cluster around its base in both temperate and Northwest Atlantic waters.

<i>Stichodactyla helianthus</i> Species of sea anemone

Stichodactyla helianthus, commonly known as sun anemone, is a sea anemone of the family Stichodactylidae. Helianthus stems from the Greek words ἡλιος, and ἀνθος, meaning flower. S. helianthus is a large, green, sessile, carpet-like sea anemone, from the Caribbean. It lives in shallow areas with mild to strong currents.

<i>Epiactis prolifera</i> Species of sea anemone

Epiactis prolifera, the brooding, proliferating or small green anemone, is a species of marine invertebrate in the family Actiniidae. It is found in the north-eastern Pacific. It has a feature rare among animals in that all individuals start life as females but develop testes later in their lives to become hermaphrodites.

<i>Adamsia palliata</i> Species of sea anemone

Adamsia palliata is a species of sea anemone in the family Hormathiidae. It is usually found growing on a gastropod shell inhabited by the hermit crab, Pagurus prideaux. The anemone often completely envelops the shell and because of this it is commonly known as the cloak anemone or the hermit-crab anemone.

<i>Peachia</i> Genus of sea anemones

Peachia is a genus of sea anemone in the family Haloclavidae. Members of this genus typically burrow into soft substrates. The only part of the animal that is normally visible is the oral disc and tentacles which lie flat on the sand in a star shape. The type species is Peachia cylindrica.

<i>Actinodendron arboreum</i> Species of sea anemone

Actinodendron arboreum, commonly known as tree anemone or hell's fire anemone, is a species of sea anemone in the family Actinodendronidae. It is native to the Indo-Pacific where it grows at depths of down to 28 metres (92 ft). Most sea anemone species are harmless to humans, but A. arboreum is highly venomous and its sting can cause severe skin ulcers.

<i>Phyllodiscus</i> Genus of sea anemones

Phyllodiscus is a monotypic genus of sea anemones in the family Aliciidae. The only species is Phyllodiscus semoni, commonly known as the night anemone, which is native to shallow seas in the central Indo-West Pacific, such as Indonesia, the Philippines and southern Japan. It is venomous and can cause a painful, long-lasting sting to humans. It is called unbachi-isoginchaku in Japanese which translates as "wasp-sea anemone".

<span class="mw-page-title-main">Relicanthus daphneae</span> Species of marine invertebrate

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<span class="mw-page-title-main">Actinostoloidea</span> Superfamily of sea anemones

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<span class="mw-page-title-main">Mesentery (zoology)</span> Membrane inside the body cavity of an animal

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<i>Aiptasia mutabilis</i> Species of sea anemone

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