''Epiactis prolifera'', the brooding, proliferating or small green anemone, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine invertebrate in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Actiniidae.Fautin, D. (2010). ''Epiactis prolifera'' Verrill, 1869. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=283435 on 2011-07-20 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 A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The ...

later in their lives to become

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

Description

The brooding anemone grows to three centimetres high and up to five centimetres in diameter and varies in colour, usually being greenish-brown but sometimes brown, pink, red or dull green. There are fine white lines starting at the mouth and spreading radially across the oral disc and further white lines occur on the column and pedal disc.''Epiactis prolifera''
Cowles, David. Walla Walla University
/ref> The lower part of the column and pedal disc are occasionally blue. There are often radiating pale and dark lines on the edges of the pedal disc and the lower part of the column. The mouth is surrounded by 48 to 96 short, conical

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s each tipped with a terminal pore.

Distribution and habitat

The brooding anemone is found in shallow areas of the north-east

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. The highest density is on or under rocks in the

sublittoral The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely in ...

zone, in surge channels, on rock shelves and areas exposed to wave action. It is often found in areas encrusted with coralline algae and sometimes grows on the leaves of eelgrass. It cannot tolerate exposure to the drying air and sunlight. The brooding anemone moves around over the substrate to a greater extent than do other anemones.

Biology

''Epiactis prolifera'' is a protogynic hermaphrodite. The young all start life as females but when the pedal disc is about two centimetres in diameter, they develop

on the

mesentery In human anatomy, the mesentery is an Organ (anatomy), organ that attaches the intestines to the posterior abdominal wall, consisting of a double fold of the peritoneum. It helps (among other functions) in storing Adipose tissue, fat and allowi ...

and spend the rest of their lives as hermaphrodites.Encyclopedia of Life
/ref> This means that the population consists of a large number of young females and a small number of older hermaphrodites. Reproduction is not limited to any particular season. Sperm is released into the

water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...

and after cross-fertilisation (or sometimes self-fertilisation), the young remain within the mother's gastrovascular cavity during their early development. The mother then expels a mass of eggs and mucus through her mouth and they spread across her oral disc. Cilia move some of them down the column and they become attached to the base of the column with

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

, and perhaps also nematocysts. The larvae develop tentacles of their own and grow in this protective environment for at least three months. When they reach about four millimetres in diameter, they separate from their mother and move away to live independently. If the anemone is damaged and broken in pieces, the various fragments are each able to grow into a new individual. The diet consists of small

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s and

jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

. The prey is immobilised by the nematocysts in the tentacles which inject toxins, then passed by the tentacles through the mouth and into the gastrovascular cavity. Any undigested remains are expelled through the mouth.

Ecology

Despite their stinging nematocysts, brooding anemones are a favoured prey for certain other animals. Many

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs, belonging to the order Nudibranchia, that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have b ...

s seem to be immune to the toxin and both eat them and can store the unused nematocysts for their own defence. Predators include the nudibranch '' Aeolidia papillosa'', the leather star '' Dermasterias imbricata'' and certain fish, such as the mosshead sculpin ('' Clinocottus globiceps''). This anemone sometimes displays mutualism by attaching itself to a

hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...

or decorator crab. The anemone provides protection for the host from predators and itself benefits by being able to consume food fragments discarded by the crab. The

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

, '' Doridicola sunnivae'', is an

ectoparasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

of the brooding anemone.World of Copepods
/ref>

References

{{Taxonbar, from=Q2241181 Actiniidae Cnidarians of the Pacific Ocean Animals described in 1869 Taxa named by Addison Emery Verrill