''Bougainvillia muscus'' is a marine

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

, a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of hydroid in the suborder

Anthomedusae Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular group. It has also been called Gymnobl ...

Taxonomy

In 1844, van Beneden named the hydroid form of this species as ''Eudendrium ramosum''. Strethill Wright showed that it did not belong in the genus ''Eudendrium'' and placed it in ''Atractylis''. Later Allman placed it in ''Bougainvillia'' on the basis of its similarity to ''

Bougainvillia britannica ''Bougainvillia britannica'' is a marine invertebrate, a species of hydroid in the suborder Anthomedusae. Description The polyp grows singly from a stolon or has a few branches. It has long pedicels and medusa buds develop in clusters on branc ...

''. Strethill Wright reared some medusae to maturity and decided that the species was in fact ''Bougainvillia britannica''. However, confusion remained because the three hydroid forms, ''B. ramosa'', ''B. fruticosa'' and ''B. muscus'' were so similar.The Medusae of the British Isles
/ref> The name ''B. ramosa'' has been widely used for this species in the past but ''B. muscus'' is now the accepted name.

Description

''B. muscus'' is a

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...

hydroid forming irregular, straggling branched bushes. The individual polyps have two rings of

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 pointing alternately upwards and downwards. The colony may grow to about 120 millimetres in height with polyps up to three millimetres long.Encyclopedia of Marine Life of Britain and Ireland
/ref> The hydranths are cylindrical or fusiform and are bright red or pink. The form of the hydroid is very variable and this was one of the reasons for the taxonomical confusion. In the "''muscus''" form, single polyps or short branches emerge from a

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

. In the "''fruticosa''" form, the hydrocaulis is much branched and grows to fifty millimetres in height. The perisarc rises to the base of the tentacles which may form a corrugated or membranous cup. In the "''ramosa''" form, this cup is larger and the hydranth can almost completely retreat inside it. These forms have been shown to be environmentally induced forms and all three can be derived from the "''muscus''" form.Hallez, 1905

Distribution and habitat

The hydroid ''B. muscus'' is widely distributed around the British Isles. It favours sheltered waters and is tolerant of low salinity levels. The medusae have been recorded around the coasts of Britain, the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

, south-west

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, the

Isles of Scilly The Isles of Scilly (; kw, Syllan, ', or ) is an archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, is the most southerly point in Britain, being over further south than the most southerly point of the ...

, the

Bay of Biscay The Bay of Biscay (), known in Spain as the Gulf of Biscay ( es, Golfo de Vizcaya, eu, Bizkaiko Golkoa), and in France and some border regions as the Gulf of Gascony (french: Golfe de Gascogne, oc, Golf de Gasconha, br, Pleg-mor Gwaskogn), ...

, the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

and near

Rhode Island Rhode Island (, like ''road'') is a U.S. state, state in the New England region of the Northeastern United States. It is the List of U.S. states by area, smallest U.S. state by area and the List of states and territories of the United States ...

in the United States.

Biology

The ''B. muscus'' hydroid buds and forms medusae by

asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

. When these mature, sexual reproduction occurs, the fertilised eggs settle out and new hydroids are formed. The hydroid grows rapidly and may starts to produce medusae when as little as seven weeks old. The medusae grow on the side branches and become free swimming when they are released. At first they are less than one millimetre in diameter but soon swell and the umbrella become globular in shape. There is a short stomach and sometimes an umbilical canal. There are four short, unbranched oral tentacles which are usually turned up. There are four radial canals and four marginal bulbs, each with two tentacles. At the base of these tentacles there are single

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

. The stomach and marginal bulbs are pink or yellowish-brown while the ocelli are black or dark red. As the medusa grows, the oral tentacles branch but the general form of the medusa remains much the same. The gonads develop on the margins and may extend onto the underside of the umbrella beside the radial canals. Ripe ova can be found on mature medusae.

References

{{Taxonbar, from=Q1935239 Bougainvilliidae Animals described in 1863 Taxa named by George Allman (natural historian)