Excoecaria agallocha (Blind Your Eye) W IMG 6949

''Excoecaria agallocha'', a

mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...

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 ...

, belongs to the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Excoecaria ''Excoecaria'' is a plant genus of the family Euphorbiaceae, formally described by Linnaeus in 1759. The genus is native to the Old World Tropics (Africa, southern Asia, northern Australia, and assorted oceanic islands). Etymology Genus name, ...

'' of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Euphorbiaceae Euphorbiaceae, the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of a genus in the family. Most spurges, such as ''Euphorbia paralias'', are herbs, but some, e ...

. The species has many common names, including blind-your-eye mangrove, blinding tree, buta buta tree, milky mangrove, poisonfish tree, and river poison tree. Most of the names refer to its toxic properties or its propensity to cause blindness when its

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...

comes into contact with the eyes. This plant grows in saline or brackish water in

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

mangrove forests, in a distribution bounded to the west by

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, to the north by

Bangladesh Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...

, to the south by

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. Within Australia, it thrives from northern

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

along the northern coastline around to

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

Description

Mangrove swamps form a type of coastal

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

found in the tropics and subtropics. Within a mangrove forest, the most salt-tolerant species occur near the ocean. ''Excoecaria agallocha'', known as a back mangrove, is found at higher elevations back away from the ocean where salinity is lower. Mangroves of this plant surround the ancient Thillai Chidambaram Temple in

Tamil Nadu Tamil Nadu (; , TN) is a States and union territories of India, state in southern India. It is the List of states and union territories of India by area, tenth largest Indian state by area and the List of states and union territories of India ...

. This small tree species may grow up to 15 m high. Trees are either male or female (dioecious). Male flowers form drooping tassels, while female flowers appear as shorter spikes. Pollinators such as bees commonly visit the flowers. The fruit is a small dark capsule. The plant is well-protected by chemical defenses; these include diterpenoids, triterpenoids and flavonoids. The milky

of ''Excoecaria agallocha'' is very poisonous and powerfully irritant, which is not unusual in milky species of plant in the family Euphorbiaceae. Contact with skin causes irritation and rapid blistering; slight contact with eyes can cause temporary blindness, hence the common names that refer to blindness. Even the generic name is from the Latin for "blinder".

William Bligh Vice-Admiral William Bligh (9 September 1754 – 7 December 1817) was an officer of the Royal Navy and a colonial administrator. The mutiny on the HMS ''Bounty'' occurred in 1789 when the ship was under his command; after being set adrift i ...

in his book ''Voyage to the South Sea'' mentioned that he was already aware of this hazard when he embarked on the voyage that ended in the notorious

mutiny on the Bounty The mutiny on the Royal Navy vessel occurred in the South Pacific Ocean on 28 April 1789. Disaffected crewmen, led by acting-Lieutenant Fletcher Christian, seized control of the ship from their captain, Lieutenant William Bligh, and set h ...

, having learned of it in 1777 from Captain

James Cook James Cook (7 November 1728 Old Style date: 27 October – 14 February 1779) was a British explorer, navigator, cartographer, and captain in the British Royal Navy, famous for his three voyages between 1768 and 1779 in the Pacific Ocean an ...

during the time that he served as Cook's

sailing master The master, or sailing master, is a historical rank for a naval officer trained in and responsible for the navigation of a sailing vessel. The rank can be equated to a professional seaman and specialist in navigation, rather than as a military ...

. Several of the men that Cook had sent ashore to cut wood had been blinded for a time. He accordingly instructed his men not to cut that type of tree when he sent them ashore in Tahiti to gather wood and water in 1789. It was just as well that he did so, because even the smoke from the burning wood is poisonous and can harm the eyes, so it would not have been useful as fuel.

Taxonomy

''Excoecaria agallocha'', a

, belongs to the

'' of the

Ecology

The latex produced by ''E. agallocha'' contains a variety of

phytotoxins Phytotoxins are substances that are poisonous or toxic to the growth of plants. Phytotoxic substances may result from human activity, as with herbicides, or they may be produced by plants, by microorganisms, or by naturally occurring chemical reac ...

, including the excoecariatoxins, which are powerful irritants to the skin, eyes and mucous membranes. Despite the powerful chemical defense mechanisms of this plant, ''E. agallocha'' is the sole food source for the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e of the mangrove jewel bug ('' Calliphara nobilis''), a

phytophagous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

species of jewel bug found in

mangrove forests in some parts of Asia. Like many other species of

aposematic Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste or ...

scutellerids, ''C. nobilis'' is able to sequester chemical compounds from its host plants that are toxic to their predators, and use them towards its own defenses. These chemical compounds are concentrated and stored in a pair of scent glands located on the

metathorax The metathorax is the posterior of the three segments in the thorax of an insect, and bears the third pair of legs. Its principal sclerites ( exoskeletal plates) are the metanotum (dorsal), the metasternum (ventral), and the metapleuron (lateral) ...

of the adults and

nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...

. When these insects are threatened or handled, they can secrete an irritating and toxic fluid from these glands as a deterrent to potential predators.

Uses

Even dried and powdered leaves retain the poison and can kill fish very quickly or be used on a poison dart. ''Excoecaria agallocha'' has been found to have various medicinal and pharmacological benefits, including the treatment for epilepsy, ulcers, leprosy, rheumatism, and paralysis. Owing to its complex chemistry, the plant may have many new medicinal uses.Konoshima,T, T. Konishi, M. Takasaki, K. Yamazoe, and H. Tokuda. 2001. Anti-tumor-promoting activity of the diterpene from Excoecaria agallocha. II Biological and Pharmaceutical Bulletin 24:1440-1442.

References

External links

Milky mangrove in Australia

Biology of mangroves
{{Taxonbar, from=Q5419710 agallocha Plants described in 1759 Flora of Asia Flora of Australia Taxa named by Carl Linnaeus Dioecious plants Poisonous plants