''Perna perna'', the brown mussel, is an economically important mussel, a bivalve mollusc belonging to the

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

Mytilidae Mytilidae are a family of small to large marine and brackish-water bivalve molluscs in the order Mytilida. One of the genera, '' Limnoperna'', even inhabits freshwater environments. The order has only this one family which contains some 52 gener ...

. It is harvested as a food source but is also known to harbor toxins and cause damage to marine structures. It is native to the waters of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

, and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

and was introduced in the waters of North America.

Description

''Perna perna'' is usually 90 mm long although it can reach sizes of up to 120 mm. The mussel is easily recognized by its brown color but its identifying characteristic is the "divided posterior retractor mussel scar". Its pitted resillal ridge also differentiates the mussel from other bivalves. Similar species include the European mussel, ''

Mytilus galloprovincialis The Mediterranean mussel (''Mytilus galloprovincialis'') is a species of bivalve, a marine mollusc in the family Mytilidae. It is an invasive species in many parts of the world, and also an object of aquaculture. Systematics ''Mytilus gall ...

'', and the black mussel, '' Choromytilus meridionalis''. The European mussel is similar in shape and color to the brown mussel and shares its native habitat on the south-western coast of Africa. The European mussel is also more resistant to human disturbance such as use for baits and consumption. It is out-competing the brown mussel as it is more resistant to certain

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s. The black mussel has similar shape and size although it lacks the distinguishable pitted resillal ridge. The brown mussel can also be mistaken for the more famous greenish-brown species ''

Perna viridis ''Perna viridis'', known as the Asian green mussel, is an economically important mussel, a bivalve belonging to the family Mytilidae. It is harvested for food but is also known to harbor toxins and cause damage to submerged structures such as d ...

'', as their color and shell shape can change depending on environmental conditions.

''Perna perna'' var. ''elongata''
Right and left valve of the same specimen: File:Perna perna 01.jpg, Right valve File:Perna perna 02.jpg, Left valve

Habitat and distribution

The brown mussel is native to the

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 ...

and

sub-tropical The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north a ...

regions of the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and Western Indian Ocean . It is found in waters off the west coast of Africa and the coast of South America up to the Caribbean, as well in the East Coast of Africa and Madagascar. It is accidentally introduced as an invasive species to the coast of

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

via the

boat hulls A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...

and water ballasts of ships from

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

. Its distribution include:

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

. The brown mussel naturally colonizes rocky shores but can also attach to submerged man-made objects such as navigation buoys, petroleum platforms and shipwrecks. The adult brown mussel can tolerate a temperature range of 10 to 30 °C and a salinity range of about 15 to 50 ppt. Its colonization of the hard strata improves that surface's marine ecology. The colonization increases surface area, encouraging other marine organisms such as limpets,

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

s, barnacles,

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...

s and

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e to settle there as well.

Ecology and life history

The mussel utilizes

external fertilization External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body. It is contrasted with internal fertilization, in which sperm are introduced via insemination and then ...

during the spawning season between May and October although this is also reported to occur in December. The two sexes release eggs and sperm to the water during spawning to produce

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod ...

larvae. Fifteen hours after fertilization the larvae have well-developed hinge teeth. Ten to twelve days after fertilization the larvae undergo metamorphosis where byssal threads are secreted. The larvae then settle on rocky surfaces. The brown mussel is a filter feeder and feeds on phytoplankton,

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

and suspended organic materials. It is plagued by the parasite ''Proctoeces maculatus'' and an unidentified bucephalid sporocyst which castrates both sexes. On the African coastline it is preyed upon by the whelk '' Nucella cingulata'', lobsters, octopuses, gulls and the African black oystercatcher. On the South American coastline, it provides food for '' Callinectes danae'', '' Cymatium parthenopeum'', '' Chicoreus brevifrons'', '' Thais haemastoma'', and '' Menippe nodifrons''.

Importance to humans

''Perna perna'' is harvested as a food source in Africa and South America. The bivalve is considered for cultivation as it can grow quickly to the commercial size of 60 to 80 mm in just 6 or 7 months. It is also well-suited to tropical and subtropical regions. However, the mussel can harbor

saxitoxin Saxitoxin (STX) is a potent neurotoxin and the best-known paralytic shellfish toxin (PST). Ingestion of saxitoxin by humans, usually by consumption of shellfish contaminated by toxic algal blooms, is responsible for the illness known as paralyt ...

from consumed dinoflagellates. Its consumption has caused outbreaks of

paralytic shellfish poisoning Paralytic shellfish poisoning (PSP) is one of the four recognized syndromes of shellfish poisoning, which share some common features and are primarily associated with bivalve mollusks (such as mussels, clams, oysters and scallops). These shellfi ...

. The brown mussel is known to aggregate in such large amounts that it is able to sink

navigational buoys Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

. It also coexists with the Asian green mussel in fouling water pipes and marine equipment. It is less resistant to

chlorination Chlorination may refer to: * Chlorination reaction In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transform ...

than ''

'' and thus easier to control. However, it is recommended that the concentration of chlorine used for chlorination be above the tolerance level of ''Perna viridis'', the tougher of the two biofouling mussels.

References

* Dautzenberg, Ph. (1929). ''Contribution à l'étude de la faune de Madagascar: Mollusca marina testacea. Faune des colonies françaises, III (fasc. 4)''. Société d'Editions géographiques, maritimes et coloniales: Paris. 321-636, plates IV-VII pp. * MacNae, W. & M. Kalk (eds) (1958). ''A natural history of Inhaca Island, Mozambique''. Witwatersrand Univ. Press, Johannesburg. I-iv, 163 pp.
''The sea shells of Dar es Salaam: Part 2: Pelecypoda (Bivalves)''. Tanganyika Notes and Records 63
* Richmond, M. (Ed.) (1997). ''A guide to the seashores of Eastern Africa and the Western Indian Ocean islands.'' Sida/Department for Research Cooperation, SAREC: Stockholm, Sweden. . 448 pp. * Steyn, D.G. & Lussi, M. (1998) ''Marine Shells of South Africa. An Illustrated Collector’s Guide to Beached Shells''. Ekogilde Publishers, Hartebeespoort, South Africa, ii + 264 pp. page(s): 202 * Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). ''European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification.'' Collection Patrimoines Naturels, 50: pp. 180–213 * Gofas, S.; Afonso, J.P.; Brandào, M. (Ed.). (S.a.). ''Conchas e Moluscos de Angola = Coquillages et Mollusques d'Angola. hells and molluscs of Angola'' Universidade Agostinho / Elf Aquitaine Angola: Angola. 140 pp.
Branch, G.M. et al. (2002). ''Two Oceans''. 5th impression. David Philip, Cate Town & Johannesburg
* Ardovini, R.; Cossignani, T. (2004). West African seashells (including Azores, Madeira and Canary Is.) = Conchiglie dell'Africa Occidentale (includes Azzorre, Madeira e Canarie). English-Italian edition. L'Informatore Piceno: Ancona, Italy. . 319 pp. * Streftaris, N.; Zenetos, A.; Papathanassiou, E. (2005). ''Globalisation in marine ecosystems: the story of non-indigenous marine species across European seas.'' Oceanogr. Mar. Biol. Annu. Rev. 43: 419-453 * Turgeon, D. D., W. G. Lyons, P. Mikkelsen, G. Rosenberg, and F. Moretzsohn. 2009. ''Bivalvia (Mollusca) of the Gulf of Mexico, Pp. 711–744'' in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M Press, * Huber M. (2010) ''Compendium of bivalves. A full-color guide to 3,300 of the world’s marine bivalves. A status on Bivalvia after 250 years of research''. Hackenheim: ConchBooks. 901 pp., 1 CD-ROM

External links

{{Taxonbar, from=Q3017896 Mytilidae Molluscs of the Atlantic Ocean Marine molluscs of Africa Marine molluscs of Europe Molluscs of South America Molluscs of Chile Commercial molluscs Molluscs described in 1758 Taxa named by Carl Linnaeus