| Marimo | |
|---|---|
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| Marimo inLake Akan in Japan | |
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Scientific classification | |
| Kingdom: | Plantae |
| Division: | Chlorophyta |
| Class: | Ulvophyceae |
| Order: | Cladophorales |
| Family: | Pithophoraceae |
| Genus: | Aegagropila Kützing |
| Species: | A. brownii |
| Binomial name | |
| Aegagropila brownii (Dillwyn) Kützing | |
Marimo[a] (also known asCladophora ball,moss ball,moss ball pet, orlake ball) is a rare growth form ofAegagropila brownii (a species of filamentousgreen algae) in which the algae grow into large green balls with a velvety appearance.
The species can be found in a number of lakes and rivers in Japan andNorthern Europe.[1] Colonies of marimo balls are known to form inJapan andIceland, but their population has been declining.[2]
Marimo were first described in the 1820s byAnton E. Sauter, found inLake Zell,Austria. The genusAegagropila was established byFriedrich T. Kützing (1843) withA. linnaei as the type species based on its formation of spherical aggregations, but all theAegagropila species were transferred to subgenusAegagropila of the genusCladophora later by the same author (Kützing 1849). Subsequently,A. linnaei was placed in the genusCladophora in the Cladophorales and was renamedCladophora aegagropila (L.) Rabenhorst andCl. sauteri (Nees ex Kütz.) Kütz. ExtensiveDNA research in 2002 returned the name toAegagropila linnaei. The presence ofchitin in the cell walls makes it distinct from the genusCladophora.[citation needed]
The algae was namedmarimo by the Japanesebotanist Takiya Kawakami in 1898.Mari is a type of bouncy play ball;mo is a generic Japanese term for plants that grow in water. The native names inAinu aretorasampe ('lake goblin') andtokarip ('lake roller').[3] They are sometimes sold inaquariums under the name "Japanese moss balls" although they are unrelated tomoss. In Iceland the lake balls are calledkúluskítur by the local fishermen atLake Mývatn (kúla meaning 'ball',skítur meaning 'muck') where the "muck" is any weeds that get entangled in their fishing nets. The generic nameAegagropila is Greek for 'goat hair'.[citation needed]
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The algae has three growth forms:
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The existence of marimo colonies depends on the adaptation of the species to low light conditions, combined with the dynamic interaction of wind-induced currents, light regime, lake morphology, bottom substrate, and sedimentation.
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The growth rate of marimo is about 5 mm (0.2 in) per year. InLake Akan in Japan they grow particularly large, up to 20–30 cm (8–12 in).Lake Mývatn, Iceland, had dense colonies of marimo that grow to about 12 cm (5 in) in diameter and formed well defined patches on the lake floor at depths ranging from 2–2.5 m (6.6–8.2 ft).
The round shape of the marimo is maintained by gentle wave action that occasionally turns it. The best environment for that are shallow lakes with sandy bottoms.[2]
The balls are green all the way round which guarantees that they canphotosynthesize no matter which side is turned upwards. Inside, the ball is also green and packed with dormantchloroplasts which become active in a matter of hours if the ball breaks apart. The wave action also cleans the balls ofdead organic material.
As some colonies have two or even three layers of marimo balls, wave action is needed to tumble them around so each ball reaches the light. The spherical shape has a lowsurface-area-to-volume ratio compared to aleaf, which limitsphotosynthesis and therefore limits the maximum size of the marimo balls.
Marimo's preferredhabitat is in lakes with a low or moderate biological activity, and with moderate or high levels ofcalcium.[2]
The species is mainly found in the areas of Europe previously covered inglaciers (Northern-Europe), and in several places in Japan. It has been found in North America, but it is rare, as well as in Australia.[2]
The species is sensitive to the amount of nutrients in the water. Anexcess of nutrients (due to agriculture andfish farming), along with mud deposition from human activity are thought to be the main causes for its disappearance from many lakes.[2]
The species still exists inLake Zell in Austria (where it was first discovered in the 1820s) but the lake ball growth form has not been found there since around 1910. The same has happened in most locations in England and Scotland, where mainly the attached form can be found.[2]
Dense colonies of marimo were discovered inLake Mývatn in Iceland in 1978, but they have shrunk considerably since then. By 2014 the marimo had almost completely disappeared from the lake due to an excess of nutrients.[4] The ecosystem is now improving and small marimo balls are forming again.[5][6]
The species can still be found in several places in Japan, but populations have also declined there.[2] At Lake Akan, a great effort is spent on the conservation of the lake balls.
The marimo has been aprotected species in Japan since the 1920s, and in Iceland since 2006. Lake Akan is protected as anational park and Lake Mývatn is protected as anature reserve.
Marimo balls are a rare curiosity. In Japan, theAinu people hold a three-day marimo festival every October at Lake Akan.[3][7]
Because of their appealing appearance, the lake balls also serve as a medium forenvironmental education. Small balls sold assouvenirs are hand rolled from free-floating filaments.[citation needed] A widely marketedstuffed toy character known asMarimokkori takes the anthropomorphic form of the marimo algae as one part of its design.
Marimo are sometimes sold for display in aquariums, typically cultivated inUkrainian lakes such as theShatskyi Lakes.[2] Balls sold in Japanese aquarium shops are of European origin,[2] as collecting them from Lake Akan is prohibited.[7]
In the mangaOne Piece and its adaptation, the Straw Hat Crew's swordsman, Zoro, is often referred to as "Marimo Head" due to his spiky green hair.
On 2 March 2021,[8] theUnited States Geological Survey was notified thatzebra mussels had been discovered in moss balls sold in pet stores across North America.[9] By 8 March, invasive zebra mussels had been detected in moss balls in 21 states.[8] These discoveries were prompted by the initial find at a SeattlePetco.[10] Owners of fish tanks were urged to decontaminate the moss balls by boiling, freezing, or bleaching them before disposing of them to prevent spread to local waterways.[10] Petco[11] andPetSmart[12] voluntarily recalled moss balls in their stores. If the mussels reach open water inWashington, they could cost the state $100 million each year in maintenance for power and water systems.[10]
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