Editing Marimo

{{Short description|Species of algae}}
{{Speciesbox
 | name = Marimo
 | image = Marimo lake akann.jpg
 | image_caption = Marimo in [[Lake Akan]] in Japan
 | image2 = Co je to řasokoule.jpg
 | genus = Aegagropila
 | parent_authority = [[Friedrich Traugott Kützing|Kützing]]
 | species = linnaei
 | authority = Kützing
}}

'''Marimo'''{{efn|From the Japanese {{lang|ja|マリモ}} or {{lang|ja|毬藻}}, literally 'ball seaweed'}} (also known as '''Cladophora ball''', '''moss ball''', '''moss ball pet''', or '''lake ball''') is a rare growth form of '''''Aegagropila linnaei''''' (a species of filamentous [[green 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 and [[Northern Europe]].<ref>{{harvnb|Boedeker|Eggert|Immers|Smets|2010}}: [https://academic.oup.com/view-large/figure/94377148/bio.2010.60.3.5-f04.jpeg Figure 4]</ref> Colonies of marimo balls are known to form in [[Japan]] and [[Iceland]], but their population has been declining.<ref name="population-decline">{{Cite journal|last1=Boedeker|first1=Christian|last2=Eggert|first2=Anja|last3=Immers|first3=Anne|last4=Smets|first4=Erik|year=2010|title=Global Decline of and Threats to Aegagropila linnaei, with Special Reference to the Lake Ball Habit|journal=BioScience|volume=60|issue=3|pages=187–198|doi=10.1525/bio.2010.60.3.5|doi-access=free}}</ref>

==Classification and name==
Marimo were first described in the 1820s by [[Anton Eleutherius Sauter|Anton E. Sauter]], found in [[Lake Zell]], [[Austria]]. The genus ''Aegagropila'' was established by [[Friedrich Traugott Kützing|Friedrich T. Kützing]] (1843) with ''A. linnaei'' as the type species based on its formation of spherical aggregations, but all the ''Aegagropila'' species were transferred to subgenus ''Aegagropila'' of the genus ''Cladophora'' later by the same author (Kützing 1849). Subsequently, ''A. linnaei'' was placed in the genus ''Cladophora'' in the Cladophorales and was renamed ''Cladophora aegagropila'' (L.) Rabenhorst and ''Cl. sauteri'' (Nees ex Kütz.) Kütz. Extensive [[DNA]] research in 2002 returned the name to ''Aegagropila linnaei''. The presence of [[chitin]] in the cell walls makes it distinct from the genus ''[[Cladophora]]''.{{Cn|date=May 2021}}

The algae was named ''marimo'' by the Japanese [[Botany|botanist]] Takiya Kawakami in 1898. {{transliteration|ja|Mari}} is a type of bouncy play ball; {{transliteration|ja|mo}} is a generic Japanese term for plants that grow in water. The native names in [[Ainu language|Ainu]] are {{lang|ain|torasampe}} ('lake goblin') and {{lang|ain|tokarip}} ('lake roller').<ref name="marimo-festival">Irimoto, Takashi. 2004. [https://web.archive.org/web/20110722073711/http://ir.minpaku.ac.jp/dspace/bitstream/10502/1053/1/SES66_004.pdf Creation of the Marimo Festival: Ainu Identity and Ethnic Symbiosis]. Senri Ethnological Studies 66:11–38.</ref> They are sometimes sold in [[aquarium]]s under the name "Japanese moss balls" although they are unrelated to [[moss]]. In Iceland the lake balls are called {{lang|is|kúluskítur}} by the local fishermen at [[Mývatn|Lake Mývatn]] ({{lang|is|kúla}} meaning 'ball', {{lang|is|skítur}} meaning 'muck') where the "muck" is any weeds that get entangled in their fishing nets. The generic name ''Aegagropila'' is Greek for 'goat hair'.{{citation needed|date=March 2020}}

==Growth forms==
{{Unreferenced section|date=April 2021}}
[[File:Marimo1.jpg|thumb|Three common growth forms of ''Aegagropila linnaei'': as a ball, free-floating filaments, and growth on rocks.]]
The algae has three growth forms:

* It can grow on rocks, usually found on the shaded side of the rocks.
* It can exist as free-floating filaments. Small tufts of unattached filaments frequently form a carpet on the muddy lake bottom.
* It can form a lake ball where the algae grow into sizable balls of densely packed algal filaments that radiate from the center. The balls do not have a [[seed|kernel]] of any sort.
[[Image:Marimo colony.svg|left|thumb|380px|A cross section of a marimo colony in Lake Mývatn.]]
{{Clear}}

==Ecology==
{{More citations needed section|date=May 2021}}
[[File:Lake_Akan_Kushiro_Hokkaido_Japan05n.jpg|thumb|[[Lake Akan]] and Mount Oakan in Japan.]]
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.

=== Size ===
[[File:Gałęzatka kulista (Cladophora aegagropila).jpg|thumb|Marimo in an aquarium]]
The growth rate of marimo is about {{convert|5|mm|in|1|abbr=on}} per year. In [[Lake Akan]] in Japan they grow particularly large, up to {{convert|20|–|30|cm|in|round=0.5|abbr=on}}. [[Mývatn|Lake Mývatn]], Iceland, had dense colonies of marimo that grow to about {{convert|12|cm|in|0|abbr=on}} in diameter and formed well defined patches on the lake floor at depths ranging from {{convert|2|–|2.5|m|ft|abbr=on}}.

=== Shape ===
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.<ref name="population-decline"/>

The balls are green all the way round which guarantees that they can [[Photosynthesis|photosynthesize]] no matter which side is turned upwards. Inside, the ball is also green and packed with dormant [[chloroplast]]s which become active in a matter of hours if the ball breaks apart. The wave action also cleans the balls of [[detritus|dead 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 low [[surface-area-to-volume ratio]] compared to a [[leaf]], which limits [[photosynthesis]] and therefore limits the maximum size of the marimo balls.

=== Habitat ===
Marimo's preferred [[habitat]] is in lakes with a low or moderate biological activity, and with moderate or high levels of [[calcium]].<ref name="population-decline" />

=== Distribution ===
The species is mainly found in the areas of Europe previously covered in [[glacier]]s (Northern-Europe), and in several places in Japan. It has been found in North America, but it is rare, as well as in Australia.<ref name="population-decline" />

===Population decline===
The species is sensitive to the amount of nutrients in the water. An [[Eutrophication|excess of nutrients]] (due to agriculture and [[fish farming]]), along with mud deposition from human activity are thought to be the main causes for its disappearance from many lakes.<ref name="population-decline" />

The species still exists in [[Lake 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.<ref name="population-decline" />
[[File:Mývatn-pjt.jpg|thumb|320x320px|[[Mývatn|Lake Mývatn]] in Iceland.]]
Dense colonies of marimo were discovered in [[Mývatn|Lake 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.<ref>{{Cite news|url=https://www.mbl.is/frettir/innlent/2014/05/02/einkenni_myvatns_ad_hverfa/|title=Einkenni Mývatns að hverfa|date=2014-05-02|work=[[Morgunblaðið]]|language=is}}</ref> The ecosystem is now improving and small marimo balls are forming again.<ref>{{Cite web|url=https://icelandmag.is/article/unexpected-good-news-lake-myvatn-large-quantities-marimo-wash-ashore|title=Unexpected good news from lake Mývatn: Large quantities of Marimo wash ashore|website=Icelandmag}}</ref><ref>{{Cite web|url=https://icelandmag.is/article/great-news-myvatn-lake-unique-marimo-colonies-grow-second-year-a-row|title=Great news from Mývatn lake: Unique marimo colonies grow second year in a row|website=Icelandmag}}</ref>

The species can still be found in several places in Japan, but populations have also declined there.<ref name="population-decline" /> At Lake Akan, a great effort is spent on the conservation of the lake balls.

The marimo has been a [[Conservation status|protected species]] in Japan since the 1920s, and in Iceland since 2006. Lake Akan is protected as a [[national park]] and Lake Mývatn is protected as a [[nature reserve]].

== Cultural aspects ==
[[File:Marimo-youkan.JPG|thumb|''[[Yōkan]]'' confection shaped like marimo, sold near [[Lake Akan]]]]
[[File:Aegagropila conical flask.jpg|thumb|''A. linnaei'' grown in a conical flask at home.]]
Marimo balls are a rare curiosity. In Japan, the [[Ainu people]] hold a three-day marimo festival every October at Lake Akan.<ref name="marimo-festival" /><ref name="nytimes">{{Cite news|url=https://www.nytimes.com/2018/08/24/science/marimo-floating-algae-balls.html|title=The Mysterious Green Orbs That Float by Day and Sink at Night|last=Klein|first=JoAnna|date=2018-08-24|work=The New York Times|access-date=2019-05-21|language=en-US|issn=0362-4331}}</ref>

Because of their appealing appearance, the lake balls also serve as a medium for [[environmental education]]. Small balls sold as [[souvenir]]s are hand rolled from free-floating filaments.{{citation needed|date=May 2019}} A widely marketed [[stuffed toy]] character known as [[Marimokkori]] takes the anthropomorphic form of the marimo algae as one part of its design.

Marimo are sometimes sold for display in aquariums, typically cultivated in [[Ukraine|Ukrainian]] lakes such as the [[Shatskyi Lakes]].<ref name="population-decline" /> Balls sold in Japanese aquarium shops are of European origin,<ref name="population-decline" /> as collecting them from Lake Akan is prohibited.<ref name="nytimes" /> 

In the manga [[One Piece]] and its adaptation, the Straw Hat Crew's swordsman, Zoro, is often referred to as "Marimo Head" due to his spiky green hair.

==Contamination==
On 2 March 2021,<ref name="USGS-moss-zebras" /> the [[United States Geological Survey]] was notified that [[zebra mussel|zebra mussels]] had been discovered in moss balls sold in pet stores across North America.<ref>{{cite web|url=https://www.fws.gov/fisheries/ANS/zebra-mussel-disposal.html|title=Zebra mussel disposal|website=FWS|date=26 April 2021 }}</ref> By 8 March, invasive zebra mussels had been detected in moss balls in 21 states.<ref name="USGS-moss-zebras">{{cite web|url=https://www.usgs.gov/news/invasive-zebra-mussels-found-pet-stores-21-states|title=Invasive Zebra Mussels Found in Pet Stores in 21 States|website=USGS}}</ref> These discoveries were prompted by the initial find at a [[Seattle]] [[Petco]].<ref name="WashDeptFish" /> 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.<ref name="WashDeptFish">{{cite web | title=State asks public to inspect aquarium moss and prevent movement of invasive mussels | website=[[Washington Department of Fish and Wildlife|Washington Department of Fish & Wildlife]] | date=2021-03-04 | url=http://wdfw.wa.gov/news/state-asks-public-inspect-aquarium-moss-and-prevent-movement-invasive-mussels | access-date=2021-04-27}}</ref> Petco<ref name="Petco-moss">{{cite web | title=Recalls & Advisories | website=[[Petco]] | url=http://www.petco.com/content/petco/PetcoStore/en_US/pet-services/help/recalls.html | access-date=2021-04-27}}</ref> and [[PetSmart]]<ref name="Petsmart-moss-balls">{{cite web | title=Voluntary Product Withdrawal: Marimo Moss Balls | website=Heart of [[Petsmart]] | date=2021-03-06 | url=http://www.petsmartcorporate.com/product-notices/voluntary-product-withdrawal-marimo-moss-balls/ | access-date=2021-04-27}}</ref> voluntarily recalled moss balls in their stores. If the mussels reach open water in [[Washington (state)|Washington]], they could cost the state $100 million each year in maintenance for power and water systems.<ref name="WashDeptFish" />

==See also==
*[[List of Special Places of Scenic Beauty, Special Historic Sites and Special Natural Monuments|List of ''Special Natural Monuments'' in Japan]]
* ''[[Codium bursa]]'', a round marine algae
* [[Red moss]], another species of algae used in freshwater aquascaping

== Notes ==
{{Notelist}}

==References==
{{Reflist}}

==Bibliography==
{{Refbegin}}
* {{cite journal|doi=10.1023/b:aeco.0000032090.72702.a9|title=The ecology of Lake Myvatn and the River Laxá: Variation in space and time|journal=Aquatic Ecology|volume=38|issue=2|pages=317–348|year=2004|last1=Einarsson|first1=Árni|last2=Stefánsdóttir|first2=Gerdur|last3=Jóhannesson|first3=Helgi|last4=Ólafsson|first4=Jón S.|last5=Már Gíslason|first5=Gísli|last6=Wakana|first6=Isamu|last7=Gudbergsson|first7=Gudni|last8=Gardarsson|first8=Arnthor|bibcode=2004AqEco..38..317E |s2cid=30398384}}
* {{cite journal|doi=10.1046/j.1529-8817.2002.01151.x|title=PHYLOGENETIC RELATIONSHIPS WITHIN CLADOPHORALES (ULVOPHYCEAE, CHLOROPHYTA) INFERRED FROM 18S rRNA GENE SEQUENCES, WITH SPECIAL REFERENCE TO AEGAGROPILA LINNAEI 1|journal=Journal of Phycology|volume=38|issue=3|pages=564–571|year=2002|last1=Hanyuda|first1=Takeaki|last2=Wakana|first2=Isamu|last3=Arai|first3=Shogo|last4=Miyaji|first4=Kazuyuki|last5=Watano|first5=Yasuyuki|last6=Ueda|first6=Kunihiko|bibcode=2002JPcgy..38..564H |s2cid=84081568}}
* {{cite journal|doi=10.2307/3545053 |jstor=3545053 |title=Photosynthesis and Production of Epilithic Algal Communities in Thingvallavatn |journal=Oikos |volume=64 |issue=1/2 |pages=222–240 |year=1992 |last1=Jónsson |first1=Gunnar St. |last2=Jonsson |first2=Gunnar St. |bibcode=1992Oikos..64..222J }}
* Nagasawa, S., Wakana, I. and Nagao, M. 1994. Mathematical characterization of photosynthetic and respiratory property regarding the size of Marimo's aggregation. Marimo Research 3:16–25.
* Yoshida, T., Nagao, M., Wakana, I. and Yokohama, Y. 1994. Photosynthetic and respiratory property in the large size spherical aggregations of "Marimo". Marimo Research 3:1–11.
* Yoshida, T., Horiguchi, T., Nagao, M., Wakana, I. and Yokohama, Y. 1998. Ultrastructural study of chloroplasts of inner layer cells of a spherical aggregation of "Marimo" (Chlorophyta) and structural changes seen in organelles after exposing to light. Marimo Research 7:1–13.
* Wakana, I. 1992. A bibliography relating to "Marimo" and their habitats. Marimo Research 1:1–12.
{{Refend}}

==External links==
{{Commons category|Aegagropila linnaei}}
*[https://mossballpets.com/pages/a-love-story Ainu Tribe - Legend of the Marimo]
*[http://web-japan.org/atlas/nature/nat15.html Lake Akan and marimo in the Japan Atlas]

{{Taxonbar|from=Q149096}}
{{Authority control}}

[[Category:Pithophoraceae]]
[[Category:Commemoration of Carl Linnaeus]]
[[Category:Taxa named by Friedrich Traugott Kützing]]
[[Category:Algae species]]
[[Category:Aquarium plants]]