Marimo (Aegagropila linnaei)
Marimo - Aegagropila linnaei
Aegagropila linnaei, known as Marimo (literally "ball seaweed") in Japanese and as Cladophora ball, Lake ball, Mossimo or Moss Balls in English, is a species of filamentous green algae
(Chlorophyta) family Cladophoraceae, found mostly in a number of lakes in the northern hemisphere. A marimo is a rare growth form of the species where the algae grow into large green balls with a velvety appearance. Colonies of such balls are only known to form in Iceland, Scotland, Japan, Estonia and, in 2014,
They were first discovered in the 1820s by Anton E. Sauter in Lake Zell, Austria. The genus Aegagropila was established by Friedrich T. Kutzing (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 genus Cladophora later by the same author (Kutzing 1849). Subsequently, A. linnaei has been accommodated in the genus Cladophora in the Cladophorales and has been renamed Cladophora aegagropila (L.) Rabenhorst and Cl. sauteri (Nees ex Kutz.) Kutz. 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.
The plant was named "marimo" by a Japanese botanist Tatsuhiko Kawakami, in 1898 (Meiji 31). Mari is a bouncy play ball. Mo is a generic term for plants that grow in water. The native names in Ainu are torasampe (lake goblin) and tokarip (lake roller). They are sometimes sold in aquaria under the name "Japanese moss balls" although they are unrelated to moss. In Iceland the lake balls are called kuluskitur by the local fishermen at Myvatn (kula = ball. skitur = muck) where the "muck" is any weeds that get entangled in their fishing nets. The generic name "Aegagropila" (Áåãáãñüðéëá) is Greek for "goat hair".
So, how does this species of alga form itself into a ball? The answer is not
mystical, though it is quite specific. To start with, the ball form of this alga is not the only way it
grows. There are three growth forms. One is epilithic (growing on rocks) and is usually found on the shaded side of the
rocks. Another growth form lives as free-floating filaments, as small tufts of unattached filaments that frequently form a carpet on the muddy lake
bottom. The third growth form is the lake ball proper, where the algae grow into sizable balls of densely packed algal filaments that radiate from the
center. The balls do not have a kernel of any sort. Populations will also form as mats on the lake
bed, carpeting rocks and other debris. When pieces break off and become free
floating, tidal action gently rolls them around. As they grow and move, they become tangled up and gradually form themselves into this spherical
shape. The overall shape and survival of the alga in this form is reliant on this tidal
motion. All parts of the ball actively photosynthesize and if it is not exposed to light all
over, the shaded parts die and the ball will be no longer. Luckily, the alga reproduces vegetatively so the broken parts can still go on
The existence of Marimo colonies in Lake Akan, Hokkaido in Japan and in Lake Myvatn in Iceland 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. The growth rate of Marimo is about 5 mm per year. In Lake Akan they grow particularly large, up to 20–30 cm (8–12 inches). Myvatn, Iceland, has dense colonies of marimo that grow to about 12 cm in diameter and form well defined patches on the lake floor at depths ranging from 2–2.5 m. The colonies were discovered in 1978 but have shrunk considerably in size since then. The round shape of the marimo is maintained by gentle wave action that occasionally turns it. The balls are green all the way round which guarantees that they can photosynthesize no matter which side is turned upwards. Inside, the ball is also green and packed with dormant chloroplasts which become active in a matter of hours if the ball breaks apart. The wave action also cleans the balls of detritus. 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.
Sadly, marimo balls are not doing too well in the wild. As we have seen with so many other
species, human impacts are taking their toll on Aegagropila linnaei.
Eutrophication, logging, and development within the watersheds that feed these lakes are causing the once clear waters to become quite
murky. As this issue increases, the alga can no longer photosynthesize on a level that can sustain its
populations. Acid rain is another big issue. Marimo balls tend to grow in calcareous
lakes. As the water acidifies, they are unable to cope. Finally, one of the other issues facing the marimo balls is their
popularity. In some areas, they are being harvested for the aquarium trade at unsustainable
levels. One source claims that a majority of marimo balls for sale in aquarium shops are sourced from the
Ukraine, which means that those populations are under serious pressure.
The rapidly declining population of lake balls in Myvatn is of special concern, but for unknown reason some of the main patches have all but vanished in recent years. At Lake Akan a great effort is spent on the conservation of the lake balls. This includes an annual three day marimo festival in which the Ainu people, the indigenous people of Hokkaido, play an important part. Because of their appealing appearance the lake balls also serve as a medium for environmental education. They bear a certain likeness to the Earth in being green and round and in their need to rotate in order to receive light on all sides. In Japan the marimo has been a protected species since as early as 1920, defined as a natural treasure. Small balls sold as souvenirs are hand rolled from free-floating filaments. The marimo was given a status of protected species in Iceland in 2006. Both Lake Myvatn and Lake Akan are protected, the former as a nature reserve, the latter as a national
park. The Netherlands is also waking up to the decline of this species. Until more can be
done, it is best to only buy from nursery grown sources. Formation of the balls has been done in an artificial
setting. Truly, no species is safe from the irresponsible nature of modern man.
Since the initial discovery of the Marimo, it has become a popular “pet” for aquarium
owners. In order to preserve the natural Marimo, artificial ones are grown and
sold. Although a ball of algae may not seem like an exciting pet, there are actually several reasons why the Marimo is so
popular. They require almost no care or attention to grow, and they can exist without sunlight in any type of
aquarium. The Marimo is also very interesting to watch, as it floats up and down depending on changes in the environment and the amount of light it
receives. This movement actually causes many people to mistake the Marimo for a type of aquatic
Artificial Marimos can exist in water that is kept at room
temperature. As long as the water is changed on a weekly basis the Marimo will live and
grow. This form of algae does not require natural sunlight, and it can complete the photosynthesis process using any type of light it has access
to. With the correct environment a Marimo can live up to 100 years.
Awareness of the unique nature of the marimo has not gone unnoticed in the rest of Japanese culture. A widely marketed stuffed toy character known as Marimokkori takes the anthropomorphic form of the marimo algae as one part of its design.
Most importantly, the Marimo represents love, at least according to Japanese
folklore. In the country, a legend surrounds the Marimo and its connection to a tribal chief’s
daughter. According to the story, the girl ran away with her lover when her father didn’t approve of their
relationship. Their love was so strong that many people believe their spirit gave birth to the Marimo and still exists within it
today. Because of this story, the Marimo is known as the “love plant,” as it is said that the algae can recognize true
love. In fact, many people choose to give a Marimo to the person they hope to spend the rest of their lives