What are Stoneworts?

A group of freshwater green algae (order Charales) exhibiting thallus differentiation into rhizoids and stems with whorls of branchlets that are frequently coated with calcareous deposits.


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Stonewort Algae Classification

  • Kingdom: Plantae

  • Division: Charophyta

  • Class: Charophyceae

  • Order: Charales


Description of Stonewort Algae

The Charales are found in both freshwater and brackish settings around the world and have huge, macroscopic thalli that can grow up to 120 cm in length. They are branching, multicellular, and photosynthesize with chlorophyll. The unicellular oospore is its only diploid stage in the life cycle. Stoneworts get their name from the fact that the plants can become coated in lime (calcium carbonate) over time. The "stem" is actually a central stalk of multinucleated, large cells. They are distinctive in that each node in the stipe has a whorl of miniature branchlets, which gives them a superficial resemblance to the genus Equisetum. The phenomena of cytoplasmic streaming can be seen in these whorls.

According to Groves and Bullock-Webster, there are roughly 400 species worldwide, with 33 in Britain and Ireland, although Stewart and Church (1992) decrease this to 21.

The Characeae family of plants is the dominant plant life in some of Nicaragua's volcanic crater lakes, which can reach depths of more than 20 metres in some cases. All of the Characeae at Lake Apoyo was devoured by introduced tilapia (Oreochromis niloticus).


Habitat of Stonewort Plant

The majority of Characeae live in freshwater, usually in still, clear water, where their rhizoids connect to the substrate. They might be ephemerals or pioneer colonisers. They are often found in low to medium nutrient-rich water, and eutrophication causes them to disappear. Some stoneworts may thrive in brackish or maritime environments, and they can be found in Australia's ephemeral saline lakes, which have double the salinity of saltwater.


Life Cycle

When mature, a layer of sterile cells protects the antheridia (or globules) and oogonia (or nucules); the oogonium is rectangular in shape and consists of a single egg, whereas the spherical antheridium is packed with threadlike cells that make spermatia. As a result, if the Charales should be called that, they have the most complicated structure of all green algae. The land plants' putative sibling group is likewise known as brittleworts or skunkweed. The fragility of their lime-encrusted stems, as well as the unpleasant odour they emit when trod on, inspired these unusual labels.


Starry Stonewort

Starry stonewort is an invasive green alga that can grow tall and dense, producing carpets on the ground that obstruct enjoyment and may dispense with native plant species.

Nitellopsis obtusa is the scientific name for starry stonewort. It's a charophyte, a type of freshwater green algae that includes muskgrasses and stoneworts (Chara and Nitella species), both of which are native to Minnesota. Parts of Europe and Asia are home to the starry stonewort. It is uncommon in much of its natural area, and it is listed as endangered in Japan and as a conservation concern in the United Kingdom.


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Starry Stonewort Classification

  • Kingdom: Plantae

  • Division: Charophyta

  • Class: Charophyceae

  • Order: Charales

  • Family: Characeae

  • Genus: Nitellopsis

  • Species: N. obtusa


Starry Stonewort Description

Starry stonewort resembles several native charophytes in appearance, but it is larger and more robust. It's a green macroalga with whorls of long, slender branchlets coming off of main shoots in clusters of four to six. Male antheridia (orange reproductive structures) are found at branchlet nodes. The starry stonewort gets its name from its little, white bulbils that are shaped like stars.


Habitat of Starry Stonewort

Starry stonewort was originally discovered in North America near the St. Lawrence River in 1978, and it has since expanded inland. It can now be found throughout much of Michigan's Lower Peninsula, as well as various parts of New York State. It's also been discovered in Indiana, and in southeastern Wisconsin in 2014. It was discovered for the first time in Minnesota in 2015. (Lake Koronis, Stearns Co.).


Starry Stonewort Effects

Starry stonewort can obstruct boating and other recreational activities where it grows profusely and forms surface mats. Native plants may be displaced, and fish and other animals may be harmed as a result of dense development. The ecological effects of starry stonewort are little understood, and there has been little published research to date.


Life Cycle

Unlike many plants and algae, which have both male and female reproductive organs, starry stonewort is dioecious, meaning that individuals are either male or female. Surprisingly, the greatest evidence so far suggests that the populations in the United States are exclusively male, while there may be females who have yet to be discovered. This suggests that starry stonewort expansion is most likely due to the human movement of fragments from lake to lake. Starry stonewort, for instance, generates little, star-shaped structures known as "bulbils," which allow it to reproduce vegetatively (clonally).

FAQs (Frequently Asked Questions)

1. Why is Chara Known as Stonewort?

Ans. Because its plant body is coated with calcium carbonate, the algae Chara is known as stonewort. Because of its stem-like and leaf-like form, it resembles terrestrial plants. The stem is essentially a central stalk made up of multinucleated, large cells.

2. What Type of Life Cycle Does Chara Have?

Ans. The oospore nucleus divides into four haploid daughter nuclei, three of which degenerate. When the oospore or zygote germinates, haploid protonema is produced. Chara's plant body is haploid, with the oospore being the only diploid phase in the life cycle. A haplontic life cycle is present.

3. When Did the Stoneworts Come into Existence?

Ans. Stoneworts were abundant during the dinosaur era, reaching a peak population around 70 million years ago. When the dinosaurs vanished 65 million years ago, they took a hit and have been progressively diminishing since.

4. Is Starry Stonewort a Plant?

Ans. While starry stonewort appears to be a genuine plant, it is actually a rooted alga descended from some of the earliest life forms on Earth and thought to be the ancestors of all plants by scientists. It is a highly invasive plant because of its capacity to destroy ecologically sensitive places and spread rapidly.