Pond plum

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Pond plum
Pond plums (Nostoc pruniforme) on the bank of the pond

Pond plums ( Nostoc pruniforme ) on the bank of the pond

Systematics
Department : Cyanobacteria (Cyanobacteria)
Class : Cyanobacteria (Cyanobacteria)
Order : Nostocales
Family : Nostocaceae
Genre : Nostoc
Type : Pond plum
Scientific name
Nostoc pruniforme
( L. ) C. Agardh ex Bornet & Flahault , 1886

The pond plum ( Nostoc pruniforme ), also called water or sea ​​plum , is a freshwater species of cyanobacteria that forms conspicuous colonies in the form of gelatinous balls. In terms of appearance and external consistency, these are reminiscent of a fruit, for example a grape or a small plum. It should be noted that such or similar gelatinous spheres on or in water can also be traced back to other organisms and that the fruit-shaped colonies of Nostoc pruniforme are a rare occurrence overall.

features

Nostoc species consist of long, unbranched, flexible threads or cords of cells. The individual cells of each thread are spherical to barrel-shaped and about 5 µm in size. The cell chains contain sections of one or more brownish-yellow heterocysts that are responsible for binding nitrogen. The strings of thread are often wound around each other and form a common bearing in a spherical jelly. In the pond plum, these balls can reach a diameter of about one to two centimeters. Outwardly, they have a thin, rough, brown-green skin; inside they consist macroscopically of a soft to firm gelatinous, semi-transparent to milky-cloudy mass.

Occurrence

Pond plums are cosmopolitan and occur in lakes and ponds benthically (close to the ground) free-swimming or on bank mud. The distinctive spheres sometimes collect at certain points on the bottom of the water as a result of currents or wave drift. Nostoc pruniforme shows fish-rich, quite clean, mesotrophic to slightly eutrophic inland waters and used to be common in northern Germany, for example. Today they are only found scattered or rarely there; in Europe it is now considered an endangered species . Regionally, the pond plum is even assessed as threatened with extinction.

Possible confusion

Pond plums ( Nostoc pruniforme ) on scanner; the outer skin of one ball was opened to demonstrate the soft interior

Spherical gelatinous deposits, which can be found in bodies of water, on their banks or on soaky soil, are formed by a large number of single-cell colonies, including some other cyanobacteria. Various other Nostoc species, for example, occur much more frequently than the pond plum treated here. Species of the genus Gloeotrichia , such as G. echinata , also form gelatinous balls several millimeters in size that float freely in the water. In these, the radially arranged trichomes protrude far from the bearings, so that they have a hairy or prickly appearance.

Some green algae (Chlorophyta) also form gelatinous conglomerates when they accumulate. These so-called coccal green algae include those of the genus Haematococcus or the alga Chaetophora pisiformis , which is very common in streams and forms up to pea-sized, dark green, hemispherical to spherical thalli from a tough, cartilaginous gelatinous mass. Green, irregularly shaped, gelatinous structures, which can be colonies of ciliates or the rotifers Conochilus , can often be observed in water bodies .

The probability that you actually have pond plums in front of you when you find floating or clinging greenish "glibber balls" in the garden pond is very low, if only because of their rarity and specific environmental requirements. In most cases it is likely to be colonies of cells from other species. Their unequivocal determination is usually only possible under the microscope.

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literature

  • Bellmann / Hausmann / Janke / Kremer / Schneider: unicellular organisms and invertebrates. Without molluscs and arthropods . Steinbach's natural guide, Mosaik-Verlag, Munich 1991. ISBN 3-576-06495-8

Individual evidence

  1. ↑ D. Mollenhauer, R. Bengtsson & E.-A. Lindström: Macroscopic cyanobacteria of the genus Nostoc: a neglected and endangered constituent of European inland aquatic biodiversity. European Journal of Phycology (1999), 34: 349-360. ( English abstract online )
  2. ↑ Lothar Täuscher: Revision of the checklist and red list of candelabras and prodromus of a red list of cyanobacteria / blue-green algae, red, yellow-green, brown and green algae of the state of Brandenburg. ( PDF online )

Web links

Commons : Nostoc pruniforme  - collection of images, videos and audio files