Hydrurus foetidus

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Hydrurus foetidus
Systematics
Heteroconta
without rank: Golden brown algae (Chrysophyceae)
Order : Hydrural
Family : Hydruraceae
Genre : Hydrurus
Type : Hydrurus foetidus
Scientific name of the  genus
Hydrurus
C. Agardh
Scientific name of the  species
Hydrurus foetidus
( Villars ) Trevisan

Hydrurus foetidus is a freshwater algae belonging to the golden brown algae (Chrysophyceae). Unlike the mostly single-celled representatives of the class, it forms large, macroscopically recognizable thalli, which are noticeable by a characteristic, quite unpleasant odor ("foetidus" means smelly). The species is widespread worldwide and prefers cold, flowing, mostly very nutrient-poor waters, for example glacial streams in the Alps.

description

The colony-like thalli of Hydrurus foetidus are quite diverse, depending on the site conditions. Typically it forms dark brown to golden yellow colored filamentous jelly tubes, which can be richly branched and then appear bush-like or feather-like (growth form arbuscular, from Latin arbusculum for little tree). These can reach a length of up to 30 centimeters. Young specimens or those under unfavorable growing conditions form flat, smooth or gelatinous coatings on hard substrates such as stones or wood. In the homogeneous, colorless jelly, there are numerous, individual, irregularly or in a row arranged cells with a diameter of 8 to 12 micrometers, without any concentration in the edge area, whereby the end cells at the tip of the thallus are larger than the others. The entire thallus is wrapped in a carbohydrate sheath. The cells are spherical or elliptical, or pear-shaped. Microscopically, only one band-shaped or trough-shaped, bilobed chloroplast can be seen per cell , which is located in the front (apical) part of the cell. A pyrenoid is present, but mostly only recognizable by the outer cells. At the edge of the cells there are often vesicles that store the storage carbohydrate chrysolaminarin , often one prominent vesicle per cell. Each cell has several contractile vacuoles , often two or three.

The thalli of the species have a distinctive, unpleasant “fishy” smell, especially when rubbed with the finger.

The cell colonies grow at the top, with the vegetative cells simply dividing long. In the event of disturbances and under unfavorable conditions, each cell divides into two flagellated zoospores , which are released into the surrounding water. The zoospores have a tetrahedral to teardrop-shaped shape, they have two unequally long (anisoconous) flagella , the short flagellum is rudimentary and hardly recognizable. At a favorable point, on a hard substrate, the zoospore can establish itself and grow into a new thallus. Most of the cells are usually transformed into zoospores synchronously, and the thallus perishes. In addition, the species can form permanent cells called stomatocysts with a wall that is silicified by the inclusion of silicon dioxide, which is lens-shaped and winged in the middle. The stomatocysts are probably formed through sexual reproduction, but this is not yet understood in detail for the species.

Typical cell colonies of the species are distinctive due to their shape, color and smell. Flat coatings can resemble the species Phaeodermatium rivulare , with which the species often occurs together. The cells of Phaeodermatium are smaller, more irregularly shaped and are closer together. Also Celoniella palensis may look similar.

Ecology and location

Hydrurus foetidus grows on the bottom of the water ( benthic ), perched on a hard substrate. It occurs exclusively in fresh water, always in running waters . Under favorable conditions it can form dense coatings on the entire river bed. The species prefers cold waters, it declines above 10 to 12 ° C water temperature and dies above 16 ° C (cold stenothermal ). In culture it thrives best at a water temperature of 2.6 ° C. It develops year-round in arctic latitudes and high mountains, in warmer climates, as it has already been in Central Europe, predominantly in the winter months, often with mass occurrences immediately after the snowmelt. Sometimes a secondary maximum is developed in autumn before the light enjoyment becomes too low for the species in winter. In middle latitudes, without ice cover, it can build up dense stands even in the middle of winter. The species thrives best in clean, nutrient-poor waters (xeno- to oligosaprob in the saprobic system ), but also occurs in nutrient-rich waters of higher trophic and saprobic, up to moderately polluted (mesosa samples). It is promoted by moderately high phosphate levels in the water and can use organic phosphate sources. It occurs in both lime-poor and lime-rich waters. The species prefers areas with high flow velocities in water bodies (rheobiont, prefers “lotic” conditions). In Austria, together with the red alga Lemanea fluviatilis , it is a typical form of alpine mountain streams and springs. Here it can be of great importance for the community. In North America, where it is common in mountain streams both in the west and in the east, the slippery river bed caused by the alga sometimes leads to falls in mountain hikers.

distribution

The species is distributed almost worldwide. It occurs in Europe, Asia, North and South America, Australia and New Zealand and Antarctica. It is particularly common in arctic latitudes, for example on Greenland and Spitsbergen, but it is also not uncommon in central Europe in cold waters. Towards the equator, the cold stenothermal species quickly becomes rarer and only occurs here in mountains. In some southern regions, such as Croatia or Turkey, it was only recently detected.

A unicellular form, which is very closely related according to genetic findings, turned brown on King George Island , Antarctica and on Svalbard, snowfields trickled through by meltwater. Such algal blooms are also known from other representatives of the Chrysophyceae. Although closely related, it is probably a different, previously undescribed species. Hydrurus foetidus itself has also been reported as a coating in similar situations, although it is unclear whether this information actually refers to one of the closely related forms.

Systematics and taxonomy

The species was first described as Conferva foetida by the botanist Dominique Villars in his Histoire des plantes du Dauphiné , published in 1789 , the genus Conferva L. is now considered the noun dubium . In 1803, Jean-Pierre Vaucher re- described it as Ulva foetida . In 1824, the biologist and clergyman Carl Adolph Agardh described the genus Hydrurus in his work Systema Algarum , the type species Hydrurus vaucheri , which he also newly described, is now a synonym for Hydrurus foetidus . The genus is usually considered to be monotypical , but some old, presumably synonymous names such as Hydrurus subramosus Wartmann or Hydrurus ducluzelii C. Agardh have not yet been verified on the basis of type material, so that taxonomists maintain them as (dubious) formal species. Carl Adolph Agardh described a total of four species, some of which have been formally classified as varieties of Hydrurus foetidus , but are no longer differentiated today.

The genus was combined, with three others, into a family Hydruraceae, which has been described as the only family of the order Hydrurales. This is mainly characterized by the shape of the zoospores.

After genetic analyzes based on the ribosomal RNA , the position of Hydrurus within the (monophyletic) golden brown algae was confirmed. However, the resolution within the group was poor, so that an exact phylogeny of the group could not be given.

Individual evidence

  1. ↑ Hydrurus C. Agardh. MD Guiry in Guiry, MD & Guiry, GM 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.Retrieved December 13, 2017
  2. ↑ David M. John: The Freshwater Algal Flora of the British Isles: An Identification Guide to Freshwater and Terrestrial Algae. Cambridge University Press, 2002. ISBN 978-0-521-77051-4 . Hydrurus on page 239.
  3. ^ A b John D. Wehr & Robert G. Sheath: Freshwater Algae of North America. Ecology and Classification. Elsevier (Academic Press), Amsterdam etc. 2003. ISBN 978-0-12-741550-5 .
  4. ↑ a b Antje Gutkowski & Julia Foerster: Benthic algae without diatoms and Characeae. Identification aid. LANUV worksheet 9 PDF download
  5. ↑ a b Dag Klaveness (2017): Hydrurus foetidus (Chrysophyceae) —an inland macroalga with potential. Journal of Applied Phycology 29: 1485-1491. doi: 10.1007 / s10811-016-1047-5
  6. ↑ E. Rott, M. Canto Nati, L. Füreder, P. Pfister (2006): Benthic algae in high altitude streams of the Alps - a neglected component of the aquatic biota. Hydrobiologia 562 (Ecology of High Altitude Aquatic Systems in the Alps): 195-216. doi: 10.1007 / s10750-005-1811-z
  7. ^ Hydrurus foetidus (Villars) Trevisan. MD Guiry in Guiry, MD & Guiry, GM 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.Retrieved December 13, 2017
  8. ↑ O. Komárek & J. Komárek (1999): Diversity of freshwater and terrestrial habitats and their oxyphototroph microflora in the Arctowski Station region, South Shetland Islands. Polish Polar Research 20: 259-282.
  9. ↑ Igor Stanković & Patrick Leitner (2016): The first record of Hydrurus foetidus (Villars) Trevisan (Ochrophyta: Chrysophyceae) in Croatia with ecological notes. Natura Croatica 25 (2): 223-231. doi: 10.20302 / NC.2016.25.18
  10. ↑ Fatma Çevik, Brian A. Whitton, Okan Ötztürk (2007): A New Genus Record for the Freshwater Algal Flora of Turkey. Turkish Journal of Botany 31: 149-152.
  11. ↑ Daniel Remias, Steffen Jost, Jens Boenigk, Johann Wastian, Cornelius Lütz (2013): Hydrurus-related golden algae (Chrysophyceae) cause yellow snow in polar summer snowfields. Phycological Research 61: 277-285. doi: 10.1111 / pre.12025 (open access)
  12. ↑ Hans R. Preisig: A modern concept of chrysophyte classification. in Craig D. Sandgren, JP Smol, J. Kristiansen (editors): Chrysophyte Algae: Ecology, Phylogeny and Development. Cambridge University Press, 1995. ISBN 978-0-521-46260-0 . Hydrurales on page 61.
  13. ↑ Dag Klaveness, Jon Bråte, Vishwanath Patil, Kamran Shalchian-Tabrizi, Ragnhild Kluge, Hans Ragnar Gislerød. Kjetill S. Jakobsen (2011) The 18S and 28S rDNA identity and phylogeny of the common lotic chrysophyte Hydrurus foetidus. European Journal of Phycology 46 (3): 282-291. doi: 10.1080 / 09670262.2011.598950