Ectocarpales

from Wikipedia, the free encyclopedia
Ectocarpales
Leathesia difformis

Leathesia difformis

Systematics
Domain : Eukaryotes (eukaryota)
without rank: Diaphoreticks
without rank: Sar
without rank: Stramenopiles (stramenopiles)
without rank: Brown algae (Phaeophyceae)
without rank: Ectocarpales
Scientific name
Ectocarpales
Bessey

The ectocarpales are a group of brown algae (Phaeophyta). With around 670 species it is the most species-rich taxon of the brown algae. A well-known and widespread representative is z. B. Ectocarpus .

features

Outwardly, the sporophyte and gametophyte are identical. One speaks of the isomorphic generation change . In some species it is weakly heteromorphic. Since the generation change comprises the haploid gametophyte and the diploid sporophyte, i.e. different nuclear phases, the generation change is also heterophasic.

They have one or more chloroplasts with pyrenoid per cell.

Gametophyte

The haploid gametophyte is usually a tufted, branched thread thallus . The sexual organs, the gametangia, are formed on the side or at the thread ends . These are multicellular (plurilocular), whereby not every cell forms gametes . In order for the gametes to become free, the inner walls of the gametangium dissolve and the gametes step outside at the tip of the gametangium. The gametes are morphologically identical. In many species of ectocarpus , however, there is a physiological anisogamy : some gametes, which are defined as female or '-' gametes , quickly come to rest, throw off their flagella and use the attractant ectocarpus to attract the male '+' gametes .

Sporophyte

After fertilization, the zygote develops into the sporophyte without resting . This is often a little less branched and a little coarser than the gametophyte. The sporophyte forms many egg-shaped, unicellular (unilocular) so-called sporocysts. After a meiosis, many meiozoospores, flagellated meiospores, are formed in them, which develop into new gametophytes after they have been released. The sex determination is carried out haplogenotypically.

Deviations

There are deviations from the isomorphic, heterophasic generation change described above in numerous species. Some species renounce sexuality. In other species, a generation can create itself immediately.

distribution

Like most of the brown algae, the representatives of the order grow in the sea. Some representatives such as some Ectocarpus and Pylaiella species grow epiphytically on larger brown algae, with gametophytes and sporophytes often specializing in different substrate plants.

Systematics

The taxon of the Ectocarpales was set up by CEBessey in 1907 (in: A synopsis of plant phyla . Nebraska University Studies 7, pp. 275–373). It is currently divided into 7 families with around 150 genera and around 695 species (according to AlgaeBASE 2014).

Elachista fucicola , Chordariaceae (epiphytic to Fucus serratus )
Ectocarpus siliculosus , Ectocarpaceae
Colpomenia peregrina , Scytosiphonaceae
Scytosiphon lomentaria , Scytosiphonaceae

Some common genera are:

literature

Individual evidence

  1. ↑ Sina M. Adl et al .: The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists. In: The Journal of Eukaryotic Microbiology 52 (5), 2005; Pages 399-451. doi : 10.1111 / j.1550-7408.2005.00053.x .
  2. ^ MD Guiry in Guiry, MD & Guiry, GM 2018. AlgaeBase . World-wide electronic publication, National University of Ireland, Galway. As of December 21, 2018

Web links

Commons : Ectocarpales  - collection of images, videos and audio files