Scytothamnus australis
| Scytothamnus australis | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | SAR |
| Superphylum: | Heterokonta |
| Class: | Phaeophyceae |
| Order: | Scytothamnales |
| Family: | Scytothamnaceae |
| Genus: | Scytothamnus |
| Species: | S. australis |
| Binomial name | |
|
Scytothamnus australis (J.Agardh) J.D.Hooker & Harvey, 1845 |
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Scytothamnus australis is a brown alga species in the genus Scytothamnus found in New Zealand. It is a sulphated polysaccharide and the type species in the genus.
The species contains the phlorotannins trifucol, tetrafucol A, tetrafucol B, cis-pentafucol A, diphlorethol A and triphlorethol A.
"Scytothamnus australis" has a southern circumpolar distribution and has been recorded to have been present from the waters of southern Australia, New Zealand and Chile.
"Scytothamnus australis" is a larger, more robust species than "Scytothamnus fasciculatus", but possesses a similar branching pattern and broadly comparable vegetative anatomy.
As with the other species of "Scytothamnus", "Scytothamnus australis" has a stellate (star-shaped) chloroplast with a central pyrenoid and is perforated by channels of cytoplasm.
"Scyhtothamnus australis" has a unilocular sporangia reproductive structure which means that it can produce meiospores or asexual spores. The gametophytes are dioecious (Dioecy) but no structural difference can be detected between the gametangia of male and female isolates. In "Scytothamnus australis" the gametes vary considerably in size, ranging from 3-6 ~tm in diameter.
Unilocular sporangia develop scattered over most of the thallus except in the areas immediately below growing tips. When sporogenesis occurs close to the tips of branches the apical cells are generally no longer active. Sporangial initials are from the cells forming the thallus surface. They can be distinguished at an early stage by their size and by the presence of numerous electron transparent vesicles. The adjacent vegetative cells (any of the cells of a plant or animal except the reproductive cells) are smaller in size and are filled almost completely with densely packed physodes (any of various vesicular intracellular inclusions of brown algae that are of uncertain constitution and function). As the sporangium develops and enlarges further the nucleus and chloroplasts divide a number of times. The sporangium is egg-shaped and lies within the cortical (cells in the cortex) and medullary (or pith) cells. It is slightly narrower where it touches the surface. In the beginning the nuclei are in a central position, each being closely linked with a chloroplast. In the course of the first few divisions the chloroplast loses its characteristic star-shaped shape and the pyrenoid becomes smaller and occupies a side position. Subsequently the nuclei are concentrated near the outer areas of the cytoplasm, and flagella appear to divide into separate types within vesicles before the division of individual meiospores (spores produced by meiosis). The chloroplasts meanwhile have largely regained a star-shaped form with a central pyrenoid. Mature sporangia appear as dark-brown spots on the thallus. The entire contents of a sporangium are discharged together with a mass of sticky material. As it slowly disperses the meiospores swim free. The side biflagellate (has two flagellate) meiospores contain one chloroplast with an eyespot (eyespot apparatus) and are capable of motion for a relatively short period of no more than 15 min. Upon settling they become spherical, measuring 6.5-11 gm in diameter.Each meiospore contains one to four relatively large lipid bodies in addition to the more numerous, smaller physodes.
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