''Scytothamnus australis'' is a brown alga species in the genus ''

Scytothamnus ''Scytothamnus'' is a brown algae genus in the family Splachnidiaceae. Species * '' Scytothamnus australis'' (J.Agardh) J.D.Hooker & Harvey - type * '' Scytothamnus fasciculatus'' (J.D.Hooker & Harvey) A.D.Cotton * '' Scytothamnus hirsutus'' S ...

'' 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 A is a fucol-type phlorotannin found in the brown algae '' Ascophyllum nodosum'', '' Analipus japonicus'' and '' Scytothamnus australis''. In ''A. japonicus'', 5'-bromo- and 5'-chlorotetrafucol-A can also be detected. References ...

, tetrafucol B, cis-pentafucol A, diphlorethol A and triphlorethol A.

Distribution

''Scytothamnus australis'' has a southern

circumpolar distribution A circumpolar distribution is any range of a taxon that occurs over a wide range of longitudes but only at high latitudes; such a range therefore extends all the way around either the North Pole or the South Pole. Taxa that are also found in isolat ...

and has been recorded to have been present from the waters of southern Australia, New Zealand and Chile.

Description

''Scytothamnus australis'' is a larger, more robust species than ''Scytothamnus fasciculatus'', but possesses a similar branching pattern and broadly comparable vegetative anatomy.

Cell structure

As with the other species of ''Scytothamnus'', ''Scytothamnus australis'' has a stellate (star-shaped) chloroplast with a central

pyrenoid Pyrenoids are sub-cellular micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., & Raven, J. A. (2005). CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. Annu. Rev. Plant Bio ...

and is perforated by channels of

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

Reproductive structure

''Scytothamnus australis'' has a

unilocular A locule (plural locules) or loculus (plural loculi) (meaning "little place" in Latin) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usu ...

sporangia reproductive structure which means that it can produce meiospores or asexual spores. The

gametophytes A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sex ...

are dioecious (

Dioecy Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

) but no structural difference can be detected between the

gametangia A gametangium (plural: gametangia) is an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploi ...

of male and female isolates. In "Scytothamnus australis" the gametes vary considerably in size, ranging from 3-6 ~tm in diameter.

Life cycle

Sporogenesis Sporogenesis is the production of spores in biology. The term is also used to refer to the process of reproduction via spores. Reproductive spores were found to be formed in eukaryotic organisms, such as plants, algae and fungi, during their norma ...

Unilocular sporangia develop scattered over most of the

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

except in the areas immediately below growing tips. When

sporogenesis Sporogenesis is the production of spores in biology. The term is also used to refer to the process of reproduction via spores. Reproductive spores were found to be formed in eukaryotic organisms, such as plants, algae and fungi, during their norma ...

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 Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

. 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 Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

) and medullary (or

pith Pith, or medulla, is a tissue in the stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other ...

) 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

becomes smaller and occupies a side position. Subsequently the nuclei are concentrated near the outer areas of the

, and

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

appear to divide into separate types within

before the division of individual meiospores (

spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

produced by meiosis). The

chloroplasts A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...

meanwhile have largely regained a star-shaped form with a central

. Mature sporangia appear as dark-brown spots on the

. 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 A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

) meiospores contain one

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

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.

Gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic d ...

Meiospore germination is usually bipolar or tripolar and they develop into densely branched thread-like microthalli. The filaments are 10-15gm in diameter in both species. Growth is the result of both terminal and intercalary(located between its daughter cells) cell divisions, and in older microthalli longitudinal intercalary divisions are common. The cells contain a star-shaped chloroplast having a typical

. The way microthalli will develops depend on the conditions in which they are cultured. Prior to

gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic d ...

the vegetative cells of the

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

contained a number of large

. Several changes occur following the onset of

. In the

smooth endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(ER) became noticeable and the number of membrane-bound electron-dense (possibly lipid) bodies increased. At a later stage these bodies accumulated in the

. There is a single

Golgi body The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles insi ...

in the cell which appears to be closely linked with the

. The transition to the next stage is marked by the shrinking of the cytoplasm away from the cell wall. Following this,

appear within cytoplasmic vesicles and the paired

centrioles In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers (Pinophyta), flowering plants (angiosperms) and most fungi, and are ...

of the vegetative cells take on the function of basal bodies (organelles that form the base of a flagellum or cilium). The

gains

mastigonemes Mastigonemes are lateral "hairs" that attach to protistan flagella. Flimsy hairs attach to the flagella of euglenid flagellates, while stiff hairs occur in stramenopile and cryptophyte protists.Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1 ...

and takes up an external position. At the same time the volume of

extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

material increases. The

at this stage occupies a position next to the developing

and the

with the

contain a noticeable core of electron-dense material. An eyespot develops in the chloroplast which had retained its star-shape throughout

. The internal walls of the

gametangium A gametangium (plural: gametangia) is an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid s ...

then dissolve and the contents are expelled into the sea-water.

Fertilization

Gametes A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

are released together with various fragments of

. The gametes of both sex are anatomically indistinguishable and remain able to move for periods of up to approximately 30 minutes. Fusion was never observed in clonal cultures. However, female

were identified in some fertile cultures after a volatile (

volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...

), scented compound was detected during a parallel investigation of pheromone production. Fertilization was a not very noticeable process by which motile (able to move) gamete (male) approached an unmoving one (female) and, following contact, the two cells fused rapidly. Many

zygotes A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

having two eyespots and two

can be identified in this process. The development of zygotes and unfused gametes follow the same pattern leading directly to the formation of

parenchymatous Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word � ...

sporophytes A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygot ...

. Germination results in a branched filament having a terminal (not produced within the organism) hair. Cells of the filament, frequently those lying next to a hair are transformed into peaks and developed into erect,

. Numerous hairs and erect fronds were often formed on the same individual. A variable, but usually small, proportion of unfused

gametes A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

give rise to another generation of

. After

had been maintained in culture for prolonged periods, exceeding 2 years, they failed to respond to the short-day stimulus, appearing to have lost the capacity to produce

References

External links

algaebase
{{Taxonbar, from=Q7439708 Scytothamnales Species described in 1845