BIO 4320 – marine algers systematikk og biologi

Division ”CHLOROPHYTA”

Chlorophyta

Origin of chloroplast

Phylogeny of Chlorophyta sensu lato

Chlorophyta sensu lato

5-10 classesFreshwater and marine;ca. 5000 species

Division characteristics

morphology

• Flagellates, colonies• Filaments • Parenchymatic

Ulva Dunaliella

Division characteristics• Isokont swarmers• ”smooth” flagella or covered by scales• Stellate transition zone (flagella apparatues)• Dobble chloroplast membrane• Chloroplasts with 2-6 thylakoids, grana• Green chloroplast with:

chlorophyll a og b

β-karoten and xanthophyls• Some have pyrenoid (in chloroplast)• Storage product: starch (in chloroplast)

Bloom on the Southern coast of

Norway

Chloroplast pigments

chlorophyll a + b

carotenoids

• β-karoten

Xanthophylls

• lutein

• violaxanthin

• neoxanthin

flagella

”smooth” in Chlorophyceae

with organic scales in Prasinophyceae

Flagellar transition zone

from van den Hoek et al. 1995

sheding of flagella

from van den Hoek et al. 1995

flagellar roots of UTC

UTC clade = Ulvophyceae-Trebouxiophyceae Chlorophyceae

Chlorodendrales moved from Prasinophyceae to Chlorophyta

Prasinophyceae may be split into several classes

UTC clade

Microtubular roots of UTC

Microtubular roots run beneath the cell membrane to the posterior part of the cell

• anchor the flagella to the cell

• constitute a tubular cytoskeleton

4 flagellar roots:

• 2 consist of 2 microtubuli

• 2 consist of 4 (usually) microtubuli

Microtubular roots of UTC

Microtubular roots run in oppsite directions forming a cross-like pattern in apical view

3 principal arrangements can be distinguished based on displacement of basal bodies

Characterized as cruciate (three types)• clockwise • opposite• counterclockwise

multilayered structure

Cruciate

UTC-clade (a-c) CW

CCW

DO

MLS

Ulvophyceae

Chlorophyceae

Trebouxiophyceae

Charophyceae

Prasinophyceae

Prasinophyceae

Flagellar apparatues

Chlorophyceae cruciate and clock wise flagellar bases

from van den Hoek et al. 1995

2 flagella

4 flagella

Chlamydomonas reinhardtii flagellar bases and roots

from van den Hoek et al. 1995

(connective fibres omitted)

1 o’clock – 7 o’clock type

Clockwise:

Chlamydomonas reinhardtii flagellar bases and roots

from van den Hoek et al. 1995

upper striated connective

lower striated connective

connective fibres with centrin

Chlamydomonas reinhardtii rhizoplast

from van den Hoek et al. 1995

rhizoplast

nucleus

connective fibres

Contraction/relaxation

contracted

relaxed

Mitosis

• open; nuclear membrane disperse during metaphase (Charophyceae)

• closed; nuclear membrane is persistent (many UTC)

• Trebouxiophyceae; closed mitosis with metacentric spindle

(see fig 16.8)

U

T

C

clade

Present in brackish water

Cell wall

Cells are

• naked

• with cell wall

• or covered with organic scales

Cell divisionCytokinesis• by furrowing (Prasino-,Trebouxiophyceae)

• by phycoplast-furrowing (chlorophyceae)

Mode of division of systematical importance

Mitosis and cell division

8 different modes have been distinguished

occurrence

• freshwater, brackish water, salt water• rock pools, ponds and snow• humid soil, tree trunks, stones

• Tropical, temperate and polar milieu

diversity

• Cell size from < 1 μm to 20-30 cm

• Flagellates, coccoids, colony forming, filamentous and parenchymatic