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Traditionally members of the Chlorophyta
Considered separate from Chlorophytes based on ultrastructural studies
Now a single Class: Charophyceae
Green Algal Traits of Charophytes
Chlorophylls A & B
Aquatic habit- like Greens
Haploid cells with meiosis occurring in zygote
Unique Traits of Charophytes
Flagella attached laterally
Microtubular cytoskeleton and flagellar root system unique
Nuclear envelope breaks down during mitosis (open spindle)
Spindle microtubles form perpendicular to cell division plane ...
Phycoplast (Green Algae) vs. Phragmoplast (Charophytes)
filaments and unicells, no flagellated stages, sex by conjugation
Klebsormidium: filament looks like Ulothrix
Coleochaete: epiphyte gowing as a flattened disc over the substrate. Possesses a number of advanced features...
Advanced features of Coleochaete
Only one zoospore per vegetative cell
Zygote remains on mother plant and becomes covered by surrounding vegetative cells (placenta)... a higher plant trait.
Chara: Commonly called Stoneworts or Brittleworts grow in shallow alkaline lakes.
Up to 2 feet tall with whorls of short branches
May be encrusted with Calcium carbonate
Sterile cells surround sex organs...
Important organism as an evolutionary bridge between green algae and mosses
Nitella: Used in studies on cytoplasmic streaming.
Streaming rates up to 60 microns/sec.
Cytoplasmic streaming due to actin molecules moving along myosin filaments. ATP hydrolysis.
Reproduce by conjugation: two filaments come together, produce extensions, fuse.
Cell contents round up to form gametes
One gamete migrates to other and fuse to form a zygote.
Unicells with elaborate shapes and divided into two semicells Reproduce by conjugation
Single-celled flagellates living in freshwaters and marine environments
Chlorophylls A & B
Storage Storage product- paramylin (b1,3 glucan). Membrane bounded.
Cell wall without cellulose (pellicle)
No sexual reproduction reported (?)
Chromosomes permanently condensed
eyespots (separate from chloroplast)
1,2,4 flagella with fine hairs along length
flagella cross-section shows a paraflagellar rod
Euglenoid flagella emerge from anterior invagination of cell (the reservoir)
Heterotrophic euglenoids use reservoir in feeding
Collection of orange-red lipid drops
At anterior end of cell
Independent of chloroplast
Contains B-carotene & xanthophylls
Euglenoids use stigma and flagella to orient toward (+ phototaxis) or away (- phototaxis) from light.
Usually orient toward dim light
Flagellar rod region acts as light shield to regulate phototaxis
Eyespot interacts with flagellar rod to sense light direction
As cell swims it rotates, causing the eyespot to shade flagellar swelling
In (+) phototaxis cell orients so to minimize shading
Mutant cells without flagellar rod do not respond to light, even with eyespot...?
Unique to the Division
Not cellulose- mostly protein (80%)
Made of spiral protein strips which overlap each other- making an alternating ridge/groove pattern
Sliding of pellicle strips allows for a distinctive flowing movement (Metaboly)
Occurs when cells are not swimming
In Euglena gracilis cells are round in early light and elongate by mid-day
Metaboly rhythm is circadian (ie. controlled by an internal clock)
Phototaxis: phototaxis only operative during the light period, light introduced during the dark period does nothing
Mitosis: cell division begins at start of dark period
Vertical movement in mud flats: rise to surface during low tide, go deeper as tide rises
Only by asexual reproduction... Longitudinal division
Nuclear envelope remains intact
Asexual thick-walled cysts may form during stress.
No sex reported...
Unusual in that they are surrounded by 3 membranes
Inner two from ancestry green algal plastid, outer membrane from euglenoid itself.
species with 2 emergent flagella (one forward, one dragging), show metaboly, not phagotrophic.
Possess 2 flagella but only one (with swelling) emerges from reservoir
Includes green and colorless species
Euglena, Trachelomonas, Astasia, Colacium
Astasia is a colorless form of Euglena.
Colacium libellae lives in winter in the warm(er) rectum of damselfly larvae
Colorless cells with a feeding apparatus
Take up and ingest food particles, other organisms
Examples: Peranema, Entosiphon.
Peranema cells may hunt in "packs" and rip away at prey cells,, tearing holes in them and "sucking" out cell contents.
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