Lab. 4

Practical Algae

Phylum: Cyanophyta (Blue-green algae) Wena Sh. Tawfeeq Asisstant lecturer MSc. Contaminant hydrogeology

2016-2017 UOS/Biology Department E-mail: [email protected] Room 3140

General Characteristics • The only group of algae which are prokaryotic (lack a nuclear envelope) • their photosynthetic lamellae (thylakoids) are single or unstacked and distributed peripherally in the cytoplasm and not within a membrane-bounded chloroplast.

• Some genera can produce toxins; Cyanotoxins (neurotoxins and hepatotoxins). • Some genera are able to fix atmospheric N2 to NH3 or NO3

• Flagella are completely absent, some are capable of gliding movement (they possess two additional layers outside of the cell wall).

• The major components of the photosynthetic light-harvesting system are chlorophyll a in the thylakoid membrane, and the phycobiliproteins (C-phycocyanin, allophycocyanin Cphycoerythrin, and phycoerythrocyanin. • Food is stored in the form of glycogen (carbohydrate) and cyanophycin • (combined nitrogen). • Cell walls are made up of a peptidoglycan with a lipopolysaccharide layer outside (gram negative bacteria). • A sheath (capsule or extracellular polymeric substances (EPS)) composed of mucilage and a small amount of cellulose is commonly present in some members. The sheath protects cells from drying.

• Gas vacuoles aid buoyancy in planktonic species allowing the cells to control their position in the water column. • Heterocyst: thick walled cell, homogenous, pale-yellowish contents and appear empty. Larger than vegetative cells, and photosynthetically inactive. • They are the site of nitrogen fixation. • Heterocyst is found in most filamentous blue-green algae (Nostocales and Stigonematales) except in the members of Oscillatoriales.

• Akinetes (resting spores): they are specialized thick walled resistant cells formed generally in some blue-green algae (order Nostocales and Stigonematales). They are resistant to unfavorable environmental conditions, new filaments are produced by germination of akinetes. They are recognized by their larger size relative to vegetative cells and conspicuous granulation due to high concentrations of glycogen and cyanophycin. • Akinetes only occur in cyanophyta that form heterocyst.

Morphological Forms • • • 1. 2. 3.

Unicellular – with mucilaginous envelope Colonial (Aggregate of cells) Filamentous Unbranched Branched False branched

Synechococcus Microcystis Oscillatoria Stigonema Scytonema

Trichome – row of cells

} Mucilaginous sheath - layer of mucilage outside of the cell wall.

Filament

Reproduction

• Sexual reproduction is absent. • Asexual reproduction predominates involving binary fission, multiple fission resulting in endospores (baeocytes) and hormogonia (short gliding trichomes). • Cell divisions is the common mode of reproduction in the unicellular forms. • Filamentous forms and colonial forms are reproduced by fragmentation. The fragmented portion get separated, float away and grow into new individuals.

• Endospores (Baeocytes): are true reproductive cells formed in blue-green algae which are produced by internal division of the protoplast.

• Hormogonia: Hormogonia (or hormogones), which are characteristic of all truly filamentous Cyanophyta, are short pieces of trichome that become detached from the parent filament and move away by • gliding, eventually developing into a separate filament. Hormogonia are distinguished from vegetative filaments by their gliding motility, the small size of their cells and the absence of heterocysts.

Classification Of Cyanophyta Freshwater blue-green algae can be divided into four main orders depending on general morphology, presence/absence of specialized cells and the nature of branching in filamentous forms. i. Order: Chroococcales ii. Order: Oscillatoriales iii. Order: Nostocales iv. Order: Stigonematales

Order: Chroococcales • The simplest blue-green algae, occurring essentially as solitary cells (no filamentous forms), typically enclosed by a thin layer of mucilage. • The cells may remain as single cells, or be aggregated into plate-like or globular colonies. • Typically planktonic with some colonial forms (e.g. Species of Microcystis)

Phylum Cyanophyta Order Chroococcales Genus Microcystis

Phylum Cyanophyta Order Chroococcales Genus Gleocapsa

Order: Oscillatoriales • Filamentous algae, lacking heterocyst and akinetes. • These relatively simple algae occur as planktonic (some bloom forming) or benthic aggregations.

Phylum Cyanophyta Order Oscillatoriales Genus Oscillatoria

Phylum Cyanophyta Order Oscillatoriales Genus Spirulina

Order: Nostocales • A diverse group of filamentous algae, planktonic or benthic. • With heterocyst and akinetes, but not showing true branching filaments. • The most common method of reproduction is by hormogonia.

Phylum Cyanophyta Order Nostocales Genus Nostoc

Phylum Cyanophyta Order Nostocales Genus Anabaena

Phylum Cyanophyta Order Nostocales Genus Gloeotrichia

Order: Stigonematales • Filamentous algae, with heterocyst and akinetes and showing true branching.

Phylum Cyanophyta Order Stigonematales Genus Stigonema

1. Anabaena (350X) 2. Anabaena (350X) 3. Anabaena (175X) 4. Nodularia (350X) 5. Cylindrospermum (175X) 6. Arthrospira (700X) 7. Microcoleus (350X) 8. Phormidium (350X) 9. Oscillatoria (175X) 10. Aphanizomenon (175X) 11. Lyngbya (700X) 12. Tolypothrix (350X) 13. Entophysalis (1000X) 14. Gomphosphaeria (1000X) 15. Gomphosphaeria (350X) 16. Agmenellum (700X) 17. Agmenellum (175X) 18. Calothrix (350X) 19. Rivularia (175X) 20. Anacystis (700X) 21. Anacystis (175X) 22. Anacystis (700X)

References • Bellinger E.G., Sigee D.C. (2010) freshwater algae: identification and use as bioindicators. • Bilgrami, k.S. And saha, L.C. (2004) A text book of algae. New delhi (india). • Lee, r. E. (2008) phycology. 4th ed.