130 



KINGDOMS MONERA AND PROTISTA: 



BLUE-GREEN ALGAE 

 "unicellu lar " 



colonial 



some macroscopic types 



Figure 8.2 Blue-green algae types. 



bodies or pigment-containing bodies called plastids; 

 from none to many small central vacuoles (probably 

 not true vacuoles); cell wall usually two-layered; no 

 flagellae but waving, gliding, and circular movements 

 are fairly common. 



Autrition: primarily photosynthetic; some carry 

 on chemosynthesis. 



Rcfnodiutiim: asexual by division (amitotic by con- 

 striction of the body, probably never mitotic but 

 some species apparently segregate chromosome- 

 like bodies), by fragmentation of colonies or fila- 

 ments, or by spores; sexual processes are unknown 

 if present at all. 



(kcurrnicc: mostly fresh water, floating, attached 

 to objects, or bottom dwelling; some are marine and 



distributed as the fresh-water forms; others form 

 layers upon moist rocks or soil or are under ground; 

 others occur in hot springs that approach the boiling 

 point, many of the species in mineral springs causing 

 calcium and other carbonates to be precipitated; a 

 few are enslaved within other algae, protozoans, 

 and fungi; some combine with fungi to produce 

 lichens; some are parasitic; about 2500 species. 



Do not expect to recognize blue-green algae by a 

 constant color clue. In nature, only about half are 

 blue-green; the others are purple, red, orange, green, 

 blue, or some intermediate hue. Some are black. 



Many are microscopic, occurring as individuals in 

 fresh or salt water plankton. Others are fairly 

 conspicuous, globular or encrusting, jelly-like to 

 leathery masses upon objects. Most are nonmarine. 

 On rocks or soil they may be the first invading or- 

 ganisms. They are particularly suited (owing to their 

 photosynthetic capabilities) to invading rocks and 

 starting the process of soil formation. Many appear 

 to sustain themselves by exclusive use of inorganic 

 materials. Such Cyanophyta can be observed in the 

 free-living state and along their margins they may be 

 invaded by fungi. Such a fungus is entrapping, 

 perhaps enslaving, the blue-green alga cells; even- 

 tually, an intimate organization of alga cells and 

 fungus filaments will produce a single, integrated 

 structure, a lichen. Therefore, although lichens 

 often are the first "organisms" to invade a bare 

 rock, blue-green algae can cause lichens to be the 

 second stage. 



Like bacteria, blue-green algae are cosmopolitan 

 but closely tied to moist environments. Certain soil 

 inhabitants especially resemble bacteria. These 

 Cyanophyta range several feet down in the soil 

 where they either are dormant, or are saprophytic 

 like the associated bacteria. Higher in the soil, with 

 bacteria some are involved in nitrogen fixation. In 

 fact, some apparent bacteria may actually be blue- 

 green algae that have lost their chlorophyll. 



Their importance in water, fresh or salt, tends to 

 be minimized. Aquatic species, along with true 

 algae in the ocean and various aquatic plants in 

 fresh water, are primary producers. All these or- 

 ganisms, through photosynthesis, are the primary 

 converters of inorganic materials to nutrients and 

 producers of oxygen in aquatic areas. 



These monerans seem as ecologically significant 

 and perhaps as numerous in arctic habitats. Here, 



