14 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



DESCRIPTION OF THE GENERA 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Chlorococcales 

 Family Scenedesmaceae 

 GENUS ACTINASTRUM Lagerheim, 1882 (fig. 1) 



MORPHOLOGY 



Cells are ovoid, oblong, or club shaped and radiate from a common 

 center. Cell diameter ranges from about 1 to 6 ^m, and cell length 

 varies from about 10 to 35 fim. Chromatophores are parietal. Coenobia 

 generally contain 4, 8, or 16 cells. 



REPRODUCTION 



The protoplast is divided into 4, 8, or 16 autospores by transverse and 

 longitudinal division. The daughter cells, joined in fasciculate bundles, 

 are released following rupture of the parent-cell wall. Following 

 release, the cells separate outwardly from the point where the cells 

 touch. 



OCCURRENCE 



Actinastrum is widely distributed in the euplankton. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 ■ 



pH 5.7 - 



Dissolved oxygen milligrams per liter .8 - 



Specific conductance micromho 10 



Total alkalinity milligrams per liter 3 



Total hardness do 6 



Total nitrogen do .01- 



Total phosphorus do .0 - 



SPECIES INFORMATION 



Refer to Smith (1920) and Prescott (1962). 



