28 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Chlorococcales 

 Family Oocystaceae 

 GENUS DICTYOSPHAERIUM Nageli, 1849 (fig. 8) 



MORPHOLOGY 



Cells are spherical, ovoid, ellipsoidal, or reniform and range from 3 to 

 10 /*m in diameter. Each cell contains a single, cup-shaped, parietal 

 chromatophore. Cells are connected by branching threads. Colony is 

 embedded in a copious, homogeneous, gelatinous sheath. 



REPRODUCTION 



Antherozoids (generally 16 or 32) from a male colony swarm around 

 one of 2 eggs released by a female colony. An antherozoid and an egg 

 become laterally fused to form a zygote. Division of the zygote forms a 

 daughter colony. Asexual reproduction of a cell into 2 to 4 autospores 

 precedes the movement of the daughter cells to the tips of segments 

 formed by the partial splitting of the parent-cell wall. 



OCCURRENCE 



The alga is of widespread distribution. It is found most often in soft 

 to semihard waters. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 36.0 



pH 4.6 - 9.6 



Dissolved oxygen milligrams per liter .1 - 19.7 



Specific conductance micromho 10 -50,000 



Total alkalinity milligrams per liter - 440 



Total hardness do 5 - 1,900 



Total nitrogen do .00- 19.0 



Total phosphorus do .0 - 2.9 



SPECIES INFORMATION 



Refer to Tiffany (1934), Smith (1920), and Prescott (1962). 



