38 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Volvocales 

 Family Volvocaceae 

 GENUS PANDORINA Bory, 1824 (fig. 13) 



MORPHOLOGY 



Cells are pyriform, spherical, or angular and generally 7-18 fim in 

 diameter. Each cell had 2 flagella of equal length. The single 

 chromatophore is cup shaped. Four, 8, 16, or 32 cells are mutually com- 

 prised in the periphery of a colony and enclosed by a copious, 

 homogeneous envelope. 



REPRODUCTION 



Following a state of colonial dormancy, all cells within the colony 

 undergo simultaneous division into daughter colonies. Each cell of the 

 daughter colony develops 2 flagella, and a new colony is formed. Sexual 

 reproduction is anisogamous. Free-swimming male gametes fuse ter- 

 minally or laterally with somewhat larger free-swimming female 

 gametes. The quadriflagellate zygote looses its flagella and develops a 

 cell wall. Zygote development results in biflagellate zoospores, which 

 secrete a gelatinous envelope and divide into a new colony. 



OCCURRENCE 



The alga is rarely found in abundance but frequently occurs in the 

 euplankton of hard bodies of water. It also is found frequently among 

 dense growths of algae in shallow waters rich in nitrogenous matter 

 (Prescott, 1962). 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 



pH 5.2 - 



Dissolved oxygen milligrams per liter 1.3 - 



Specific conductance micromho 11 



Total alkalinity milligrams per liter 7 



Total hardness do 6 



Total nitrogen do .01- 



Total phosphorus do .0 - 



SPECIES INFORMATION 



Refer to Smith (1920, 1931) and Prescott (1962). 



