82 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Naviculaceae 

 GENUS GYROSIGMA Hassall, 1845; emend., Cleve, 1894 (fig. 

 35) 



MORPHOLOGY 



Cells generally are solitary and free floating, sometimes in gelatinous 

 tubes. They are elliptical to lanceolate in girdle view. Cells are sigmoid 

 in outline and generally attenuated toward the acute or broadly round- 

 ed poles. Intercalary bands and septa are lacking. The sigmoid raphe 

 has small central and polar nodules. Transverse striations cross 

 longitudinal striations at right angles. There are two chromatophores, 

 which are smooth or irregularly shaped plates. 



REPRODUCTION 



The protoplasts of 2 approximate cells each form 2 gametes. Con- 

 jugation results in the formation of 2 auxospores. 



OCCURRENCE 



The genus is widely distributed. It generally is indicative of alkaline 

 waters. Some species can tolerate brackish conditions. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 34.0 



pH 4.3 - 9.0 



Dissolved oxygen milligrams per liter 1.1 - 19.3 



Specific conductance micromho 32 -47,800 



Total alkalinity milligrams per liter - 386 



Total hardness do 8 - 2,000 



Total nitrogen do .06- 27.0 



Total phospnorus do .0 - 4.0 



SPECIES INFORMATION 



Refer to Boyer (1927a) and Patrick and Reimer (1966). 



