Salinity-related polymorphism in the brackish-water diatom <i>Cyclotella cryptica</i>

Abstract

The brackish-water diatom Cyclotella cryptica is a polymorphic species. Nine clones are capable of producing the valve pattern characteristic of the species C. meneghiniana, as well as the C. cryptica pattern. A study of the effects of salinity and freshwater conditions on the morphology of the valve shows that the cryptica pattern is produced in salinities of about 4.3‰ to full-strength seawater, 28.7‰. The "meneghiniana" pattern is the freshwater or low salinity (1.4‰) form. Characteristics of the valve morphology and life history stages which distinguish C. cryptica from C. meneghiniana and Cyclotella sp., clone 03A, are presented and discussed.