On the life history of the marine plankton diatom Stephanopyxis palmeriana

Abstract

1. The cell diameter of Stephanopyxis palmeriana ranges between 19 and 156 μ. The pleural structure is considered to be specific for the genus. The interphasic nucleus lies in the discus of the hypovalva. 2. The cell size can be manipulated during the vegetative phase through SiO2-deficiency followed by frustule regeneration. 3. Only 19 to 60 μ wide cells are capable of forming gametes and auxospores. Differentiation begins after light intensity is suddenly increased from 400 to 4000 Lux, and temperature from 15° to 21° C. 4. Only 19 to 90 μ wide cells are capable of forming resting spores. These are produced in the presence of phosphate-deficiency; maximum production occurs at 12° C. After correction of the phosphate-deficiency, resting spores germinate. 5. Morphologically, the life history (formation of gametes, auxospores, resting spores) conforms essentially with the findings on Stephanopyxis turris (v. Stosch &Drebes 1964). 6. The most important factors controlling the life cycle are cell size, temperature, light and nutrients. The effects which these factors produce in S. turris are compared with those observed in S. palmeriana. © 1966 Biologischen Anstalt Helgoland.