ULTRASTRUCTURE AND PHOTOTACTIC ACTION SPECTRA OF TWO GENERA OF CRYPTOPHYTE FLAGELLATE ALGAE, CRYPTOMONAS AND CHROOMONAS

摘要

A comparative action spectroscopical study was made on phototaxis in two genera of cryptomonads (cryptophyte flagellate algae), namely. Cryptomonas (rostratiformis) and Chroomonas (nordstedtii and coerulea). The two genera differ in their characteristic phycobilin pigmentation and. among three species. only Chroomonas coerulea possesses an eyespot. The two species with no eyespot, Cryptomonas rostratiformis and Chroomonas nordstedtii, exhibited positive phototaxis, showing very similar action spectra characterized by a broad band in the region from 450 nm to 650 nm. with an action maximum at about 560 nm: these features are essen tially the same as those observed previously for Cryptomonas strain CR-1. In Cryptomonas rostratiformis, a small peak was also found at 280 nm in the UV-B/C region. Chroomonas coerulea, with eyespot, did not exhibit distinct positive phototaxis in a wide spectral region at any given. even very low. light intensity, but exhibited negative phototaxis of spectral sensitivity maximal at 400-450 nm. These results indicate that the positive phototaxis of Cryptomonas (rostratiformis mis and CR-1) and Chroomonas nordstedtii is mediated by the same, yet unidentified photoreceptor(s). Chroomonas nordstedtii, possessing no phycoerythrin absorbing at 545 nm, also exhibits positive phototaxis at ca. 560 nm, and this result disfavors the so fur proposed possibility that the positive phototaxis of the cryptophytes may be mediated by phycobilin pigments. On the other hand. the spectral characteristics of negative phototaxis of Chroomonas coerulea can possibly be ascribed to the presence of an eyespot. [References: 37]