Algae containing chlorophylls a and c

Although chlorophyll a is always present in the algae to be considered in this chapter, the amount of chlorophyll c is sometimes small. Chlorophyll b is always absent (but see Dinophyta, p. 95).

The “a+c” algae show a number of organizational trends resembling those seen in the Chlorophyta. There are also features not represented in living Chlorophyta, but possibly present at some stage in their evolutionary history. The chlorophyll c-containing algae are sometimes referred to collectively as the “chromophyte algae”. The first four divisions considered here constitute the “heterokont algae” (Table. 2.1), and have a number of basic features in common, relating principally to the flagella and chloroplasts. Besides (where two are present) the inequality and difference in ornamentation of the flagella, the chloroplast is typically surrounded (in addition to its normal envelope) by a fold of endoplasmic reticulum. This “chloroplast endoplasmic reticulum” is part of the general endoplasmic system, connected with the outer membrane of the nuclear envelope. It is not, however, confined to the heterokonts, but is found also in the Haptophyta (p. 93) and Cryptophyta (p. 96), not regarded as closely allied to the heterokont algae.

CHRYSOPHYTA

Habitat Aquatic (mainly freshwater), often common in plankton.

Pigments Chlorophylls a, c;β-carotene; fucoxanthin conspicuous, but other xanthophylls also present.