Chapter 16

Heterokontophyta

BOLIDOPHYCEAE

This is a small order of flagellated marine picophytoplankton that is related to the diatoms (Bacillariophyceae) (Guillou et al., 1999). The cells contain chlorophylls a, c1, c2, c3, -carotene, diatoxanthin, and fucoxanthin, as do the diatoms, It is probable that the diatoms originated from a motile ancestor similar to those in this class (although there is no report of silicification in the Bolidophyceae).

Bolidomonas is a unicell with a long tinsel flagella bearing tripartite tubular hairs and a shorter smooth flagellum (Fig. 16.1). The cell is only 1.2m in diameter and has a simple internal organization. There is one plastid, mitochondrion, and Golgi apparatus. There are two membranes of chloroplast endoplasmic reticulum, with the outer membrane continuous with the outer membrane of the nuclear envelope. The DNA is contained within a ring-shaped genophore and there is no eyespot.

REFERENCE

Guillou, L., Chretiennot-Dinet, M.-J., Medlin, L. K., Claustre, H., Loiseaux-de Goer, S., and Vaulot, D. (1999). Bolidomonas: a new genus with two species belonging to a new algal class, the Bolidophyceae (Heterokonta). J. Phycol. 35:368–81.

Fig. 16.1 Semidiagrammatic drawing of the cytology of

Bolidomonas. (CE) Chloroplast envelope; (CER) chloroplast endoplasmic reticulum; (H) tripartite flagellar hair;

(N) nucleus. (Adapted from Guillou et al., 1999.)