Description of Haematococcus

Cells solitary, ovoid to ellipsoidal, with broadly rounded ends; protoplast separated from cell wall to which it is connected by thin branched or unbranched cytoplasmic strands; space between cell wall and protoplast filled with watery mucilage; 2 equal flagella; chloroplast more or less cup-shaped, sometimes reticulate; chloroplast green but cells often appear orange or reddish due to extraplastidial carotenoid (haema-tochrome or astaxanthin) pigments; pyrenoid(s) 1, 2 or several; eyespot large, hardly visible in haematochrome-containing cells; nucleus more or less central; contractile vacuoles several to many (up to 60); asexual reproduction by formation of usually 4 (rarely 2 or 8) zoospores; sexual reproduction isogamous, usually 16, 32 or 64 gametes formed per cell, after fusion producing thick-walled zygotes; aplanospores, palmellae and amoeboid stages known; nutrition phototrophic, or chemo- or photo-organotrophic; species characteristic of ephemeral rainwater pools on bare rock and in artificial basins (e.g., ornamental ponds).