 
 
|  Family: Unicellular or Colonial; cell body spherical, with one or more spiny projections; 
a single cup-shaped chloroplast with a pyrenoid; asexual reproduction by zoospore or autospore; 
sexual reproduction by fertilization between egg and sperm. Genus: Colonial; cell body with 2 or more spiny hairs (Illustrations of The Japanese Fresh-water Algae, 1977). Species: 
 | 
 50 μm
 50 μm
 100 μm
 100 μm
 150 μm; x 400 :
 150 μm; x 400 : 
 31 μm
 31 μm
 63 μm
 63 μm
 94 μm; x 640
 94 μm; x 640
 
 
 
Micractinium pussillum Fresenius var. elegans G. M. Smith: a colony of 4-32 spherical cells, cell body 3-5 μm diam., with 2-3 needle-like projections 20-30 μm long, a single cup-shaped chloroplast with a pyrenoid (Illustrations of The Japanese Fresh-water Algae, 1977).