Euglenoids reproduce asexually by dividing lengthwise into two. They do not reproduce sexually. Diatoms Diatoms are probably the most abundant aquatic eukaryotes in number of individuals and species. They live singly or in simple filaments or colonies, they occur in either type of aquatic environment. They reproduce sexually and are basically non motile.
Most unicellular algae are haploid but diatoms are diploid.
They contain chlorophyll a and c and the accessory pigment fucoxanthin , a carotenoid that give them a yellow-brown color. They store food as oil and the polysaccharide chrysolaminarin . The most distinctive feature of diatoms is the intricately patterned cell wall. The two piece cell wall is impregnated with silica. Silica does not decay so large amounts of glasslike material is deposited on the ocean floor as the diatoms die.