Chrysomonadida

(invertebrate zoology) An order of yellow to brown, flagellated colonial protozoans of the class Phytamastigophorea.

An order of the class Phytamastigophorea. Chrysomonads, also known as Chrysomonadina, are usually small flagellates. They are yellow to brown because of phycocrysin in the usual one or two chromatophores, but some lack chromatophores. Many species form diagnostic siliceous cysts. Palmelloid colonies (Hydrurus) consist of a tough, gelatinous matrix holding many nonflagellate cells. Starch is not formed, but fats are, and the refractive carbohydrate leucosin is common. The flagella are usually two, rarely three, and are subequal. Nuclei are small. See also Phytamastigophorea.