The thallus of Thraustochytrids superficially resembles that of an epibiotic monocentric chytrid in having a roughly spherical shape with ‘rhizoids’ at its base.
•These ‘rhizoids’ are, in fact, the slime net produced by one basal sagenogen.
•The thallus is surrounded by Golgi-derived scales forming a wall, but the slime net does not extend over the thallus.
Sexual reproduction is unknown, but asexual biflagellate heterokont zoospores are released from the main body of the thallus, and these can settle onto a suitable substratum, giving rise to new thalli.
•Thus, these zoospores of Thraustochytriales are mitospores formed following mitosis, in contrast with those of Labyrinthulales which are meiospores, i.e. formed by meiosis.
Although Thraustochytrid zoospores lack a recognizable eye-spot, they are phototropic, reacting to light of blue wavelengths such as that produced by bioluminescent bacteria.
•Chemotropism has also been described for Thraustochytrid zoospores, and both sensual responses may enable zoospores to locate potential food sources.
•These are important as nutrient supplements, and Thraustochytrid oils might eventually be able to compete with fish oils on the market.