Fairy shrimps have recently been considered for use in larval fish rearing, because of their size and their nutritional value. This study presents the results obtained for Thamnocephalus platyurus, a species from Central and South America, which was already mass cultured successfully in the United States in a flow-through system. Cysts and instar I nauplii have an unfavourably large size: mean diameter 278 μm and 240 μm for untreated and decapsulated cysts, respectively; mean naupliar length 436 μm. However, the species shows an interesting pattern in its fatty acid methyl ester (FAME) profile, especially with regard to polyunsaturated fatty acids (PUFA). In particular, T. platyurus cysts are characterized by significant levels of the 18:2 and the 20:5w3, and by the presence of the 22:6w3, which are normally absent in Artemia cysts.