Cyst size variability in invasive American Artemia franciscana Kellogg, 1906 (Branchiopoda: Anostraca) in Asia: a commercial approach

Artemia is the most common live food which is used in aquaculture worldwide. This study reports on biometrical variation of introduced American Artemia franciscana cyst from 24 non-native localities and two native habitats in Asia and USA, respectively. Results showed the largest diameter of untreated cyst, diameter of decapsulated cyst and thicker chorion ordinarily belong to invasive populations. Because of the small cysts, which have an effect on increasing quantity per unit weight and could be the cause of increased hatching efficiency, commercial productions of A. franciscana cyst from native sources should potentially be considered higher quality than productions from non-indigenous environments. Principal Component Analysis revealed that all cyst batches from San Francisco Bay were classified in one group and the most invasive populations could arrange in other separated group. Although, diameter of decapsulated cyst and chorion thickness showed a negative and significant correlation among invasive populations, there was no significant relationship within native populations. These observations contrast with biometrical patterns of parthenogenetic populations.