Morphology and Ultrastructure of cysts in different species of the brine shrimp, Artemia from Southern India

Surface topography and ultrastructure of dried cysts of Artemia parthenogenetica (Vedaranyam population) and bisexual Artemia sp. (Kelambakkam population) were studied electron microscopically in order to identify the bisexual strain, inhabiting Covelong salterns, Kelambakkam, South India. The scope of this study is to provide substantial information for further characterization of these Artemia strains by the comparison of the cyst morphology and ultrastructure. A cyst of Artemia franciscana was used as a reference cyst for comparison. Scanning electron microscopic studies on cyst morphology revealed that the surface is smooth with no significant variation among the three Artemia strains studied. Transmission electron microscopic observations on the ultrastructure of the cyst both parthenogenetic and bisexual forms showed an apparent variation in thickness of the cortical layer. In Kelambakkam population of Artemia, the architecture of alveolar meshes is tightly arranged and is similar in shape. But they show minor variations in the arrangement of pores in the matrix and in the length of the cortical layer, compared to A. franciscana. In A. parthenogenetica, they are loosely arranged and are oval in shape. The present study clearly documents that the Artemia species, colonized in Kelambakkam saltpan is A. franciscana; thus, the variation in the cyst ultrastructure is much pronounced and a taxonomically important parameter for the genus Artemia.