Ultrastructure features of the tertiary envelope in the cyst of the brine shrimp Artemia franciscana (Anostraca)

Abstract

The brine shrimp is an important experimental organism in developmental biology and a key larval food in aquaculture. Morris and Afzelius established the basic ultrastructure of cyst and embryo membranes of Artemia and a subsequent report provided some additional features. A better understanding of the cyst shell structure and composition are prerequisites to elucidating the physical and biochemical processes of the hatching events. In the present study, scanning and transmission electron microscopy were used to visualize the internal features of the maternally produced pigmented tertiary envelope (TE) of the hatched brine shrimp cyst shell. This combined SEM and TEM approach revealed several previously unrecognized features.Utah biotype cysts, from Sanders Brine Shrimp Company Inc., Ogden, Utah, U.S.A., were hatched over 24 hrs in saltwater. Hydrated cysts were fixed in 3% glutaraldehyde, post-fixed in 1% osmium tetroxide, dehydrated in an ethanol series, and critical-point dried or embedded in Epon. In some cases, the critical-point dried cyst shell was fractured before sputter-coating with gold/palladium for SEM.