Eggs produced by four Acartia species from the Solent-Southampton Water estuarine system were examined. Acartia tonsa produced two morphologically distinct types of eggs, which were identified as subitaneous and diapause. Diapause eggs from this species were spiny while the subitaneous form had a relatively smooth chorion surface; a second subitaneous egg was produced by A. tonsa, which had significant spine extensions on the surface. Acartia margalefi, A. discaudata, and A. clausiproduced only smooth eggs, which were identified as subitaneous. Observations under scanning electron microscopy (SEM) revealed consistent interspecific variations in the texture of the chorion surface of both subitaneous and diapause eggs in all species.
