Comparative observations on the external morphology of subitaneous and diapause eggs of Acartia species from Southampton Water

[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. clausi produced 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. Les oeufs produits par quatre especes d'Acartia du systeme estuarien Solent-Southampton ont ete examines. Acartia tonsa a produit deux types d'oeufs morphologiquement distincts, qui ont ete identifies comme oeufs immediats et oeufs de diapause. Les oeufs de diapause de cette espece presentaient des epines tandis que la forme immediate avait une surface chorionique relativement lisse; un second type d'oeuf immediat a ete produit par A. tonsa, qui avait, a sa surface, des extensions epineuses importantes. Acartia margalefi, A. discaudata et A. clausi n'ont produit que des oeufs lisses, qui ont ete identifies comme oeufs immediats. Des observations realisees en microscopie electronique a balayage ont releve des variations interspecifiques significatives de la texture de la surface du chorion chez les oeufs immediats comme chez les oeufs de diapause de toutes les especes. , 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. clausi produced 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. Les oeufs produits par quatre especes d'Acartia du systeme estuarien Solent-Southampton ont ete examines. Acartia tonsa a produit deux types d'oeufs morphologiquement distincts, qui ont ete identifies comme oeufs immediats et oeufs de diapause. Les oeufs de diapause de cette espece presentaient des epines tandis que la forme immediate avait une surface chorionique relativement lisse; un second type d'oeuf immediat a ete produit par A. tonsa, qui avait, a sa surface, des extensions epineuses importantes. Acartia margalefi, A. discaudata et A. clausi n'ont produit que des oeufs lisses, qui ont ete identifies comme oeufs immediats. Des observations realisees en microscopie electronique a balayage ont releve des variations interspecifiques significatives de la texture de la surface du chorion chez les oeufs immediats comme chez les oeufs de diapause de toutes les especes. ]