Seasonal variation in the egg morphology of the copepod Eurytemora americana and its relationship with reproductive strategy in a temperate estuary in Argentina

BERASATEGUI A. A.; HOFFMEYER, M. S; DUTTO, M. S.; BIANCALANA, F.

ICES JOURNAL OF MARINE SCIENCE

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2012 vol. 69 p. 380 - 388

1054-3139

Seasonal variation in the morphology of Eurytemora americana eggs and its relationship with reproductive strategy were studied in theBahı´a Blanca Estuary. Eggs from field females were analysed morphologically by optical (OM) and electron microscopy [scanning electronmicroscopy (SEM)?transmission electron microscopy (TEM)] during the population pulse. Additionally, egg-carrying females were incubatedsimulating in situ environmental conditions to evaluate the resting egg character. Subitaneous and resting eggs were indistinguishableby OM, but showed different chorion appearance under SEM and TEM. Sinuous patterned chorion eggs, mainly produced duringthe period of population growth, were classed as subitaneous eggs based on their high level of hatching success. Eggs with a sponge-likeappearance, produced after the population peaked, were classed as diapause eggs based on their inability to hatch even under favourableconditions. There were significant differences in egg size through the population pulse and diapause eggs were significantly bigger thansubitaneous eggs. The observation of both morphotypes in egg-carrying females after peak population abundance confirms the existenceof a transitional reproductive stage before the exclusive production of diapause eggs at the end of the pulse. Diapause egg productionenables E. americana to resist adverse conditions, ensuring its survival in temperate estuaries.