[en] Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four coral species-three collected from a barrier reef in Madagascar (Acropora digitifera (Dana, 1846), Echinopora hirsutissima Milne-Edwards & Haime, 1849 and Porites (Synaraea) rus Forskal, 1775)) and one cut from an aquarium-grown coral (Pocillopora damicornis (Linnaeus, 1758)-and from the hermatypic (zooxanthellae-containing) sea anemone Aiptasia pulchella (Carlgren, 1943). Zooxanthellae from bleached animals showed different stages of degradation or disorganization. Some were free, detached from the host gastroderm, associated or not with host-cell remains. Others were vacuolated, with abundant reserve material globules and angular holes probably created by the loss of crystalline material during cutting. Experimentally heat-shocked P. damicornis harboured, moreover, a greater number of dividing algae. Bleached individuals were found to vary as regards their response to stress, and zooxanthellae expelled from heat-shocked anemones showed a greater mitotic index and a higher survival rate than algae extracted or naturally externalized from healthy individuals. We propose a combination of morphological criteria for use in diagnosing the health state of algae-cnidarian symbiosis, so vulnerable in the case of bleaching.
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Ladrière, Ophélie ; Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Ecologie animale et écotoxicologie
Compère, Philippe ; Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Département des sciences et gestion de l'environnement
Decloux, Nicole ; Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Département des sciences et gestion de l'environnement
Vandewalle, Pierre ; Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Morphologie fonctionnelle et évolutive
Poulicek, Mathieu ; Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Ecologie animale et écotoxicologie
Language :
English
Title :
Morphological alterations of zooxanthellae in bleached cnidarian hosts
Alternative titles :
[fr] Altérations morphologiques de zooxanthelles d'hôtes cnidaires atteints de blanchissement
Publication date :
2008
Journal title :
Cahiers de Biologie Marine
ISSN :
0007-9723
Publisher :
CNRS - Cahiers de Biologie Marine, Roscoff, France
Volume :
49
Issue :
3
Pages :
215-227
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
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