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See detailMoult-related changes in the integument, midgut, and digestive gland in the freshwater amphipod gammarus pulex
Trevisan, Mélissa ULg; Leroy, Delphine; Decloux, Nicole ULg et al

in Journal of Crustacean Biology (2014), 34(5), 539-551

On the basis of macroscopic aspects (body and eye colour, lipid droplets), it was possible to sort specimens of Gammarus pulex (Linnaeus, 1758) into five categories that correspond to moult periods and ... [more ▼]

On the basis of macroscopic aspects (body and eye colour, lipid droplets), it was possible to sort specimens of Gammarus pulex (Linnaeus, 1758) into five categories that correspond to moult periods and stages (A, B, C, D1 and D2) based on integument features (tergite cuticle stiffness, layers and thickness). These stages also correspond to changes in digestive tract histology (gut content, cell ultrastructure, and lipid storage). With reference to the pereion tergite integument, this makes it possible to standardize moulting stage terminology and criteria with those applied to decapods while validating a quick, simple, moult-staging method that avoids injury and informs us about the physiology of the whole organism. The moult cycle was very short (about 12-15 days), with a "virtual," practically non-existent, anecdysis or "integument resting period" between post-ecdysis and pre-ecdysis. The pore canals previously known to be "open to the outside" appeared closed at early post-ecdysis by a lipid-rich fillng material that could be responsible for the cuticular waterproofing barrier allowing mineral deposition. In the digestive tract, the main structural changes were late post-ecdysial loss of midgut cells and digestive gland B-cells (probably by extrusion) when restarting the feeding cycle. Pre-ecdysial increase and post-ecdysial decrease in storage lipids are also obvious. We present a quick moult-staging method to sort a great number of G. pulex for physiological or toxicological assays investigating how animals at specific periods of their moult cycle respond to both natural and anthropogenic environmental changes. [less ▲]

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See detailMorphological alterations of zooxanthellae in bleached cnidarian hosts
Ladrière, Ophélie ULg; Compère, Philippe ULg; Decloux, Nicole ULg et al

in Cahiers de Biologie Marine (2008), 49(3), 215-227

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 ... [more ▼]

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. [less ▲]

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