11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5.100
The Effect Of Different Flow Regimes On The Long-Term Skeletal Growth And
Physiology Of The Scleractinian Coral Galaxea Fascicularis in A Closed Aquarium
System
Miriam SCHUTTER* 1,2 , Max JANSE 3 , Ronald OSINGA 1 , Johan VERRETH 1 , René
WIJFFELS 2
1 Aquaculture and Fisheries, Wageningen University, Wageningen, Netherlands,
2 Bioprocess Engineering Group, Wageningen University, Wageningen, Netherlands,
3 Burgers Zoo, Arnhem, Netherlands
Water flow is one of the most important abiotic factors influencing the growth of
scleractinian corals. Different aspects of flow, such as speed, turbulence and direction,
affect prey capture efficiency, exchange rate of dissolved gasses and nutrients, and
removal of sediment or mucus.
A long term experiment was performed in a closed aquarium system (Burgers Ocean, the
Netherlands) to examine the effect of different flow regimes (1 cm/s, 10 cm/s, 20 cm/s
and 25 cm/s, alternating, bidirectional flow) on long-term growth. Ten nubbins (single
polyp clones of a coral colony) of Galaxea fascicularis were used for each treatment.
Growth of these nubbins was measured for a 42 week period by determination of buoyant
weight and by making polyp counts (every six weeks), and by image analysis for surface
area (every three weeks).
In concurrent short-term incubation experiments, the feeding efficiency (uptake of
Artemia nauplii) and the metabolic rates (photosynthesis and respiration) of these corals
under the selected flow regimes was studied in a respirometric flow cell. These short term
experiments may provide an explanation for the observed differences in growth.
So far, it is found that the coral nubbins grow less in the zero flow regime, while they
grow most at 25 cm/s. Not much difference is found in growth between 10 and 20 cm/s.
Water flow speed seems to have little effect on photosynthetic rate and a much larger
effect on respiration rate. Feeding seems neither enhanced nor impaired at higher flow
speeds.
5.101
Segmented Gastric Cavity Of The Stony Coral
Michal RAZ BAHAT* 1 , Zehava UNI 2 , Buki RINKEVICH 1
1 zoology, National Institute of Oceanography, Israel Oceanographic and Limnological
Research, Haifa, Israel, 2 Zoology, Faculty of Agriculture, Hebrew University, P.O. Box
12, Rehovot, Israel, Rehovo, Israel
The digestive system of the stony coral has not been yet investigated thoroughly. The
literature describes the polyp’s digestive system schematically, as a blind sac divided into
compartments by mesenteries lined with the gastrodermis tissue and with numerous
mucus cells. This study investigates, in various methods, the detailed morphology and the
enzymatic function of coral’s digestive cavity.
Observing histological sections along the gastric cavity of the small-polyp coral
Stylophora pistillata, by light microscopy, we found that the polyp’s digestive system
along the oral-aboral axis, is divided into several segments of different cell types and
distribution. Using SAM, we investigated the structure and surface area of the gastric
cavity walls, and found that they change, gradually, from the pharynx towards the basal
plate. In order to elucidate whether the observed morphological characteristics are
functional as well, we tested the activities of some digestive enzymes and found a
differential abundance along the gastric cavity. This insight into the segmented gastric
cavity provides a new perspective of the coral’s digestive system.
5.102
The Tropical Sea Anemone aiptasia Pallida As A Lab Model For The Study Of Coral
Bleaching
Ophélie LADRIÈRE* 1 , Stéphane ROBERTY 1 , Charlotte BAUDESSON 1 , Philippe
COMPÈRE 2 , Fabrice FRANCK 3 , Mathieu POULICEK 1
1 Unit of Marine Ecology, Laboratory of Animal Ecology and Ecotoxicology, University of
Liège, Liège, Belgium, 2 Unit of Ultrastructural Morphology, Laboratory of Functional and
Evolutive Morphology, University of Liège, Liège, Benin, 3 Unit of Plant Biochemistry,
University of Liège, Liège, Belgium
Bleaching is still among major events threatening coral reefs. New tools have to be developped
to better understand the mechanisms leading to this pathology : we studied the use of the
hermatypic anemone Aiptasia pallida as experimental model for coral bleaching. Aiptasia
appears as a good candidate as it is easy to maintain in aquarium and subjected to bleaching like
corals.
Both morphological and physiological approaches were performed to investigate the
ultrastructure of the anemone tissues (TEM) and the zooxanthellae photophysiology
(chlorophyll a fluorescence, respiration and pigmentation).
Experiments under light and dark stress reveal that anemone tissues ultrastructure can be
differently affected. In darkness, the ectoderm activity is reoriented to capture prey by
increasing cnidocyte density. In contrast, intense light affects especially the gastroderm :
intercellular spaces increase, the expulsion of intact algae in the gastric cavity and the
degradation of zooxanthellae inside vacuoles seem to reduce the zooxanthellae density,
chloroplast thylakoids lose their parallel arrangement.
The analysis of the fluorescence induction curve appears as a powerful tool to analyse the
physiological events series previous to bleaching. Although no significant zooxanthellae density
reduction was observed, the decrease of pigments concentrations indicates that light or dark
stresses induce anemone bleaching. Under strong light intensity, A. pallida zooxanthellae show
an increased proportion of PSII QB non reducing, leading to partial photoinhibition. This
phenomenon favours the ROS production that damages cellular structures of host and
zooxanthellae. In darkness, there is no photosynthesis; anemones have therefore to find other
feeding sources, as suggested by the ultrastructural approach.
As the present results confirm some of those obtained on scleractinians, A. pallida can be
regarded as a good model for coral bleaching studies and has numerous advantages for
experimentation.
5.103
The Tissue-Skeleton Interface in the Scleractinian Coral Stylophora pistillata
Eric TAMBUTTÉ* 1 , Denis ALLEMAND 1 , Didier ZOCCOLA 1 , Anders MEIBOM 2 , Severine
LOTTO 3 , Natacha CAMINITI 1 , Sylvie TAMBUTTÉ 1
1 Centre Scientifique de Monaco, Monaco, Monaco, 2 Laboratoire d'Etude de la Matière
Extraterrestre, Museum National d'Histoire Naturelle, paris, France, 3 Centre Scientifique de
Monaco, Monaco, France
Stylophora pistillata is a coral for which numerous physiological data on calcification are
available through detailed laboratory studies. However, for this species, as well as for most
other species, the cellular tissue is poorly described at the microscopic level. The aim of the
present work is to provide histological observations of the coral tissue at the interface with the
skeleton, using Stylophora pistillata as a model, and to discuss these observations in the context
of the morpho-functional aspects of biomineralization. The approach is top-down, i.e., it starts
from a macroscopic level with observations made on a microcolony-level and proceeds to a
sub-microscopic level with observations made on the cells and the corresponding skeletal
surface. Several important observations can be made: 1) At all scales of observation, there is a
precise morphological correspondence between the tissues and the skeleton. 2) The distribution
and density of desmocyte cells, which anchor the calicoblastic ectoderm to the skeletal surface,
vary spatially and temporally during skeletal growth stages 3) The calicoblastic cell layer differs
dramatically between regions corresponding to different ultra-structural components of the
skeleton. From the base to the tip of coenosteal spines, the histology of coral tissues changes
from four epithelial layers to two epithelial layers that completely lack endoderms. These
findings have important implications for models for vital effects in coral skeletal chemistry and
isotope composition.
283