CONTENT - International Society of Zoological Sciences

ICZ2008 – Abstracts S20
Biodiversity and colonization of Antarctic cold waters: the
importance of symbioses associated to echinoids
Clotilde Hardy 1 , Thomas Saucède 1 , Bruno David 1 , Chantal De
Ridder 2 and Thierry Rigaud 1
1
Biogéosciences, CNRS/Université de Bourgogne, 6 bvd Gabriel,
21000 Dijon, France
2
Laboratoire de Biologie Marine, Université Libre de Bruxelles,
1050 Bruxelles, Belgium
Among the main factors that control the structure of Antarctic
benthic communities, the nature of the bottom and interspecific
relations play an important part. Hard bottoms are not a common
feature of Antarctic marine environments, and hard substrates,
either biotic or abiotic, are generally colonized by many epibiotic
invertebrates. Since primary spines of ctenocidarids - one
subfamily of highly endemic Antarctic echinoids - are devoid of
epithelium and of any anti-fouling system, they offer a hard
substrate to many invertebrates. Even as one of the most speciose
group of invertebrates in the Antarctic, echinoids (and their
symbionts) may be at last of some importance for the diversity of
Antarctic benthic ecosystems. To test the hypothesis, abundance,
distribution, richness, diversity and similarity of symbionts present
on two ctenocidarids (Notocidaris mortenseni and Ctenocidaris
nutrix) have been compared with those of epibionts present on
abiotic substrates (drop stones). Echinoids and stones were
collected during the expedition ANTXXIII/8 (winter 2006-2007) in
contrasted stations and areas of the Weddell Sea (Atka Bay),
South Shetlands (Elephant Island) and Antarctic Peninsula (Larsen
embayments in which iceshelves very recently collapsed). Our
results demonstrate the importance of cidarids for local diversity
and show contrasted patterns, likely due to contrasted conditions
(latitude, depth and currents) prevailing in sampling areas. In the
Larsen area, symbiotic communities distinguish by a low diversity
and a strong similarity with epibionts present on stones, what is
congruent with the conditions prevailing in Larsen: relatively poor
and newly colonized habitats, both for benthic and symbiotic
communities.
Feeding and gut symbionts of decapod crustaceans
associated to deep-sea wood falls: ultrastructural, trophic and
molecular approaches
Caroline Hoyoux 1 , Magali Zbinden 2 , Sarah Samadi 3 , Gilles
Lepoint 1 , Pierre Becker 4 , Chantal De Ridder 4 , Renaud Berlémont 5 ,
Moreno Galleni 5 , Françoise Gaill 2 and Philippe Compère 1
1 Université de Liège, Dept. Sciences et Gestion de
l’Environnement, B-4000 Liège, Belgium; 2 Université Pierre et
Marie Curie, UMR 7138 CNRS, F-72252 Paris cedex 05, France; 3
Muséum National d’Histoire Naturelle, UMS 2700 CNRS, F-72252
Paris cedex 05, France; 4 Université Libre de Bruxelles, Biologie
Marine, B-1000 Bruxelles, Belgium; 5 Université de Liège, Dept.
des Science de la Vie, B-4000 Liège, Belgium
Almost unknown few years ago, wood falls in the deep sea are
now the subject of recent studies showing their importance as
nutriments on the deep-sea floor. They support original
ecosystems, with a macrofauna dominated by molluscs and
crustaceans that belong to taxa also found in other reducing
chemosynthetic environments as hydrothermal vents and whale
falls. Because previous studies pointed out digestive and
chemosynthetic bacterial symbioses in mollusc species from
sunken woods, many questions arise about crustaceans, their role
in the degradation of wood, their feeding biology and their
microbial associations.
An ultrastructural survey of the gut content and gut lining in 12
crustacean species collected during 4 oceanographic cruises on
sunken wood accumulations, near Pacific islands (Solomon,
Vanuatu), pointed out 2 xylophagous and 2 detritivorous species
(Munidopsis spp. and Callianassa spp.) harbouring resident,
potentially symbiotic, gut microorganisms. These microorganisms
mainly consist of bacteria and fungi attached to the hindgut cuticle
lining. Determinations of stable isotope ratio ( 13 C/ 12 C, 15 N/ 14 N) are
carried out to specify or confirm the diet and the trophic level of the
species, as well as the possible implication of the gut
microorganisms. Currently, the identification of the gut
microorganisms is in progress by sequence analyses of the 16S
- 81 -
rRNA gene. Finally, finding genes for cellulose hydrolysis is in
process by metagenomic analysis of bacterial gut communities.
The authors thank the National fund for Scientific Research
(FNRS-Belgium conv. FRFC n° 2.4.594.07.F) for the financial
support.
Extraordinary high diversity of siliceous sponges play an
important ecological role in the deep Southern Ocean
Dorte Janussen
Forschungsinstitut und Naturmuseum Senckenberg, Senckenberganlage
25, D-60325 Frankfurt am Main, Germany
Sponges are important in marine benthic ecology by providing
habitates for a variety of other organisms, ranging from microbial
to megafaunal communities. Furthermore, large siliceous sponges
(mainly of the class Hexactinellida) commonly possess prominent
siliceous “needles”, which remain as spicule mats after death of
the sponges and thus structure the sea floor and provide attractive
substrates for the settlement of larvae. Rich associations of
Porifera are thus linked with high benthic diversity and abundance
of other animal phyla. This is obvious in the Southern Ocean,
particularly on the Antartic shelf, where extraordinarily high sponge
abundance and biomass are correllated with diverse associations
of especially crustaceans, polychaetes and echinoderms. From
bathyal to abyssal depths, most of the largely endemic Antarctic
shelf sponge fauna is successively replaced by cosmopolitan taxa,
and simultanously, the distribution of sponges and other sessile
animals is becoming increasingly patchy. However, the diversity of
especially the Hexactinellida (glass sponges) at above-species
taxonomic levels is significantly higher in the Antarctic deep-sea
than on the shelf. Especially bathyal depths between 1000m-
2000m are characterized by rich associations of siliceous sponges,
including both shallow and deep water taxa. This is due to the fact
that on the Southern Ocean slope, eurybath species of endemic
shelf species (e. g. Rossella spp.) co-occur with cosmopolitan
deep-sea taxa (such as Bathydorus and Caulophacus spp.).
With their structuring properties and large body size of many
Antarctic siliceous sponges, these hghly diverse taxa play a crucial
role for the colonization of deep-sea bottoms.
Long-term monitoring of sunken wood colonization in the
shallow water mangrove swamp of Guadeloupe (F.W.I.)
Mélina Laurent 1 , Nadine Le Bris 2 , Françoise Gaill 3 and Olivier
Gros 1
1 UMR-CNRS 7138, Systématique-Adaptation-Evolution, Equipe
« Symbiose ». Université des Antilles et de la Guyane. UFR des
Sciences Exactes et Naturelles, Département de Biologie. B.P.
592. 97159 Pointe-à-Pitre Cedex, Guadeloupe. France.
2 IFREMER Département Etude des Ecosystèmes Profonds. Zone
de la Pointe du Diable, BP70. 29280 Plouzané. France. 3 UMR-
CNRS 7138, UPMC, 7 Quai Saint Bernard. 75005 Paris, France
We realized experimental immersion of Cocos nucifera wood
pieces in a mangrove swamp of Guadeloupe (16’N 61.5W) West
Indies. Regular sampling allowed to study the kinetic of wood
colonization from the very first days to several months of
immersion. The organisms observed during the first week of
immersion, are the ciliates Heterotrichea and Oligohymenophora
and few nematodes. Bryozoans appear after 10 days and annelids
after 20 days. After the first month, the abundance of ciliates and
nematodes decrease, while several invertebrates including new
ciliates, platyhelminthes, ascidians, annelids, bryozoans,
crustaceans, gastropods, and few vertebrates as Gobiidae and
Bleniidae colonize the wood.
After the second month, the fauna abundance and diversity
increase, with the apparition of cnidarians and echinoderms.
Chemical monitoring (pH and hydrogen sulfide) realized with
autonomous probes revealed sulfide contents reaching almost
millimolar levels at the wood surface within 2.5 days through the
first month, before a rapid decrease to sub-micromolar levels. A
significant relationship between the presence of organisms and
sulfide levels was suggested. This hypothesis was sustained by
the detection of bacterial ectosymbionts using hybridization
experiments, SEM and TEM observations in some of the
invertebrates encountered.