CONTENT - International Society of Zoological Sciences

ICZ2008 – Abstracts S20
Integument, moult cycle and bacterial ectosymbionts
relationships in the deep-sea hydrothermal vent shrimp,
Rimicaris exoculata : a review
Philippe Compère 1 , Magali Zbinden 2 , Laure Corbari 1 , Marie-Anne
Cambon-Bonavita 3 , Gilles Lepoint 1 , Bruce Shillito 2 and Françoise
Gaill 2
1 Université de Liège, Dept. Sciences et Gestion de
l’Environnement, Institut de Chime (B6c), allée de la chimie, 3, B-
4000 Liège, Belgique
2 UMR 7138 ‘Systématique, Adaptation et Evolution’, Université
Pierre et Marie Curie, 7 Quai St Bernard, F-75252 Paris Cedex 05,
France ; 3 IFREMER, Laboratoire de Microbiologie des Environnements
Extrêmes, Centre de Brest, BP 70, F-29280 Plouzané,
France
The Rimicaris exoculata shrimps are considered as the primary
consumers dominating the fauna of Mid-Atlantic Ridge (MAR)
hydrothermal vent ecosystems. These shrimps harbour in their
dilated gill chambers an important ectosymbiotic community of
chemoautotrophic bacteria associated with iron oxide deposits.
Observations in scanning and transmission electron microscopy
realised over the past 5 years give new insights in the
establishment and functioning of the supposed ectosymbiosis in
close relation with the shrimp integument. The distribution of the
bacteria give evidence of three functional compartments in the gill
chambers while their internal ultrastructure suggests the presence
of various bacterial strains and metabolisms as also supported by
genetic analyses. The survey of the moulting stages and the
determination of their ratio in the shrimp population reveal a high
moulting rate and the periodic bacterial re-colonisation of the gill
chamber by the bacterial symbionts after each exuviation. TEM
observations also showed the deposition of cuticle and the
ultrastructure of the epidermis at each moulting stage.
Characteristics of the gills as well as of inner walls of the gill
chambers (inner branchiostegites) colonised by the bacteria are
those of permeable/transporting tissues (thin cuticle, numerous
mitochondria, membranes infoldings, sulphide-oxidising bodies)
suggesting the possibility of symbiont-host transtegumental
transfers. The bacterial metabolism and the hypothesis of direct
nutritional transfer through the shrimp integument are investigated
using cold and radioactive tracers. The authors thank the belgian Fund
for Joint Basic Research (FRFC-Belgium, conv. n° 2.4594.07.F) and the
IFREMER (France) for the financial support.
Do the hydrothermal vent fluid characteristics influence on
the ectosymbiotic bacteria and associated minerals in the
shrimp Rimicaris exoculata ?
Laure Corbari 1 , Marie-Anne Cambon-Bonavita 2 , Magali Zbinden 3 ,
Françoise Gaill 3 and Philippe Compère 1
1 Univ. Liège, Lab. de Morphologie fonctionnelle et évolutive, Unité
de Morphologie ultrastructurale, allée de la chimie, 3, 4000 Liège,
Belgium; 2 Laboratoire de Microbiologie et Biotechnologie des
Extrêmophiles, Ifremer, centre de Brest, BP 70, F-29280 Plouzané,
France; 3 UMR CNRS 7138 ‘Systématique, Adaptation et Evolution’,
UPMC, 7 Quai St Bernard, 75252 Paris Cedex 05, France
The shrimps Rimicaris exoculata are the primary consumers
dominating the fauna of many hydrothermal vent sites Mid-Atlantic
Ridge (MAR). They harbour in their gill chambers a rich
ectosymbiosis of chemosynthetic bacteria that are supposed to be
fuelled by vent fluid reduced compounds. Up to now, most of the
recent studies considered shrimps from the Rainbow vent field
(36°14.0’N) while it has an atypical fluid composition, rich in Fe 2+
and relatively poor in HS - . They considered the distribution of
bacteria in the shrimp gill chambers as well as their morphotypes,
phylotypes and metabolisms. They also showed the rapid
development of the bacterial colonisation in phase with the shrimp
moult cycle and the deposition of heavy bacteria-associated Fe 3+ -
oxides. Interestingly, the TAG vent field (26°08.0’N), characterised
by a sulphide-rich and iron-poor, fluid, also harbours an important
shrimp population. For comparison, the bacterial population and
the associated-minerals were characterised by electron
microscopy and EDAX in shrimps from the TAG vent fields and
followed throughout the shrimp moult cycle.
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Differences were neither obtained in the shrimp moult cycle nor in
the bacterial colonisation of the new cuticle after exuviation. The
bacteria morphotypes also appear identical in both sites. Genetic
analyses have indicated that the bacteria are of the same genera
(mainly epsilon and gamma Proteobacteria) but the species seems
to be different between TAG and rainbow. In contrast, obvious
differences are revealed in the deposition of mineral. In TAG
shrimps, a diffuse sulphide precipitate, giving grey-coloured
shrimps, precedes iron oxide deposition that occurs less rapidly
than in Rainbow shrimps. Moreover, the importance of minor
elements (Si, Ca, P) is increased in accordance with the TAG vent
fluid composition. The authors thank the Belgian fund for Joint
Basic Research (FRFC-Belgium; conv. n° 2.4594.07.F) and
Ifremer (France) for the financial support.
New digestive symbioses in the hydrothermal vent
Amphipoda Ventiella sulfuris.
Laure Corbari 1 , Françoise Gaill 2 and Philippe Compère 1
1 Université de Liège, Dept. Sciences et Gestion de
l’Environnement, Institut de Chime (B6c), allée de la chimie, 3, B-
4000 Liège, Belgium ; 2 UPMC, UMR CNRS 7138 ‘Systématique,
Adaptation et Evolution’, 7 Quai St Bernard, 75252 Paris Cedex 05,
France
Ventiella sulfuris is the most abundant amphipod species
inhabiting the Eastern Pacific Rise (EPR 9°N) vent fields. This
endemic species is commonly encountered near colonies of
Pompeii worms Alvinella pompejana. That these species could
live in a close trophic association never was further investigated. V.
sulfuris specimens were collected during the oceanographic cruise
LADDER II to the Bio9 (9°50.3’ N, 2508m depth) hydrothermal
vent site. Looking for associated microorganisms, the integument
and the digestive tract of the amphipod were observed in light
microscopy (LM) and electron microscopy (SEM, TEM). The
cuticle surface of the outer body and appendages appeared free of
microorganisms. In contrast, the observation of the digestive tract
revealed two important bacterial colonisations located in the
mesenteron and in the proctodeum respectively. Both exhibit
typical characteristics of symbioses. In the mesenteron, long
bacteria are inserted between microvilli of endodermic epithelial
cells. In the proctodeum, large densities of rods cover the cuticular
walls. Examination of the gut content showed abundant fragments
of annelid cuticle, most probably from A. pompejana, as well as
mineral particles and diatom frustules. These results reveal new
potential bacterial symbioses in vent crustaceans and point out the
importance of amphipods in the trophic relationships of
hydrothermal vent ecosystems.
The authors thank the belgian Fund for Joint Basic Research
(FRFC-Belgium, conv. n° 2.4594.07.F) for the financial support.
The LADDER project was funded by NSF Ocean Sciences grant
OCE-0424953.
Temperature resistance studies on deep-sea vent shrimp
Delphine Cottin, Juliette Ravaux, Nelly Léger and Bruce Shillito
UPMC, UMR 7138, "Systématique, Adaptation et Evolution",
75005 Paris, France
The deep-sea hydrothermal vent ecosystem is an extreme
environment characterized by great spatial and temporal
instabilities and especially in terms of temperature. In this
environment, the temperature can vary from 2°C to more than
50°C in a few centimeters. As a consequence, in addition to a high
ambient hydrostatic pressure, the vent fauna have to deal with
harsh and highly unstable thermal conditions with frequent
temperature burst. The caridean shrimp Rimicaris exoculata and
Mirocaris fortunata dominate the vent megafauna at many of the
hydrothermal vent field at the Mid-Atlantic Ridge. The first one,
Rimicaris exoculata which forms dense swarm around the black
smoker chimneys, is found in the hottest end part of the edifice,
where it maintains close proximity to the superheated fluid. The
second one, Mirocaris fortunata, is more broadly distributed across
the vent-fluid influence gradient and thus is supposed be a less
thermotolerant species. We performed in vivo experiments on R.
exoculata and M. fortunata in pressurized aquaria to determine
their upper thermal limit and we found that both species does not
tolerate sustained exposure to temperature above 37°C. These