Rapport de Campagne - Station Biologique de Roscoff

COMPTE RENDU DE CAMPAGNE A LA MER SUR UN NAVIRE Ifremer
H OP E 99
URM 7
Nom : DIXON
Prénom : David
Campagne : HOPE 99
Navire : L'ATALANTE - Submersible: NAUTILE
Organisme maître d'oeuvre : URM 7
Chef de mission : F. LALLIER
Seconde partie: du 27 avril au 22 mai 1999
Participants associés :
David POND
Institution : SOC - Southampton, UK Bruce SHILLITO
Rappel des Objectifs
• Vent Toxicology
• PLASMA plankton sampler
• Cytogenetics
Travaux réalisés
• As above
• Discovery of new vent symbiosis in a serpulid polychaete
Commentaires
Activities carried out during the second leg of the HOPE99 cruise at 9° and 13°N on the
East Pacific Rise fall into four main categories: vent toxicology, PLASMA sampling (focusing
on fatty acids and stable isotopes), cytogenetics, and the discovery of a new ecto-bacterial
symbiosis in the vent serpulid Laminatubus alvini.
Vent toxicology These experiments were aimed at studyng the sensitivity of two
polychaete species, Hesiolyra bergi and Paralvinella grassleii, to DNA damage inflicted by
different concentrations of hydrogen peroxide, a reference genotoxin. The two species were
selected because they live in slightly different vent habitats and both are known to survive for
extended periods in the laboratory at 1 atmosphere. An additional component of this work was
to investigate DNA repair after the removal of the toxicant, at 1 and 260 bars. It was observed
that condition and survival was better at the worm‚s environmental pressure, this applied
particularly to P. grasleii which, in keeping with previous observations made on Arenicola
marina, needs the support of its tube to regulate body volume; the paralvinellid worms exposed
at 1 atmosphere developed haemotomas. In contrast, the errant polychaete, Hesiolyra, showed no
external signs of decompression damage (possibly a little bleeding in some cases), apart from
reduced activity (narcosis?) which was probably the reflection of impairment of the neural
pathways caused by pressure change. It is interesting to note that when the hydrostatic pressure
was returned to 260 bars, the worms recommenced crawling/swimming behaviour within 1 hour.
These and other experiments were carried out in collaboration with Bruce Shillitoe. This
included the investigation of the effects of increased temperature (up to 40°C) on DNA integrity;
both species showed reduced survival above 30 - 36°C which casts doubt on some former claims
that vent polychaetes can withstand temperatures of 100°C. It should be noted that Hesiolyra is
a commensal of Alvinella pompejana, and lives in the same habitat. In Southampton and
Plymouth, a combination of gel electrophoresis and image analysis will be used to detect single
and double-strand DNA breaks in preserved tissue samples from the cruise.
PLASMA plankton sampler Plankton samples were collected, in collaboration with David
Pond, for lipid and stable isotope analysis. The primary aim being to compare the lipid and
HOPE 99 Page 224 RAPPORTS SCIENTIFIQUES