title: Thermal limit for metazoan life in question: in vivo heat tolerance of the Pompeii worm.
abstract: The thermal limit for metazoan life, expected to be around 50°C, has been debated since the discovery of the Pompeii worm Alvinella pompejana, which colonizes black smoker chimney walls at deep-sea vents. While indirect evidence predicts body temperatures lower than 50°C, repeated in situ temperature measurements depict an animal thriving at temperatures of 60°C and more. This controversy was to remain as long as this species escaped in vivo investigations, due to irremediable mortalities upon non-isobaric sampling. Here we report from the first heat-exposure experiments with live A. pompejana, following isobaric sampling and subsequent transfer in a laboratory pressurized aquarium. A prolonged (2 hours) exposure in the 50-55°C range was lethal, inducing severe tissue damages, cell mortalities and triggering a heat stress response, therefore showing that Alvinella's upper thermal limit clearly is below 55°C. A comparison with hsp70 stress gene expressions of individuals analysed directly after sampling in situ confirms that Alvinella pompejana does not experience long-term exposures to temperature above 50°C in its natural environment. The thermal optimum is nevertheless beyond 42°C, which confirms that the Pompeii worm ranks among the most thermotolerant metazoans.
authors.affiliation: Adaptations aux Milieux Extrêmes, UMR CNRS 7138, Université Pierre et Marie Curie - Paris 06, Paris, France. juliette.ravaux@snv.jussieu.fr
authors.forename: Juliette
authors.initials: J
authors.lastname: Ravaux
authors.forename: Gérard
authors.initials: G
authors.lastname: Hamel
authors.forename: Magali
authors.initials: M
authors.lastname: Zbinden
authors.forename: Aurélie A
authors.initials: AA
authors.lastname: Tasiemski
authors.forename: Isabelle
authors.initials: I
authors.lastname: Boutet
authors.forename: Nelly
authors.initials: N
authors.lastname: Léger
authors.forename: Arnaud
authors.initials: A
authors.lastname: Tanguy
authors.forename: Didier
authors.initials: D
authors.lastname: Jollivet
authors.forename: Bruce
authors.initials: B
authors.lastname: Shillito
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology*; D000818:Animals; D004780:Environment, Controlled; D020869:Gene Expression Profiling; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D018869:Heat-Shock Response / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D011077:Polychaeta / Q000235:genetics / Q000502:physiology*; D011312:Pressure; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013696:Temperature
chemical_list: D018840:HSP70 Heat-Shock Proteins