(pO 2 ≈ 5 mmHg) for 10 days. Both the protein and mRNA levels of HIF1- α were reduced during hypoxia, while the level of Factor Inhibiting HIF (FIH-1) increased 4-fold. Although there were significant increases in both VEGF-A and VEGF-C (but not VEGF-D), there was a reduced capillary density in the brain after 10 days of hypoxia. We conclude that, while HIF is likely to be important for local responses to tissue hypoxia in many organisms, a well-adapted facultative anaerobe like the crucian carp probably has to suppress HIF levels and HIF responses during global hypoxia (i.e. hypoxia that is affecting all tissues simultaneously). To allow HIF to stimulate angiogenesis in all tissues would probably be maladaptive, since the fish would have to pay high costs for cell proliferation and for pumping increased blood volumes. In fact, our results show that not even the brain, which has particularly high energy needs, is allowed an increased capillary density in hypoxia. doi:10.1016/j.cbpa.2008.04.270 A6.16 Mechanisms and evolution of hypoxia tolerance in sculpins J. Richards, M. Mandic (University of British Columbia) A comparative phylogenetically independent contrast analysis was employed to investigate the adaptive traits involved in hypoxia tolerance in eleven species of sculpin, a group of closely related fish species that inhabit the marine near-shore environment. Hypoxia tolerance was evaluated by determining each species critical oxygen tension (P crit ) and there is a tight correlation between P crit and the distribution of species along the near shore environment. Animals with low P crits inhabit the most oxygen variable environments. Approximately 83% of the variation in P crit could be explained by variation in routine oxygen consumption, gill surface area, and whole red blood cell Hb-oxygen binding affinity. Whole blood cell Hb-oxygen binding affinity was primarily dictated by the intrinsic properties of isolated Hb. doi:10.1016/j.cbpa.2008.04.271 A6.17 Defending against hypoxia: Behavioural, physiological and biochemical strategies of hypoxia survival in nearshore marine sculpins M. Mandic (University of British Columbia); K. Sloman (University of Plymouth); J. Richards (University of British Columbia) Behavioural responses and metabolic profiles were assessed in 11 species of sculpins, which are known to differ in their hypoxia tolerance. Aquatic surface respiration and aerial emergence was employed by all intertidal, hypoxia tolerant sculpins in response to decreasing water oxygen tensions with these behaviours occurring at a much reduced frequency among the less hypoxia tolerant deep-water species. Liver glycogen, glucose and ATP, and the activities of major glycolytic enzymes (e.g. hexokinase, lactate dehydrogenase) were determined for all species of sculpins. Application of phylogenetically independent contrasts was used to determine if metabolic capacity for substrate-level phosphor- ylation differed in relation to hypoxia tolerance. Exposure of three differentially tolerant species to a relative hypoxia exposure of 40% P crit illustrate a dramatic variation in mortality rates between the species. These results suggest that differences in energy provision during hypoxia may underlie hypoxia tolerance and species distribution along the nearshore environment. doi:10.1016/j.cbpa.2008.04.272 A6.18 Respiratory adaptations of a deep-sea hydrothermal crustacean: The case of Segonzacia mesatlantica M. Bruneaux (Station Biologique de Roscoff, CNRS–UPMC); J. Pasquier (CNRS–UPMC); P. Terrier (CNRS–ULP); E. Leize (CNRS–ULP); F. Lallier (CNRS–UPMC); F Zal (CNRS–UPMC) Deep-sea hydrothermal vents are hypervariable environments in which large changes of physico-chemical parameters (O 2 ,H 2 S, heavy metals, temperature, pH) occur rapidly. These changes modulate O 2 availability at short scale, both spatially and temporally. Organisms inhabiting these areas, such as the crab Segonzacia mesatlantica, have to maintain an adequate O 2 supply to their tissues in these harsh con- ditions. Hemocyanin, the crustacean blue respiratory pigment respon- sible for O 2 -transport, exists as hexamers and dodecamers of 75 kDa subunits. Several known effectors can modulate their O 2 -binding properties (temperature, pH, divalent cations, organic ions). Phenotypic plasticity at the subunit level also exists for some species. In order to better understand the respiratory adaptations of S. mesatlantica (Chausson et al., 2004; Sanglier et al., 2003), individuals were collected during an oceanographic cruise on the Mid-Atlantic Ridge (Momareto 2006) and acclimated under their habitat pressure to two different temperatures and oxygenation levels EXOCET/D program. Hemolymph was analysed and hemocyanin was structurally character- ized by multi-angle laser-light scattering (MALLS) and electrospray mass spectrometry (ESI-MS) Bruneaux et al. (in press).O 2 -binding properties were also investigated. In all experiments, hemocyanin was the major protein in the hemolymph. Urate levels increased in acclimated indi- viduals compared to control ones, whereas no clear lactate response was observed. Mg 2+ concentration changed slightly under hypoxia. Dodeca- mers and hexamers proportions also varied between conditions. From a functional point of view, S. mesatlantica hemocyanin exhibits a large Bohr effect and is sensitive to Mg 2+ and lactate. These results can be compared with data from littoral species such as the crab Carcinus maenas to highlight specific adaptations to the hydrothermal environment. References Chausson, et al., 2004. Micron 35, 31–41. Sanglier, et al., 2003. J. Am. Soc. Mass Spectrom.14, 419–429. EXOCET/D program, FP6 GOCE CT 2003-505342. Bruneaux et al. (2008), CPPS, in press. doi:10.1016/j.cbpa.2008.04.273 A6.19 Critical oxygen tension and the effect of hypoxia on the oxygen consumption of the striped catfish, Pangasius hypophthalmus (Pangasiidae) S. Lefevre (The University of Aarhus); M. Bayley (The University of Aarhus); T. Wang (The University of Aarhus); H. Malte (The University of Aarhus); D. Huong (Can Tho University); N. Cong (Can Tho University) S119 Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S115–S123