Oxygen-binding properties of cephalopod blood with special reference to environmental temperatures and ecological distribution
✍ Scribed by Brix, O. ;Bårdgard, A. ;Cau, A. ;Colosimo, A. ;Condò, S. G. ;Giardina, B.
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 819 KB
- Volume
- 252
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
The oxygen-binding properties of the blood of the cephalopods Todarodes sagittatus, Loligo vulgaris, Architeuthis monachus, and Octopus vulgaris were studied in relation to temperature and pH. The data obtained at pH 7.4 were compared with previously reported data on nine species of cephalopod over the actual range of temperatures at which the animals live in an attempt to define the role of temperature as an effector in the process, and to demonstrate the extent to which temperature influences the ecological range of the various species.
For most cephalopods we found Bohr and Haldane factors of lower than -1.0, a result that implies that the Bohr shift does not facilitate the unloading of 02, but may improve the loading of O2 with increased ventilation. The functional significance of the Bohr and Haldane effects appears, thus, to involve stabilization of pH by the isohydric transport of COz.
Our results further demonstrated a significant decrease in oxygen affinity with temperature for all cephalopods studied. This relationship was more pronounced for the cephalopods from colder waters than for those from the tropics. Furthermore, a significant increase in cooperativity with decreasing affinity for oxygen was found when we compared these oxygen-binding parameters at pH 7.4 and at the temperatures of the natural habitats of the various cephalopods. The respective relationships between the Hill coefficient (ns0) and the oxygen tension at half-saturation (P5,,) allowed us to separate the cephalopods into three distinct groups: 1) the Sepia species; 2) all the squids except Architeuthis; and 3) all the Octopus species, plus Architeuthis and Nautilus, this third group being the most sluggish group examined. Furthermore, the most sluggish species, those in group 3, have the highest reported functional buffer capacities, 7-19 mM COz + pH-' . mM 02-', while the more active species have functional buffer capacities in the range of 4-7 mM CO, . pH-' . mM 0,-'. The relationship between P5,, and n50 optimizes the utilization of O2 over the entire range of Ps0 reported.