To survive in the hydrothermal vent environment, the fauna have adaptations which allow exposure to a range of temperatures, while maintaining a supply of oxygen to their tissues and avoiding the toxic effects of their environment. Simple exclusion of the dissolved toxins would seem to be untenable when one considers the fact that these animals are aerobic and must utilise respiratory surfaces for gas exchange. This is especially true for the chemoautotrophic symbiont-containing animals, because they have the added requirement of supplying reduced sulphur compounds, usually the toxic gas hydrogen sulphide, to their symbionts. Understanding how the vent fauna tolerate and thrive in this hostile environment has been the focus of a majority of the physiological investigations of these animals. In parallel with these studies, biologists have long recognised the importance of characterizing the microhabitats occupied by the vent fauna. However, we have also recognized the difficulty in doing so because not only are the microhabitats temporally variable, but some of the spatial gradients of temperature and dissolved gasses are arguably the greatest of any habitat on the planet. For example, temperature gradients of well over 100oC per cm are not uncommon in chimney environments, and can exceed 300oC per cm on flanges. A review of some thermal tolerance investigations of vent fauna provides an excellent overview of the variety of approaches available to deep-sea physiological ecologists interested in such questions. |
