High-hydrostatic-pressure optical chamber system for cultivation and microscopic observation of deep-sea organisms

We developed and tested a high-pressure optical chamber system for cultivation and microscopic observation of deep-sea organisms. The system is composed of an optical chamber, a highpressure pump, a pressure sensor and a microscope. The chamber has an observation cavity, 2 cultivation cavities and 2 sapphire windows. The pump is employed for perfusion of culture medium and for increasing the pressure. The pressure sensor monitors the pressure in the chamber. The microscope is used for observing samples through the sapphire windows. In the future, the optical chamber system could be used alone for short-term research or be connected to a large high-pressure vessel to create a flow-through system for long-term research. Using the system, the swimming activity of Bosmina longirostris (Branchiopoda: Cladocera) was observed at different pressures. Swimming activity increased with increasing compression up to 30 MPa. During decompression, this activity reappeared when pressure decreased to 45 MPa and increased with further decreasing pressure.