The photo shows a stainless steel pressure chamber which is used –among other methods- to induce ploidy in fish. This chamber is designed to place a pressure on fertilized eggs in a value as read in the meter gauge in “psi” which stands for pounds per square inch. The psi values often range from 6000 – 8000 even though most pressure chamber can produce up to 10,000 psi. The timing of exposing fertilized eggs to the pressure varies as the pressure is applied to newly fertilized eggs (in case of triploidy) or before the first cell division in case of tetraploidy induction. The duration as well the effective values of the pressure shock varies according to fish species and the induction strategy. The chamber is equipped with depressurized device to relieve the pressure when the shock duration ends.
Note: this photo was taken in 1993 for myself at the Southeastern Fish Cultural Laboratory in Marion, Alabama, USA during a research project on the induction of tilapia triploidy and tetraploidy.