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Tuatara: Volume 11, Issue 3, September 1963

Incidence of Pyrosoma atanticum Peron off Oamaru

page 208

Incidence of Pyrosoma atanticum Peron off Oamaru

During May-June of This year Pyrosoma was plentiful about 20 miles off Oamaru; pelagically in water of over 50 fathoms. As concentrations of these colonies were disturbed by the propeller of the vessel, large areas astern were brilliantly lit by hundreds of iridescent blue-green lights. This occurred for some hours during the night on each occasion. The propeller disturbance appears to agitate these animals it has this effect on other phosphorescent species) and the greatest concentration of display was always immediately astern. A large plastic bucket of specimens was taken by dip-net. As each specimen was cleared from the water and carried inboard, it glowed and sparkled like iron at welding heat when taken from a forge. Most specimens were about 12 inches long — one being 18 inches and 2 1/2 inches in tubular diameter. After a few minutes the glow of the captured animals subsided but could be brilliantly revived by tapping the bucket smartly on the deck, when a halo of light would envelope the bucket and shine through the sides. They died tubular (not flat as usual) and changed to a delicate rose-pink when immersed in 5% formalin.