SH 171 Summer-2020

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courtesy ella cedarholm

around the ship’s deck like “a fireball.” In 1849 T. H. Huxley wrote in his diary or the “beautiful Pyrosoma” that were “shining like white-hot cylinders in the water.” An English surgeon named Frederick Bennett left one of the most colorful published descriptions of pyrosomes. Bennett was generally not prone to absurd exaggeration, yet he seemingly could not help himself when it came to writing about pyro- common body to move around and For our part, we kept one of our somes. Like Péron, Bennett found thus have better access collectively largest pyrosomes in a bucket. By the them in enormous numbers in the to capture phytoplankton and then next day it was no longer clear, but equatorial Atlantic. had turned orange and The pyrosomes were more rigid, looking in “their zenith of and feeling more like splendor,” he wrote, a dog toy. The waters aggregating in such north of Aotearoa densities that the New Zealand, where whalemen could fill we sailed during those any number of buckthree nights, are faets with them and mous for exceptionthat the mass of pyroally large pyrosomes. Pyrosoma Atlanticum: published in Annales du Muséum d’histoire naturelle, 1804. somes created such a The longest we caught glow in the water that the animals excrete water and waste out their was about a foot long; our chief scirendered “all surrounding objects vis- common core. This collective filtering entist onboard told us that on a previible during the darkest night, and helps them move their body along, ous voyage in these waters, the ship permitting a book to be read on the allowing them to control a bit of their had sailed over pyrosomes bigger than deck, or near the stern-cabin windows vertical motion and even forward pro- boulders—so large that the crew of a ship.” pulsion. Each individual zooid has thought at first they were about to run Pyrosomes float freely at sea, what scientists believe to be cells with aground. Since Péron’s day, marine anywhere from at the surface to as bioluminescent bacteria within a pair biologists have since identified sevfar down as 3,000 feet. They are filter- of organs. The pyrosome’s famous eral different species of pyrosome, ing organisms, joined together in a bioluminescence has been recorded which include individuals that grow to as a range of blues, greens, and pinks. enormous lengths. In 2018, a few hunThe glow helps them attract phyto- dred miles to the south of where we plankton toward their collective body sailed, two SCUBA divers happened and perhaps communicate with their upon one of these giant pyrosomes fellow zooids to adjust their vertical that was more than twenty-five feet motion up or down the water column long. In 1969, even closer to our track, based on the movements of their food biologists found one that was about sources—usually in response to the thirty feet long with a diameter of sun—and perhaps to escape ending three feet! It’s enough to make a sailor run out of…er…glowing terms. up a snack for turtles and dolphins. Marine scientist Ella Cedarholm uses her headlamp to illuminate a recently caught pyrosome in the lab on board SSV Robert C. Seamans For more “Animals in Sea History” go to www.seahistory.org or educators.mysticseaport.org.

“Sea History for Kids” is sponsored by the Henry L. & Grace Doherty Charitable Foundation

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