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THE MAINE EVENT: FALL 2004 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 7 • Monday, September 20, 2004 Dispatch by Per Flood - Bathybiologica, Norway 
The wind calmed a little today, and we hoped for another two exciting deep water dives in the
underwater canyons on the continental slope on the south side of Georges Bank. Unfortunately, the
sea takes longer than the wind to subside, and our experienced submersible crew decided the
prevailing weather conditions were still unsafe to launch and recover the submersible. Hoisting 14
tons of sophisticated hardware and 4 passengers onboard the deck of a ship rolling and heaving at
the sea surface far from shore is not a trivial task.
In this interim some of us caught up on sleep, which was kept to a minimum after our last two very successful dives. Others found an opportunity for more experiments on a few animals that were still healthy. One of them was the beautiful hydromedusa Halitrephes maasi (picture shown in Dispatch 2). I examined one of its tentacles that had detached and observed two kinds of stinging cells (known as nettle cells or nematocysts); one type large and one type small. The larger type was organised like most 
nematocysts with a long tube coiled inside a capsule. The pressure inside this
capsule is high and when the nematocyst is stimulated, the coiled tube is extruded almost
instantaneously to about 100 times the length of the capsule.
Any organism coming close to the tentacle will be stung. During the discharge phase the tube is turned inside-out in a fraction of a second. It is like turning 30 yards of garden hose inside out from one end to the other in less than 10 seconds! Chemical fluids stored within the nematocyst capsule are the driving force for this eversion process. Furthermore, this liquid may contain highly toxic substances that can paralyse or kill prey in a matter of seconds. One of the toxins present in the nematocysts of the Portuguese man-o-war (Physalia physalia) a million times stronger than cobra toxin! The small nematocysts of the Halitrephes tentacle have a structure distinct from that of all previously known nematocysts (more than 30 distinct types are recognized!). 
Rather than being
coiled inside the nematocyst capsule, the tube curves around the outside of the capsule. Further, upon firing of these nematocysts, nothing happens to the coiled tube and only a short
pointed structure extends from the capsule. What is the function of this new kind of
nematocyst?
Well, so much for a windy and wavy day for one of us onboard R/V SEWARD JOHNSON II. Another, tiny, tiny piece in the big puzzle of nature has been brought to our attention. We don't have much precise knowledge about the weaponry of most cnidarians. Why do most of these animals have five or more types of nematocysts in their tentacles? 
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