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THE SEA OF CORTEZ Exploring Beneath Steinbeck's Wake MISSION DISPATCH 6 • 03/27/03 Edie Widder - HARBOR BRANCH Oceanographic Institution The ROV Tiburon is a technological marvel, manifesting a degree of complexity that seems at odds with its reliability. Today is the first day we've lost dive time to technical difficulties. It's 11 AM and the ROV is still on deck. Normally it's in the water by 6:30 AM and stays down until well after supper. But near the end of yesterday's dive an alarm in one 
of the pressurized electronics bottles signaled a problem. Repairs have gone on through the night and into the morning.
While the ROV crew is hard at work, the rest of us catch up on data logs or, in my case, web dispatches.
We have been exploring basins, vents and seamounts, always maintaining our emphasis on the midwater fauna. I miss the immediacy and three-dimensionality that submersible diving affords and especially the opportunity to observe bioluminescence with my own eyes, but I am reveling in this opportunity to explore the largest habitat on our planet - the midwater - for such extended periods of time. For once, there is no sense of hurry - no concerns about running out of battery power - so we can indulge in long periods of observation on a single animal. On one dive we came upon a giant medusa called Stygiomedusa gigantean. The genus name, Stygiomedusa, is derived from the river Styx and literally means medusa of the lower world. The species name, gigantean, refers to its size, which is impressive. Compared to the fragile transparent jellies that we're used to seeing, this giant seemed out of place with its dark pigmentation and arms undulating and rolling in the ROV-induced current, looking more like thick satin drapes than diaphanous jelly. Living within the folds of these drapes was a fish (15 cm for scale) that had found a place to hide in a world without hiding places.  We spent even longer observing this fragile ctenophore, Thalassocalyce inconstans, (pictured right) which literally means changeable sea-cup. Although we have seen many of these, we almost didn't recognize this one because it had its bell fully expanded in feeding mode. Inside the bell was a recently captured, but still very much alive euphausiid (krill). What made these observations so interesting was the behavior of the euphausiid. Bill Hamner, who has spent many hours observing both euphausiid and jelly behavior in situ, provided a running commentary on what we were seeing. This is another wonderful advantage of ROV observations - to have so many trained observers in the same room sharing knowledge and making suggestions for where to concentrate observations. Hamner pointed out how the krill was swimming in the center of the bell, carefully avoiding contact with the sides and not darting about as it would if it were out in the open. Later, when the ctenophore gradually deflated its bell and the euphausiid did make 
contact with the sides, it appeared dead, but Hamner claimed it was just playing dead. Sure enough, much later, when it was
being pulled toward the ctenophore's mouth, it struggled violently in a last ditch effort at escape - but to no avail.
The ROV is more than just a powerful tool for observation and exploration; it also permits the collection of even very fragile specimens. This is made possible thanks to these collection devices, called detritus samplers. Originally invented by Harbor Branch engineer Chris Tietze, it would be hard to overstate how important they have been to advancing the field of midwater biology. Collection is essential for full identification, including DNA analysis, and for laboratory investigations like my bioluminescence studies. This jelly, Paraphyllina, is one whose bioluminescence I've been studying. When disturbed it releases sticky luminescent particles that adhere to a predator. Like the exploding paint packets in stolen moneybags used to mark the money and the robber 
for easy identification, these glowing particles illuminate the jelly's attacker for easy capture by larger predators. These
particles are released at the slightest touch so if it weren't for the ability to capture a specimen such as this, virtually
untouched, it would be problematical to learn about its remarkable pyrotechnic defense.
The ROV is now repaired and back in the water. Because it got such a late start it will be a relatively short dive, only 6 hours, but that's still plenty of time to record a new behavior, discover a new organism and collect animals for laboratory study. 
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