What is it? A beaded necklace? Red blood cells? No, it’s the Portuguese Man o’War (Physalia physalis), magnified 30 times. Though it resembles a jellyfish, the Portuguese Man o’War is a siphonophore, a colony of organisms that work together. The sting of the venom in the tentacles’ nematocysysts is incredibly painful, though rarely deadly. This photo, taken by Alvaro Migotto of the University of São Paulo in Brazil, won 6th prize in the 2009 Olympus BioScapes Interational Digital Imaging Competition.
Notorious for its painful, powerful sting, the Portuguese Man o’ War has a gas-filled floating chamber that supports the tentacles, which bear sting cells. Shown are the pink batteries of stinging cells and a delicate muscular band responsible for the high contractibility of the tentacles.
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My colleague Megan Gambino visited the Smithsonian Tropical Research Institute earlier this year to watch coral spawn. A report appears in the December issue of the magazine, and she also blogged about the experience over at Around the Mall. We asked her if anything interesting got left out of her previous reports. Yes, lots, she replied, and wrote this:
This past September, I joined marine scientist Nancy Knowlton, of the National Museum of Natural History; her colleague Don Levitan, of Florida State University; and a crew of research divers on their annual coral spawning trip. Just days after the September full moon, a mass coral spawning happens at their study site, a 260-foot arc of reef about 20 minutes by boat from the Smithsonian Tropical Research Institute’s field station in Bocas del Toro, Panama, and each year, since 2000, they have been there to collect data.
Knowlton, a renowned coral reef biologist, has been called Dr. Doom for the grim, but realistic, picture she paints of reefs suffering worldwide. (Her husband Jeremy Jackson, also a prominent marine scientist, is Dr. Gloom.) But she has also been billed as a savior. Vanity Fair, in its May 2007 “Green Issue,” called her a “mind aquatic” that our future, and our lives, may depend on. Along with other marine scientists, Knowlton has been trying to help reefs survive by better understanding coral reproduction.
A close up view of a Montastraea franksi colony spawning (credit: NOAA)
Early in Knowlton’s career, the assumption was that most coral colonies picked up sperm and brooded embryos internally—and some do. But in 1984, Science published the first description of a dramatic mass-spawning event witnessed on Australia’s Great Barrier Reef. Around that time, research biologists were observing the phenomenon in the Caribbean as well. From this, scientists deduced that the majority of corals—called “broadcast spawners”—actually reproduce in this way. Many are hermaphrodites, meaning they release gamete bundles containing both eggs and sperm. But, unable to self-fertilize, they synchronize their spawning with neighboring corals. The more scientists study the annual orgies, the better they have become at predicting when they will happen. The corals appear to use three cues: the full moon and sunset, which they can sense through photoreceptors; and, most likely, a chemical that allows them to smell each other spawning.
Knowlton’s team has been monitoring three closely related coral species—all dominant reef builders in the Caribbean—called the Montastraea annularis complex. What they have found is that M. franksi, one of the species, spawns on average 100 minutes after sunset and M. annularis and M. faveolata, the other two, follow about 100 minutes later, typically five and six days after the September full moon. Over the nine years of the project, the researchers have spotted, flagged, mapped and genetically identified over 400 spawning coral colonies.
As with any long-term study, the scientists’ questions have evolved. At first, they wondered how the three species, spawning at or close to the same time, didn’t hybridize. Their lab tests show that of the three, the early spawner and one of the later spawners are reproductively compatible. But they have found that the hour and a half or so between the species’ peak spawning times is enough time for the gametes to disperse, dilute, age and effectively be rendered unviable. In fact, their data indicates that if corals spawn just 15 minutes out of sync with the majority, their chance at reproductive success is greatly reduced. The looming question now is, what will happen to fertilization rates as coral colonies become few and far between?
By the third of four nights of diving (and no spawning), the suspense was building. The divers playfully suggested playing Barry White as mood music and gorging, pre-dive, on aphrodisiacs like oysters and strawberries.
Around 7:25 PM, just as everyone was slinking into their wetsuits, sea worms called palolo worms began spawning around the boat. The worms break in half and the tail section swims to the surface and releases eggs or sperm in a cloud of bioluminescence.
“This is it,” said Knowlton. “Everybody’s in the mood for sex.”
The water got buggy and electric, and like clockwork, the coral colonies started spawning around 8:20, one triggering another triggering another. The tapioca-like gamete bundles, about two millimeters in diameter and containing about 100 eggs and one million sperm, lifted in unison, slowly drifting to the surface.
The dive team observed 162 different coral colonies set or spawn, and the next night, they saw another 189. Knowlton surfaced that final night, exhilarated. What did you think? She asked each of the divers. Amazing, huh? She didn’t want to get out of the water and grabbed hold of the side of the boat, arching her back, her eyes cast toward the sky. Even the stars looked like gametes.
Thomas Vignaud of Marseille, France took this photograph, labeled Young fish dart by a jellyfish in the sea, in the Mediterranean Sea in September 2007. With it, he won the Natural World Category of Smithsonian magazine’s 5th Annual Photo Contest.
Have you taken an amazing photograph? Hurry up and enter our 7th Annual Photo Contest. The deadline is Tuesday, December 1, 2009, at 2pm Eastern Standard Time (EST).
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Scientists from Britain and Japan used sophisticated techniques to study the feeding behavior of the black-browed albatross (Thalassarche melanophrys) at sea. A lot of useful information came out of this study, but the single item you will likely hear most about is a really cool photograph, taken by the albatross itself, of a killer whale.
It is difficult to study albatross because they fly hundreds of kilometers across open ocean, flying faster than a boat can sail, to find food. Since you can’t just follow them, and since their open ocean feeding area is very large, observing albatross feeding behavior can’t be done reliably.
The new study addressed this problem by using miniature digital cameras attached to the backs of four birds breeding at colonies on Bird Island, South Georgia in the Southern Ocean. The resulting pictures showed albatrosses foraging in groups while at sea to collect food for their chicks. The cameras included a depth meter and a thermometer. The depth information was intended to indicate when the albatross would dive underwater for food, and the temperature meter indicates when the bird is settled on the sea surface or dives into water.
The following diagram shows what these information resulting from an instrument-fitted albatross flight looks like:
Diagram of albatross flight, courtesy of PLoS One
The X-axis is time, showing that this particular flight that took over two hours. The squiggly line along the top indicates temperature and the vertical lines along the lower part of the chart indicate depth. The bird appears to make four dives and later on sits on the water for a while (indicated by the cooling down without a dive event). The camera took photographs on a regular basis, and the Xes in the diagram indicate a photograph with another organism in it, generally another albatross. This shows that the albatross tracked in this diagram dived and presumably fed in the vicinity of other birds. The X with the red circle indicates a photograph of special interest, this one:
Albatrosses following an orca. Courtesy of PloS One
Here you can see two birds, one higher and one lower than the bird with the camera, and the three birds together seem to be closing in on a whale. This is an orca, a.k.a. killer whale.
This image showed that the killer whale broke the surface and that three other albatrosses were also apparently following the whale. This image was, unfortunately, followed by subsequent images that were obscured by feathers. However, the rapidly decreasing external temperature suggests that the bird landed on the sea surface after the encounter with the killer whale…
The camera is small, weighing about 82 grams. Although the camera slightly changes the aerodynamic shape of the albatross, it did not affect the breeding success of the study birds. In all, over 28,000 pictures were taken with the albatross mounted cameras. According to Dr Richard Phillips from British Antarctic Survey (BAS), “These images are really interesting. They show us that albatrosses associate with marine mammals in the same way as tropical seabirds often do with tuna. In both cases the prey (usually fish) are directed to the surface and then it’s easy hunting for the birds.”
I’m Greg Laden, and I usually blog at here at Scienceblogs.com and Quiche Moraine. I’m a biological anthropologist interested in human evolution, the biologies of race and gender, human hunter-gatherers, science education and African prehistory. I’ve been asked to fill in here at Surprising Science for a couple of weeks, and I promise to try not to break anything while I’m here. On to my first post.
The Eastern Pacific black ghost shark. Photo courtesy of California Academy of Sciences
A new species of fish has been named from specimens collected over the last several decades off the coast of California. It is called Hydrolagus melanophasma, and will go by the common name “Eastern Pacific black ghost shark.” This is the first new species of cartilaginous fish to be described from California waters since 1947, and is a member of the Chimaeridae family. Technically, according to ichthyologist Doug Long of the California Academy of Sciences, Hydrolagus melanophasma is “a big weird looking freaky thing. They have some shark characteristics and they have some that are very non-shark.”
Chimaeridae is a family of fish related to sharks. Sometimes they are called ratfish. Sometimes they are called ghost sharks. Some have a venomous spine on their backs. They live in the ocean, usually quite deep, and the most recently discovered species in this family is gaining fame because it is said to have its sex organ on its head.
The ghost shark's tentaclum on its head is used to facilitate copulation with a female. It is not sufficient for reproduction. Photo courtesy of California Academy of Sciences
This “sex organ on the head” is actually quite normal for ghost sharks, though it is one of the big differences this sort of fish has with sharks. The feature in question is a tentaculum. A tentaculum is any of several sensory organs found on fish. In male ghost sharks the tentaculum is specially adapted as a grasping organ used during mating. So it is not the male’s penis, but rather, a grabby thing that the male uses to facilitate copulation with the female. So, referring to the ghost shark’s tentaculum as a “sex organ” on “its head” is a little like calling a finely chosen wine and just the right music a sex organ …. perhaps related to sex, but not sufficient for reproduction, anatomically speaking.
Hydrolagus melanophasma, was described in the September issue of the journal Zootaxa by a research team including California Academy of Sciences David Ebert (also with Moss Landing Marine Laboratories) and Douglas J. Long (also with the Oakland Museum of California) and Kelsey James, a graduate student at Moss Landing Marine Laboratories, and Dominique Didier from Millersville University in Pennsylvania.
The closest living relatives of the Chimaeras are sharks, and the Chimaera-shark split is probably about 400 million years ago, which is a long time ago by any standards. Chimaeras have cartilage instead of bone for skeletons, as do sharks. Chimaeras were once a very diverse and abundant group of species, and today are present in all oceanic waters though rare in any given locality.
The genus Hydrolagus means “water rabbit‚” and is so named because of its grinding tooth plates that resemble a rabbit’s front teeth. The term “melanophasma” means “black ghost” which is a refernce to the common term “ghost shark” as well as its dark, nearly black color. Hydrolagus melanophasma was originally collected as early as the mid 1960s, but went unnamed until now because its taxonomic relationships were unclear. This fish is found in deep water and is believed to range from the coast of Southern California, along the western coast of Baja California, and into the Sea of Cortez (Gulf of California). This species is known from a total of nine preserved museum specimens, and from video footage taken of it alive by a deep-water submersible in the Sea of Cortez.
The University of Cambridge Department of Engineering hosted a photography contest earlier this year, and the winners have just been announced. The photo above, Project Pebble, won first prize. Two engineering students, Ben Sheppard and Robbie Howshall, set out to design a low-cost, deep-sea photographic vessel (current vessels for taking pictures deep underwater are far from cheap) and came up with Pebble, which cost only £1800 (about $3000). The photo above was taken during pool trials. Pebble was deployed in the sea North of Scotland (59˚ 03.76 N 07˚ 13.17 W) on May 21. Sadly, when the researchers returned to the site the next day, Pebble was gone. They suspect that a fishing vessel picked it up accidentally.
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Golden jellyfish in Palau's Jellyfish Lake (credit: Michael Dawson, University of California at Merced)
Most of the organisms living in the oceans are tiny, but they have a big effect on ocean mixing, according to a new study in Nature. Bioengineers from CalTech investigated this effect in Palau by adding a fluorescent dye to water near jellyfish to see what would happen when the jellies swam through. To the scientists’ surprise, the dye traveled along with the jellyfish for long distances. Jellyfish and other marine organisms regularly migrate to the ocean surface during the day. Extrapolating from their experiment, the bioengineers calculated that the amount of mixing from this migration is as much as a trillion watts of energy, about equivalent to the effects of the winds and tides.
Earlier this year, I read Flotsametrics and the Floating World, by Curtis Ebbesmeyer and Eric Scigliano, about ocean currents, how they have influenced history, and human impacts on the vast seas. (We published an excerpt, “Borne on a Black Current,” earlier this year.)
Ebbesmeyer, an oceanographer, is perhaps best known for his work tracking bath toys and sneakers to map the ocean’s flow. But it was the chapters in which he and Scigliano described the acres and acres of plastic junk floating across the seas, washing up on distant shores by the ton and being consumed by wildlife, that I found most disturbing. And it’s not just the plastic that we toss away that’s the problem. Those bath toys and sneakers have come from container ships that lost their cargo. Other lost shipments are not nearly so innocent, Ebbesmeyer writes:
Greenpeace estimates that 10 percent of the 100 million tons of plastic produced each year worldwide ends up in the sea. That global production includes, by various estimates, 500 billion to 1 trillion plastic bags. It takes just one bag to choke a hungry sea turtle. If that 10 percent estimate holds for bags, then enough drift into the sea each year to kill all the sea turtles in the world thousands of times over. One shipping container holds about 5 million plastic bags, and I know of at least two such containers lost in the Turtle Gyre [in the North Pacific]. No one knows what happened to their 10 million bags. The shipping industry is proud that it’s reduced its annual loss rate from about ten thousand to two thousand containers out of roughly 100 million shipped each year. I tell them it only takes one to cause a catastrophe.
Captain Charles Moore, of the Algalita Marine Research Foundation, found the Great Pacific Garbage Patch during a 1997 yacht race. (Ebbesmeyer has tallied eight garbage patches in total: four in the Pacific, three in the Atlantic and one in the Indian Ocean.) Since then, he has worked to understand how the plastic influences marine life and to make people aware of the problem. He gave the Ted Talk above in February of this year. The pictures are gut-wrenching.
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