The world's oceans teem with something like 700,000 to 1 million species, up to two-thirds of which biologists have never named or characterized [source: Appeltans et al.]. But even the species with which we are best acquainted -- the clams and trout we eat, the jellyfish we fear and the puffer fish that we fear and eat -- retain the power to surprise.
All of these unknown creatures underscore the challenges that marine biologists face, the most obvious of which is access. Perhaps a species dives too deeply or wanders off into the oceanic unknown for decades at a time. Possibly, it makes sounds too faint to pick up or only reveals its true colors within strange visual wavelengths. And of course, the complex interplay between human fishing, hunting and technology, and the fauna of the world's seas and oceans, provides its own unique issues. (Think redistribution of invasive species through vehicles of international trade, or the impact of boat engine sounds on some sea life.)
But the steady stream of new facts about species both familiar and strange testifies to the march – or swim -- of progress in the field. To help you get your feet wet, we've selected an Admiral's sampler of recent discoveries, and it won't cost you so much as a ride with a mad submarine captain. Enjoy.
Parents shudder to think of their children as aimless drifters, yet until recently that's what marine biologists thought was literally true of some sea turtle hatchlings. But when researchers from the National Marine Fisheries Service in Miami used tiny satellite trackers to follow the movements of small green (Chelonia mydas) and Kemp's ridley (Lepidochelys kempii) wild-caught turtles, they were in for a surprise. Compared to a control group of free-floating inanimate objects, the young turtles moved faster and along different paths [sources: Putman and Mansfield; Zielinski].
This finding, along with an earlier study of loggerhead (Caretta caretta) hatchlings, is changing how we view the life cycles of young sea turtles. After hatching, many sea turtles, including the species studied, spend several years unobserved on the open ocean, a mysterious interim that marine biologists call the "lost years" [sources: Mansfield et al.; Putman and Mansfield; Skwarecki]. Based on certain evidence, such as small turtles occasionally turning up where ocean currents would naturally carry them, scientist believed that juvenile sea turtles engaged in "passive migration" at the whim of the sea. These two studies show that at least three species influence their fates by swimming.
The Great Barrier Reef evolved over millions of years to support one of the most diverse collections of animals anywhere. But today its 7,700 square miles (20,000 square kilometers) of coral communities are threatened by sediment, pollution, crown-of-thorns starfish and shifts in temperature and chemistry [sources: ABC; UNESCO].
Now there's some good news, at least as far as coral trout (Plectropomus genus) are concerned. According to a 10-year progress report, the commercial fish have benefited significantly from a sixfold expansion of no-take zones begun in July 2004. The move, which upped the protected areas from 5 percent to nearly one-third of the study area, was controversial because some feared it would increase fishing intensity in nonprotected areas. Instead, trout in no-take zones grew beyond minimum catch sizes and, because larger trout tend to make more babies than smaller trout do, produced enough offspring to keep surrounding zones at break-even levels. Some evidence also suggests that reduced fishing around no-take zones helped coral recover because it reduced damage from fishing lines, which can scar coral and open it up to infection [sources: ABC; Milius].
Unfortunately, such programs might only work on individual commercially fished areas. In parts of the world where survival is a catch-as-catch-can prospect, poaching, loopholes and other regulatory challenges persist. Meanwhile, global warming remains the single greatest threat to reefs worldwide [sources: ABC; Milius].
Like sea turtles during their aforementioned "dark years," many young fish have long been regarded as passive creatures, floating where time and tide might carry them. And as with the turtles, researchers have begun to question that received wisdom. For example, when scientists involved in the Great Barrier Reef study we just mentioned tracked the movements of larval coral trout, they found that the baby fish could swim against the current and navigate by sun and smell back to their coral home [source: ABC]. Other fish larvae can control their vertical position in the water and find beneficial places to flap their fins [source: Milius].
Moreover, a study in the October 2014 issue of Biology Letters has revealed for the first time that one-month-old gray snappers (Lutjanus griseus) can make growls and knocking vocalizations that might aid them in schooling in the dark. A similar mechanism has been proposed for aiding adult fish in schooling [source: Milius]. Unfortunately, the discovery also demonstrates yet another aspect of life in the big briny that might be perturbed or even damaged by human activities, such as the sounds produced by boat motors.
An animal's adaptability is tied to its genetic makeup, but for a long time we've had a limited window into how this process works. It goes something like this: DNA is copied into RNA, which codes for particular proteins and lays out the proper amino acid sequence for building them. You can change how those proteins are expressed, says the model, but if you want different ones, then for the most part, you need different DNA. Editing RNA is possible, but rare and usually not important.
Well, don't tell that to squids and octopuses, both of which majorly edit their RNA, according to recent research. This tweaking enables the cephalopods to build proteins for which their DNA lacks a blueprint. In fact, it allows them to make several different proteins from identical strands of RNA [sources: Alon et al.; Baggaley].
Researchers suspect that such abilities might exist elsewhere in the animal world and could provide a more rapid response to environmental requirements than waiting for DNA mutations. At least one octopus study, published in the February 2012 issue of Science, bears this out. It reveals that Antarctic and Arctic species of octopuses use RNA editing to correct neural imbalances brought on by colder waters [sources: Courage; Garrett and Rosenthal].
Plumping up isn't the only protective option for a puffer fish. It also can defend itself via its onboard tetrodotoxin -- one of the most toxic poisons known. But unless we're actually eating fugu, as Japanese gourmands call it, it's the puffing that typically comes to mind. It's right there in the name.
Until recently, scientists thought that puffer fish accomplished their ballooning by "holding their breath" -- that is, by shutting down their gills and pulling in oxygen from the surrounding water using capillaries in their skin [sources: Diep; Zielinski]. It's an image in keeping with the fish's appearance -- the pursed lips, the wide eyes, the engorged Dizzy Gillespie "cheeks" -- but it also turns out to be a lot of hot air.
According to a study published in the December 2014 edition of Biology Letters, the puffery has more to do with gulping than gasping. It turns out that a puffer fish actually bloats itself by trapping large gulps of seawater in its stomach, then clamping the organ off at either end. Far from holding its breath, it continues to respire through its gills all the while, which is just as well, because the process costs the fish dearly in terms of oxygen consumption and is therefore quite tiring [sources: Diep; McGee and Clark; Zielinski].
To anyone who's ever compared a beached-and-bleached seashell to that of a living snail in the ocean, the ravages of age and weathering are clear. These blanching effects can frustrate fossil hunters, who must sometimes rely on color patterns to distinguish one shell from another.
But according to research by San Jose State University geologist Jonathan Hendricks, just because we can't see the patterns doesn't mean they aren't still there. Take the shells of ancient cone snails, for example. Under normal light, their bone-white forms are indistinguishable, but place them in ultraviolet light and they erupt in sublime swirls and polka-dot patterns not seen in their modern descendants. Hendricks used the technique to identify 28 species among a group of 4.8-million- to 6.6-million-year-old Dominican Republic shells, 13 of which constituted new discoveries [sources: Fessenden; Hendricks; Thompson].
Ultraviolet -- the same wavelength used in black lights -- has revealed other aspects of the biological world previously hidden to human eyes. Many scorpions fluoresce in it. Some butterflies use UV-visible patterns to lure mates, while the carnivorous pitcher plant species Nepenthes khasiana uses it as a beacon to lure ants to their deaths [source: Stromberg]. For paleontologists, UV light can hint at plumage patterns on feathered dinosaurs [source: Switek].
As for the shells, more work remains before scientists can determine why they fluoresce in UV wavelengths, a process that appears to relate to oxygen exposure [sources: Thompson].
Cows. They've been blamed for the Great Chicago Fire, for blowing up barns with their flatulence and for plunging towns into darkness by rubbing electrical poles [sources: AP; BBC]. But thanks to a genetic analysis of tuberculosis DNA taken from a trio of 700- to 1,000-year-old Peruvian skeletons, they might at long last be in the clear for a more serious crime: originating the bacterium that later jumped species to cause tuberculosis in humans. According to research published in the Aug. 20, 2014, issue of Nature, that dubious distinction now belongs to seals [sources: Bos et al.; Saey].
Actually, the pinnipeds didn't so much originate the disease as transport it to the New World. The new research suggests that TB originated in Africa about 4,000 to 4,400 years ago and produced seven strains, some of which jumped to animals and then later back to humans. The seal explanation is supported by the fact that ancient Peruvians used tools made from seal remains and depicted seals and seal hunting on their pottery [source: Doucleff]. The theory helps to explain how they could have become infected with TB when no land route to the New World existed at the time [sources: Bos et al.; Saey].
The thing about sinking structures offshore is that certain kinds of sea life love nothing better than a foundation, an anchor amid the sea's shifting tides where they can build, find food or just hang out. We've encouraged reefs to form by taking advantage of this fact, and opportunistic mussels and crabs have gravitated toward the shelter offered by offshore windmills' sunken bases for similar reasons [source: Zielinski].
Of course, where there's forage, there's bound to be foragers, as Deborah J.F. Russell of the University of St. Andrews in Scotland found when she and her colleagues used GPS devices to track the movements of harbor and gray seals (Phoca vitulina and Halichoerus grypus) near offshore wind farms in Europe. As described in the July 21, 2014, issue of Current Biology, they observed that 11 out of 200 seals made a series of beelines to each turbine, tracing out a clear grid pattern that matched the turbines' configuration and lingering at each "node" to look for food [source: Rosen]. Since the wind farms were somewhat recent additions, chances are good that the elite 11 were particularly pioneering pinnipeds [sources: Russell et al.; Zielinski].
The vast majority of cancers remain in our innards, turning our own bodies against us. We don't think of them spreading to other hosts like a blight or a disease. Yet, biologists have discovered at least two cancers that do exactly that: One threatens Tasmanian devils and spreads through biting, and another is transmitted sexually among dogs. Now, according to an article in the journal Cell, they've found a third, a leukemia-like agent that has been attacking soft-shell clams (Mya arenaria, aka steamers and little necks) from Maine to the Chesapeake for the past 40 years [sources: Dallas; Gorman; Metzger et al.].
Researchers have long known about the clam cancer, but have focused their search for a cause on environmental elements and, more recently, a possible virus. But when they examined the DNA of cancerous cells from clams across the region, they found something quite surprising. Instead of resembling the genes of their host clams as expected, the cancer cells were clones of a single genetic source, presumably some cancerous "clam zero" from which the cancer had initially escaped and spread [sources: Dallas; Gorman; Metzger et al.]. Such a mechanism is risky for the cancer, not only because its cells cannot long survive outside their host, but also because they must face a victim's immune defenses every time they spread [source: Gorman].
The researchers plan to look into similar illnesses that strike cockles, mussels and oysters to see if a similar marine metastasis affects them as well [source: Gorman].
Jellyfish have long been a source of concern for swimmers, fish farmers and any machine with an oceanic intake. But they've more recently become a headache for oceanographers, who must puzzle out why jellyfish blooms are on the rise, and how that rise threatens to upset the balance of life in Earth's oceans -- and that's just among the living [sources: Flannery; Gorman]. Because dead jellyfish apparently pose a problem as well: When large die-offs occur, it appears that their bodies just jelly up the ocean floor, where scavengers seemingly turn up their collective noses at them [sources: Gorman]. Or so we thought.
Thanks to experiments conducted by Andrew Sweetman of the International Research Institute of Stavanger and his colleagues, published in the December 2014 issue of Proceedings of the Royal Society B, we now know that scavengers such as crabs and hagfish actually chow down on jellies with at least as much relish as they do mackerel. This is important, because it means that jellyfish are an integral part of the carbon cycle, and not some kind of carrion cul-de-sac [sources: Gorman; Sweetman et al.].
So why the mix-up? It's possible that previous observations only caught mass die-offs and/or that observations took place in areas that lacked jelly-eating scavengers. In other areas, the rapidity with which jellyfish are eaten (around two hours, in the experiment) might have removed any contrasting cases before they would have been observed [sources: Gorman; Sweetman et al.].
HowStuffWorks looks at the phenomenon of half and half animals.
Author's Note: 10 Recent Breakthroughs in Marine Biology
This article was enormously fun. I only wish that I'd had more space to describe the methods used in some of these ingenious studies. I hope you'll have a chance to look some of them up.
As much as I enjoy reading about newly discovered species, I think I get an even bigger thrill from learning some new fact about a familiar creature or, better still, finding out that a long-accepted idea does not hold water after all. In researching this article, I found examples of all three.
More Great Links
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