Wonders Under the Sea

Three ocean creatures have surprised scientists with new discoveries of previously-unknown capabilities.

Deep-divers:  Devil rays are among the fastest deep-diving swimmers, scientists at Woods Hole Oceanographic Institute found (BBC News).  Previously thought to be surface dwellers, these members of the Mobula ray family surprised scientists when logging devices were attached to the fish (see photo in the article of a scuba diver attaching one with a polespear: it doesn’t harm the animal, but shows how big they are compared to a man).  The devil rays “plunge nearly 2km below the ocean surface, making some of the deepest and fastest dives ever observed in the sea.” Very few fish are known to dive that deep.  The record holder is a mammal, the beaked whale, that can dive almost 3km down.

How can their brains stay warm at such depths?  It’s been known for 3 decades that the brains of devil rays contain specialized tissue called rete mirabile, a sponge-like mesh of large and small arteries.  “It was a mystery as to why they had this system, which is a way of keeping brain activity high, even in a cold environment,” one researcher commented.  Now they know why; the fish need warmth when they speed down into the icy depths.  They’re also impressive migrators.  For the 15 months they were monitored, “Devil rays travelled up to 3,800km from the Azores in the North Atlantic” to the coast of Chile.

Another stunning photo in the article shows four members of a related ray, the flying bentfin ray, leaping high out of the water as if they are having fun.  In another article about rays, UC Santa Barbara described the work of Doug McCauley, who studies the giant manta rays at Palymra Atoll where they congregate in large numbers.  “There is very little known scientifically about manta rays,” McCauley said, who, working at UCSB’s Department of Evolution, Ecology and Marine Biology, seemed more focused on their ecology than their evolution.

Clam with a flash:  Where’s that disco light coming from?  It’s the disco clam, Ctenoides ales, featured on Science Daily.  A video on Live Science shows it in action, flashing its lights to a supplied beat (or watch a shorter clip on Nature News without the music and ads).  Science Daily reports how Lindsey Dougherty, a graduate student at UC Berkeley figured out how it works: “the mirror is actually a highly reflective, densely packed layer of silica spheres a mere 340 nanometers across never before seen in animals.”  Nature News agrees that this appears to be unique in nature as a light-flashing technique; it’s not bioluminescence, and it’s not photonic crystals.  The silica mirrors allow the clams to reflect the whole visible spectrum as white light.  “The researchers do not yet know what purpose the disco clam’s photonics serve.”

Whatever its purpose, it could be a trick worth learning. Other ‘animal photonics’ have inspired engineers seeking new ways to manipulate light, and C. ales might do the same. Dougherty is particularly impressed with how well the reflectors work in low light. “There could be biomimicry potential in low-light situations or in environments that are dominated by blue-green wavelengths,” for instance underwater, she says.

Octopus genius:  An expert on octopuses (that’s the correct plural form) spoke with National Geographic about the eight-tentacled cephalopods.  Author of the book Octopus! The Most Mysterious Creature in the Sea, Katherine Harmon Courage is clearly jazzed about her subject.  The octopus has a number of amazing traits that seem to defy its evolutionary classification.  For one, the octopus shows evidence of tool use.  It can solve mazes.  It is a master of camouflage.  And it has one of the most advanced eyes of any animal.

Speaking of the octopus eye, it is similar in many ways to the human eye, though far from any evolutionary relationship.  Courage, though, was not cowardly about affirming evolution achieved this unexpected convergence: “Our common ancestor was a sightless marine worm, so it’s fascinating to think that from this ancestor so many different types of vision and eye have evolved—and how our eye and the octopus’s eye are so similar.”  Evolution, in fact, is the source of her love for these creatures:

I just love that they’re so different from us but seem to be so complex and sophisticated. They have so much to teach us about evolution, about how their brains work, and I think it’s an important exercise for our brains to figure out.

She was clearly impressed with all she learned about the creatures.   One of her pet octopuses, named Billy, figured out within an hour how to open a child-proof jar.  Later, Billy remembered how to do it in minutes, indicating a good working memory.  The interviewer noted that some compare octopus brain power to that of dogs.  They’re playful and will make eye contact to check you out, Courage said in response.  “It has really opened my eyes to the possibilities of evolution.”

The previous entries on disco clams and devil rays did not mention evolution at all.

Not just slime:  Readers of Current Biology’s primer on Algae might be surprised to find out that the term “algae” is not strictly-defined group, but a catch-all category for any “organism carrying out oxygen-producing (oxygenic) photosynthesis that is not a ‘higher plant’.”  Given that broad definition, the diversity of algae is astonishing: everything from cyanobacteria (less than a micrometer) to diatoms (200,000 species) to kelp forests 60 meters long with 14 cell types.  Algae can be colored red, green, blue-green, brown, black, or transparent.  Dinoflagellates are considered algae.  So are the abundant foraminifera that leave shells in vast numbers.  Some use sexual reproduction; others are asexual.  Most grow in water, but some can survive in soil, and the algae that form symbiotic colonies with fungi can grow in the most harsh deserts.  Given this diversity, the word “algae” seems more a lumping term of convenience than a real taxon.

Algae deserve better than the slimy reputation they get, John A. Raven and Mario Giordano hasten to tell us:

Algae frequently get a bad press. Pond slime is a problem in garden pools, algal blooms can produce toxins that incapacitate or kill animals and humans and even the term seaweed is pejorative — a weed being a plant growing in what humans consider to be the wrong place. Positive aspects of algae are generally less newsworthy — they are the basis of marine food webs, supporting fisheries and charismatic marine megafauna from albatrosses to whales, as well as consuming carbon dioxide and producing oxygen.

We use algae for soil conditioning, Petri dish culture, and a source of vitamin supplements.  Algae are being studied as alternative energy sources.  Given that “half of global primary productivity (carbon dioxide assimilation and oxygen production)” comes via algae, we should respect them more.  And surely, anything that can create food from sunlight using the complex process of photosynthesis is really a champion in the global economy.

Philip Ball began Nature’s article began in just-so story format, “How the disco clam got its flash,” but failed to deliver a Darwinian tale.  Instead, he inquired “what purpose the disco clam’s photonics serve.”  Didn’t Darwin try to ban teleology from science?

The octopus lady didn’t explain how her evolved brain could figure out anything.  Did she ever consider that the thing an octopus “could teach us about evolution” is that evolution is wrong?  “It has really opened my eyes to the possibilities of evolution,” she said.  That’s what Darwin divination does.  It’s like LSD, a mind-expanding, imagination-promoting, escape from reason that causes brain damage.