It may look like a deep-space photo from the early days of the Hubble telescope. But it’s actually a new – and very small – kind of life from the ocean, measuring about 2 microns across. The discovery is one of two fantastic but largely overlooked ocean discoveries reported in this week’s Science.
The hubbub comes from that little golden-orange flash nestled in among the green and blue. That’s fluorescence from a “phycobiliprotein,” a kind of protein previously known from the only distantly related cyanobacteria (the oft-misnamed and entirely non-algal “blue-green algae” ).
That flash of color in the picture is a real alga – a eukaryote, a creature more closely related to us than it is to bacteria. But having said that much, it’s not clear what kind of algae it’s related to. DNA tests indicate it has no obvious relatives, not among other exceedingly tiny plankton (officially, the “picoplankton”) or anywhere else in the plant or protist kingdoms. So the scientists did the taxonomic equivalent of shrugging their shoulders, and dubbed the new life form a “picobiliphyte.”
It seems it’s always the case that as soon as you discover something you realize it’s been there all along. Picobiliphyte DNA has now turned up in sea water samples from the Arctic Ocean, North Atlantic, English Channel, and the Mediterranean (though the cells were rarer in warmer water).
The second discovery was made deep inside these funky tubeworms (at left), and deep beneath the sea. Woods Hole Oceanographic Institution’s great magazine Oceanus has the story.
Tubeworms lead lives that are decidedly peripheral. They don’t have mouths or digestive systems. In undersea gardens around volcanic vents, the 6-foot-long tubeworms simply cling to the dark basalt and wave in the hot, dark currents.
They don’t really do much, at least by animal standards. Vivid red lips adorn one end, but it turns out they simply transport water and nutrients inside the animal, where symbiotic microbes do the hard work. In what seems a remarkable degree of interdependence, the tubeworm gathers raw materials, and the microbes make supper.
The news here is that at least some tubeworms contain microbes that can switch between two completely different ways of making sugar out of carbon dioxide. One method (a version of photosynthesis’s Calvin cycle) requires considerable energy to accomplish; the other method works on a shoestring, but shuts down when oxygen levels are high.
In the chaotic waters around vents, tubeworms are alternately buffeted by torrents of cool sea water and scalding vent water. Along with the temperature swings come shifts in available oxygen and other nutrients. By having both pathways available to them, the microbes can roll with the changes, keeping the nourishment coming.
It’s astonishing to me. What we’re talking about – the ability to turn the inorganic world around us into food – is the greatest evolutionary trick ever devised. Indeed, mounting evidence suggests that it was here, around age-old hydrothermal vents where nutrients and heat are plentiful, that life first sparked out of the primordial soup. Seems phenomenal enough to have one method for doing it, let alone one plus a backup.