Historically, how could tubeworms and their other vent colleagues have spread to vents that were more radically isolated from each other? It turns out, there might be some handy stepping stones between vents that are more widely dispersed.
Have you ever caught yourself idly wondering, just what happens to whales when they die? Well, it turns out that there's something called a "whale fall," which refers to a dead whale sinking down to the bottom of the ocean. There, it becomes food. A lot of food. The microbes that tuck into the whale's soft tissue produce hydrogen sulfide. Sound familiar? That's the stuff those vent bacteria love to feast on. And the bacteria like to live in symbiotic bliss with tubeworms. In fact, studies have shown that whale falls have 10 species in common with vents [source: Shank]. Two of them are miniature versions of the giant vent tubeworms to which they're related. These little worms also live symbiotically with bacteria, and it appears they co-evolved with whales over the past 40 million years [source: MBARI].
Another stepping stone for chemosynthetic deep-sea fauna like tubeworms may be something called "seeps." These are areas in shallower waters where methane and hydrogen sulfide seep from the ocean floor, supporting a variety of chemosynthetic species. The tubeworms that live at seeps aren't the same as the ones that cluster around vents, but they share enough in common to make some researchers theorize that species could migrate back and forth between seeps and vents.
In the past few centuries, yet another stepping stone has been introduced: shipwrecks. As the wood from old shipwrecks decays, it produces the chemical nutrients those marine bacteria crave.
Taken together, whale falls, seeps and shipwrecks might help to explain how deep-sea critters like tubeworms survive and disperse themselves across the vast tracts of the ocean floor.