During spring and summer in the Salish Sea, we often encounter thousands of these little floating hydroids. Commonly known as ‘by-the-wind sailor’, ‘sea raft’ or by their scientific name, ‘Velella velella’, each little ‘boat’ is actually thousands of individual polyps that are the preliminary stage of a small jellyfish. Each raft has a rigid ‘sail’ structure that acts as an airfoil that tends to sail downwind at a small angle – no tacking has been invented yet, so bad navigation is frequent. Sometimes things really go wrong and they all end up on shore, stranded in rotting beach piles that dogs love to roll in. As I mentioned, each of these, boat and sail, is a carnivorous colony of hydroids with stinging tentacles that hang down beneath the raft. These are used to sting passing plankton that the tentacles then pass over to the waiting central mouth that distributes food to polyps by small connecting tubes.

 

While each ‘raft’ is somewhat like a coral reef, these colonies of polyps are the first phase of a two-part life. There are different types of polyps in each ‘boat’, just like bee colonies. Some are feeders with reproductive parts, some are protective. The reproducers become thousands of tiny jellyfish over several weeks. For some reason, these young don’t seem to get captured by the hanging deathtraps beneath the raft. Like a coral colony, the polyps need a water environment but have figured out how to do that by simply living on the surface while clinging to bottom of a raft of their own making. The sail helps distribute them ocean-wide so they don’t need a shallow reef to cling to. I guess you might say they take their reef with them. Next time you see these floating by, gently pick one up and carefully view the underside where the real action is.

 

Larry Eifert paints and writes about the Pacific Northwest from Port Townsend. His large-scale murals can be seen in many national parks across America, and at larryeifert.com.

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