The ocean really is home to a wide range of remarkable creatures. One of them is the sea dragon - a member of the same group as sea horses and pipefish. And according to Clay Small, a research assistant professor at the University of Oregon, "Sea dragons are oddballs in a group of already oddball fish." So what exactly makes them stand out from the rest?
Protruding from the bodies of these unusual fish are thin, stem-like spikes with small, ruffly fins that resemble leaves on branches. Like their relatives, the sea horses, it's the males who become pregnant and carry the offspring. But that's not the only strange thing about these attention-grabbing creatures. Scientists have discovered that they're actually missing their ribs and teeth. So they decided to conduct a study that would examine sea dragons a little more closely, hoping to get to the bottom of these animals' missing body parts.
Their research found that sea dragons are missing a key group of genes that other vertebrates would normally have. These genes are responsible for directing direct the development of the face, teeth, and appendages, as well as parts of the nervous system. "There's a lot of interest in how malleable to evolution things like the head and face are," senior research associate Susie Bassham said. Thanks to the extreme evolutionary differences that sea dragons have managed to develop in a short period of time, they make great case studies for a question like Bassham's. The beginning of the branch that sea horses and sea dragons evolved from dates back about 50 million years - a fairly short time in evolutionary terms.
After sequencing the genomes of two sea dragon species, leafy and weedy sea dragons, researchers compared the genetic sequences to pipefish and sea horses, in addition to other bony fish like zebrafish and stickleback. Similar to pipefish and sea horses, sea dragons were missing a chunk of genes that guide development. Researchers interpreted this as a possible clue to the origins of their unique form. "We could see that the support structures for the leafy paddles appeared to be elaborations of spines, and then the fleshy appendages were added to the ends," Bassham says. "It lent evidence to the idea that these (ornaments) are evolutionarily derived from spines." Thanks to the ongoing research by these experts, we keep unearthing more of the secrets that lie in the deep waters of the ocean. Stay tuned for more!