Hoping to discover why the unusual creatures are upright swimmers instead of horizontal ones, and why the male members experience pregnancy rather than the females, a group of researchers has successfully sequenced the genome of a seahorse species for the very first time.

In addition to these anatomical oddities, seahorses also lack tails, teeth, and pelvic fins, and their entire bodies are covered by bony plates – not to mention horse-like heads and a tail that they use to grasp onto corals and seagrasses to avoid being swept away by a current, said Reuters.

To better understand these unique creatures, scientists at Germany’s University of Konstanz and colleagues from China and Singapore sequenced and analyzed the genome of a species called the tiger tail seahorse. Their findings were published online Thursday in the journal Nature.

“As a seahorse biologist, it is terrifically exciting,” Tony Wilson, an associate biology professor at Brooklyn College in New York who did not take part in the study, told the Los Angeles Times. He went on to explain that the genome sequence could help scientists better understand how the unique traits of seahorses developed, and how they are expressed on the genetic level.

Findings may help explain lack of pelvic fins, male pregnancy

Seahorses originally diverged from other bony fishes during the Cretaceous period, roughly 100 million years ago, and researchers have long been puzzled by their unusual morphology and odd reproductive patterns, the Times said. While the authors caution that their analysis of the seahorse genome is in its early stages, they have already made some interesting discoveries.

For instance, they have learned that the seahorse genome lacks the genes required for the coding of enamel, which would explain why they lack teeth. In addition, the creatures appear to lack the genes that regulate the growth of pelvic fins. To test if this is why seahorses lack pelvic fins, they removed these same genes from a zebrafish, and found that this was indeed the case.

The research team also found gene duplications during the evolution of the seahorse, which may explain male pregnancy among these creatures. As they explained in a statement, when a copy of a gene is created, it can fulfill a new function, and in this case, the duplicate DNA might regulate the pregnancy by coordinating the hatching of embryos’ with the male’s brood pouch. Once their embryos hatch, genes activate to allow the newborn fish to exit the brood pouch.

The study also uncovered evidence that seahorse DNA and proteins evolved much more quickly than their closest relatives, such as sea dragons and pipe fish. They currently have no explanation for why this is the case, the Times said, but the authors said that their work will help scientists to better understand the genetic underpinnings of the evolution of these unusual organisms.

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Image credit: Thinkstock

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