Researchers Gain Insights into the Evolution of Seahorses

A team of researchers has just analyzed the genome of an odd animal—the seahorse. Seahorses, which are unique in many ways, have an especially unusual genome. The details are in a paper that was just published in the journal Nature.

Seahorses are odd fishes from the Hippocampus genus. They swim upright and use their unusual prehensile tails to grip onto kelp, coral, and other objects. They have bony plates for protection, instead of the usual fish scales, and they lack the caudal fin found in other fish. A more well-known trait (but even odder) is how they reproduce—the male is the one to give birth and care for the offspring. The female deposits eggs into his pouch and that’s the end of her involvement. The evolution of the seahorse has fascinated scientists for ages.

Scientists from around the world collaborated to analyze the entire genome of the tiger tail seahorse (Hippocampus comes). The team wanted to compare seahorses to other vertebrates to determine how an animal could evolve such a unique body type and lifestyle so quickly. After extensive genomic analysis, the researchers could already see that seahorses had evolved at a much faster rate than other fish species. Seahorses completely lacked genes that are found in other vertebrates, including the tbx4 gene. The tbx4 gene is responsible for fins in fish and legs in land-dwelling creatures such as humans. Seahorses completely lacked the gene, explaining the lack of caudal fins. They also lacked other regulatory genes; genes that are found in most animals but expressed differently from animal to animal to produce variation. In the case of the seahorse, the animals lost genes rapidly and quickly gained new traits such as the prehensile tail and bony plates.

The team’s findings provide new insights into the evolution of one of the world’s oddest animals, the seahorse. The animal’s genome provides evidence of very rapid evolution, partially due to the early loss of key genes found in other vertebrates. This allowed unusual traits to develop, resulting in the seahorse’s unique morphology.

REFERENCE

Lin et al. The seahorse genome and the evolution of its specialized morphology. Nature (2016).

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