Analysis of the seahorse genome provides insights into the genetic basis of the unique traits of these creatures, such as their equine body shape and male pregnancy. The study, published in Nature this week, highlights the evolution of the seahorse genome, suggesting a higher evolutionary rate compared with the genomes of its close relatives (such as pipefish or seadragons).
Seahorses have a number of remarkable features that distinguish them from other fish and animals. For example, they have a long tube-shaped snout with a small mouth and no teeth, and it is the males that carry developing embryos in a brood pouch. Byrappa Venkatesh and colleagues sequence and analyse the genome of the tiger tail seahorse, Hippocampus comes, to understand the components of the genome that contribute to these unique features.
Five genes that have been associated with hatching of embryos in other fish are highly expressed within the male brood pouch, the authors report. They also observe altered expression of some regulatory elements that they think might have had a role in the evolution of the seahorse’s body shape. In addition, lack of genes that may be responsible for producing mineralized teeth are thought to contribute to the snout that makes the head of H. comes resemble that of a horse. They also find that the absence of a gene called tbx4, a known regulator of limb development, in the seahorse lineage may have had a role in the loss of pelvic fins.