Why do they lack teeth? And why do the males brood?
The tiger tail seahorse Hippocampus comes (pictured here) joins the ranks of animals such as humans, ostriches and yaks – it's had it genome sequenced.
Researchers form China, Germany, Singapore, the UK and US published their work in Science.
Seahorses have a number of remarkable features that distinguish them from other fish and animals. For instance, 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.
Genes that are associated with hatching of embryos are highly expressed within the male brood pouch, the authors report. They also observe a loss of some potential regulatory elements that they think might have had a role in the evolution of the seahorse’s body shape. In addition, H. comes lacks genes for enamel proteins that may have led to the loss of mineralised teeth, which is thought to contribute to the evolution of a tube-like snout and small mouth.
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.