Not only male pregnancy. The seahorses also amaze and excel in their ability to prey: during most of the day the seahorses swim in the sea with their heads tilted down and close to the body. But when they notice the prey passing over them, they raise their heads with great speed and catch it.
Seahorses are considered particularly poor swimmers, but despite their relative slowness they manage to devour small and agile fish. In a new study by Tel Aviv University, the researchers were able for the first time to characterize the wonderful prey ability of seahorses and found that they are able to move their heads from bottom to top at a tremendous speed of 2 thousandths per second. The fast movement of the head is accompanied by a strong stream of water that sucks the small fish directly into the mouth of the horses.
The research was conducted under the leadership of Prof. Roy Holtzman and research student Corinne Jacobs from the School of Zoology at the George S. Wise Faculty of Life Sciences and the Steinhart Museum of Nature at Tel Aviv University. The study was published in the Journal of Experimental Biology.
The researchers explain that seahorses are fish endowed with a variety of unique features such as male 'pregnancy', square spinal vertebrae and of course the unique eating mechanism: during most of the day the seahorses swim in the sea with their heads tilted down and close to the body. But when they notice the prey passing over them, they raise their heads with great speed and catch it. According to Prof. Holtzman, when hunting, the seahorses turn their bodies into a kind of spring: they stretch an elastic tendon using the back muscles and use the neck bones as a 'trigger', just like a bow gun. The result is faster than the fastest muscle contraction anywhere in the animal world.
But until now it was not clear to science how the spring mechanism allows horses to actually eat. As anyone who has ever tried to catch a fly from a teacup knows, water is a viscous medium and the fish has to open its mouth to create a current that draws the prey in. But how do the horses coordinate between sucking the prey and moving the head?"
In their new study, the researchers from Tel Aviv University were able to characterize and quantify the movement of seahorses by photographing their attack at a speed of 4,000 images per second - and a laser system for imaging the currents in the water. This measurement showed that the "bow gun" system serves two purposes: moving the head and creating extremely fast suction currents, 10 times faster than fish of a similar size - which allows the seahorses to catch particularly elusive prey items.
The new measurements also help to shed light on the morphology of the different seahorses, which differ from each other in the length of their snouts. "Our research shows that the length of the horses' nose determines the speed of head movement and the speed of the suction currents," adds Prof. Holzman. "Evolutionarily, the horses have to choose - a small nose for strong suction currents and a moderate head lift or a long nose for fast head lift and weak suction currents. This choice is of course in line with the available diet: species with a long snout catch smaller and more agile animals and species with a short snout catch heavier and bulkier animals."
According to Prof. Holtzman, seahorses are not a special case of the impressive spring mechanism. In fact, seahorses belong to a family of fish with the appropriate scientific name Misfit Fish ("abnormal fish"), which includes species such as oboes, chess-heads and flutes.
"These fish are called that because of their strange shape, which allows the stretching of the body to spring. The big question is what is the evolution of the spring mechanism - how was it created and when did it develop. I hope that our new research will lead to further studies, which will help solve the riddle of spring fish".
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It's a shame you didn't attach a video :(