Off the coast of Greece, an individual striped dolphin (Stenella coeruleoalba) has been spotted. While this is not unusual in itself, the reason this dolphin is making waves (pun intended) is due to a rather strange variation in the appearance of its flippers. The flippers on both sides of the animal look hooked, giving the appearance of thumbs.
Researchers from the Pelagos Cetacean Research Institute have seen the dolphin engaging in normal behaviors with its pod in the Gulf of Corinth, within the Ionian Sea between mainland Greece and the Peloponnese peninsula.
Striped dolphins are a fairly common species, with males typically 2.7 meters (9 feet) long and weighing around 158 kilograms (350 pounds), while females are 2.4 meters (8 feet) and 150 kilograms (330 pounds). They are a very social species and travel in large groups of as many as 100 individuals, known as pods. They are energetic, fast, and nimble through the water, and will even leap as high as 6 meters (20 feet) above the surface, according to the National Oceanic and Atmospheric Administration.
"It was the very first time we saw this surprising flipper morphology in 30 years of surveys in the open sea and also in studies while monitoring all the stranded dolphins along the coasts of Greece for 30 years," Alexandros Frantzis, the scientific coordinator and president of the Pelagos Cetacean Research Institute, told Live Science.
As for the cause of the unusual flipper, it is most likely a problem that arose during the genetic development of the dolphin in the womb.
Human and dolphin anatomy is remarkably similar when it comes to the wrists and hands. “Dolphins, their ends are exactly like ours, they have segments that compose the wrists, the segment that composes the metacarpal bone and the segments that compose our fingers,” said Professor Bruno Cozzi, author of Anatomy of Dolphins and veterinary anatomy specialist, during an interview with IFLScience.
“Their fingers come together in a unique order, with very tough connective tissue. In this case, one of the buds, instead of sticking together with the other ones, has remained separate, and this probably happens in the first to second month of fetal life. It is difficult to say which part without an X-ray,” continued Cozzi. "Some abnormality has happened during development, one in a million".
Cozzi is confident that the cause of the flipper variation is not a result of injury. “It’s genetic. How can I tell? Because with a trauma or injury it would only be on one side to cause the variation. It is on both sides, bilaterally on the dolphin, so it’s genetic.”
Cozzi wonders if the genetic trait will be passed on to any offspring the dolphin might have, but thinks it is unlikely: “It is most likely a recessive [trait], it's not dominant.” However if you were to see the same variation in the flippers [in the offspring], it would mean that a [trait] that has been buried by evolution as useless is coming back again, but it's absolutely not likely”.
Fortunately, Cozzi does not think the dolphin will suffer negative consequences as a result of the variation in flipper appearance. “Since they are not using their flippers in a prehensile way, [it] won’t affect the dolphin too much. Maybe slightly less performance in swimming.”
On a positive note the dolphin has been seen "swimming, leaping, bow-riding, playing" according to Frantzis, so is likely living a normal dolphin lifestyle and is not affected by its unusual flippers.