A group of fishers off the coast of the Netherlands found a two-headed porpoise, marking the first time such specimen has ever been found. Scientists said upon hearing about the discovery that it is the first case they have heard of conjoined twin harbor porpoises.

The fishermen documented the moment and took pictures of the two-headed porpoise. Scientists noted that with a single body and two full grown heads, this is a case of partial twinning. They pointed out that the sighting is extremely rare.

Image credit: Henk Tanis / New Scientist
Image credit: Henk Tanis / New Scientist

The two-headed porpoise was thrown back into the ocean

This marks the 10th known case of conjoined twins that has been reported in cetaceans, a group of animals that includes dolphins and whales.

“The anatomy of cetaceans is strikingly different from terrestrial mammals with adaptations for living in the sea as a mammal. Much is unknown,” said Erwin Kompanje at the Erasmus MC University Medical Center in Rotterdam in the Netherlands, and one of the authors of the paper describing the discovery, according to New Scientist. “Adding any extra case to the known nine specimens brings more knowledge on this aspect.”

However, the scientists weren’t able to conduct any examination of the specimen, as the fishers who made the discovery returned the twins – which researchers believe were probably already dead when caught- to the ocean. They thought it would be illegal to keep such a specimen, but the photographs they took of it proved to be enough for the researchers to write the paper.

Image credit: Mirror
Image credit: Mirror

Kompanje noted he was devastated when he learned the specimen had been thrown back into the sea, as he does not expect to see anything like it again in his life.

“For a cetologist, this is a real horror,” he said, according to Miami Herald.

Conjoined twins may be more common, but they are never found due to vast size of the oceans

Kompanje said that they are almost confident that the twins died shortly after birth, due to the fact that their tail had not stiffened, which is necessary for newborn porpoises to be able to swim. Other signs that noted their age were a flat dorsal fin, which should have become vertical soon after entering the ocean water, as well as hairs on the upper lip that should fall out shortly after birth.

The researchers noted that partial twinning can happen in two ways. The first occurs when two initially separate embryonic discs can fuse together, and the other way occurs when the zygote partially splits during the early development process.

“Normal twins are extremely rare in cetaceans,” noted Kompanje, according to New Scientist. “There is simply not enough room in the body of the female to give room to more than one fetus.”

Kompanje added that is likely that most conjoined twins will go unnoticed because of the immense size of our oceans. He noted that conjoined twins will be more common than the 10 cases that are known to the date, but we are unaware of such cases because they are born at sea and are never found.

Source: New Scientist