Dutch fishermen, towing their trawl nets in the North Sea, near the Netherlands, have come across an extremely rare catch -- a two-headed porpoise.
Their sighting, described in a paper published in the Journal of Natural History Museum Rotterdam, is the first ever confirmed case of parapagus dicephalus in porpoise. Parapagus dicephalus, or partial twinning, occurs when an animal has a single body and two fully grown heads. So far, the porpoise is the 10th confirmed case of partial twinning in cetaceans, which include whales and dolphins.
"The anatomy of cetaceans is strikingly different from terrestrial mammals with adaptations for living in the sea as a mammal. Much is unknown," said author Erwin Kompanje, from the Erasmus MC University Medical Center in Rotterdam, in a report from New Scientist. "Adding any extra case to the known nine specimens brings more knowledge on this aspect."
The fishermen who stumbled across the anomalous creature took a few snaps of the porpoise before returning it back to the ocean. They thought holding on to such specimen is illegal. Nevertheless, the photographs taken by the fishermen were enough to confirm amazing discovery.
The researchers noted that the two-headed porpoise was a male and most likely to be dead when found by the fishermen. There are clear indications that the porpoise is a newborn that died shortly after birth. Some of the indications include the presences of hair and umbilical opening at the top of its head. Additionally, its dorsal fins were not yet erect and the tale had not yet stiffened.
Partial twinning or symmetrical conjoined twin can occur when two separate embryos fuse together or a zygote can only partially split during the early development process. Twins are very rare in porpoise. On average, a porpoise could produce only one offspring every one to two years.
Listed as "Least Concern" under the IUCN Red List, porpoise population around the world reaches nearly 700,000 with over half of them residing in the North Sea.
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