30-million-year-old Fossil Reveals Evolution of Suction Disc on Sharksuckers

The remoras, popularly known as sharksuckers hitch a ride on other marine animals by sticking to them using suckers located on their head. A 30-million-year-old fossil has revealed how the suckers evolved over the years.

The study was conducted by scientists from Oxford University and London's Natural History Museum who found that ancient remoras had these suckers on their backs. It was only later that these modified dorsal fins migrated to the head of the fish. Currently, all remoras have suckers on their heads.

Researchers have shown that ancient fish called Opisthomyzon is just outside the evolutionary tree of all living remoras of today. This fish had a primitive sucker construction that cannot be found any more in the modern remoras. Analysis of this ancient fish helped researchers uncover the evolutionary track of modern remora sucker.

"The remora sucker is a truly amazing anatomical specialisation but, strange as it may seem, it evolved from a spiny fin," said Dr Matt Friedman of Oxford University's Department of Earth Sciences, lead author of the report.

'In this fossil the fin is clearly modified as a disc but is found on the back of the fish. It enables us to say that fin spines on the back broadened to form wide segments of a suction disc. After the disc evolved, it migrated to the skull, and it was there that individual segments became divided in two, the number of segments increased, and a row of spines was developed on the back of individual segments," Friedman added, according to a news release.

The study is published in the journal Proceedings of the Royal Society B.          

Sharksuckers or remoras belong to the family Echeneidae and are found in all warm seas including Western Atlantic, Pacific Ocean and Indian Ocean. They can be spotted by the sucking dish that's located on the top of their heads. Remoras are slender and live off of scraps of food rejected by their host. These fish are sometimes used by fishermen to catch large fishes.