Julia Sklar, reporter
(Image: Dave Johnson)
This spectacular headpiece isn't the latest head-turning
fashion in hats. Instead, this remora is sporting the feature that gives the fish its
nickname, "sharksucker": a sucking disc on top of its head, allowing it to
benignly attach itself to other sea creatures.
The disc's ribbed appearance gives a clue to its intriguing
origin: the sucker develops from the same larval
bones that grow into dorsal fins in other species, despite their drastically
different shapes on the adult fish.
By using a red dye to stain the bones of larval remoras, researchers were able to track the
growth of what would become the sucking disc. At the same time, they followed
the development of dorsal bones in a different kind of fish. They noticed that the
dorsal fins and sucking discs developed in exactly the same way in both animals,
up to a certain point.
The pivotal moment comes when the bones of the remora's dorsal
fin begin to expand and inch forward, towards the head. By the time the fish is 30 millimetres long,
the dorsal fin bones have become a fully formed sucking disc about 2 millimetres
long. Inside, the sucker keeps many structures in common with a dorsal fin, with
minuscule fin spines and supporting bones. However, the remora's bones underpin
movable slats that open and close to create suction.
Ralf
Britz of the Natural History Museum in London, who worked on the study, said the sucker reminded him of Linnaeus's observation of nature's
magnificent ability to recycle
useful parts.
"What keeps impressing me when I study the development of
some of the weirdest structures in the fish world is that natura non facit saltus, "nature does not make jumps", and even the
strangest anatomical modifications happen through small gradual changes in
development," Britz says.
In 2006, Britz was a member of the team that discovered the
world's smallest vertebrate, the Sumatran fish Paedocypris progenetica, which also flaunts
an unusual gripping fin.
Journal reference: Journal of Morphology, DOI: 10.1002/jmor.20105
Fishy origin of remora's shark-sucking hat
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Fishy origin of remora's shark-sucking hat
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Fishy origin of remora's shark-sucking hat
