There's more than a twist to this tail. One of the ocean's most strangely shaped creatures is even more special than we knew. Seahorses have tails that are paradoxically rigid and flexible at the same time. Now we have insight into how they have such contradictory characteristics.
Dominique Adriaens of Ghent University in Belgium and his colleagues were fascinated by the way seahorses anchor themselves by wrapping their tails around vegetation, as shown in the image above. Despite being covered in armour, the tip of the seahorse tail remains flexible enough to unwind itself after grasping an object, as shown in the video (top).
The team created a 3D computer model to reconstruct seahorse tail movement so they could analyse how specific tisses and bones contribute to grasping and different degrees of bending.
A close-up from one of the simulations (shown below) depicts the backbone in purple and consecutive sheets of connective tissue, which supports and connects other tissues, in different colours on top. The model reveals that each sheet of tissue stretches across many vertebrae in the tail, something that has been seen only in seahorses. It is this support of several vertebrae without fixing them firmly together that might both allow flexibility and encourage rigidity.
Surprisingly, the team says, tails of different species of seahorse show greater variation in anatomy than expected, despite having the same bones and muscles.
A better understanding of the appendage could help develop tough, flexible armour or slender grasping robots.
The work was presented today at the annual meeting of the Federation of American Societies for Experimental Biology in Boston, Massachusetts.
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