[Coral-List] Why the seahorse tail is square

Douglas Fenner douglasfennertassi at gmail.com
Fri Jul 3 01:07:11 EDT 2015

When it's hip to be square     in Science magazine

Most animals and plants approximate a cylinder in shape, and where
junctions occur (as with branches of trees or limbs on animals), those
corners are “faired,” meaning smoothly curved so that one surface grades
into the next (*1*). When living organisms deviate from the norm, there's
usually a good biomechanical reason: a clue to some specific problem that
needs to be solved. Among their suite of unusual characteristics, seahorses
possess a true oddity: a prehensile tail with a square, rather than round
or elliptical, cross-sectional shape. On page10.1126/science.aaa6683
<http://www.sciencemag.org/lookup/doi/10.1126/science.aaa6683> of this
issue, Porter *et al.* (*2*) report that there are distinct mechanical
advantages to being square. Using three-dimensional (3D) printing to
construct physical models, the team demonstrates that the multiplated
anatomy of the square seahorse tail shows greater resistance to mechanical
deformation than a similar model that has a round cross section.


not open-access, but the author's address is given.

based on the original article:

Porter et al  Why the seahorse tail is square.  Science

3D-printed models show that square profile seahorse tails have better crush
resistance and grasping ability than do circular ones.

Whereas the predominant shapes of most animal tails are cylindrical,
seahorse tails are square prisms. Seahorses use their tails as flexible
grasping appendages, in spite of a rigid bony armor that fully encases
their bodies. We explore the mechanics of two three-dimensional–printed
models that mimic either the natural (square prism) or hypothetical
(cylindrical) architecture of a seahorse tail to uncover whether or not the
square geometry provides any functional advantages. Our results show that
the square prism is more resilient when crushed and provides a mechanism
for preserving articulatory organization upon extensive bending and
twisting, as compared with its cylindrical counterpart. Thus, the square
architecture is better than the circular one in the context of two
integrated functions: grasping ability and crushing resistance.


Not open access, but the author's email is given

Cheers,   Doug

Douglas Fenner
Contractor with Ocean Associates, Inc.
PO Box 7390
Pago Pago, American Samoa 96799  USA

phone 1 684 622-7084

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website:  http://independent.academia.edu/DouglasFenner

blog: http://ocean.si.edu/blog/reefs-american-samoa-story-hope

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