  Numerous ingenious engineering designs and devices have been the product of
bio-inspiration. Bone, nacre, and other such stiff structural biological
materials (SSBMs) are composites that contain mineral and organic materials
interlaid together in layers. In nacre, this lamellar architecture is known to
contribute to its fracture toughness, and has been investigated with the goal
of discovering new engineering material design principles that can aid the
development of synthetic composites that are both strong and tough. The
skeletal anchor fibers (spicules) of $\textit{Euplectella aspergillum}$
($\textit{Ea.}$) also display a lamellar architecture; however, it was recently
shown using fracture mechanics experiments and computations that the lamellar
structure in them does not significantly contribute to their fracture
toughness. An alternate hypothesis$-$load carrying capacity (LCC)
hypothesis$-$regarding the lamellar architecture's functional significance in
$\textit{Ea.}$ spicules is that it enhances the spicule's strength, rather than
its toughness. From the ecology perspective the LCC hypothesis is certainly
plausible, since a higher strength would allow the spicules to more firmly
anchor $\textit{Ea.}$ to the sea floor, which would be beneficial to it since
it is a filter feeding animal. In this paper we present support for the LCC
hypothesis from the solid and structural mechanics perspective, which, compared
to the support from ecology, is far harder to identify but equally, if not
more, compelling and valid. We found that when the spicule functions in a
knotted configuration a reduced bending stiffness benefits its load carrying
capacity, and that for a wide class of materials that are consistent with the
spicules' axial symmetry, sectioning a cylindrical tube into an assembly of
co-axial tubes can reduce the tube's bending stiffness.
