Times of the Islands Winter 2023/24

green pages newsletter of the department of environment & coastal resources
body and a hard outer shell. However, over the course of
their evolution, cephalopods lost this protective covering
in favor of more sophisticated “squishy” defenses, such as
crypsis, enhanced predator detection abilities (sight and
“smell”), and a complex nervous system. Cephalopods
do not have the rigid system of either internal or external
hard structures (bones or exoskeletons) that we and
many other animals use to get around. In human bodies,
our bones work together with our cartilage, muscles,
ligaments, and tendons to produce movement. The muscles
are attached to the rigid skeleton which provides
anchor points and support against which muscles can
push and pull. Octopods, by contrast, lack this support,
and instead utilize the pressure created by the fluid-filled
tissues inside their bodies to provide support for limb
movement.
Instead of bones or an exoskeleton, octopods are
composed almost entirely of soft muscle and tissue. The
muscles of octopod arms are organized into two groups
which perform opposing but complementary actions to
produce movement: While one group of muscles contracts
to provide force, the other group relaxes, causing it
to elongate and stretch, thus causing limb extension. The
general lack of hard parts in their bodies allows octopods
a wider range of motion than other species, since they
are not limited by the range of motion of a joint, but can
bend a limb almost anywhere along its length. Moreover,
the lack of hard parts in the octopod body (except the
beak) gives them the ability to squeeze through any gap
or hole in the substrate that is wider than that beak.
So, if they don’t have any rigid structures, how do
octopods use their limbs to walk or run? Rather than utilizing
bendable limbs with a joint like vertebrates and
arthropods do, octopods use either a smooth continuous
rolling motion along the length of two arms, or alternate
between a stiffened LIV and RIV. In the algae octopus,
coconut octopus, and sand octopus, bipedal locomotion
is achieved by the octopod rolling backwards along the
rearmost pair of arms (IV), while the common octopus
“hops” backwards on two arms of the same side, such as
RIII and RIV or LII and LIII.
Stepping into the light:
Discovering bipedalism in other octopods
Bipedal locomotion has now been documented in four
genera of octopods living in three ecologically-distinct
regions: the Indo Pacific, the Mediterranean, and the
tropical western Atlantic. One of these was discovered
recently by students and scientists at the School for Field
Studies Center for Marine Resource Studies (CMRS) on
South Caicos in the Turks & Caicos Islands in the Fall of
2021.
The research team (nicknamed “NoctoSquad”)
“stumbled” upon this fascinating behavior while filming
Callistoctopus furvus for a directed research project on
octopus foraging and skin patterning. In these video
sequences, three C. furvus can be seen “walking” bipedally
using mainly arms LIV and RIV on fifteen separate
occasions from anywhere between one and a dozen steps.
While doing so, the octopuses turn brown and engage in
the flamboyant display, causing them to resemble strands
of brown algae floating nearby. Recognizing the importance
of the first sightings of this behavior in this genus
and species of octopus, faculty and staff of the CMRS
published their observations in the Journal of Molluscan
Studies. Their observations were also notable in that the
individuals that engaged in this behavior were distinctly
larger than was thought possible for bipedalism to occur
in octopuses.
Bipedalism is likely even more widespread among
octopods than currently recognized. More observations
of octopod behavior in the wild are needed, especially as
new species of octopods are discovered or reclassified
every year. (Currently there are around 300 species.)
Formal research is critical to this effort, but so too is
“community-” or “citizen-” science. Anyone living in proximity
to an ocean can grab their mask, fins, and camera
and non-invasively (no touching!) document cephalopods
or other marine animals in their native habitats, no credentials
needed. So, get out there and explore! a
This article was originally published on OctoNation.
com, https://octonation.com/bipedal-locomo-
tion-two-legged-walking-in-octopods/?fbclid=IwAR2L-
Hjf5Sf9tsHy5p_9HI04-zZlTFvvcsbN-2-XZbzgtGKfTFY-
9JrEGHwFc.
For detailed article references or more information
about The School for Field Studies, contact Director Heidi
Hertler on South Caicos at hhertler@fieldstudies.org or
visit www.fieldstudies.org.
36 www.timespub.tc