(photo credit:Zvika Livnat for BGU)
Even though most creatures use any of a variety of types of camouflage,
scientists know very little about the way effective camouflage is created and
its characteristics. Cephalopods – the molluscan class that includes octopuses –
are considered the most developed, from an evolutionary point of view, of any
It is known that their flexible nervous system allows the
cephalopods to change the color and even the texture of their skin to adapt to
their environment. The existence of large numbers of sea predators is the
driving force selecting for the development of various defensive mechanisms and
behaviors, including camouflage. The best way to avoid becoming lunch is to make
sure that nobody else sees you.
But the cephalopods, which look like they
have a low IQ, are even more clever, according to findings by Ben-Gurion
University doctoral student Noam Josef, supervised by Dr. Nadav Shashar,
recently published an article on the subject in the journal PLoS One that
aroused much interest among scientists. The BGU team did their research at the
Eilat campus for marine biology and biotechnology research, along with
colleagues at the Naples Zoological Station, creating mathematical tools to
analyze photographs, the environmental parameters and the amount of information
collected to create a believable disguise.
The Israelis flew to the
island of Capri to photograph two local specimens – Octopus cyanea and Octopus
vulgaris – with their Italian colleagues. Each of the images was taken from
above, as if it were viewed from the level of a shark, and in gray tones
(because octopuses are color blind). From the photos, they chose a white
rectangle containing the cephalopod’s “head” without the eight legs. A computer
program compared that section to other parts of the picture, looking for similar
The most similar textures and shades on the octopus’s head did
not appear on the seabed near the octopus.
Instead, 10 of 11 of the
creatures adapted themselves to objects lying on the seabed such as corals,
rocks, odd bits of colored sand and algae spots.
An octopus that sits on
coral has to be camouflaged to avoid large fish swimming above, as well as eels
and other predators that attack from the sides, the team said.
enemies attack from different angles, they will view the octopus against
different backgrounds. Thus it is “logical,” they continued, that the creature
does not try to produce perfect camouflage on its skin. Even after it “dresses”
to “disappear,” sometimes they “err” and remain partially visible. The
environment of coral reefs is so complex that just adopting the main
characteristics of the objects can serve the octopus better than becoming
absolutely invisible, they said. The marine researchers discovered special
pigment cells in the octopus skin that helps them create camouflage. Some cells
reflect light while others disperse it.
But the team said that more
questions than answers remain. “What are the visual hints that these living
creatures use? How do octopuses suit their colors even though they are color
blind? What data is transmitted from the eye to the brain? And what does the
octopus really see? We are still far from completely understanding the
principles of [natural] camouflage. We must continue to search for pieces of
information, if we can find them at all.”
RETURNED AND QUOTED
Dr. Amit Tzur, a
Bar-Ilan University “Returning Scientist,” is one of a team of MIT and Harvard
Medical School researchers whose study on mammalian cell growth and size
regulation was recently published in the prestigious science journal Nature
An important area of Tzur’s research focuses on controlling the
growth of dividing cells, which double their size during their life cycle so
that at the time of division, the cell is twice the size it was at birth. This
process, known as cell growth, occurs with precision and amazing
Because the cells maintain their size from generation to
generation, it is likely that during the process of division and growth they
actually “speak” to one another.
For years, it has been known that in
single-cell organisms, such as yeast, there is an intracellular link that
synchronizes the division mechanism with the growth mechanism.
multi-cellular organisms, cell division and cell growth may be inspected
separately via signals emanating from outside the cell. For years it was thus
believed that there is no need for an intracellular mechanism that synchronizes
the division mechanism with the growth mechanism, similar to that of single-cell
Theoretically, it is possible to trace such a mechanism by
accurately measuring cell size during its lifetime and calculating the rate of
cell growth. But until recently, it was impossible to perform these measurements
in multi-cell organisms and, therefore, this question remained unanswered. Far
more complex is to monitor the growth concomitantly with the cell cycle
progression, so one can report the relationship among size, growth and the
cell’s milestones throughout its life cycle.
The study combined expertise
in cellular biology, computational biology and cutting-edge engineering to show
that mammalian cells, similar to single-cell organisms, have an ability to sense
their size and regulate cell division.
Since the size of the cell is so
vital to the functioning of the tissue to which it belongs, maintaining constant
cell size is critical – thus the importance of this mechanism. The discovery was
made in the framework of Tzur’s post-doctoral research at Harvard Medical School
and is a follow-up to an initial breakthrough. He and his research team are now
attempting to learn how this mechanism works in the cell and what its
implications are in normal and cancerous cells.
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