‘Brainy’ octopuses teach camouflage to BGU team

Even though most creatures use some variety of camouflage, scientists know very little about the way it is created.

By JUDY SIEGEL-ITZKOVICH
Octopus 370 (photo credit: Zvika Livnat for BGU)
Octopus 370
(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 sea creatures.
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 images.
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.
Since 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 Methods.
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 timing.
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.
In 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 organisms.
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.