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New Insights into the Language of the Oval Squid
Looking at the creatures in an aquarium, you may have noticed that most of the time they peacefully swim around in proximity to one another, but sometimes they do exhibit aggressive behavior. Exploring the body language related to these behavior patterns, a research team led by Professor Chiao Chuan-chin of NTHU’s Institute of Systems Neuroscience has made groundbreaking discoveries on the mechanism by which oval squid quickly change color and exhibit spots and stripes on their head, tentacles, and fins.
 
Their paper titled “Quantitative Analysis of Dynamic Body Patterning Reveals the Grammar of Visual Signals during the Reproductive Behavior of the Oval Squid Sepioteuthis lessonianahas been published in Frontier in Ecology and Evolution, and reports on their findings have also appeared on the science news websites EurekAlert! and Science Daily.
 
As stated in EurekAlert! “William Shakespeare wrote with a quill, Helen Keller liked her typewriter, and the oval squid prefers to use its body, when it comes to expressing love. But unlike these famous authors, the romanticisms of Sepioteuthis lessoniana were unknown, until now.”
 
Changing color faster than a chameleon
 
Prof. Chiao pointed out that because chameleons rely on endocrines to change their body color, they change color relatively slower. By contrast, cephalopods (including oval squids, cuttlefish, and calamary squid) change color more quickly, since they use their neural system to control the pigment cells on the surface of their body. Thus they can change body color and body surface patterns several times in a single second—the fastest known color change in the natural world. In the films taken during the research project, squid can be seen changing body color and pattern seven times in ten seconds.
 
While it was already known that oval squid (also called bigfin reef squids) change body color and body patterns, the details relating to these changes remained unknown. While studying the squid, Chiao’s students Lin Chun-yen and Tsai found that while engaging in such behaviors as parallel swimming, defending, competing, and mating, they quickly exhibit specific changes in appearance. The research team has summarized these changes into 27 body color components, each of which has a different significance.
 
Signs of victory
 
Lin, the first author of the paper and a doctoral student at the Institute of Molecular Medicine, said that normally the oval squid has a relatively light body color that doesn’t change very much. However, its appearance changes significantly when excited, as when males engage in fighting and when a female refuses to mate. For example, when males fight they exhibit dark black spots on the edge of the fins, and broken stripes sometimes appear on the head, tentacles, and body; moreover, the winner displays a body color which is darker than that of the defeated.
 
As for mating behavior, they found that when the male approaches the female from behind, his head and tentacles darken, stripes appear on the center of his body, and a dark band appears on the edge of his fins. At this time, if the female’s body color doesn’t change, this indicates that she accepts the male and is ready to mate. While mating, two dark eyespots appear on the male’s fins, and disappear once mating is completed. Interestingly, they found that these eyespots also appear during feeding.
 
Chiao pointed out that a particular body color component may appear in many different kinds of behavior, so a given component takes on a precise significance only in a particular situation, rather like the way in which a given word can have various meanings, only one of which applies in the context of a particular sentence.
 
Diving into hardship
 
Studying the language of squid may be interesting, but also has its share of difficulties. A licensed diver, Lin has spent lots of time in the waters off Taiwan’s northeast coast using an underwater camera to record the oval squid’s every move.
 
He said that two or three times during the research successive typhoons swept away all the squid eggs, and that once they were all eaten by a huge sea turtle. And to top it off, sometimes the underwater visibility was so poor that he couldn’t even see his own hand in front of his face.
 
A new approach to studying animal communication
 
Tsai used his expertise in large data analysis to find suitable quantitative methods for deciphering the visual signals transmitted by the oval squid. He said that analyzing twenty seconds of film required spending dozens of hours.
 
As an undergraduate Tsai majored in life sciences, but it was in his minor in electrical engineering that he learned statistical analysis, demonstrating the importance of interdisciplinary study.
 
Chiao pointed out that the results of the study were made possible by augmenting observation with comprehensive data analysis.
 
For Lin, one of the most interesting observations was that even though a group of squid is engaged in the same behavior, they don’t necessarily display the same appearance, leading him to wonder about individual communication styles, local language variations and other such issues awaiting future research.
 
Related findings on giant squid
 
Another research team led by Chiao has also studied giant squid (Architeuthis dux), and some of their findings have recently been reported in the New York Times. The report states that despite having eyes the size of a basketball, the giant squid’s optical lobe is relatively small. Scholars speculate that this may be due to the giant squid having relatively less need for such visually guided communicative behavior as camouflage and body patterning, since it lives deep in the sea, in contrast to such shallow water cephalopods as oval squid and cuttlefish.
 
"After all, when you live in near-total darkness, what you’re wearing does not really matter," said Chiao in an interview with the Times.
 
Only found in the deep sea, and strong enough to capsize a boat, giant squid are probably the source of legendary sea monsters, and are still something of a mystery to marine biologists. This is probably due to the fact that most of the giant squid seen by people are already dead, and usually consist of little more than a carcass floating in the water or a skeleton beached on the shore. But in January last year Taiwanese fishermen accidentally caught a giant squid in the waters off Yilan, providing scientists with a rare opportunity to examine a relatively intact specimen.
 
The largest giant squid ever measured was 13 meters long. The adult male caught near Taiwan was four meters long, with a torso about 89 cm long, and its eyes were 8 cm in diameter.
 
Huge eyes for detecting natural enemies
 
Why does the giant squid need such huge eyes? Chiao believes that large eyes can detect natural enemies, such as sperm whales, from a distance.
 
The New York Times report refers to a paper recently published in Royal Society Open Science titled “Mismatch Between the Eye and the Optic Lobe in the Giant Squid” authored by Chiao and his students Liu Yung-chieh and Liu Tsung-han, together with Dr. Su Chia-hao, Research Fellow Yu Chun-chieh from the Institute for Translational Research in Biomedicine of Kaohsiung Chang Gung Memorial Hospital.
 
Chiao pointed out that the study of the giant squid’s brain structure can help us to further explore the evolution of the nervous system of deep sea animals.
 
As soon as the giant squid was caught last year, Chiao and his students immediately took it to National Chung Hsing University for dissection and measurement. Chiao said that he is grateful to the Institute for Translational Research in Biomedicine at Chang Gung Memorial Hospital in Kaohsiung for providing the high-resolution nuclear magnetic resonance imaging equipment they used to analyze the giant squid’s optical lobes. Following the dissection, the giant squid specimen was sent to the National Museum of Natural Science for permanent preservation.
 

A research team led by Prof. Chiao Chuan-chin of NTHU’s Institute of Systems Neuroscience has recently discovered the mystery surrounding the mechanism by which the oval squid quickly changes its appearance. Another research team also led by Chiao has discovered that despite having eyes the size of a basketball, the giant squid’s optical lobe is relatively small. (Illustration by Chen Yin-peng.)

A research team led by Prof. Chiao Chuan-chin of NTHU’s Institute of Systems Neuroscience has recently discovered the mystery surrounding the mechanism by which the oval squid quickly changes its appearance. Another research team also led by Chiao has discovered that despite having eyes the size of a basketball, the giant squid’s optical lobe is relatively small. (Illustration by Chen Yin-peng.)


Schematic representations of the 27 chromatic body pattern components of adult oval squids.

Schematic representations of the 27 chromatic body pattern components of adult oval squids.

Changes in body color after mating.

Changes in body color after mating.

Changes in male’s body color while fighting.

Changes in male’s body color while fighting.

Lin Chun-yen of the Institute of Molecular Medicine, Prof. Chiao Chuan-chin of the Institute of Systems Neuroscience, and Tsai Yueh-chun of the Institute of Systems Neuroscience (left to right).

Lin Chun-yen of the Institute of Molecular Medicine, Prof. Chiao Chuan-chin of the Institute of Systems Neuroscience, and Tsai Yueh-chun of the Institute of Systems Neuroscience (left to right).

Male and female oval squids swimming in parallel.

Male and female oval squids swimming in parallel.

Lin using an underwater camera to film the oval squid.

Lin using an underwater camera to film the oval squid.

Despite having huge eyes, the giant squid’s optical lobe is relatively small. (Illustration by Chen Yin-peng.)

Despite having huge eyes, the giant squid’s optical lobe is relatively small. (Illustration by Chen Yin-peng.)

 

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