Under the surface of the seas, where sounds choke and words do not exist, some species have developed unsuspected forms of communication. Among them, the cuttlefish use their body as a real instrument of expression, combining precise gestures, changing motifs and vibrational waves. This tank language, long went unnoticed, begins to deliver its secrets thanks to the tools of modern ethology, revealing a complexity that evokes the communication systems of the most advanced vertebrates.
The study shows that the cuttlefish reacts to these signs when they are shown in video, but above all, they respond more frequently when the video is in the right direction, as if an inverted image lost its social meaning. This “mirror response” evokes imitation or gestural dialogue behaviors. Researchers see it as an intentional and structured form of communication, never described in these animals.
As Science Alert points out, this type of interaction recalls certain more familiar animal body languages, such as those of monkeys or birds, but expressed here in a marine and sprawling universe.
When water becomes a message vector in the tank language
The exchange is not limited to what the cuttlefish sees. He also involves what she feels. The wave movements of the arms create mechanical waves in water, perceived by specific sensory organs. In their experience, Cohen-Bodenès and Neri recorded these vibrations using hydrophones, then replayed them to other cuttlefish through aquatic speakers. Result: the cuttlefish responds more readily to the real signals than to their inverted or blurred versions.
This suggests that these gestures produce a recognizable vibratory signature, informing information. Two structures could be responsible for it. Statocysts, which allow cephalopods to detect movements and orientation of the body, and a form of side line similar to that of fish. These systems capture the low water fluctuations around the animal. The most fascinating is that this vibratory response does not seem instinctive or reflex. It is often accompanied by changes in colors, orientation or bodily attitudes which suggest an active interpretation of the message. For the first time, an aquatic gestural language is as tactile as it is visual.
The emergence of a multimodal language
The combination of gestures, body patterns and vibrations make up what researchers call a multimodal communication. This means that signals are perceived both by sight and by touch, as in the case of sounds in terrebrates. An inverted video or a vibrational signal played upside down lose their effectiveness. The cuttlefish seems sensitive to the temporal and directional structure of the message.
The study also shows that the cuttlefish produces these signs in a diversity of contexts – confrontation, hunting, exploration – but that they always follow recognizable patterns. This evokes a form of elementary syntax, where each gesture could mean something according to the sequence in which the cuttlefish express it. Even in not yet mature juveniles, some gestures appear spontaneously, suggesting that it is not a simple behavior learned, but perhaps a shared repertoire, specific to the species. By combining several senses at the same time, the cuttlefish multiply the expression channels to strengthen the scope of their messages.
Evolutionary convergence with the social languages of vertebrates
What strikes biologists is the similarity of this communication with certain behaviors observed in very different species. Researchers readily compare this form of submarine gesture language to that of certain social fish, frogs, or even primates.
Like birds of birds or human facial expressions, “Arm Wave Signs” follow a clear and recognizable structure. The stronger reaction in the face of authentic signals shows that the cuttlefish perceives more than a simple movement. They decode real information. This recalls facial recognition in humans, where an inverted face blurs our reading of emotions. In both cases, the brain treats signals in a specialized and sophisticated manner.
This amazing parallel between cephalopods and vertebrates evokes an evolutionary convergence. Very distant species have developed comparable visual languages. Each adapts to its environment, but follows similar constraints. The gestural language of the cuttlefish, as strange as it seems, perhaps illuminates the deep roots of animal communication.
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