2023-06-23 11:00:08
Alien species or underwater beauty? No need to dive among the coral reefs of tropical seas to discover the splendours offered by the world of silence.
A shell opens and looks at you with its hundreds of elementary eyes, the role of which remains to be better understood. Olivier Dugornay, Ifremer, Provided by the author
The European scallop Pecten maximus, species (In life sciences, the species (from the Latin species, “type”) emblematic of the temperate waters of the English Channel, well known to gourmets for the flavor of its nuts , but also pilgrims for the symbolism it represents on the way to Santiago de Compostela, presents a singularity (In general, the word singularity describes the singular character of something or…) less known: implanted all along its mantle, it has a row of “ocelli”, elementary eyes of color (The color is the subjective perception that the eye has of one or more wave frequencies… ) Blue green.
They are not always easy to observe with the naked eye. Here, four of its magnificent ocelli surrounded by dozens of sensory tentacles are photographed in close-up, in the natural environment of our shell, whose valves are slightly ajar to facilitate breathing and filtration (Filtration is a separation process that allows us to separate… .) nutrients (phytoplankton). It has about 200 throughout its mantle (the organ (An organ is a set of tissues contributing to the realization of a function…) which surrounds the soft tissues of the scallop shell, and which secretes its outer shell).
See to move better?
The scallop is a bivalve mollusc which, unlike its cousins ​​oyster (The term oyster (or oyster) covers a certain number of groups of marine molluscs…) and mussel, is not attached to its support and has the ability to make short trips, thanks to active swimming: by suddenly snapping its two valves, a shell produces a powerful jet of water that allows it to quickly flee backwards in the face of a predator (A predator is a living organism that kills prey for food or for…). She can also, by arranging her mantle in an adequate way, advance gradually by producing two side jets of less power (The word power is used in several fields with a particular meaning:).
Few studies have been conducted on the visual abilities of the scallop and the role that these ocelli could have in its behavior.
Biologists have long considered that the ocelli of a shell allow it to capture the differences in luminosity in its surrounding environment, at best certain slow movements. Recently, the results of a study conducted by Israeli researchers have proven that the ocelli of the shell have a complexity (Complexity is a concept used in philosophy, epistemology (for …) remarkable in comparison to the human eye for example.
These elementary eyes thus have both a lens and a concave mirror, like a telescope, which focus the light sources (Light is all the electromagnetic waves visible by the eye…) on a double retina (The retina is the sensitive organ of vision. Of diencephalic origin, it is a…) allowing the creation of complex images. The first retina would react to relatively dark and moving elements, triggering defense or flight reflexes. The images produced by the second (Second is the feminine of the adjective second, which comes immediately after the first or which…) retina remain more enigmatic for the moment (The moment designates the smallest constituent element time. The moment is not…), but we know that they concern more the periphery (The word periphery comes from the Greek peripheria which means circumference. More…) of the field of vision: they could provide useful information to control and guide the movements of the scallop when it moves by hydropropulsion, or to allow it to evaluate the static characteristics of its habitat.
Many unknowns remain as to the real importance of the vision of scallops on their behavior. Can it allow active escape from predators? This would suppose a capacity to recognize these predators, which the ganglionic nervous system of the shell does not allow a priori…
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