BIO
Nudibranchs possess fantastic colors. They truly deserve to be called the “jewels of the sea” and should inspire jewelry designers. Only a few flatworms (planarians) can rival them in beauty, although these have a simpler body structure.
Ceratosoma trilobatum
Discovering a nudibranch you’ve never seen before is always an exciting experience. Nature’s boundless creativity, which has produced these unpredictable shapes and color palettes, is astonishing and stimulates our imagination. Fortunately, these animals are so diverse that the risk of seeing them all is slim… In the Mediterranean, for example, there are over 400 species of nudibranchs…
Nudibranchs (Phylum Mollusca, Class Gastropoda) belong to the order Opisthobranchii (gills behind the heart).
Given the great diversity of families, genera, and species, I will limit myself here to describing the main common characteristics :
- They have soft bodies, and most lack an external protective shell.
- These organisms possess a foot of variable shape and significant adhesive power; a small part of the foot can attach the animal to the substrate.
- The back may be smooth or adorned with numerous protuberances (cirri).
- The tactile organs are primarily the oral tentacles and the rhinophores (small horns located posteriorly to the mouthparts). These rhinophores, which are more or less retractable, are composed of small, lamellar layers (which act as sensory transmitters). Their great variability in shape, color, and number makes them a classic criterion for the systematics of these mollusks. Respiration occurs via gills located in the posterior part of the animal. These gills can retract into the mantle cavity at the slightest sign of danger. Most nudibranchs are carnivores that roam the seabed in search of small crustaceans, sponges, ascidians, and bryozoans, among others. Some, like the nudibranchs of the genera Elysia or Aplysia (sea hare), are strict herbivores. All these nudibranchs, regardless of their diet, use the same technique to feed themselves, namely the use of a veritable rasp (the radula) composed of numerous teeth mounted on a flexible muscle.
François Zylberman