🛸🫀 Even if you don’t see it at the first glance, chiton have a well defined anatomy underneath the shell plates. There is a circulatory system with a heart, a digestive system, a nervous system, a reproductive system… The “head” is under the cephalic plate, that can be distinguished with its typical V-shape (left side of the 3rd panel).

👅🦷 On the anterior side, you can find the mouth and the radula, a special “teethed tongue” that chitons use to scrape calcareous algae of the rocks. Chitons also have a brain-like structure, in the form of a nerve ring located around the mouth.

🦶🪨 Just like other mollusks, they have a strong muscular foot to help them firmly attach to the substrate. It’s the equivalent of a very strong sucker! Try to remove a chiton from its rock, you will see!

🐚🧥 Did you know that mollusks shells are formed, repaired and maintained by a part of the anatomy called the mantle. In the case of our chiton, it’s called the mantle girdle.

😈🪲 This small isopod of the intertidal zone is 6 to 7mm long, and also called horned isopod. You can easily guess why!

🦷🦷 The name ‘bidentata’ (latin for ‘two-toothed’) comes from the two tooth-like projections on its back, which are unique to males of this species. It makes the pleotelson a key feature for the identification of the sex and the species. In 𝘋𝘺𝘯𝘢𝘮𝘦𝘯𝘦 𝘣𝘪𝘥𝘦𝘯𝘥𝘢𝘵𝘢 males, the 6th segment is longer and have this typical pointy shape.

⚧️⚧️ This is a great exemple of 𝘀𝗲𝘅𝘂𝗮𝗹 𝗱𝗶𝗺𝗼𝗿𝗽𝗵𝗶𝘀𝗺, that refers to differences in appearance, size, or other characteristics between males and females of the same species. Sexual dimorphism can be observed in many animal species, including mammals, birds, reptiles, fish, and insects.

🏊‍♂️🦶Uropods are paired appendages found at the rear end (posterior) of crustaceans, such as lobsters, crabs, shrimp, and isopods. Their structure and function can vary widely but they are typically used for locomotion and swimming.

👁️👁️The 2 small eye spots are not very developed and probably provide a quite basic vision. On the contrary, rhinophores – the two rolled antenna at the front of the head – are the main sensory organs of sea slugs.

👃💧Coming from the greek [rhino-] = nose, rhinophores can sense chemicals diluted in the sea water, like an aquatic sense of smell. They likely help the animals to locate food sources, predators, and partners of the same species.

⚧️🌀 Indeed, even if this sacoglossan species is a simultaneous hermaphrodite, the animals need to find a partner and act both as a male and female during cross-fertilisation. When they are done, the eggs are laid in a nice spirale on an algae, I hope to find one soon to show you!

🔰🫀 The two fleshy protrusionson each side of the body are called parapodia. On the inner side, we can see a network of dorsal vessels distributing the hemolymph – the equivalent of blood – from the heart to the entire body. This little guy has kept his parapods closed the whole time, but they sometimes extend to maximize the surface area, catch the sun’s rays and photosynthesize!

🔪🤕 Fun fact, a closely related species of sacoglossan (E.marginata) can perform an extreme form of autotomy. They can shed their entire body from the neck if they are attacked! The head is then sufficient to initiate a whole body regeneration and completely restore a functional body in no more than 18 days! Authors proposed that this amazing ability is facilitated by the endosymbiodic chloroplasts that provides energy independantly of food ingestion… I really wonder if Elysia viridis have the same surviving skills 🤔

🦐🌋The anatomy of the barnacle – as adults, represent a unique example of modified crustaceans, resembling a sessile “shrimp” affixed to rocky substrates. Their calcareous shell plates serves as both protection and anchorage.

💧🚪Sessile (fixed) animals in the intertidal zone have evolved strategies to combat desiccation between high tides, like these opercular plates that help them retain moisture. It’s all about survival skills!

➿🦶Ever wondered where the name 𝘊𝘪𝘳𝘳𝘪𝘱𝘦𝘥𝘪𝘢 comes from? It’s derived from the Latin words 𝘤𝘪𝘳𝘳𝘪𝘵𝘶𝘴 “curly” and 𝘱𝘦𝘥𝘪𝘴 from 𝘱𝘦𝘴 “foot”. Together, it means “curly-footed”, as a reference to the barnacle’s distinctive curled legs used in filter-feeding.

📚🙇 Charles Darwin wasn’t just about finches and evolution. He spent eight years studying barnacles (1846-1854), laying the groundwork for Cirripedia studies, and eventually influencing his groundbreaking theories of natural selection. Even the father of evolution had a barnacle phase!