🤔 🌱 The most likely hypothesis is that one of them reproduced asexually by 𝙞𝙣𝙩𝙚𝙧𝙣𝙖𝙡 𝙗𝙪𝙙𝙙𝙞𝙣𝙜. A bit inside one anemone (a bud) basically detached in the internal cavity to form a new animal, that was then ejected by the mouth!! Isn’t it amazing?!

Asexual reproduction or cloning is actually a common ability of sea anemones!

🚻 🤰 They can also reproduce sexually. Even if it is likely that one animal here is a female and the other a male… it’s impossible to tell from the external morphology! Similarly to asexual reproduction, this species (Actinia equina or prasina) has an internal development and would give birth to live young and not larvae like other anemone species. And yes, that means they can be considered viviparous, which is much less common in invertebrates than in vertebrates!

👶⁉️ But in the case of sexual reproduction, I would guess that more than one baby would have been produced… Any thoughts? Another hypothesis?

 Do you see the lump on the animal on the right?

It is a quite common isopod parasite of this squat lobster species, Pleurocrypta sp. (longibranchiata or galateae). It is hidden in the branchial cavity of our squat lobster, and feeds on its hemolymph.

Isopods of this family are all ectoparasites of decapods (shrimps, crabs, etc…), and represent  7.7% of all isopods species. There is more exemples of parasitic isopods around the globe, as you can see below in the picture from a review. 

If you don’t know what an isopod is, great news! I will introduce a common free-living species (non-parasitic) of our tidal pools very soon 🙂 

🪸🪨 Sea anemones are often considered as sessile or fixed animals. And at the beginning, I would just realize that they regularly changed position overnight. I had no idea that they moved that much!

😴🕑 If you look continuously at them, their movements are so slow that they are almost unnoticeable to the human eye.

⏭️🦶 But accelerated x120 times like in this video, it becomes very clear! They first detach or “pop” the foot, usually firmly attached to the substrate, and then use waves of contractions to awkwardly “walk” or crawl around, until they find another suitable location to attach!

Back in the lab in Switzerland, we had to prepare Artificial Sea Water (ASW), basically dissolving a mix of salts mimicking sea water. Now, the whole process is much much simpler 🤪

🌊 Did you know that seawater has a salinity concentration of about 35 ppt (≈ 3.5%).

🩸 For example, (mammals) blood has a salinity concentration of about 9 ppt (≈ 0.9%).

🌊 ↗️ 🩸 This makes Seawater hypertonic to blood because it contains a higher concentration of solutes!

ARTHROPODA

Ostracoda

Ostracods, with their weird clam-like morphology and too many legs, are surprising in so many aspects!

🌎🏞️ They are abundantly present in nearly all known aquatic habitats on earth, from the oceanic abyss to temporary inland water bodies or even semi-terrestrial habitats such as soils with leaf litter! Maybe it is because of their carapace with two valves enclosing the soft body, that protects the organism against the potential dangers of the aquatic milieu 🤔…

⏰🪨 For all of these reasons, ostracods are also the most common arthropods in the fossil record. Study of ostracods fossils are often used in paleoenvironment and paleoclimatic studies, who would have guessed?!

ECHINODERMATA

Ophiuroidea

⭐️🌟⭐️ Did you know that Brittle Stars are relatives of starfish? Yep, they belong to the same family! That explains why they also have 5 arms…

💪🔄 🦾 As you can see, these arms are very delicate, but guess what, they can fully regenerate! That probably explains why this guy have 3 shorter arms, indicating he might have lost them at one point…

😱🔪💪 And wait, there is even more! Brittle stars can also perform 𝗮𝘂𝘁𝗼𝘁𝗼𝗺𝘆, meaning they can voluntarily detach their arms as a defense mechanism. Talk about a handy escape plan!

🐍💪🐍  Brittle stars are 𝒐𝒑𝒉𝒊𝒖𝒓𝒐𝒊𝒅𝒔, a name derived from the Greek words 𝘰𝘱𝘩𝘪𝘴 (“serpent”) and 𝘰𝘶𝘳𝘰𝘴 (“tail”) perfectly describing their snakelike, scale-covered arms. I just love watching as they gracefully move away!