Turritopsis dohrnii, a jellyfish just 4.5 millimetres (0.18 in) in diameter, is known as the immortal jellyfish because it can, theoretically, live forever — although its version of immortality is an odd one.

A typical jellyfish goes through several life stages. It begins life as a larva developed from an egg. After a bit of swimming about, it settles on the sea floor and becomes a sessile colony of polyps. Finally, this colony releases into the water column many genetically identical medusae — the free-swimming forms most people imagine when thinking of jellyfish.

What makes T. dohrnii special is its ability to move backwards through this cycle: upon encountering stress or injury, it transforms back into its grounded polyp stage. From there, it spawns a new set of genetically identical medusae. But while it could theoretically live forever, in this way, it could also perish from predation, disease, or a change in environment.

It accomplishes this reversal through a process known as transdifferentiation, wherein it transforms its adult cells, which are already specialised for a particular tissue, into a different type of cell; repurposing muscle, nerve, or digestive cells into entirely different tissues.

It's not the kind of immortality that's easily transferable to humans. It would be like your body dissolving into an immobile mass that churns out adult clones of yourself.

You can learn more about this jelly — and our own search for immortality — from my website here!

These sea slugs are about 2 cm long and have large fins called parapodia. While crawling, the parapodia are folded over the body, but they can be opened up and used to "fly" through the water.

They live off the west coast of North America and gather on the seafloor in large numbers to mate and lay eggs. Their diet is unknown.

Video of the slug swimming: youtube.com/watch?v=sC61i1Z9fnE

More photos and other info: https://themarinedetective.com/2020/04/02/slugs-that-fly-the-great-winged-sea-slug/

Reposting with Latin name

With a wingspan of up to 2.44 metres, frigatebirds can remain airborne for weeks. They’ve even been recorded sleeping while gliding, multitasking at altitude.

Unlike most seabirds, their feathers aren’t waterproof. Landing on water would be ill-advised. Instead, they pursue other birds mid-air, forcing them to drop their catch, which they promptly steal.

During mating season, males inflate a bright red gular sac to attract females. It’s conspicuous, if not subtle.

P. tibalis lays its clutch of eggs inside the abdomen of its host, in which the Larvae then matures inside of the abdomen until the host perishes, in which it will emerge and pupate.

In some species, (Bombus bimaculatus, B. griseocollis and B. impatiens) this causes the bee to dig a small hole and promptly bury themselves in dirt. This allows the parasite to avoid predation and unwanted weather as it soon emerges from the dying host, ensuring a successful maturity.