Marine Invertebrates

Sea Urchin: The Animal That May Not Actually Age

The red sea urchin may live past 100 years with no measurable decline. A Caribbean cousin lost 98% of its population twice; in 2022, scientists found out why.

Nudibranchs: The Venom Is Stolen, the Regrowing Head Isn't

True nudibranchs steal their prey's stinging cells and fire them back as weapons. The sea slug that regrows its own head after losing it belongs to a different order entirely.

Sand Dollar: The Animal That Clones Itself to Survive

A living sand dollar is purple, not white, and its larvae clone themselves when they sense a predator. Juveniles even fill their gut with iron-rich sand as ballast.

Sea Cucumber: The Animal That Breathes Through Its Anus

A sea cucumber breathes through its anus, defends itself by firing its own organs at predators, and its digestion measurably buffers coral reefs.

Moon Jellyfish: NASA Sent 2,478 of Them Into Orbit in 1991

A 1991 NASA mission sent thousands of moon jellyfish into orbit to study human balance. A 2021 genetic study found the species everyone assumed was one is actually at least 28.

Limpet: The Snail With the Strongest Teeth on Earth

A 2015 study measured limpet teeth at up to 6.5 gigapascals, the toughest biological material ever recorded, beating spider silk and rivaling Kevlar.

Ribbon Worm: A 180-Foot Record Nobody Has Matched Since

A single 1864 specimen is the whole basis for the bootlace worm's longest-animal record; live specimens top out near 2 meters, and a relative taints oysters with tetrodotoxin.

Brittle Star: The Animal That Sees Without Eyes

A landmark 2001 study on brittle star vision was overturned in 2018, and a 2024 genome study ties their arm regrowth to how vertebrates heal wounds.