The Ocean's Weirdest Creatures: 7 Animals That Break the Rules

The ocean is full of animals that seem to break the rules of biology. Some have extra hearts, some fight with slime, and one fuses permanently to its mate. Here are seven of the weirdest, each with a full story to read.

1. Anglerfish: A Mate for Life, Literally

In some deep-sea species, the tiny male bites the female and fuses to her, sharing her blood for the rest of his life. One female was caught with eight males attached. Read the anglerfish story.

2. Hagfish: Fights With Slime

A hagfish can release slime that swells in seawater and clogs a predator's gills, then ties itself in a knot to wipe itself clean. Read the hagfish story.

3. Giant Pacific Octopus: Three Hearts, Blue Blood

Two hearts pump blood through the gills, a third pumps it around the body, and copper makes the blood blue. Read the octopus story.

4. Pufferfish: Balloon, Poison and Sand Art

Pufferfish gulp water to inflate, many carry a toxin deadly to people, and one small species carves a two-meter sand circle to court a mate. Read the pufferfish story.

5. Mantis Shrimp: The Fastest Strike

Its club-like limbs strike at about 23 meters per second, strong enough to smash snail shells. Read the matchup.

6. Pistol Shrimp: A Bubble That Bangs

Its claw snaps shut so fast it creates a collapsing bubble, a loud bang and a flash of light. Read the matchup.

7. Sea Otter: Keeps a Rock in Its Pocket

Sea otters stash food and a favorite rock in skin pockets under their arms, then use the rock to crack shells on their chests. Read the sea otter story.

Frequently Asked Questions

What is the weirdest animal in the ocean?

Contenders include the deep-sea anglerfish, whose males fuse to females, and the hagfish, which fights predators with slime.

Why does an octopus have blue blood?

Its blood carries oxygen with copper instead of iron, which makes it blue.

Which ocean animal is the loudest?

The pistol shrimp's claw snap is one of the loudest sounds in the ocean.

Related Stories

• 10 Real Animals With Superpowers
• Anglerfish Mating
• Hagfish Slime

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Sources

• Natural History Museum: The Bizarre Love Life of the Anglerfish: anglerfish fusion
• Zintzen et al. (2011), Scientific Reports: Hagfish Predatory Behaviour and Slime Defence Mechanism: hagfish slime
• National Geographic: Pufferfish: inflating and toxin
• Kawase et al. (2013), Scientific Reports: Huge Geometric Circular Structures in the Reproduction of a Marine Pufferfish: sand circles
• Versluis et al. (2000), Science: How Snapping Shrimp Snap: pistol shrimp
• NOAA Ocean Today: Sea Otter Anatomy: otter pockets
• Wikipedia: Octopus: three hearts and copper-based blue blood

More true animal stories: From Paw to Tail Blog