Cephalopoda › Octopoda › Octopodidae
Common octopus
Up to 500,000 eggs
Its body holds about 500 million neurons, nearly comparable to dogs.
Field Guide · Chapter 17 of 29
Sea creatures
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Cephalopoda › Octopoda › Octopodidae
Greater blue-ringed octopus
Up to 10 cm, with arms
This small octopus makes a poison like the one in puffer fish.
Cephalopoda › Oegopsida › Ommastrephidae
Humboldt squid
Mantle up to 2 m
It flashes red and white across its whole body when other squid are near.
Cephalopoda › Nautilida › Nautilidae
Chambered nautilus
Can grow to 20 cm long
Its eyes have no lens, so they work like a pinhole camera.
Bivalvia › Ostreida › Ostreidae
Eastern oyster
Up to 50 gallons a day
Each oyster strains up to fifty gallons of water through its body every day.
Scyphozoa › Semaeostomeae › Cyaneidae
Lion's mane jellyfish
Bell up to 180 cm
Larger ones may trail tentacles as long as 30 m.
Anthozoa › Actiniaria › Actiniidae
Beadlet anemone
Up to 192 tentacles
It is the only sea anemone species that broods its young.
Echinoidea › Camarodonta › Strongylocentrotidae
Purple sea urchin
About 10 cm across
By the strictest count, this urchin and people share 7,700 genes.
Asteroidea › Valvatida › Acanthasteridae
Crown-of-thorns starfish
25 to 35 cm adults
Adults of this starfish can kill entire coral colonies.
Asteroidea › Forcipulatida › Asteriidae
Common starfish
Up to 52 cm across
A starfish can lose an arm and grow a new one.
Malacostraca › Decapoda › Portunidae
Atlantic blue crab
Up to 23 cm wide
A female blue crab mates only once in her life, at her final molt.
Malacostraca › Decapoda › Macrocheiridae
Japanese spider crab
3.7 m claw to claw
Its legs reach up to 3.7 metres from claw to claw, the greatest leg span of any known arthropod.
Malacostraca › Stomatopoda › Odontodactylidae
Peacock mantis shrimp
Punch over 80 km/h
A club-shaped smasher reported to throw the fastest punch of any living animal.
Malacostraca › Decapoda › Paguridae
Common hermit crab
Body up to 8 cm
In warmer parts of its range, a sea anemone often grows on its borrowed shell.
Demospongiae › Dictyoceratida › Spongiidae
Bath sponge
Down to 100 metres
Roman soldiers once padded their helmets with this sea sponge.
Polychaeta › Arenicolidae
Lugworm
Grows to 13 cm long
The coiled sand on a low-tide beach is made by a worm that is rarely seen.
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