Doug Perrine / Knobby sea stars (Pentaceraster cumingi) aggregating on seabed, probably gathering for mating, Makako Bay, North Kona, Hawaii, Pacific Ocean.

Joel Sartore / Photo Ark / Indian red sea star (Fromia indica) portrait, The National Aquarium, Abu Dhabi. Captive, occurs in Indian and Pacific Ocean.

Alex Mustard / Blunt arm sea star (Pentaster obtusatus) skin detail, Bali, Indonesia, Java Sea.

David Fleetham / Close up view of five parasitic snails (Eulimidae) attached to the underside of a Knobby seastar (Pentaceraster cumingi), Hawaii, Pacific Ocean.

Sergio Hanquet / Necklace starfish (Fromia monilis) portrait, Ari Atoll, Maldives, Indian Ocean.

Sergio Hanquet / Necklace starfish (Fromia monilis) resting on coral reef, Ari Atoll, Maldives, Indian Ocean.

Sergio Hanquet / RF - Necklace starfish (Fromia monilis) on coral reef, Ari Atoll, Maldives, Indian Ocean. (This image may be licensed either as rights managed or royalty free.)

David Fleetham / Close up of skin on Knobby seastar (Pentaceraster cumingi), Hawaii, Pacific Ocean. Usually found below 30 metres.

Shane Gross / Underwater seascape showing Sunflower sea star (Pycnopodia helianthoides), Orange sea cucumbers (Cucumaria miniata) and Sea urchins (Strongylocentrotus sp.), Barkley Sound, Vancouver Island, British C...

Tony Wu / Female Cushion star (Culcita novaeguineae) spawning by climbing to top of reef to release eggs visible as cloud of tiny white dots. East China Sea, Kagoshima Prefecture, Japan.

Franco Banfi / Starfish shrimp (Zenopontonia soror) on a Panamic cushion sea star (Pentaceraster cumingi) close up, Espiritu Santo Island, Baja California, Mexico, Sea of Cortez.

Franco Banfi / Starfish shrimp (Zenopontonia soror) on a Panamic cushion sea star (Pentaceraster cumingi) close up, Espiritu Santo Island, Baja California, Mexico, Sea of Cortez.

Franco Banfi / Starfish shrimp (Zenopontonia soror) on a Panamic cushion sea star (Pentaceraster cumingi) close up, Espiritu Santo Island, Baja California, Mexico, Sea of Cortez.

Franco Banfi / Panamic cushion sea star (Pentaceraster cumingi) feeding on a dead eel on the seabed, Espiritu Santo Island, Baja California, Mexico, Sea of Cortez.

Sergio Hanquet / Blue starfish (Coscinasterias tenuispina) regenerating an arm, Tenerife, Canary Islands, Atlantic Ocean.

Lynn M. Stone / Ochre sea stars (Pisaster ochraceus) clinging to barnacle-encrusted rock at low tide, Lone Ranch Beach, Brookings, Oregon, USA. July.

Lynn M. Stone / Ochre sea stars (Pisaster ochraceus) on rock at low tide, Lone Ranch Beach, Oregon, USA. July.

Lynn M. Stone / Leather sea star (Dermasterias imbricata) on Rockweed at low tide, Lone Ranch Beach, Brookings, Oregon, USA. July.

Lucas Bustamante / Panamic cushion star / Cortez starfish (Pentaceraster cumingi) two arms reaching over rock, with two Galapagos sea slugs (Tambja mullineri) close by, North Seymour Island, Galapagos National Park, Pac...

Georgette Douwma / Composite image of echinoderms on black background. Top row from left: Featherstar (Crinoidea), Luzon starfish (Echinaster luzonicus), Mosaic cushion star (Halityle regularis). -Central row from...

Claudio Contreras / Panamic cushion sea star (Pentaceraster cumingi) on sea floor. Huatulco Bays National Park, Oaxaca state, Mexico, Pacific Ocean. November.

Claudio Contreras / Panamic cushion sea star (Pentaceraster cumingi) detail. Huatulco Bays National Park, Oaxaca state, Mexico, Pacific Ocean. November.

Alex Mustard / Detail of gills on the surface of a large Sun star (Solaster sp.), Browning Pass, Vancouver Island, British Columbia, Canada, Pacific Ocean.

Franco Banfi / Sea star, probably (Glabraster antarctica) on a rock, Antarctic Peninsula, Antarctica, Southern Ocean.

Franco Banfi / Estrella sea star (Labidiaster annulatus) outstretched on a pink rock, Antarctic Peninsula, Antarctica, Southern Ocean.

Franco Banfi / Estrella sea star (Labidiaster annulatus) outstretched on kelp, Antarctic Peninsula, Antarctica, Southern Ocean.

David Fleetham / Leather starfish (Dermasterias imbricata) portrait, British Columbia, Canada, Pacific Ocean.

Georgette Douwma / Severed arm of Porous starfish (Fromia milleporella) on black background, regenerating six arms, West Papua, Indonesia, Indo-Pacific.

Georgette Douwma / Ochre sea star (Pisaster ochraceus) on black background, Olympic National Park, Washington, USA, Pacific Ocean.

Georgette Douwma / Luzon starfish (Echinaster luzonicus) comet, regenerating new body from one of its arms as a process of asexual reproduction, on black background, Komodo National Park, Indonesia, Indo-Pacific.

Georgette Douwma / Luzon starfish (Echinaster luzonicus) comet, regenerating new body from one of its arms as a process of asexual reproduction, on black background, Komodo National Park, Indonesia, Indo-Pacific.

Henley Spiers / Common sunstar (Crossaster papposus) on a seabed covered with Common brittlestar (Ophiothrix fragilis), Shetland, Scotland, North Sea, UK. May.

David Fleetham / Catala's seastar (Thromidia catalai) portrait, Hawaii, Pacific Ocean.

Franco Banfi / Yellow sun seastar (Solaster endeca) and Dead man's finger (Alcyonium digitatum) on rock, Trondheimfjord, Norway, North Atlantic Ocean.

Franco Banfi / Common sunstar / Solaster (Crossaster papposus) in front of a kelp forest, Trondheimfjord, Norway, North Atlantic Ocean.

Franco Banfi / Common sunstar / Solaster (Crossaster papposus) on a rock, Trondheimfjord, Norway, North Atlantic Ocean.

Franco Banfi / Common sunstar / Solaster (Crossaster papposus) in front of a kelp forest, Trondheimfjord, Norway, North Atlantic Ocean.

Shane Gross / Painted sea star (Orthasterias koehleri) close-up detail of tufts of gills and spines surrounded by pedicellariae, Vancouver Island, British Columbia, Canada, Pacific Ocean.

Magnus Lundgren / Cushion star (Culcita novaeguineae), detail, Triton Bay, West Papua, Indonesia, Pacific Ocean.

Tui De Roy / Horrid sea star (Paulia horrida) on reef, Fernandina Island, Galapagos, South America, Pacific Ocean.

David Fleetham / An Elegant starfish (Fromia elegans) on hard coral, Fiji.

David Fleetham / Fisher's seastar (Mithrodia fisheri) on corals, Hawaii.

Sergio Hanquet / Red starfish (Echinaster sepositus), Tenerife, Canary Islands.

David Fleetham / Commensal shrimp (Periclemenes soror) camouflaged on Cushion starfish (Culcita novaeguineae) Philippines.

Alex Mustard / Orange sunflower star (Pycnopodia helianthoides) beneath a forest of giant bull kelp (Nereocystis luetkeana). Browning Pass, Port Hardy, Vancouver Island, British Columbia, Canada. Queen Charlotte Str...

Alex Mustard / Biscuit seastar (Tosia australis) on a sandy seabed. Blairgowrie, Mornington Penisular, Victoria, Australia. Port Philip Bay, Bass Strait.

Alex Mustard / Red and white starfish (Luidia maculata) crawls over the seabed. Sydney, New South Wales, Australia. South Pacific Ocean

David Hall / Leather star (Dermasterias imbricata), Browning Pass, Queen Charlotte Strait, British Columbia, Canada. April.

David Hall / Morning sun star (Solaster dawsoni), Browning Pass, Queen Charlotte Strait, British Columbia, Canada. May.

David Hall / Spiny red star (Hippasteria spinosa) Browning Pass, Queen Charlotte Strait, British Columbia, Canada. October.

Georgette Douwma / Translucent coral goby (Bryaninops erythrops) with parasite under gill, resting on Starfish (Asteroidea). Derawan Islands, East Kalimantan, Indonesia.

Franco Banfi / Red sea star (Echinaster sepositus), South Tenerife, Canary Islands, Atlantic Ocean.

Georgette Douwma / Luzon sea star (Echinaster luzonicus) regenerating a new body from severed arm. Tulamben, Bali, Indonesia.

Georgette Douwma / Luzon sea star (Echinaster luzonicus) regenerating a new body from severed arm. Tulamben, Bali, Indonesia.

Georgette Douwma / Luzon sea star (Echinaster luzonicus) regenerating a new body from severed arm. Tulamben, Bali, Indonesia.

Georgette Douwma / Severed arm of a Luzon sea star (Echinaster luzonicus) starting to regenerate a new body . Tulamben, Bali, Indonesia.

Georgette Douwma / Comet Luzon sea star (Echinaster luzonicus) regenerating new body from severed arm, covered with Comb jellies.. Tulamben, Bali, Indonesia.