MOLLUSKS as a phylum include snails and clams, squids and octopuses, opisthobranchs (nudibranchs), chitons, nautilus and cuttlefish. Most mollusks carry an external shell for protection, although some do not (such as the nudibranch, left below) or carry only a vestigial shell.
Spanish shawl  nudibranch, Flabellinopsis iodinea, Flabellina iodinea, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #00266, all rights reserved worldwide. Squid mating, Loligo opalescens, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02548, all rights reserved worldwide. Simnia and egg cluster on gorgonian, Delonovolva aequalis, Anacapa Island, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02556, all rights reserved worldwide.
Eastern Pacific Opisthobranchs, such as Flabellina iodinea, Spanish shawl nudibranch, Flabellinopsis iodinea, Flabellina iodinea, Image 00266 Squid, such as Loligo opalescens, Squid mating, Image 02548 Shelled mollusks, such as Delonovolva aequalis (a.k.a. Simnia vidleri), Simnia and egg cluster on gorgonian, Anacapa Island, Image 02556
MARINE ARTHROPODS include crustaceans (crabs, lobsters, shrimp and krill) and barnacles.
Pelagic red tuna crab, open ocean, Pleuroncodes planipes, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02247, all rights reserved worldwide. Hermit crab in olive shell, Pagurus granosimanus, Olivella biplicata, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #01033, all rights reserved worldwide. Krill, Baja California (Pacific Ocean), Thysanoessa spinifera, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #03117, all rights reserved worldwide.
Pelagic red crabs (Pleuroncodes planipes), Pelagic red tuna crab, open ocean, Image 02247 Hermit crab, Hermit crab in olive shell, Pagurus granosimanus, Olivella biplicata, Image 01033 Krill, Krill, Baja California (Pacific Ocean), Thysanoessa spinifera, Image 03117
CNIDARIANS (coelenterates) include jellyfish, anemones, corals and sea fans and gorgonians. They do not have true organ structures, having evolved just enough to develop tissues. Tentacles often surround the single body opening, which serves as both mouth and anus. As a phylum, cnidarians exhibit both asexual (budding) and sexual (via gametes) reproduction. Secreted cells named nematocysts are characteristic of cnidarians. These stinging cells are found in tentacles and on the surface tissue of the animal, and are used for defense and the capture of prey.
Proliferating anemone with attached juveniles, growing on kelp stipe, Epiactis prolifera, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #00573, all rights reserved worldwide. Orange cup coral, Tubastrea coccinea, Isla Champion, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #01858, all rights reserved worldwide. Hydromedusa with amphipod, open ocean, Mitrocoma cellularia, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02491, all rights reserved worldwide.
Bubbing juvenile anemones, Proliferating anemone with attached juveniles, growing on kelp stipe, Epiactis prolifera, Image 00573 Tubastrea, Orange cup coral, Tubastrea coccinea, Isla Champion, Image 01858 Gelatinous zooplankton, Hydromedusa with amphipod, open ocean, Mitrocoma cellularia, Image 02491
California Golden gorgonian in kelp forest, Muricea californica, Macrocystis pyrifera, San Clemente Island, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #01042, all rights reserved worldwide. Purple jellyfish, open ocean, Pelagia noctiluca, Guadalupe Island (Isla Guadalupe), copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #06210, all rights reserved worldwide.
Temperate Eastern Pacific gorgonians, colonial cnidarians, California Golden gorgonian in kelp forest, Muricea californica, Macrocystis pyrifera, San Clemente Island, Image 01042 Open ocean jellyfish, marine aliens, Purple jellyfish, open ocean, Pelagia noctiluca, Guadalupe Island (Isla Guadalupe), Image 06210
OTHER RIGHTEOUS AND COOL invertebrates we like to photograph include bryozoans, tunicates, hydroids and worms, genus Cypraea specimens (cowries) and genus Conus specimens.
Lightbulb tunicate, Clavelina huntsmani, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02542, all rights reserved worldwide. Feather duster worm, Eudistylia polymorpha, San Miguel Island, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #02544, all rights reserved worldwide. Glory of the Sea cone shell, gold form.  The Glory of the Sea cone shell, once one of the rarest and most sought after of all seashells, remains the most famous and one of the most desireable shells for modern collectors, Conus gloriamaris, copyright Phillip Colla Natural History Photography, www.oceanlight.com, image #08727, all rights reserved worldwide.
Cluster of lightbulb tunicates, Clavelina huntsmani, Image 02542 Feather duster worm, Eudistylia polymorpha, San Miguel Island, Image 02544 The famous Glory of the Seas cone, Conus gloriamaris, is historically one of the most sought-after and beautiful of seashells, Glory of the Sea cone shell, gold form. The Glory of the Sea cone shell, once one of the rarest and most sought after of all seashells, remains the most famous and one of the most desireable shells for modern collectors, Image 08727