Marine Arthropods

Phylum Porifera

Asymmetrical sponges with incurrent and excurrent pores (osculum); made of spongin fibers or spicules.

Spongin

Elastic protein fibers found in sponges.

Glass sponges

Sponges with silica or calcium spicules.

Phylum Ctenophora

Comb jellies with hollow body cavity, comb-like cilia, bioluminescent, no stinging cells.

Phylum Cnidaria

Jellyfish, anemones, corals; hollow cavity, blind gut, stinging cells (nematocysts).

Nematocysts

Stinging cells used for capturing prey and defense.

Medusoid

Free-swimming jellyfish form with bell and tentacles.

Hydrozoa

Man o’ War, sea nettles; colonial, tentacles with mouths, deep moderately toxic sting.

Cubozoa

Sea wasp, Irukandji; cube bell, deep very toxic sting.

Scyphozoa

Moon jellies, lion’s mane; cloverleaf top, pink color, mild sting.

Polypoid

Attached body form; mouth on top, usually stationary.

Anthozoa

Sea anemones and corals; polyp form only.

Sea anemones

Attached, can move if needed; symbiotic with fish, shrimp, crabs.

Zooxanthellae

Symbiotic algae in hard corals aiding reef growth.

Atoll

Old reef around sunken volcanic island; forms ring with lagoon; Pacific islands, Bermuda.

Phylum Echinodermata

Radial symmetry (5-part); tube feet; regenerate parts; marine benthic.

Sea stars

Echinoderms

Sea cucumbers

Benthic echinoderms with soft bodies.

Sea urchins

Spiny echinoderms; radial symmetry.

Sand dollars

Flat, burrowing echinoderms.

Crinoids

Feather stars; filter feeders with arms.

Phylum Mollusca

Soft body, muscular foot, cephalization, may have shell, eyes vary.

Polyplacophora

Chitons; 8 calcium plates; benthic algae eaters.

Gastropoda

Snails, nudibranchs; one shell or none; simple eyes; some venomous.

Nudibranchs

Gastropods without shells; may have cerata or venom.

Cerata

Projections on nudibranchs for defense or digestion.

Bivalva

Two-piece hinged shell; multiple simple eyes; filter feeders.

Mussels

Sessile bivalves; found in saltwater and freshwater.

Oysters

Sessile bivalves; saltwater only.

Clams

Mobile bivalves; dig with foot; live in FW or SW.

Scallops

Mobile bivalves; jet propulsion; saltwater only.

Cephalopoda

Brain, lensed eyes, chromatophores, arms with suckers, beak.

Nautilus

Cephalopod with external calcium shell.

Cuttlefish

Cephalopod with internal calcium shell.

Squid

Cephalopod with internal keratin shell.

Octopus

Cephalopod with no shell.