Marine Invertebrates Diversity & Relationships

Marine Invertebrates Objectives:

For six of the marine invertebrate phyla (Porifera, Cnidaria, Echinodermata, Mollusca, Annelidia, Crustacea):

Describe the key characteristics of the phylum.
List examples of organisms in the phylum.

Whether you are exploring a tide pool along the coast, snorkeling in a coral reef, or setting up a saltwater aquarium at home, marine invertebrates are the diverse and attention-grabbing animals of ocean habitats.

This video introduces marine invertebrates you are likely to encounter.

Select the tab of each invertebrate phylum for additional information

Poriferans

Phylum Porifera

Porifera (pronounce: pore-if-er-a) are commonly called the sponges. These are structurally simple animals with no distinct organs. Porifera means “pore-bearing,” and the pores are openings through which water and the microorganisms they eat enter, and wastes leave.

Phylum Cnidaria

Organisms in Phylum Cnidaria (pronounce: nigh-dare-e-ah) include the corals, hydras, jellyfish, and anemones. Some cnidarians are single organisms, others are colonies of many small organisms. Cnidarians have cnidocytes (pronounce: nigh-doh-cites), stinging cells that can stun prey or a potential predator. These cnidoctes are typically at the end of tentacles that surround the mouth.

Phylum Echinodermata

Animals in Phylum Echinodermata (pronounce: ee-kine-o-derm-ah-tah) generally have a spiny surface, echinoderm means “spiny skin.” All echinoderms have small and flexible tube-like feet for movement. Echinoderms include sea stars, brittle stars, sea urchins, sand dollars, and sea biscuits.

Phylum Mollusca

Animals in Phylum Mollusca (pronounce: mul-usk-ah) are animals with soft bodies (mollusk means soft), a muscular foot for locomotion, a mass of internal organs, and a heavy tissue called the mantle which can in many species produce a hard shell. Mollusks include snails, slugs, nudibranchs, clams, limpets, squid, and octopuses.

Phylum Arthropoda

Organisms in Phylum Arthropoda (pronounce: arth-rah-pod-ah) are animals that have body segments and jointed appendages (legs and antennae). The word “arthropod” means “jointed feet.” Marine arthropods include shrimp, crabs, hermit crabs, barnacles, amphipods, and krill.

This is an alternate view of the six commonly encountered Phyla of marine invertebrates.

These are photos of a few of the species we’ve kept in our tanks.

These “sexy shrimp” as they are called in the pet trade, communicate through their movements. These shrimp have just come together after I startled them cleaning the tank. glass.

What Phylum are shrimp classified in?

Sponges may be simpler than other animals in structure, but they still have interesting structures that vary by species.

Which Phylum are sponges classified in?

Looking for a challenge? How many different Phyla are represented by the organisms in these sketches?

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Check your knowledge. Can you:

For six of the marine invertebrate phyla (Porifera, Cnidaria, Echinodermata, Mollusca, Annelidia, Crustacea):

Describe the key characteristics of the phylum?
List examples of organisms in the phylum?

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Organism Care Guide Contents

Complete all four of these sections before taking the quiz and making your media piece.

Basic Needs

Tidal Zones

Coral Reef

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