Lesson 18: Invertebrates

Marine Biology

Classification OverviewCommon Invertebrates

KingdomAnimalia

PhlyumPorifera

Cnidaria

Mollusca

Arthropoda

Echinodermata

Spineless creatures

Invertebrates are animals that lack a backbone

You may know many examples of these creatures that live in the ocean: jellyfish, sponges, corals, crabs

Can you think of others?2

Phylum: Porifera Simple heterotrophs with two cell types:

– Collar cells have flagella and draw water into the sponge’s central cavity (diagram right)

– Epithelial cells line the sponge’s outer surface

Reproduce asexually by budding or sexually by release of sex cells (gametes) into the water

Filter feeders: feed by filtering suspended materials out of water

Sponges: Phylum Porifera

Flagellum

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Collarcell

The yellow tube sponge, purple vase sponge, red encrusting sponge and gray rope sponge

Photo: NOAA

Cnidarians include corals, anemones, sea fans, and jellyfish

Cnidarian characteristics:– Radial symmetry – they are

symmetrical around a single point, like a clock

– Two tissue layers separated by a jelly layer (mesoglea)

– Nematocysts – structures on their tentacles that have stinging toxins

Phylum Cnidaria: The stinging nettles

Cnidarian TaxonomySome Common Classes

KingdomAnimalia

PhylumCnidaria

ClassesAnthozoa – anemones,CoralsScyphozoa – jellyfishHydrozoa – fire corals,Portuguese Man-of-War

This purple striped jellyfish (Pelagia panopyra) has a potent sting

Photo:NOAA

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Some special Cnidarian species profiles

Portuguese Man-of-WarClass: HydrozoaOrder: Siphonophora

These are in a different class than jellyfish, they are colonies – specialized polypsPhoto: NOAA

Photo:

NO

AA

Fire coralClass: HydrozoaOrder: Capitata

These are in a different class than typical hard corals - you will get a mild burn if you touch them!

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Phylum Mollusca: Three defining traits

Mollusks include oysters, clams, mussels, conchs, snails, sea slugs, squid and octopuses

Most mollusks have three traits

– Mantle: a muscular bag surrounding the gills and other organs for circulation

– A muscular foot for movement– A radula: a rough scraping

appendage for feeding or protection

Mollusca TaxonomySome Common Classes

KingdomAnimalia

PhylumMollusca

ClassesGastropoda – snails, sea slugsBivalvia – clams, oysters, scallops, musselsCephalopoda – squid, octopus

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Some mollusks

OctopusClass: Cephalopoda

The foot of the octopus is divided intoeight arms.

Spiny oysterClass: Bivalvia

Bivalves have two shells and no typical“head” like other mollusks

Photos:

NO

AA

Foot

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Phylum Athropoda: Superclass/Subphylum Crustacea

Arthropods are land and sea “bugs” Crustaceans include shrimps,

crabs, lobsters, copepods and barnacles

About 1 million species exist Crustacean characteristics:

– Two pairs of antennae– Mandibles for chewing– Hard exoskeleton– Jointed legs

Crustacean TaxonomySome Common ClassesKingdomAnimalia

PhylumArthropodaSubphylumCrustacea

ClassesCirripedia – barnaclesCopepoda – copepodsMalacostraca – shrimp, lobster, crabs8

Some common crustaceans

Rock lobster

Sub-phylumCrustacea

ClassMalacostraca

OrderDecapoda

Copepod

Sub-phylum ClassCrustacea Copepoda

Order Harpacticoida

Photos:

NO

AA

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Phylum Echinodermata: The ocean’s stars

Include sea stars (starfish), sea urchins, sand dollars and sea cucumbers

Most echinoderms have these traits:

– Tube feet for motion– Radial symmetry (adults)

Symmetry around a single point

– A water vascular system that circulates seawater

Echinoderm TaxonomySome Common ClassesKingdomAnimalia

PhylumEchinodermata

ClassesAsteroidea – sea starsOphiuroidea – brittle starsHolothuroidea – sea cucumbersEchinoidea – sea urchins

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Some Echinoderms

Sunflower star

PhylumEchinodermata

ClassAsteroidea

OrderForcipulatida

Source:

NO

AA

Sea urchin

Phylum ClassEchinodermata Echinoidea

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Crustaceans supporting ecosystems

Copepods are tiny crustaceans and one of the most abundant forms of multicellular life in the ocean

Why do you think they might be important for marine food webs?

They are food for many different types of marine life including sea birds, small fish and whales

In this way, they are a very important part of marine ecosystems, providing a foundation for marine food webs

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Some of the life supported by copepods

Photos: NOAA

Copepod Herring

Tuna

Shark

Whale

Auklet

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Student activity

To figure out what types of organisms make up communities like the sample we just saw (and how many of each type there are), scientists use a process called sampling

In today’s activity, we will simulate different types of sampling methods to explore the variety of invertebrates in the ocean

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