Basic biology and classification of marine invertebrates

-Metazoan animal origins:700 million to 1.4 billion ybp

-Cambrian explosion: 600 mybp

-evolution is not progressive, no increase in complexity after origination of phyla

-many body plans are no longer around

-What caused the dramatic radiation of metazoans?

Burgess shale fossil quarry in the Canadian Rockies

Some major phyla of marine invertebrates

Porifera sponges

Cnidaria jellyfish, anemones, corals

Annelida segmented worms (e.g. polychates)

Mollusca clams, mussels, octopus, squid

Bryozoa bryozoans

Arthropoda crabs, shrimp, copepods,

Echinodermata urchins, holothuroids, sea stars

Urochordata ascidians/tunicates

You should know the phyla and examples and general characteristics of animals in each

Some basic terms:

Benthic vs. Pelagic

Sessile vs. Mobile

Solitary vs. Colonial

Sexual vs. Asexual

Encrusting vs. Upright

Autotrophic, Chemoautotrophic, Heterotrophic

Predation, Herbivory, Omnivory, Primary production

Phylum: Porifera: Sponges

-simplest multicellular animals, but not ancestral!-no true tissues-cells are independent and perform specialized functions-very efficient filter feeders

-good spatial competitors

-incurrent and excurrent canals

-asymmetrical

Sponge anatomy-built around a system of pores, chambers, and canals

-choanocyte

-spicules

Phylum Cnidaria jellyfish, anemones, corals

What makes something a Cnidarian?

-all are aquatic

-tissues present but no organs

-2 basic shapes or phases:

polyp & medusa

-nematocyst

-tentacles

-1 opening

Phylum Cnidaria jellyfish, anemones, corals

Physalia: man-o-war

Cassiopia

Phylum Cnidaria jellyfish, anemones, corals

Hydroid Sea Pen

Phylum Cnidaria jellyfish, anemones, corals

Colonial reef coral Solitary reef coral

Sea fan Anemone

Phylum AnnelidaClass Polychaeta segmented marine worms

6000 species

Segmentation

Setae

A variety of feeding modes:

Active predators, mucus bag feeders, mud-munchers and passive filter feeders

Fire worm

Feather duster worm

Christmas tree worm

-serpulids: secrete CaCo3 shell-filter feeders

Phylum Mollusca Class Gastropoda: snails and limpets

Class Polyplacophora chitons

Cyphoma Cassis

-second most diverse marine animal phyla (100,000+ species)

-no segmentation

-have complete gut

-usually have a calcareous shell

Phylum Mollusca Class Gastropoda: snails and limpets

Cone shell Conus geographus“mini melo”

-many predatory snails are highly specialized

Bivalves: clams, oysters, mussels, scallops

Phylum Mollusca

Tridacna Giant Clam

-some have autotrophic symbionts-most are active filter feeders

Cephalopods: octopods, squid, nautilus

Phylum Mollusca

Octopus-8 armsSquid-8 arms + 2 longer tentacles

Nudibranchs: sea slugs

Phylum Mollusca

Aplysia Sea Hare

-most are specialized predators

Phylum Bryozoa: bryozoans

-passive filter feeders-colonial-zoids

Phylum Arthropoda

Subphylum Trilobita

Subphylum Chelicerata horseshoe crabs, sea spiders

Subphylum Crustaea crabs, shrimp, barnacles, copepods

Subphylum Uniramia insects

-by far the largest animal phylum

-could represent several independent phyla

-mono vs. polyphyletic

-all are segmented, but segments are divided into different body regions

-appendages are paired and jointed

-all have an external skeleton

-probably derived from annelids

Phylum Arthropoda

Subphylum Chelicerata horseshoe crabs, sea spiders

Phylum Arthropoda

Subphylum Crustaea crabs, shrimp, barnacles, copepods

Blue crab

Barnacles (goose neck)

Phylum Echinodermata

Sea stars

-radial symmetry

Phylum Echinodermata

Diadema

Pencil urchin

Sand dollar

Phylum EchinodermataOphioroids (brittle stars)

Crinoids

Phylum Echinodermata

HolothuroidsSea cucumbers

Urochordata ascidians/tunicates