These two Protostomes are

important for study of genetics and development

Crustaceans and Mollusks Are Important Animals In Marine Ecosystems

Insects, Spiders, and Mites Are Important Animals In Terrestrial Ecosystems

Lophotrochozoans grow by extending size of “skeleton”

Ecdysosoans grow by shedding external skeletons

“Worms” are not always closely related.

Flatworms (Platyhelmenthes) 20,000 species

No coelom, no circulataory system.Flat bodies have high surface area:volume ratioMany parasites in this group.

Segmented (Annelid) worms 16, 500 species

Hydrostatic skeleton

Mollusca -- 93,000 speciesThe most morphologically-diverse Lophotrochozoans

Nudibranch

Chiton

Tube within tube; foot used for locomotion.

Coelom greatly reduced. Shell sometimes absent.

Major groups of mollusks

1. Bivalves (hinged shell):

clams, mussels, scallops, oysters

http://cas.bellarmine.edu/tietjen/images/giant_clam.jpg

Suspension feeders

Major groups of mollusks

2. Gastropods:

Snails, slugs, nudibranchs

http://cas.bellarmine.edu/tietjen/images/phylum_mollusca.htm

Radula for feeding.

Major groups of mollusks

3. Cephalopods (Squid and Octopus)

Foot modified into tentacles

Move by undulation & jet propulsion

Excellent vision, very smart

http://tolweb.org/tree?group=cephalopoda#titlefigcaption

Ecdysozoans grow by molting (shedding exoskeleton)

Arthropods are by far the most important group.

Relative abundance of Protostome lineages

There are

925,000

named

species

of

insects

Jointed exoskeleton: specialized eating and locomotion

Major groups of arthropods

1. Centipedes, Millipedes (Myriopods)

Major groups of arthropods

2. Spiders, Ticks, Mites, Scorpions, Horseshoe “crabs”

(Chelicerata)

Movie of embryonic horseshoe crabs athttp://www.thekarenzagroup.com/bayguardian/limulusmovie.php

Major groups of arthropods

3. Crustaceans

(Shrimp, Lobster, Crabs, Barnacles)

Major groups of arthropods

4. Insects

6 legs, four sets of mouthparts, usu four wings