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