These two Protostomes are important for study of

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 ratio Many parasites in this group.

Segmented (Annelid) worms 16, 500 species Hydrostatic skeleton

Mollusca -- 93, 000 species The most morphologically-diverse Lophotrochozoans Chiton Nudibranch

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

Major groups of mollusks 2. Gastropods: Snails, slugs, nudibranchs Radula for feeding. http: //cas. bellarmine. edu/tietjen/images/phylum_mollusca. htm

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” 1. (Chelicerata) Movie of embryonic horseshoe crabs at http: //www. thekarenzagroup. com/bayguardian/limulusmovie. php

Major groups of arthropods 3. Crustaceans 1. (Shrimp, Lobster, Crabs, Barnacles)

Major groups of arthropods 4. Insects 1. 6 legs, four sets of mouthparts, usu four wings