The Protostomes

A. The Annelids

1. Phylum characteristics
   • eucoelomate
   • metameric
2. Classes
   • Archinellida--
   • Polychaetes--extensions of body wall called parapoda. These structures have lots of setae, bristles, etc. Coelomic space passes into parapodia, incomplete septa between segments. Greater use of sinusoidal contract of longitudinal muscle bands. More efficient than nematode method, as the setae apply force to substrate which allows motion to occur in forward direction. Two major groups, sedentary and errant. Whole group is mostly marine
   • Oligochaetes --fewer setae. Terestrial or freshwater
   • Hirudinea-- leeches
     1. lack of correspondence between inner and outer segments. Presence of suckers at both ends
     2. use in medical treatment

B. Mollusks

1. General features--all derived from basic body plan
   • mantle
   • paired gills
   • foot
   • shell
   • radula
2. Classes
   • Aplacophora
   • Monoplacophora
   • Polyplacophora--Chitons
   • Gastropoda--Snails and slugs
   • Cephalopoda--Squid, nautili and octopods
   • Scaphopoda--Tooth or tusk shells
   • Bivalviaa--Clams, mussels, cockles

C. The Arthropoda

1. General Attributes
   • segmented
   • exoskeleton
   • jointed appendages
   • haemocoel
2. Major Groups
   1. Chelicerates--possess claw-like jaws. used for poking holes in prey, through which enzymes can be injected. Predator then sucks out the interior contents
      • ticks and mites
      • spiders
      • scorpions
      • pycnogonids
   2. Mandibulates--possess mandibles as main mouth part. Used for maceration of food items.
      • Crustacea
      • Hexapoda
      • Millipeds and centipeds