1. Mollusks and Annelids

2. Phylum Mollusca Gastropods, Bivalves, Cephalopods
Kingdom Animalia
Phylum Mollusca
Gastropods, Bivalves, Cephalopods

3. General Characteristics
Trochophore – larval stage of development
Two body regions
Head-foot – contains the head (mouth & sensory organs) & the foot (locomotion)
Visceral Mass –contains the vital organs covered by mantle which secretes CaCo3 to make the shell.
Bilateral symmetry w/cephalization
The use of gills to exchange gas.
Nephridia are used to remove metabolic waste
Two types of circulation
Open circulatory- blood moves through vessels & into open spaces around body organs
Closed circulatory – blood is enclosed entirely in vessels.

4. Class Gastropoda Gastropods – “stomach foot”
Snails, abalones, conchs, slugs, nudibranchs, sea butterflies, sea hares, periwinkles, whelks, limpets, cowries, and cones
Use radula-tongue like strip used to scrap food.
Open circulatory system with two-chambered heart.
Found in freshwater, saltwater & moist terrestrial habitats
Land type use modified mantle to respire and water type use gills.

5. Class Bivalvia Bivalves-two halves of shells. Clams, oysters, scallops
Open circulatory system
Shell made of CaCO3 w/ mother of pearl inside
Filter feeders that are usually sessile can move w/foot
Incurrent & excurrent siphons to move water into and out of the body for respiration w/gills and for feeding
Mostly separate sexes w/external fertilization
Size ranges from 1mm to 1.5 m

7. Class Cephalopoda “Head-foot”-squid, octopus, nautilus, cuttlefish
Closed Circulatory system
Internal fertilization
Largest brain of invertebrates
Well-developed sensory organs
Use of jet propulsion, ink sprays & camouflage

8. Class Cephalopoda Squid – 8 arms & 2 tentacles-catching prey
Octopi – 8 arms
Nautilus – 90 arms
Largest – Giant Squid up to 60 feet long
Nautilus only one w/outer shell, others have small internal shells called pens.
Photo of Colin Dunlop's cuttlefish chomping on a fish

10. Phylum Annelida Segmented worms Bilateral symmetry w/cephalization
Live in soil, freshwater, and the sea.
External bristles-setae
Most have well-developed organ systems
(Photo G. Brändle)

11. Class Oligochaeta Earthworms -Live in soil & freshwater.
Ingest soil as they burrow through
Circular & longitudinal muscles w/100 identical segments.
Hermaphroditic – internal fertilization. The clitellum aids in reproduction
Respire through their skin so must stay moist.
Use nephridia to excrete waste
Bilateral symmetry w/cephalization

12. Pathways
Food pathway
mouth - pharynx - esophagus - crop (storage)-gizzard (grinding)-intestines-anus.
The waste of earthworms is called castings.
Circulatory pathway
The blood travels to posterior via ventral blood vessel & returns to anterior via dorsal blood vessel w/aortic arches acting as a heart

13. Class Polychaeta
Sandworms, fanworms, bloodworms, lug worms, plumed worms, sea mice
Free-living marine predators
Contain a pair of appendages called parapodia which are used for gas exchange, swimming and crawling.
Have antennae and specialized mouthparts

14. Class Hirudinea Leeches Moist tropical areas Parasitic
Powerful suckers both ends with no setae
Uses anesthetic to prevent host from feeling
Can swallow 5x weight in blood
Cottobdella epshteini S.Utevsky, 1997