Phylum molusca

Phylum Molusca

85,000 species

“Soft bodied with a hard calcareous shell”

Classes

• Bivalvia “head-less”• Gastropoda “stomach-foot”• Cephalopoda “head-foot”

• Polyplacophora• Monoplacophora• Pleistomollusca• Rostroconchia• Scaphopoda• "Aplacophora“

Class Bivalvia• Like all mollusks,

– a clam has a mantle which surrounds its soft body.

– It also has a muscular foot for burrowing in mud or sand.

– The soft tissue above the foot is the visceral mass and contains the clam's body organs.

Class Gastropoda• Snails and slugs

Class Gastropoda

• Complete gut• Open circulatory system with primitive heart and

hemocyanin pigment (clear when deoxygenated and blue with oxygenated)

• Respiratory system with primitive lung or gills• Hermaphrodites that have mating behaviors

such as love darts.• Tentacle stalks with eye spots for sensing the

environment (light and dark) but mostly for touch receptors.

Class Cephalopoda

• Complete digestive system • Radula – many rows of teeth that form a beak-like

structure• Closed circulatory system - A single systemic heart

then pumps the oxygenated blood through the rest of the body

• Use hemocyanin, a copper-containing protein, rather than hemoglobin, to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when exposed to air

• Cephalopods exchange gasses with the seawater by forcing water through their gills

• Baby cephalopods look like mini-adults

• They have the most complex nervous systems of all invertebrates– Advanced vision, gravity sensors,

a variety of chemical sensors– Chromatophores for changing

color and camouflage - coloured pigments

– Some cephalopods bioluminesce, shining light downwards to disguise their shadows from any predators that may lurk below.

• Cuttlefish •http://video.pbs.org/video/1150618835/

• Octopus•http://www.youtube.com/watch?v=H8oQBYw6xxc

http://www.youtube.com/watch?v=hcyzr3zJol4