Unit 8 - Molluscs

A large muscle used for movement and attachment

Well developed with sensory organs and brain

Radula, a structure of tiny teeth used for scraping and collecting food.

Containing digestive, reproductive, excretory and circulatory organs which are surrounded by hemocoel.

The heart and some intestines.

A sheet of tissue covering the visceral mass and meeting the head and foot.

Mantle cavity, gills.

A hard protective shell.

Periostracum - Outermost organic (conchiolin) layer, Prismatic layer - Thick middle calcareous layer, Nacre - Inner calcareous layer

Nacre, Mantle, Pearls

Complete digestive system, Many scrape food from hard surfaces. The radula lies on the odontophore.

Buccal cavity leads to esophagus, leads to stomach and then intestine. The anus empties wastes into the mantle cavity.

O2 poor hemolymph flows from hemocoel to gills via afferent branchial vessels. O2 rich hemolymph from gills to atrium via efferent branchial vessels then to ventricle of heart, then leaves through aorta into the hemocoel and flows around everything.

Urine produced by the heart (atrium) fills the coelom, then enters the nephridium via the nephrostome and out via the nephridiopore.

Either Gonochoristic or Hermaphroditic, Males and females shed gametes into the water column via the nephridiopore. One or more larval stages, trochophore, veliger or parasitic glochidium.

Composed of mainly 2 cerebral ganglia connected by a nerve ring to each other, to several other ganglia, and to pedal and visceral nerve cords.

Chemomechanosensory tentacles, statocysts, complex eyes with ocelli, lens and cornea.