Systematic Position
Phylum: Mollusca
Class: Bivalvia (Pelecypoda)
Genus: Ostrea
Habit and Habitat
Marine mollusc
Found attached to rocks and hard substrata
Lives in shallow coastal waters
External Morphology
Body enclosed in two unequal shell valves
Lower valve:
Large, concave
Cemented permanently to rock
Upper valve:
Smaller and flatter
Head and foot absent
Shell
Thick, rough, irregular shell
Valves joined by hinge but movement limited
Digestive System
Complete digestive system
Radula absent
Filter feeder
Respiration
Aquatic respiration
By gills
Circulatory System
Open circulatory system
Heart three-chambered
Reproduction
Usually hermaphrodite
Fertilization mostly external
Development
Indirect development
Larval stages:
Trochophore
Veliger
Economic Importance
Important edible oyster
Shells used for lime and ornaments
Identification Points
Marine bivalve
Unequal shell valves
Permanently attached to rocks
Filter feeder
Quick Difference: Mytilus vs Ostrea
Feature
Mytilus
Ostrea
Attachment
Byssus threads
Cemented shell
Shell
Equal valves
Unequal valves
Foot
Present (small)
Absent
Habit
Colonial
Mostly solitary
