Identification of Eastern Oyster Crassostrea virginica Larvae Using Polarized Light Microscopy in a Mesohaline Region of Chesapeake Bay

Understanding the population dynamics and complete life cycle of bivalves is important for effective management of these commercially and ecologically important organisms. Most of the literature and research on bivalves to date has focused on juvenile and adult bivalves, but much less is known about larvae. The larval stage has been difficult to study due to the lack of a rapid automated approach for identifying the species. A new technique, called ShellBi, utilizes color patterns on the larval shell under polarized light to identify bivalve larvae. The objective of our research was to review the scientific basis for ShellBi and to apply it to bivalve larvae from the Choptank River in mesohaline Chesapeake Bay, with the goal of distinguishing larvae of the eastern oyster (Crassostrea virginica) from seven other species that spawn at the same time. A digital camera and polarized light microscope was used to capture images of the larval shells of the eight species under standard and cross-polarized light. Images of C. virginica were distinguishable from those of other species based on color patterns, especially at later stages of development. These images could serve as a visual guide to distinguish larvae of C. virginica from other bivalves inhabiting mesohaline tributaries of Chesapeake Bay.