Larval Identification Information

This larval identification key is presented to help separate larvae of zebra mussels, quagga mussels, and Asian clams. Only characteristics readily visible under a light microscope and suitable for rapid identification of larvae collected in routine monitoring programs are presented. The primary characteristics for preserved specimens are hinge length, shell proportion, shape, and size (Nichols and Black 1994). Secondary characteristics, such as the presence or absence of a foot or velum, are easier to see in living specimens. The development of internal organs and taxonomic features requiring dissection or scanning electron micrographs have not been addressed. Descriptions of changes that occur in internal structures and hinge development of Asian clams and zebra mussels can be found in studies such as Meisenheimer (1901), Chanley and Andrews (1971), Waller (1981), Mackie (1984), Kraemer et. al. (1986), Kraemer and Galloway (1986), and McMahon (1991).