Al. Martel et al., Distinguishing early juveniles of Eastern Pacific mussels (Mytilus spp.) using morphology and genomic DNA, INVERTEBR B, 118(2), 1999, pp. 149-164
A lack of efficient criteria by which to discriminate among Mytilus spp. in
early juveniles (similar to 0.5-5.0 mm shell length) has hindered studies
of recruitment, despite the conspicuous ecological roles played by the adul
ts on rocky shores of western North America. We present morphological crite
ria, Visible under a dissecting microscope, that distinguish sea mussels, M
ytilus californianus, from sympatric bay mussels, M. trossulus and M. gallo
provincialis. The shells of early juvenile sea mussels from southern Britis
h Columbia and from southern California have (1) a more posterior dorsal ap
ex and (2) a posterior adductor muscle (PA) attachment larger than do shell
s of bay mussels from similar locations (M. trossulus and M. galloprovincia
lis, respectively). Accuracy of these criteria was confirmed by comparing P
CR products of genomic DNA of juveniles with those of adults. Additional cr
iteria useful in identification include: (3) the proximity of the PA to the
dorsal apex Line, (4) the dorsal angle of the dissoconch, and (5) lateral
hinge-tooth demarcations. Morphological criteria identified by this study c
onstitute a fast, economical means of distinguishing early juveniles of tho
se mussels and may benefit ecological research on Mytilus.