Radular myoglobin as a molecular marker in littorinid systematics (Caenogastropoda)

Radular myoglobin (Mb) was investigated in 288 specimens of 10 littorinid s pecies using vertical polyacrylamide gel electrophoresis (PAGE) and isoelec tric focusing (IEF). Within the genus Littorina the two most basal species, L. striata and L. keenae, have Mb patterns that correspond to those of the genera Littoraria and Nodilittorina, while the sibling species L scutulata and L, plena have identical Mb profiles that consistently differ from thos e of L. littorea, L. saxatilis, L. compressa and L. areana. In contrast to previous claims, Mb does not consistently separate the sibling rough periwi nkles Littorina saxatilis and L. arcana. These data suggest (1) that the No dilittorina/Littoraria Mb profile in L. striata is not unique within the ge nus Littorina and therefore does not refute the assignment of L. striata to this genus, and (2) that L. scutulata and L. plena occupy a separate posit ion compared to the other species of the subgenus Littorina. This latter re sult supports the suggestion that L. scutulata and L. plena may constitute a separate subgeneric taxon. Finally, the IEF Mb profiles of Nodilittorina hawaiiensis and Cenchritis muricatus were nearly identical to the Nodilitto rina/Littoraria Mb pattern. Yet, PAGE of Mb in Cenchritis muricatus suggest s a tentative Mendelian polymorphism. It is concluded that littorinid Mb ma y not be a useful marker to distinguish closely related species, but rather provides information on 'higher level' systematics.