Figure 2
Morphology of a Littorina penis. (A) A photograph of L. saxatilis penis; (B) a scheme of a penis showing features important for identification—filament (f) and a row of mamilliform glands (m); (C–H) examples of penises with different numbers of gland rows; (C) multiple rows corresponds to scheme (E) (identified as L. arcana); (D) 1.5 rows (there are no glands in an opposite position, although several glands are out of the row) corresponds to scheme (G) (identified as L. saxatilis 1.5, presumably hybrids between L. arcana and L. saxatilis); (F) two rows of penial glands, as two pairs of glands are in opposite position (identified as L. arcana); (H) one even row of penial glands (identified as L. saxatilis 1 row).
