Sublittoral, western Scotland. 2014. Copyright B. Forrest
flic.kr/p/n6UtHY & flic.kr/p/n6WTou
Left: male emitting sperm in gelatinous string from posterior.
Right: female releasing ova.
Water current in pallial cavity carries sperm or ova from lateral gonopores to posterior and out through channel in raised girdle. To facilitate wide dispersal the rear half of the body is raised from the substrate during release. As fertilization is external, synchronised emission of sperm and ova is needed to ensure success; trigger in many chiton species is moon-phase/ state of tides.
A coating of dark manganese is often found on the shell of Tonicella marmorea.