Wear reduction
Wear reducing mechanisms are well-investigated in Polyplacophora and
Patellogastropoda. Here, high proportion of Fe and Si are incorporated
into a thick leading edge (surface layer), which is hard and protected
against wear (Kirschvink & Lowenstam, 1979; Kim et al., 1989; Lowenstam
& Weiner, 1989; van der Wal, 1989; van der Wal et al., 1999; Brooker et
al., 2003; Lee et al., 2003a, 2003b; Saunders et al., 2009, 2011; Weaver
et al., 2010; Wang et al., 2013; Kisailus & Nemoto, 2018; Krings et
al., 2022c). Compared to the harder outer edge, the teeth possess a
softer inner structure, which reduces crack formation (van der Wal,
1989; van der Wal et al., 1999; Grunenfelder et al., 2014). In some
paludomid and nudibranch taxa, we previously also identified an outer
layer with high Si or Ca content on the tooth region, which interacts
with the food (Krings et al., 2022a, 2023; Krings & Gorb, 2023a). This
layer, however, was very thin in comparison with that of the chitons and
limpets, rendering these teeth as lightweight structures. InGastropteron rubrum , we detected high content of Si and Ca in the
tooth regions, which interact with the ingesta. This suggests that this
also reduces wear during feeding. A similar adaptation involving the
incorporation of Si at the tooth tip and the presence of a soft tooth
base to reduce wear by foraging on hard prey, such as diatoms, has also
been found in the gnathobases of
Copepoda (Michels et al., 2012).