3D morphology of nematode encapsulation in snail shells, revealed by micro-CT imaging

Many parasites and hosts are embroiled in an on-going arms race that affects the evolution of each participant. One such battle is between parasitic nematodes and terrestrial gastropods which have co-evolved for 90–130 MY. Recently, snails have been shown to encase and kill invading nematodes using their shell as a defence mechanism. However, there is remarkably little known about this process in terms of understanding where, when and how nematodes are fixed within the shell. Also there has never been any attempt to observe this process using methods other than light microscopy. Therefore, we used micro CT scanning of a Cepaea nemoralis shell (a common host for nematodes) to 3D visualise encased nematode parasites and quantify morphological parameters. By taking this approach future studies could use micro CT scanning of fossil shells in conchology collections to understand nematode/snail co-evolution.