English Enemies of the American Slipper-limpet, Crepidula fornicata

Abstract

IN 1923 the present writer found a shell of a dead slipper-limpet (Crepidula fornicata) at West Mersea, Essex, bored extensively by the boring sponge Cliona celata. This year a good number of living slipper-limpets have been examined, and one, the fourth individual of a chain of 8 living ones, was found with the living sponge boring into the shell. In the shell of the dead animal the sponge could be seen to have bored through all parts including the shelf, but had been inhibited from perforating over almost the whole of the area on the dorsal side, where another slipper-limpet had been attached to it. In the living specimen the sponge can be seen to be forming a honeycomb mesh-work in the dorsal portion of the shell, but it has only perforated to the surface in the postero-dorsal region; the shelf of the shell is also attacked and is almost perforated in places. On the part of the shell where the next individual in the chain was sitting there is a nodular deposition of calcareous matter over strands of the sponge tissue. This deposit has been laid down, not by the owner of the shell, but by the individual sitting on the shell, and undoubtedly as a reaction to the irritation caused by the sponge. Crepidula has, therefore, found an enemy in Cliona in its new environment, and it will be interesting to know to what extent the slipper-limpet will be attacked in future in view of its economic importance.