Schelpreparatie bij Patella depressa verzameld nabij Cadiz

[Shell repair in Patella depressa from Cadiz], Shells of living Patella depressa (= P. intermedia) collected from rocks near Cabo Roche, south of Cadiz (Atlantic coast, Spain) showed different types of damage. Some specimens had repaired holes in their shells of up to several mm in diameter, or repaired breaks (see figure). By extra deposition of calcareous matter at the inside of the shell Patella had repaired this shell damage. These holes could be due to impacts of stones in the surfzone of the Atlantic Ocean, but more probably they resulted from unsuccessful attacks by pecking predators, in particular gulls, as observed in the Antarctic patellid Nacella concinna by Nolan (1991). Nolan’s material was re-studied which led to the discovery of similar repaired peckmarks in N. concinna from King George Island earlier overlooked in Cadée (1999a, b). In addition, microboring algae, had bored small holes and tunnels in the oldest part of the shells. No grazing activity on these boring algae was observed, whereas in the Antarctic limpet Nacella concinna this was very frequently observed (Nolan, 1991; Cadée, 1999a, b). Grooves of the radula of Patella or other grazers were absent. The apex of the shells, moreover, was polished, presumably due to sandblasting in the tidal zone.