Helcion pectunculus has an organized distribution within rock crevices with smaller, younger limpets towards the back of the crevice and larger, older limpets towards the crevice mouth. The crevice refuge provides H. pectunculus with a stable and buffered environment with higher relative humidities and lower rock surface temperatures than adjacent exposed rock surfaces. Limpet body temperatures were significantly lower in crevice refuges compared with limpets on adjacent exposed rock surfaces. Body temperatures never exceeded the rock surface temperatures. It is suggested that this is a result of morphological adaptations such as short spines on the shell and allometric growth (shell increasing in height faster than length). Compared with other South African patellids, less force is required to detach H. pectunculus from the substratum and individuals deprived of a crevice refuge experienced extremely high mortalities, 45% of limpets being lost during the first high tide period. |
