#2809 - Scutellastra kermadecensis - Giant Kermadec Limpet
AKA Patella (Scutellastra) kermadecensis, Patella (Scutellastra) pilsbryi and Patella kermadecensis.
An enormous limpet (possibly the world's largest) found only on the rocky shores of the volcanic Rangitāhua Archipelago (also known as the Kermadec Islands), 800-1000km NW of New Zealand. The islands are recognised by the World Wildlife Fund as a distinct ecoregion, the Kermadec Islands subtropical moist forests, and are home to 113 native species of vascular plants, of which 23 are endemic, 52 mosses, and 89 lichens and fungi. Unfortunately 152 human-introduced species of plants have also become established on the islands, and goats, cats, and rats were a disaster. At least they've now killed all the goats, and are working on doing the same with the rats and cats.
The limpets live in great profusion from the lowest intertidal to the upper subtidal, gorging themselves on algae with few competitors to worry about, apart from other limpets. That may be why the younger, smaller limpets are usually found riding around on the shells of the big ones. The smaller ones also tend to be male, and switch sexes as they grow, so sticking as close as possible to a mate may also be a factor. As one paper put it -
We found that the available rock space did not influence the size at which an individual transitioned from being a piggy to being rock-attached. Furthermore, larger rock-attached limpets were more likely to have piggies, they had more piggies, and the piggies were larger.
A fossil found in the Oligocene Isolated Hill Limestone of Mason River, Marlborough, indicates the limpets used to be more widespread, and the Kermadecs are their last stronghold.
Otago Museum, Dunedin, Aotearoa New Zealand
