by Piter Kehoma Boll
The sea is so full of different lifeforms that it is hard to leave it once we are there. Thus, we will continue in the sea this week, but moving to the middle of the Pacific Ocean, more precisely to the Hawaiian islands. There, on the shore, we can find today’s fellow.
Named Nerita picea, it is a small snail found on the rocky shores across most of Hawaii, often in aggregates. It is commonly called the Hawaiian black nerite in English but the native Hawaiians call it pipipi.
The Hawaiian black nerite measures about 1 cm in length and its shell is externally black with spiral ribs, sometimes with a thin lighter line running between them, and often with a whitish tone on the tip of the spiral. Its ribs are relatively little marked when compared to most nerite species. Internally, the shell is white. The soft parts of the body are also mostly dark in color and so is the operculum, the lid that closes the opening of the shell when the snail retracts. The foot, however, is lighter. When a live animal is picked, it quickly retracts into the shell, covering the opening with the operculum and letting a white margin around it.
Like most intertidal snails, the Hawaiian black nerite is a herbivore and grazes on algae growing on the rocks. It prefers to live at the splash zone and slightly above it, differing from its closest relative, Nerita plicata, which lives in the upper zone, avoiding the splashes.
Due to its tropical distribution, the Hawaiian black nerite reproduces continuously throughout the year. There is no sexual dimorphism between males and females, which is, I guess, “the rule” for snails.
The Hawaiian black nerite was traditionally used as food by the native Hawaiians and its shells can be found in large numbers in archaeological sites of the archipelago dating back more than a thousand years. Empty shells of the Hawaiian black nerite are also commonly used by small hermit crabs of the genus Calcinus.
Despite being a common species in Hawaii and having a historical importance as food, little seems to be known about the life history of the Hawaiian black nerite.
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References:
Dye T (1994) Apparent ages of marine shells: implications for archaeological dating in Hawai’i. Radiocarbon 36(1):51–57.
Frey MA (2010) The relative importance of geography and ecology in species diversification: evidence from a tropical marine intertidal snail (Nerita). Journal of Biogeography 37:1515–1528. doi: 10.1111/j.1365-2699.2010.02283.x
Pfeiffer CJ (1992) Intestinal Ultrastructure of Nerita picea (Mollusca: Gastropoda), an Intertidal Marine Snail of Hawaii. Acta Zoologic 73(1):39–47. doi: 10.1111/j.1463-6395.1992.tb00947.x
Reese ES (1969) Behavioral adaptations of intertidal hermit crabs. American Zoologist 9(2):343–355. doi: 10.1093/icb/9.2.343
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Earthling Nature 
Smallest hermit crab I’ve ever seen.