Comprehensive Description

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Biology/Natural History: This species unlike limpets and periwinkles is a carnivore--one of the predatory whelks known as "oyster drills" or "barnacle drills". It hunts down intertidal barnacles, mussels, and sometimes periwinkles such as Littorina sitkana and L. planaxis or the limpet Collisella scabra, and uses its radula to drill through their protective shell. The primary food of adults is the mussel Mytilus trossulus, which it prefers over M. californianus, and the barnacle Balanus glandula. After drilling the whelk injects digestive enzymes into the prey's body cavity and sucks out the dissolved tissue using its long proboscis. This species is a formidable predator that aids in controling the population of barnacles and mussels. Individual snails seem to have narrow feeding preferences, while that of the population as a whole is broader. Predators of the species include the seaster Pisaster ochraceus and the red rock crab Cancer productus. The eggs, which the species attaches to rocks, may be eaten by the purple shore crab Hemigrapsus nudus or the isopod Idotea wosnesenskii, while the young may be eaten by hermit crabs such as Pagurus hirsutiusculus.

The yellow, vase-shaped egg capsules, which are attached via short stalks to rocks well up in the intertidal and called "sea oats", are about 6-8 mm high with a suture line along one side. Each capsule holds about 550 eggs, each of which is 180 to 220 microns in diameter. Most of the eggs are infertile "nurse eggs" which the other embryos devour as they develop. Development within the capsule takes about 2.5-4 months. Ten to 20 juvenile snails hatch from each capsule (there is no free planktonic stage). A single female may produce a cluster of up to 300 capsules.

In the study by Sorte and Hofmann (2005), thermotolerance of different Nucella species along the coast was found to be correlated with the latitude range and tidal height each species occupies. N. ostrina, which occurs higher in the intertidal than does N. canaliculata in Oregon and does not extend as far north, had higher heat tolerance than did N. canaliculata. N. emarginata, which extends the farthest south, and N. ostrina, which lives higher in the intertidal, recovered more quickly from thermal exposure than did N. canaliculata and N. lamellosa, which live lower in the intertidal, and N. lima, which has a more northern range. These differences in heat tolerance may be related to HSP70 molecular chaperones.

The famous purple dye from the city of Tyre, that colored royal Roman robes, was made from a relative of Nucella. The snails were ground up in a stone mortar; different combinations made different shades of purple. The dye should be fixed with lemon juice as a mordant. The American species produce a much less brilliant purple than do the Mediterranean species.

Shell banding is controlled by a single gene locus which is separate from shell color. In California the species contains high levels of metals, such as 570 ppm copper and 1700 ppm zinc.


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© Rosario Beach Marine Laboratory

Source: Invertebrates of the Salish Sea

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