Nucella ostrina (Deshayes, 1839)

Common name: Emarginate dogwinkle, short-spired purple, northern striped dogwinkle, striped dogwinkle, ribbed dogwinkle, emarginate whelk, ribbed rock whelk, rock thais, short-spired purple snail, rock whelk

Synonyms: Nucella emarginata, Thais emarginata
Phylum Mollusca 
 Class Gastropoda
   Order Neogastropoda
    Suborder Rachiglossa
     Family Nucellidae
Nucella ostrina collected on Northwest island, Rosario Bay, WA
(Photo by: Nathaniel Charbonneau 7/26/02)
Description:  Like all members of family Nucellidae, this species has a strong shell with a well-developed spire (not more than 7 whorls), a short siphonal notch or canal but no anal notch.  The shell is not highly polished.  The animal has a horny operculum. Nucella ostrina is a snail which grows up to 4 cm long (usually less than 3 cm) with strongly developed spiral ridges. Its heavy shell has only 3 whorls.  The spiral ridges are usually white with the furrows between being a yellow, orange, brown, gray, or black. Heavier ridges often alternate with more delicate ridges, especially in less exposed situations.  The ridges may include coarse nodules.  In the most exposed sites the shell may be nearly smooth (photo).  The siphonal canal is short, and the umbilicus is closed. The columella is smooth but arched.  The operculum is dark brown with the nucleus low and to one side.  Individuals from the northern part of the range tend to be more elongated than those farther south.

How to Distinguish from Similar Species:Nucella lamellosa has longitudinal ridges or frilly lamellae as well as spiral ridgesNucella canaliculata has spiral ridges of nearly equal size, and a deep groove separating whorls.  This snail was formerly called Nucella emarginata along our coast, but now the species has been recognized as two different species. N. emarginata looks similar but is found in southern California, while N. ostrina is found mostly in more northern locations such as here. N. emarginata can be distinguished from N. ostrina by the fact that it has a thickened "parietal nub" on the shell (the edge of the aperture above the columella is thickened), while that of N. ostrina is less so), it lays eggs which are more rounded and with shorter stalks, it is less elongated than N. ostrina, and the spiral ridges are more likely to have nodules on them.

Geographical Range:  Ranges from Aleutian Islands (Alaska) to Cayucus (San Luis Obispo Co.)

Depth Range:  High intertidal to low intertidal

Habitat:  Rocky substrate where mussel beds are plentiful, mostly on the exposed outer coast.

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. canaliculataN. 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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References:
Dichotomous Keys:
  Carlton, 2007
  Flora and Fairbanks, 1966 (as Thais emarginata)
  Kozloff, 1987, 1996 (as N. emarginata)

General References:
   Brusca and Brusca, 1978
   Griffith, 1967 (as Thais emarginata)
   Harbo, 1999
   Johnson and Snook, 1955 (as Thais emarginata)
   Kozloff, 1993 (as N. emarginata)
   Lamb and Hanby, 2005
   McConnaughey and Mc'Connaughey, 1986
   Morris, 1966 (as Thais emarginata)
   Morris et al., 1980
   Niesen, 1994
   Niesen, 1997
   O'Clair and O'Clair, 1998 (as N. emarginata)
   Ricketts et al., 1985
   White, 1976

Scientific Articles:
Marko, Peter B., 1998.  Historical allopatry and the biogeography of speciation in the prosobranch snail genus Nucella.  Evolution 52:3 757-774

Sorte, Cascade J.B. and Gretchen E. Hofmann, 2005.  Thermotolerance and heat-shock protein expression in northeastern Pacific Nucella species with different biogeographical ranges.  Marine Biology 146: 985-993
 
 
 



General Notes and Observations:  Locations, abundances, unusual behaviors, etc.:
Subject in the picture above was found on Northwest Island in Rosario Bay, in a mussel bed.


This individual was found by Dave Cowles at San Simeon, CA in 1995 in a Mytilus californianus bed.  It is drilling into a mussel.


This individual is foraging among Balanus glandula barnacles, a major prey species.  Night photo by Dave Cowles, Sept 2005


The species can be found in several colors, even on the same rock.
These were photographed at beach #4, Kalaloch, July 2008 by Dave Cowles

Uncolored stripes

This individual has no color on its spiral bands but the bands clearly alternate large and small.  Otherwise it looks very much like N. canaliculata.    Photo by Dave Cowles, August 2011.

Smooth Smooth underside
Individuals in exposed situations tend to be smooth.  This individual was on the western, exposed end of Swirl Rocks, south of Lopez Island.  Identification was made with the help of George Holm.



Authors and Editors of Page:
Nathaniel Charbonneau created page 7-2002
Editors:  Dave Cowles 8-2002, 2005, 2009
              Hans Helmstetler 1-2003