Lacuna vincta (Montagu, 1803)

Common name(s): Northern lacuna, wide lacuna, northern chink shell

Synonyms: Lacuna carinata, Lacuna divaricata, Lacuna fusca, Lacuna oretusa, Lacuna pertusa,  Lacuna porrecta, Lacuna solidula, Trochus divaricata Lacuna vincta
Phylum Mollusca 
Class Gastropoda 
Order Mesogastropoda 
Suborder Taenioglossa 
Lacuna vincta, 7 mm long, found clinging to algae on dock of Friday Harbor Marina.
(Photo by: Dave Cowles, July 2014 )

Description:  Shells in Family Littorinidae have no siphonal notch.  The interior of the shell is not pearly.  An operculum is present (photo).  The height is greater than the diameter, but not several times greater.  The columella has no folds or ridges (which go transversely--in this species there may be a longitudinal set of ridges with a groove between).  Members of subfamily Lacuninae (chink shells) have a slitlike umbilicus between the columella and the body whorl (photo). Lacuna vincta has an aperture which is about half (or slightly over) the height of the shell.  The shell is tan or brown, with a broad white spiral band and a slightly glossy periostracum.  In these specimens, the open umbilicus is between two distinct white longitudinal ridges on the columella (photo).  Height to 1.6 cm.

How to Distinguish from Similar Species:Lacuna variegata has brown chevrons instead of the white stripe spiraling down the shell, and is more common on eelgrass. L. vincta also is said to have an unusually wide aperture.  The umbilicus of L. variegata is also not between 2 ridges on the columella, as it is in this species.

Geographical Range:  Alaska to California; unlikely to be found south of Washington.  Also in the north Atlantic.

Depth Range:  Intertidal

Habitat:  On algae, usually on rocky shores.

Biology/Natural History:  Females lay eggs in gelatinous doughnut-shaped masses on seaweeds.  The species has a long-lived pelagic larva.



 

References:

Dichotomous Keys:
  Kozloff, 1987, 1996

General References:
  Lamb and Hanby, 2005
  O'Clair and O'Clair, 1998
  Sept, 1999

Scientific Articles:
Fretter, V. and R. Manly, 1977.  Algal associations of Tricolia pullus, Lacuna vincta, and Cerithiopsis tubercularis (Gastropoda) with special reference to the settlement of their larvae.  Journal of the Marine Biological Association of the United Kingdom 4: pp 999-1017

Grahame, J., 1977.  Reproductive effort and r and K-selection in two species of Lacuna (Gastropoda: Prosobranchia).  Marine Biology 40: pp 217-224

Johnson, Craig R., and Kenneth H. Mann, 1986.  The importance of plant defence abilities to the structure of subtidal seaweed communities: the kelp Laminaria longicruris de la Pylaie survives grazing by the snail Lacuna vincta (Montagu) at high population densities. Journal of Experimenal Marine Biology and Ecology 97:3 pp 231-267

Thomas, Martin L., and Frederick H. Page, 1983.  Grazing by the gastropod, Lacuna vincta, in the lower intertidal at Musquash Head, New Brunswick, Canada.  Journal of the Marine Biological Association of the United Kingdom 3: pp 725-736

Web sites:


General Notes and Observations: Locations, abundances, unusual behaviors:

My first encounter with this species was individuals clinging to blades of red algae on the docks in Friday Harbor Marina, 2014.


Umbilicus
The species is shaped like a Littorinid but has a slitlike open umbilicus.  All the specimens of this species that I found had the slit between two white, parallel longitudinal ridges as seen here.


Operculum
The species has a non-calcified operculum, seen partially withdrawn inside the aperture.


Variation
This photo shows some of the variation in coloration.  The rule marks are 1 mm.  All specimens from algae on Friday Harbor Marina docks.
 


Authors and Editors of Page:
Dave Cowles (2014):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)

Salish Sea Invertebrates web site provided courtesy of Walla Walla University