Tegula funebralis (A. Adams, 1855)

Common name(s) Black turban snail, Black tegula
Synonyms:
Phylum Mollusca
 Class Gastropoda
   Subclass Prosobranchia
    Order Archaegastropoda
     Suborder Trochina
      Family Trochidae
Tegula funebralis in the intertidal at Cape Flattery.  Diameter approximately 2 cm
(Photo by: Dave Cowles July 2004)
Description:  Shell is black or purple above and white below (picture), coiled, with a definite raised spire (but the shell is only about as tall as wide), no siphonal notch or canal in aperture, interior of the shell is pearly.  Animal has an operculum which is thin and horny with spiral lines.  Columella has two small nodes (picture).  The umbilicus is closed by a callus (picture).  Shell up to 3 cm diameter.  The apex is frequently heavily worn, and shell may be encrusted with coralline algae or bryozoans.  Animal's foot is black on the sides (picture).  The black on the shell is due to a dark periostracum.

How to Distinguish from Similar Species: Tegula pulligo has an open umbilicus.  Tegula brunnea has only one node on the columella.  Both these species are brown rather than black.

Geographical Range:  Vancouver Island to Baja California

Depth Range:  Mostly intertidal

Habitat:  Rocky intertidal of the outer coast.  Rarely found in inland waters such as Puget Sound or the Straits of Juan de Fuca.

Biology/Natural History:  This species is an algal grazer, on microscopic films, attached algae, and wrack.  It prefers soft algae such as Macrosystis, Nereocystis, and Mastocarpus.  It can be very abundant and conspicuous on the open coast (picture), especially in the mid-intertidal zone.  The slipper shell Crepidula adunca settles preferentially on this species.  The symbiotic limpet Collisella asmi (small, black) is often found on the shell as well (it grazes on the microalgae on the shell) but this limpet regularly "switches" Tegula hosts while the filter-feeding slipper shell stays put.  The species is found more abundantly in open rocky areas than in areas heavily covered with algae.  The animal crawls via retrograde (front to back) locomotory waves passing asynchronously down the two sides of the foot.  They normally crawl about 0.6 to 0.8 mm/second but can nearly double this speed if they contact Pisaster ochraceous.  They are said to be negatively phototactic.  They excrete uric acid which probably helps in water conservation during low tide.  Sexes are separate.  Males tend to have paler soles of their foot than females have.  Larvae grow rapidly but large individuals grow very slowly.  Their shell produces prominent growth lines yearly.  Large individuals may be 20-30 years old.   Eaten by sea otters, red rock crab (Cancer antennarius), Pisaster ochraceous, and some predaceous snails.  It flees from Pisaster but not non-predatory seastars, and may escape predatory snails by climbing up on top of their shell.  If on a sloping surface it simply detaches and rolls down the slope.  One can observe this readily in the intertidal when approaching rocks with this species on them.  Many roll down the rocks, but a large portion of these are hermit crabs inhabiting the shell.  Were used extensively as food by California Indians.  Their empty shells are a favorite of hermit crabs.


 
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References:


Dichotomous Keys:

  Kozloff 1987, 1996
  Flora and Fairbanks, 1966

General References:
  Kozloff, 1993
  Morris et al., 1980
  Niesen, 1994

Scientific Articles:


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


This view of the underside of T. funebralis shows the operculum, the closed umbilicus (brown stain), and the two nodes on the columella (bumps just above the operculum)


Tegula funebralis are often found aggregated at low tide, as in this photo taken at Shi shi beach, August 2005.  Photo by Dave Cowles


Here is another aggregation in a tidepool, on red algae.  Photo by Dave Cowles, August 2005
Note also the eroded spire, which is common on this species.



Most Tegula funebralis have a bare shell with an eroded spire.  Some, however, such as this specimen in a tidepool at Little Corona del Mar, CA, may be completely covered
with a short, thick coat of bushy red algae.  Note also the black foot of the living snail.  Photo by Dave Cowles March 2005


This aggregation is in the intertidal at Point of Arches, south of Shi Shi Beach.
 


Tegula funebralis crawls along the sandy bottom of a tidepool near Rialto Beach, WA at low tide, leaving a trail behind it.


Authors and Editors of Page:
Dave Cowles (2004):  Created original page