Posted: Feb 15 2007
Parvanachis ostreicola (G. B. Sowerby III, 1882), Oyster Dove Shell
Abbott identifies P. ostreicola as a form of Parvanachis obesa
(C. B. Adams, 1845) found in NW Florida. Common and Scientific
Names of Aquatic Invertibrates from the United States and
Canada: Mollusks, 2nd Ed., 1998, and Malacolog accept
P. ostreicola as a separate species. Abbott describes P. ostreicola
as dark-brown and with strong spiral threads or wider incised
lines, and found in shallow water. Abbott does not picture
P. ostreicola nor is it treated in the most common shell books.
The most recent treatment of this species is in The Family
Columbellidae in the Western Atlantic Part IIa. – The Pyreninae,
George E. Radwin, The Veliger, 20(2): 119-133, 1977. Radwin
describes this species as minute (3-5 mm) with an acute spire,
a convex silhouette, slightly shouldered, apertural lip denticulate,
columella weakly dentriculate, sculpture reticulate, and there is
often a peculiar bald (unscuptured) spot on the dorsal side. Color
from reddish-brown to deep purple-black. Differs from P. obesa
by its greater proportion of body whorl to spire, less flaring
apertural lip, greater overall convexity of the spire profile,
uniform and distinct color, and consistently stronger spiral sculpture.
Radwin also describes the habitat of P. ostreicola as on oysters in
shallow, mud-bottom areas and the habitat of P. obesa as "substantially"
different - in deeper water (3 meters plus) on sand bottoms. I have
found P. ostreicola only twice, both times in NW Florida in association
with oysters. I have found P. obesa on both sides of Florida in lagoonal
waters less than 3 meters deep on sandy or sand and grassy bottoms,
but never in association with oysters.
Being so tiny, with such an acute spire and wide body whorl, P. ostreicola
is very difficult to photograph close-up and capture the entire shell in
good focus. So, to portray all its features I've presented several images
of two different shells from Cedar Key, Levy County, Florida. One
(4.7 mm, adjacent photos) has been oiled to bring out the reddish-brown
color. The other (5 mm, below) displays the dentriculate lip and columella.
2/16/2007 Herb Chapin:
There are 4 lots of Parvanachis ostreicola catalogued into the Bailey Matthews Shell Museum, all collected on or near Sanibel Island, FL. In addition I just brought back 3 specimens from our trip to Sanibel last month. All of mine are beach collected, so I can't speak to habitat.