World Congress of Malacology Antwerp ... - Unitas Malacologica

on the same plane as the aperture, i.e., it runs approximately at right angles to the apertural plane.
Therefore, it is clearly visible in lateral view and not quite so in apertural or adapertural views. The
groove curves adaxially at the tip of the also curved pillar. Male shells are distinguished because
there is no groove but a continuation of the parietal callus which, apparently “infills” the groove
described for the female shells.
The existence of such a structure, only present on the females of O. plata, may have helped the
animal glue the capsules to the apertural side of the shell, or else may have been at least related to the
process of laying capsules.
When a snail dies in the forest, how long will the shell persist?
Pearce, Timothy A.
Carnegie Museum of Natural History, 4400 Forbes Ave, Pittsburgh, Pennsylvania, 15213, USA,
Email: PearceT@CarnegieMNH.org
After snails die, their shells sometimes persist in the environment. Although some shells survive as
fossils for hundreds of millions of years, most shells decompose more quickly, probably in months or
years.
We know little about the rate at which shells decompose, and what we know is mostly anecdotal.
Nevertheless, many studies knowingly or unknowingly make assumptions about the rate of shell
decomposition. Endangered species biologists need to know how long ago a species was living at a
site having an empty shell. Using empty shells to estimate diversity of living populations requires
assuming that death assemblages accurately reflect living populations across species and localities.
However, in most cases, we do not know whether fragile and robust species, at different localities,
decompose at the same rate.
In order to determine how long empty shells persist in the forest, and to test for differences in
decomposition rate among species and among sites, I put shells in mesh litter bags at one site in
Delaware and at two sites in northern Michigan, and monitored shell weight annually for 6 years.
Results indicate that mean annual mass decrease of unbroken shells was 5-8%, with no significant
difference among localities, but some differences among species. Mean annual mass decrease of all
shells, crushed plus unbroken, was 8-13%, showing differences among sites and larger species tended
to decrease mass more slowly. Surprisingly, loss of periostracum did not increase rate of mass loss.
Molecular systematics and proposed taxonomy in Ariolimax (Stylommatophora: Arionidae)
Pearse, John S. 1 ; Leonard, Janet L. 1 ; Breugelmans, Karin 2 ; Backeljau, Thierry 2
1. Joseph M. Long Marine Laboratory, 100 Shaffer Rd, University of California, Santa Cruz, Santa
Cruz, CA 95060 USA,
Email: pearse@biology.ucsc.edu; jlleonar@ucsc.edu
2. Department of Invertebrates, Royal Belgian Institute of Natural Sciences, Rue Vautier 29,
Brussels, B-1000, Belgium,
Email: Karin.Breugelmans@naturalsciences.be; Thierry.Backeljau@naturalsciences.be
Molecular data suggest revision of the giant banana slugs of west coast of North America. The genus
Ariolimax Mörch, 1860 is currently broken into five taxa in two subgenera based on penis
morphology, Ariolimax, sensu stricto and Meadarion Pilsbry, 1948. A. (A.) columbianus columbianus
(Gould in Binney, 1851) ranges from central California to southeast Alaska while A. (A.) c.
stramineus Hempill, 1891 is found on the coast of south-central California. A. (M.) dolichophallus
Mead, 1943, A. (M.) californicus californicus Cooper, 1872, and A. (M.) c. brachyphallus Mead 1943
were known from different parts of the San Francisco Peninsula. Sequence data from 3 mitochondrial
and 2 nuclear genes revealed 5 distinct clades in an unresolved polytomy. There are two clades
within A. (A.) c. columbianus, which we propose should each have separate species ranks: A.
columbianus ranging from northwest California to southeast Alaska and A. buttoni (Pilsbry &
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