BASTERIA, 66:123-127, 2002
The urocoptid closing device, rare and remarkable (Gastropoda, Pulmonata, Urocoptidae)
E. Gittenberger
National Museum ofNatural History Naturalis, P.O. Box 9517, NL 2300 RA Leiden, The Netherlands;
& P. Mordan
Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK;
The of the device structure urocoptid closing (UCD) was studied under the SEM in the only
in which it has 40 species been reported to occur. Over urocoptid species were searched in
vain for additional occurrences. When moistened, the UCD and function in expands may an analogous the clausiliid way to clausilium. The two devices are clearly not homologous.
words: Key Gastropoda, Pulmonata, Urocoptidae, Clausiliidae,shell aperture, urocoptid clo-
sing device, clausilium.
INTRODUCTION
The wide variety ofconchological elaborations of the urocoptid columellahave been illustrated exhaustively by Pilsbry (1903, 1904), and some of these illustrations subse-
Zilch take the form of quently published by (1960). They typically one or more spiral
lamellae, which the or one may run entire length of the shell be confined to just or two whorls. Sometimes these lamellae extend into the of which ledges, edges may become serrate In the or radially spinose. genera Mychostoma Albers, 1850,and Apoma Beck, 1837, well as as in several species of Urocoptis (Spirocoptis) Pilsbry, 1902, the columella is dis- thickened. These be tinctly thickenings may single or double, and in some species may be beaded.
Axial lamellae in the lower whorls have are postulated to a protective function (Pilsbry, 1903: xvi; Gittenberger, 1996). The function of thickenings is uncertainbut they certain-
to the shell. It noticeable ly serve strengthen is that in the upper whorls of urocoptid shells which decollate, the columellais noticably thinner. Spiral thickenings and lamellae channels may additionally provide to help align and support the free retractor muscles,
principally the columellar muscle which supports the shell above the head-foot of the snail this crawling (Paul, 1983); is particularly important in groups as the Urocoptidae with elongate shells. In addition these modifications of to the columella, at least one species of urocoptid
a device. This device possesses closing urocoptid closing (= UCD) was initially observed G. H. of by Clapp Pittsburgh, Pennsylvania, but a description was first published by Pilsbry (1903: 97-98, pi. 1 figs 14-15) for the Jamaican Mychostoma album (C. B. Adams, occidentalis 1849) var. Pilsbry, 1903, for which the type locality is the Great Valley estate, 124 BASTERIA, Vol. 66, No. 4-6, 2002
Hanover, and var. minima Pilsbry, 1903, from Swift River. Pilsbry stated that the UCD resembles the clausiliumof the Clausiliidae; he describedit as a tongue-shaped, whitish process continuous with the solid axis of the shell, situated in the fifth whorl from the base. Paul (1983: fig. 4B, C [our figs 2, 3]) also illustrated the UCD, which he found in only a single population. He referred this population to a complex comprising the dex- tral forms ofMychostoma, which includes M. album, but for which he considered the epi- thet alabastrina L. Pfeiffer, 1845 (fig. 1) to have priority. This UCD was situated in whorls
4-5 where, in this species, the columella has become markedly thickened.
1-3. alabastrina unknown loca- Figs Mychostoma (L. Pfeiffer, 1845), Jamaica. 1, shell shape ofa syntype from an
the the lity; 2, 3, details of shells from Great Valley Estate, Hanover, showing location of UCD, stippled, on
1983: the columella. Scale bars 1 mm. After Paul, figs 2A, 4B, 4C.
SURVEY
electron studied the of the UCD Using a scanning microscope we structure in a dry shell of Mychostoma alabastrina (L. Pfeiffer, 1845) from Jamaica, Great Valley Estate, Hanover (fig. 4), in the collection of the National Museum of Natural History, Leiden.
The strongly wrinkled UCD (fig. 4B, C) is connected to the smooth columellaby a broad
in which zone the two extremely different surface types are connected withoutany clear boundary (fig. 4A). Gittenberger &Mordan: The urocopid closing device 125
Fig. 4. The UCD in a dry shell of Mychostoma alabastrina (L. Pfeiffer, 1845); the connection to the columella.
Jamaica, Great ValleyEstate, Hanover; Colln National Museum ofNatural History, Leiden. Scale bar 100 µm.
SEM photographby J. Goud (Leiden).
We have also undertaken broad ofthe for further a survey Urocoptidae searching any
of the UCD. This included 40 in 14 from the three sub- occurrence over species genera families Urocoptinae, Eucalodinaeand Microceraminae in the collections of the British Museum Most but (Natural History) (Table 1). were dry shells, it is possible to examine
in these for presence of a UCD a non-destructive way by using very strong transmitted recommended G. H. the letter E. R. dated light, as by Clapp, original finder, in a to Sykes
1902 and housed in the BM (NH); this was followed where necessary by internal exami-
nation ofthe shell. The small numberof alcohol-preserved shells were dissected.
UCDs were recorded only in M. alabastrina. A total of 14 lots ofM. alabastrina, all dry,
were examined; of a total of 114 individual shells, 51 (45%) contained the UCD. In all
cases the UCD occupied the 5th of 6th whorl. Pilsbry (1903: 97-98) stated that the UCD becomes flexible when wet, though it is not sufficiently large to occlude the entire cavi-
ty of the shell whorl. We were able to confirm the first part of this statement, but observed that when moistened the UCD expanded slightly, the wrinkles on its surface
disappeared, and it was in fact able to occlude the whole cavity. Pilsbry also described the made of "conchiolin covered unconsolidated structure as being with an layer of lime
crystals"; again, the first part of the statement appears to be true, but the crystals are clearly situated within the conchiolin matrix ofthe device.
DISCUSSION
Paul (1983) has undertaken a phylogenetic analysis of Jamaican urocoptid genera, in
which advanced of There to Mychostoma emerges as an group Apominae. is no reason believe that the UCD than of is anything more an autapomorphy a single species, or pos-
sibly species complex, of this genus. 126 BASTERIA, Vol. 66, No. 4-6, 2002
5, 6. alabastrina (L. Pfeiffer, 1845), the structure of the UCD, close to the end ofthe Figs Mychostoma process.
Jamaica, Great Valley Estate, Hanover; Colln National Museum of Natural History, Leiden. 6, detail of 5.
and Scale bars 100µm (5) 10 µm (6). SEM photographs by J. Goud (Leiden). Gittenberger &Mordan: The urocopid dosing device 127
The UCD attached the columella from the and the animalwith- is to distally aperture,
draws above the level ofit. The function of the UCD is therefore most probably protec-
uncertain tive as it would tendto oppose any entry from the aperture direction. It is why
the UCD is missing in slightly more than halfthe specimens that were investigated, but post-mortem loss seems the most likely explanation although there was no attachment
scar visible on the columella.
It is unlikely that this peculiar device would have a simple, single-gene background.
There is no obvious homologue structure known from closely related species.
Therefore, its evolutionary origin is unclear.
REFERENCES
of the terrestrial shells. GITTENBERGER, E., 1996. Adaptations aperture in gastropod-pulmonate
Netherlands Journal ofZoology 46: 191-205.
The and of PAUL, C.R.C., 1983. comparative anatomy systematics Jamaican Urocoptidae (Mollusca:
Pulmonata). - ZoologicalJournal of the Linnean Society 78: 1-28.
PILSBRY, H.A., 1903-1904. Urocoptidae, Achatinidae. - Manual of Conchology (2) Pulmonata 16 (61-62): 1-
128 [1903]; (63-64): 129-329, i-xl [1904].
RICHARDSON, C.L., 1991. Urocoptidae: catalog ofspecies. - Tryonia 22: 1-245
ZILCH, A., 1960. Euthyneura. In: W. WENZ, Gastropoda. - Handbuch der Palaozoologie 6 (2): 401-600.
Table 1. The urocoptid species searched. Nomenclature after Richardson (1991).
Tomelasmus acus (L. Pfeiffer, 1841), Tomelasmus humboldtii (L. Pfeiffer, 1840), Pychnoptychia
album (C. B. Adams, 1849), Mychostoma insuflatusTetrentodonJaume& Torre, 1972, Tetrentodon
[= M. alabastrinealabastrina (L. Pfeiffer, 1845)] intermedium Sowerby, 1875, Spirostemma
albocrenata (L.(L. Pfeiffer, 1863),1863), Paracallonia interruptum (L. Pfeiffer, 1857), Idiostemmaldiostemma
angustior■ (L. Pfeiffer, 1864),CapillaceaCapillacea irroratus (Gundlach, 1856), Tomelasmus
apiostoma (L. Pfeiffer, 1856),1856),EpirobiaEpirobia ipswichensis Pilsbry, 1903, Spirostemma caymanensiscaymanensis (Pilsbry, 1930),.1930), Brachypodiella keineri (L. Pfeiffer, 1846), Microceramus
chemnitzianum (Ferussac, 1821),.1821), Apoma lescallei Jaume & Torre, 1972,1972, Brachypodella
chordata: (L. Pfeiffer,Pfeiffer, 1855),Brachypodiella menkeanamenheana (L. Pfeiffer, 1853), Urocoptis
clara (L. Pfeiffer,Pfeiffer, 1865),.1865), LiocalloniaLiocallonia microstoma (L. Pfeiffer, 1861), Coelostemma
collaris (Ferussac, 1821), Brachypodiella palmeri Bartsch, 1906, Holospira
costata (Guilding, 1828), Brachypodiella plumbea (L. Pfeiffer, 1864),BadiofauxBadiofaux
cuestaiI Torre, 1930, Liocallonia poeanaCochlocinella(Orbigny, 1841), Cochlocinella
diminutum (C.B.Adams,(C.B. Adams, 1851),1851),.Apoma princeps (C.B. Adams, 1851), Spirostemma dautzenbergianadautzenbergiana (Crosse, 1890), Callonia procera (C.B. Adams, 1850), Urocoptis
dunkeri (L. Pfeiffer, 1845),1845), Spirostemma prunosa (Morelet, 1849),1849), Necocoptis
elatiorelatiorC.B.■ C.B. Adams, 1851),,1851),SpirostemmaSpirostemma pupaeformisUrocoptis(C.B. Adams, 1850), Urocoptis
eleganselegans (L. Pfeiffer, 1863),.1863), Microceramus Pycnoptychiashuttleworthiana L. Pfeiffer, 1856),Pycnoptychia
gosseiI (L. Pfeiffer,Pfeiffer, 1845), Microceramus simplex (C.B. Adams, 1849), Simplicervix
gracilis (Adams, 1851),.1851), AnomaAnoma truncatula (Lamarck, 1822), Amphicosmia
guitartii Jaume& Torre, 1972, Heterocoptis variabilisvariabilis (L. Pfeiffer, 1863),MacroceramusMacroceramus