Schistoloma alta sibuyanica Bartsch, 1915

(Sinistral Specimen On The Left)

Sinistral Schistoloma alta sibuyanica Bartsch, 1915
Sinistrality in land prosobranchs (operculate land snails) is a rare and interesting phenomenon. It is a "normal" occurrence in about six lineages of the cyclophoroidean family Diplommatinidae L. Pfeiffer, 1858, and one species, Palaina taeniolata hyalina Quadras and Möllendorff, 1894 from Guam has somewhat indifferent chirality. In the H. G. Lee collection there are 240 dextral and 4617 sinistral specimens of this tiny oddity (just under 5% dextral mutants). See: Dextral Palaina taeniolata hyalina Quadras and Möllendorff, 1894
Records for mutant reversal of coil in the cyclophoroideans, to which Schistoloma Kobelt, 1902 [type: Cyclostoma alta G. B. Sowerby II, 1842] belongs, are reported in the table below (Dautzenberg, 1914, Nisters, 1999; taxonomy and nomenclature updated by H. G. Lee). As one can see, there are twelve records from three families, Cyclophoridae Aciculidae, and Diplommatinidae, but Schistoloma Kobelt, 1902 is not in any of these three; it appears to be the first known instance of mutant reversal in the Pupinidae.

Also treated in the table is other large group of terrestrial prosobranchs, the annulariid-pomatiid stock, which arose independently of the Cyclophoroidea and comprises the terrestrial radiation of the Littorinoidea. The land snails of this superfamily also seem disinclined to reversal of coil. In fact, Watters (2006) reported only a single instance of reversal (Jacobson, 1971) in the entire (dextral) family Annulariidae Henderson and Bartsch, 1920, which numbers about 700 species. In the other littorinoidean landsnail group, the (dextral) Pomatiidae Newton, 1891, there is only one species known to exhibit reverse chirality (Dautzenberg, 1914).
 
MUTANT REVERSAL OF COIL IN TERRESTRIAL PROSOBRANCHS (sinistrality)
 
CYCLOPHOROIDEA:
Cyclophoridae:
Ditropis planorbis (Blanford, 1869) [Type of Ditropis Blanford, 1869 OD]

Aciculidae:
Acicula letourneuxi (Bourguignat, 1864)
A. lineata (Draparnaud, 1801)

Diplommatinidae:
Cochlostoma apricum (Mousson, 1847)
C. crassilabrum (Dupuy, 1851)
C. henricae henricae (Strobel, 1851)
C. hidalgoi (Crosse, 1864)
C. obscurum (Draparnaud, 1801)
C. patulum (Draparnaud, 1801)
C. septemspirale (Razoumowsky, 1789)
Diplommatina (Sinica) boettgeri Möllendorff, 1887
Diplommatina (Sinica) kiiensis Pilsbry, 1902
Nicida catathymia (Sykes, 1898)

Pupinidae:
Schistoloma (S.) alta sibuyanica Bartsch, 1915

LITTORINOIDEA:
Pomatiidae:
Pomatias elegans (Müller, 1774)

Annulariidae:
Cobolostylus jayanus (C. B. Adams, 1849)

Bartsch, P., 1915 The Philippine land shells of the genus Schistoloma Proc. U. S. N. M. 49(2104): 195-204 + 1 pl. (51).
Dautzenberg, P., 1914. XXIme assemblée générale annuelle (presidential address). Bulletin du Societé Zoologique de la France 34: 50-60.
Jacobson, M. K. and K. J. Boss, 1971. On a sinistral chondropomine from Jamaica. The Nautilus 84(4): 127-128. April.
Kobelt, W., 1902. Cyclophoridae bearbeitet. Friedländer und Sohn, Berlin. xxxix + pp. 1-662. July.
Nisters, H., 1999. Personal communication, 6 May 1999 14:49:34 PDT. Conch-L Archive 11496.
Watters, G. T., 2006. The Caribbean Land Snail Family Annulariidae: A revision of the higher taxa and a catalog of the species. Backhuys, Leiden [viii] + 1-557 + 1 pl. + 8 pp. maps + 488 pp., 10 figs., 56 maps.