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Coptocheilus altus sibuyanensis (Bartsch, 1915) |
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(Sinistral Specimen On The Left) |
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| 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 familyDiplommatinidae 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 Coptocheilus Gould, 1862 [+ Schistoloma Kobelt, 1902] [type: Cyclostoma alta G. B. Sowerby II, 1842] belongs, are reported in the table below (Dautzenberg; 1914, Nisters, 1999; Nunes and Santos, 2007; Gerber, 2009; taxonomy and nomenclature updated by H. G. Lee). As one can see, there are fifteen records from three families, Cyclophoridae, Aciculidae, and Diplommatinidae, but Coptocheilus Gould, 1862 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 the 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, until Dr. Gary Rosenberg recently found two sinistral specimens of Adamsiella irrorata in Jamaica, only a single instance of reversal in the entire (dextral) family Annulariidae Henderson and Bartsch, 1920, which numbers about 700 species, was known (Jacobson and Boss, 1971; Watters, 2006). 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:
Aciculidae:
Bartsch, P., 1915 The Philippine land
shells of the genus Schistoloma Proc. U. S. N. M. 49(2104):
195-204 + 1 pl. (51). |
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