Evolution of whole-body enantiomorphy in the tree snail genus Amphidromus

Diverse animals exhibit left–right asymmetry in development. However, no example of dimorphism for the left–right polarity of development (whole-body enantiomorphy) is known to persist within natural populations. In snails, whole-body enantiomorphs have repeatedly evolved as separate species. Within populations, however, snails are not expected to exhibit enantiomorphy, because of selection against the less common morph resulting from mating disadvantage. Here we present a unique example of evolutionarily stable whole-body enantiomorphy in snails. Our molecular phylogeny of South-east Asian tree snails in the genus Amphidromus indicates that enantiomorphy has likely persisted as the ancestral state over a million generations. Enantiomorphs have continuously coexisted in every population surveyed spanning a period of 10 years. Our results indicate that whole-body enantiomorphy is maintained within populations opposing the rule of directional asymmetry in animals. This study implicates the need for explicit approaches to disclosure of a maintenance mechanism and conservation of the genus

Letter to H.B. Stenzel from H.A. Pilsbry on 1953-11-23

Jackson School of Geoscience

Letter to H.B. Stenzel from H.A. Pilsbry on Undated

Jackson School of Geoscience

Taxonomy and distribution of species of Gastrocopta Wollaston 1878 (Mollusca: Gastropoda: Gastrocoptidae) from the Galápagos Islands (Ecuador)

A revision of Gastrocopta from the Galápagos Islands (Ecuador) is made. Four new species from Pinzón, Santa Cruz and Floreana Islands are described; species previously known are redescribed and new locations are added. Gastrocopta (Gastrocopta) reibischi is revalidated through new records from Floreana, Isabela and San Bartolomé Islands. Shell shape and the number, morphology and disposition of the apertural barriers support the discrimination of the taxa. The species have cylindrical to pupoid shells; the number of apertural barriers–differentiated as lamellae, folds and nodulae–varies between 4 and 11, almost completely occluding the aperture in the more complex cases. These structures are: angular-parietal, infraparietal, supracolumellar, columellar, subcolumellar lamellae, and supernumerary, basal, infrapalatal, lower-palatal, interpalatal, upper-palatal and suprapalatal folds. In addition to this classic scheme, a supernumerary fold and a nodule are added. Calcareous concretions–pustulae–are found in several species, mainly located in the peristome. The aulacognathous jaw and radular dentition formulae of Gastrocopta (Gastrocopta) clausa and Gastrocopta (Gastrocopta) munita, are described and photographed for the first time.Fil: Miquel, Sergio Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Brito, Fátima Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin