Amphidromus inversus (Müller, 1774)
“The specimen from the first named locality (Coast of Sambas) is sinistral, the majority of the other specimens is dextral; nearly all are rather small, measuring only 43½ and 45 mill.” (Schepman, 1896)
Müller (1774) original descriptions on Helix inversa - “Helix teſta conico-acuminata, ſiniſtrorſa, albida, ſtrigis & faſcia rufis, labro reflexo. Aliquantum major H. dextra, cum qua figura & ſtatura convenit, colore vero ſpirarumque circumaƐtione diverſa eſt. Apex teſtae acutus eſt. AnfraƐtus oƐto, ſiniſtrorſi ſtrigis rufis, oblique ſecundum longitudinem duƐtis; faſcia lata pallide rufa juxta basin. Apertura ovata, alba; labrum candidum, reflexum; labium incumbens concolor, anfraƐtus aperturam penetrans fuſcus.”
Helix inversa - “Long. 2 unc. 4 lin. Lat. 1 unc. 1 lin.” (Müller, 1774)
“Our results suggest that the studied A. inversus population is well mixed. In just 7 days, a large proportion of the population at our study site was seen to move between trees, presumably via connected branches or the forest floor. Although dispersal was mostly limited to clusters of trees with strongly overlapping crowns, individuals were also seen to cross forest gaps. Over a whole year, almost two-thirds of the individuals had moved away from their original tree, in some cases travelling the length of the entire study plot. The generation time of Amphidromus is at least 2 years (MS, unpublished data). It is thus improbable that Amphidromus populations in separate trees in a closed forest will be sufficiently isolated for coiling morphs to become randomly fixed per tree. In our study locality, we found that all trees contained random samples of dextral and sinistral individuals, with no indication of bimodality. We conclude that strong tree-level population structure is not present and is not a likely explanation for the maintenance of dimorphism. It is possible that our study site was not representative (for example, because of its relatively high population density), and tree-based populations are more strongly isolated elsewhere. However, spot checks at places in Kapas with lower population densities showed that trees with randomly mixed morphs are, in fact, the norm, and the same appears to apply to populations of A. martensi, a species from Borneo (MS and PGC, unpublished results). It is also possible that our study missed occasional long distance dispersal to isolated, empty patches of habitat, which could subsequently become fixed for one coiling morph. However, in general, Amphidromus habitat consists of continuous closed-canopy forest, and such events will not be common.” (Schilthuizen et al., 2005)
Other localities – “Coast of Sambas” leg. Hallier, “Smitau on the Kapoeas River, and Roema Manoeal on the southern foot of Mount Kenepai” leg. Buttikofer, “Mount Dadap” leg. Moret, and “Sintang” leg. Goedhuis (Schepman, 1896)