Rhodea
Chirality
18-12-2008 09:19
Chirality is the phenomenon that an assymetric
structure can come in two, non-identical,
mirror-image forms. This phenomenon can be found in
many groups of animals and plants. Land snails are
just one example, leading to sinistral specimens
besides the normal dextral ones in a population
(intra-specific chirality) or sinistral species among
other, dextral species in a group (inter-specific
chirality).
In the Neotropics there are also a few examples of chirality. In Orthalicidae there are three genera: Drymaeus, Liguus and Corona. In the Subulinidae there is an example in Rhodea. And I have seen a report on a sinistral Megalobulimus, but that may be just an aberration, just like the specimens of Rabdotus, Thaumastus and Euglandina that can be found here.
Let’s explore a bit more of it. The first example is Rhodea wallisiana Dohrn, 1875 from Colombia. This is a rare species of which only a few specimens are known, which are all sinistral.
Drymaeus provides another example of a sinistral species, D. tropicalis (Morelet, 1849) from Mexico. Also Corona perversa (Swainson, 1820) - occurring in northern Brazil and the Guianas - and C. regalis (Hupé, 1857) - the latter also westward into lowland Peru and Ecuador - are normally sinistral. There is one taxon, described as Corona incisa forma machadoensis Strebel, 1909 from “Rio Machado” [in Brazil, it might be either Edo. Rodônia, Río Ji-Paraná or Río Machado in Edo. Tocantins, Minas Gerais or Matto Grosso], which is sinistral too.
Finally there are several examples of Liguus species, normally dextral, that show chirality. The excellent website of Emilio Power [unfortunately not longer updated] provides photos of sinistral Liguus vittatus (Swainson, 1822) and L. virgineus (L., 1758).
The phenomenon of chirality presents some interesting biological questions, e.g.:
- what is the genetic basis for each of the two chiral morphs?
- what maintains the chiral dimorphism in some species (intra-specific chirality)?
- what is the role of chirality in speciation?
References:
Grego, J., Steffek, J. & Infante, A.P., 2007. Review of the genus Rhodea (Gastropoda, Pulmonata, Subulinidae), with description of two new species from Colombia. - Basteria 71: 13-28.
In the Neotropics there are also a few examples of chirality. In Orthalicidae there are three genera: Drymaeus, Liguus and Corona. In the Subulinidae there is an example in Rhodea. And I have seen a report on a sinistral Megalobulimus, but that may be just an aberration, just like the specimens of Rabdotus, Thaumastus and Euglandina that can be found here.
Let’s explore a bit more of it. The first example is Rhodea wallisiana Dohrn, 1875 from Colombia. This is a rare species of which only a few specimens are known, which are all sinistral.
Drymaeus provides another example of a sinistral species, D. tropicalis (Morelet, 1849) from Mexico. Also Corona perversa (Swainson, 1820) - occurring in northern Brazil and the Guianas - and C. regalis (Hupé, 1857) - the latter also westward into lowland Peru and Ecuador - are normally sinistral. There is one taxon, described as Corona incisa forma machadoensis Strebel, 1909 from “Rio Machado” [in Brazil, it might be either Edo. Rodônia, Río Ji-Paraná or Río Machado in Edo. Tocantins, Minas Gerais or Matto Grosso], which is sinistral too.
Finally there are several examples of Liguus species, normally dextral, that show chirality. The excellent website of Emilio Power [unfortunately not longer updated] provides photos of sinistral Liguus vittatus (Swainson, 1822) and L. virgineus (L., 1758).
The phenomenon of chirality presents some interesting biological questions, e.g.:
- what is the genetic basis for each of the two chiral morphs?
- what maintains the chiral dimorphism in some species (intra-specific chirality)?
- what is the role of chirality in speciation?
References:
Grego, J., Steffek, J. & Infante, A.P., 2007. Review of the genus Rhodea (Gastropoda, Pulmonata, Subulinidae), with description of two new species from Colombia. - Basteria 71: 13-28.