Abstract
The Camaenid genera Labyrinthus Beck, 1837 and Isomeria Beck, 1837 are mainly distributed in northern South America. Current anatomical information available for both genera is scarce, particularly that concerning Isomeria species. The morphology of the pallial organs, genital and digestive systems of three species of Labyrinthus [L. subplanatus (Petit, 1843), L. dunkeri (Pfeiffer, 1852), L. tarapotoensis Moricand, 1858] and a new species of Isomeria are described. The morphology of hooked denticles that topped wall ridges inside penis and vagina in some species of Labyrinthus and in Isomeria are species-specific characters, differing in shape and size. These structures were not sufficiently studied either in Isomeria or in Labyrinthus and are absent in all anatomically studied species of Solaropsis Beck, 1837, their sister genus. The presence of a bursa copulatrix sac reflexed over its duct is a character shared by all Labyrinthus species in which soft anatomy is known, and it was identified as a synapomorphy in a published phylogeny. Isomeria awa. n.sp. differs from other species of the genus mainly in shell morphology and characters of the distal genitalia. The presence of a stimulator-like structure in the vagina as well as the presence of a glandular pouch in the vagina are diagnostic characters of this new species, not present in the closely Camaenid related genera.
References
Baker, B. (1926) The Mollusca collected by the University of Michigan-Williamson expedition to Venezuela. Part IV. Occasional Papers of the Museum of Zoology, University of Michigan, 167, 1–49, pls. 12–19.
Bouchet, P. (1997) Inventorying the molluscan diversity of the world: what is our rate of progress? The Veliger, 40, 1–11.
Breure, A.S.H. (1984) Survey of the land Mollusca of the Sierra Nevada de Santa Marta, Colombia. In: van der Hammen, T. & Ruiz, P. M. (Eds.), Studies on tropical Andean ecosystems. Vol 2. La Sierra Nevada de Santa Marta (Colombia). J. Cramer, Berlin/Stuttgart, pp. 487–500.
Cuezzo, M.G. (1997) Comparative anatomy of three species of Epiphragmophora Doering, 1874 (Pulmonata: Xanthonychidae) from Argentina. The Veliger, 40, 216–227.
Cuezzo, M.G. & Fernández, I. (2001) A new species of the land gastropod genus Solaropsis Beck, 1837 (Helicoidea: Camaenidae) from Bolivia. The Veliger, 44, 315–324.
Cuezzo, M.G. (2003) Phylogenetic analysis of the Camaenidae with special emphasis on the American taxa (Mollusca: Stylommatophora). Zoological Journal of the Linnean Society, 138, 449–476.
Hausdorf, B. (1998) Phylogeny of the Limacoidea sensu lato (Gastropoda: Stylommatophora). Journal of Molluscan Studies, 64, 35–66.
Hausdorf, B. (2003) Systematic position and taxonomy of the genus Hirtudiscus from Colombia (Gastropoda: Scolodontidae). Journal of Molluscan Studies, 69, 179–186.
Herrmannsen, A.N. 1846. Indicis generum Malacozoorum primordia. Cassell, 590 pp.
Moricand, J. (1858) Descriptions de quelques coquilles nouvelles. Revue et Magasin de Zoologie, 10, 449–455.
Nordsieck, H. (1987) Revision des Systems der Helicoidea (Gastropoda: Stylommatophora). Archiv für Molluskenkunde, 118, 9–50.
Petit, S. (1843) Description de quatre coquilles nouvelles provenant du voyage de M. Goudot à la Nouvelle-Grenade. Revue Zoologique, Societé Cuvier, 6, 238–239.
Pfeiffer, L. (1852) Descriptions of nineteen new species of land shells, colected by M.Bourcier, Consul General, Quito. Proceedings of the Zoological Society of London, 20, 151–157.
Pilsbry, H. (1894) Manual of conchology: structural and systematics. Vol IX. Academy of Natural Sciences, Philadelphia, 366 pp.
Ploeger, S. & Breure A. S. H. (1977) A rapid procedure for preparation of radulae for routine research with Scanning Electron Microscope. Basteria, 41, 47–52.
Richardson, L. (1985) Catalog of Species: Camaenidae. Tryonia, 12, 1–479.
Schileyko, A.A. (1991) Taxonomic status, phylogenetic relations and system of the Helicoidea sensu lato (Pulmonata). Archiv für Molluskenkunde, 120, 187–236.
Solem, A. (1966) The neotropical land snail genera Labyrinthus and Isomeria (Pulmonata, Camaenidae). Fieldiana, Zoology, 50, 1–226.
Tillier, S. (1980) Gastéropodes terrestres et fluviatilles de Guyane française
Tillier, S. (1989) Comparative morphology, phylogeny, and classification of land snails and slugs (Gastropoda: Pulmonata: Stylommatophora). Malacologia, 30, 1–303.
Tompa, A. (1984) Land Snails (Stylommatophora). In: Tompa A.S., Verdonk H. H. & Van Den Biggelaar J. A. (Eds), The Mollusca, Vol. 7. Academic Press, New York, pp. 47–140.
Valdés, A. (2004) Morphology of the penial hooks and vaginal cuticular lining of some dorid nudibranchs (Mollusca, Opisthobranchia). American Malacological Bulletin, 18, 49–53.
Wiktor, A. (1987) Milacidae (Gastropoda, Pulmonata): systematic monograph. Annales Zoologici, 41, 153–319.
Wurtz, C.B. (1955) The American Camaenidae (Mollusca: Pulmonata). Proceedings of the Academy of Natural Sciences of Philadelphia, 107, 99–143. 19 Plates.
Zilch, A. (1959–60) Gastropoda: Euthyneura. In: Schindewolf, O. (Ed), Handbuch der Paläozoologie. Vol. 6 (2). Gebrüder Borntraeger, Berlin-Nikolassee, pp. 1–825.