Terrestrial Gastropods

Late Pleistocene and Holocene archaeological deposits from the central Mediterranean regions contain abundant terrestrial gastropod shell remains. Stable isotope studies of their shell carbonate are valuable proxies for various aspects of climate and environmental change such as temperature, hydrological sources and balance, as well as vegetation. Here we present stable carbon and oxygen isotope data of snail shells from several archaeological deposits in the western Mediterranean (Iberian, Italian Peninsula and Sicily). Isotope ratios differ remarkably between the Late Pleistocene, Holocene and modern shells. The results can be interpreted in terms of hydrological variations and changes in vegetation over time. Fossil shells offer the opportunity to examine the effects of past climate change on local and regional environments.

The early Middle Miocene Lake Gacko was part of the Dinaride Lake System (DLS) and gave rise to a poorly known freshwater mollusk fauna. This was subject to malacological studies from the late 19th century onwards. Herein, we provide the first thorough taxonomic survey of Lake Gacko including revisions of several taxa. A total amount of 1,077 specimens was obtained from 17 samples, comprising at least 11 freshwater and 2 terrestrial gastropod species and 6 bivalve species. So far, none of the described taxa has been documented outside the Dinarides and the DLS, respectively. The fauna shows variable overlap with other paleolakes of the DLS, proofing once more the complex biogeographic patchwork of this system. The current paleoenvironmental reconstructions are tested and refined by application of a statistical analysis. This confirms the partition of the sedimentary history of Lake Gacko into three major depositional phases responding to astronomically forced climate changes. The low diverse mollusk assemblage in the initial phase, with abundant pulmonate and rissooid gastropods, signals a more arid climate with lowered lake level. During the second interval, the fauna becomes more diverse with common rissooid and melanopsid gastropods. It represents a more humid interval with enhanced precipitation and increased lake level, entailing the installation of a perennial lacustrine environment. The final phase is a return to arid conditions with the same elements as in the initial pulmonate-rissooid assemblage. The sphaeriid Pisidium vukovici n. sp. is introduced as new species.

The bulimulid genus Bostryx Troschel, 1847 is the most species-rich genus of land snails found in Chile, with the majority of its species found only in the northern part of the country, usually in arid coastal zones. This genus has been sparsely studied in
Chile and there is little information on their distribution, diversity or ecology. Here, for the first time, a formal analysis of the diversity of bulimulids in the Región de Atacama, northern Chile, is reported. Of the seventeen species recorded for the area, most of them were effectively found in the field collections and one record was based on literature. Five taxa are described as new: Bostryx ancavilorum sp. nov., Bostryx
breurei sp. nov., Bostryx calderaensis sp. nov., Bostryx ireneae sp. nov. and Bostryx valdovinosi sp. nov., and the known geographic distribution of seven species is extended. Results reveal that the Región de Atacama is the richest region in terrestrial snails in Chile, after the Juan Fernández Archipelago. All of the terrestrial molluscan species occurring in the area are endemic to Chile, most of them with restricted geographic distributions along the coastal zones, and none of them are currently protected by law. Further sampling in northern Chile will probably reveal more snail species to be discovered and described.

The non‐indigenous Cryptozona siamensis is reported for the first time from Singapore. This terrestrial snail was discovered from the site of a former plant nursery that borders the Central Catchment Nature Reserve, and is believed to have been accidentally introduced through horticultural trade activities. Cryptozona siamensis is a potential plant pest and is known to be a host of the parasite that causes human eosinophilic meningitis, a potentially life‐threatening condition. Urgent management to control or eradicate the species is desired to curb its spread. Its distribution and status in Peninsular Malaysia is briefly discussed.

Terrestrial gastropods were collected from wetland, grassland, and forest-ed habitats throughout eastern and southcentral South Dakota from May-August of 1999 and 2000 to assess the role of gastropods in transmission of meningeal worm (Parelaphostrongylus tenuis) to white-tailed deer (Odocoileus virginianus) populations throughout the state. A total of 4,063 gastropods representing 14 species, five of which were known intermediate hosts for P. tenuis, were collected throughout South Dakota during the summers of 1999 and 2000. Significantly more (P < 0.0001) gastropods were collected from eastern than western South Dakota. Six species of snails (Zonitoides nitidus, Z. ar-boreus, Discus cronkhitei, Succinea ovalis, Gastrocopta pentadon, and Vallonia sp.) and one slug species (Deroceras laeve) accounted for 87% of the gas-tropods collected. A total of 3,468 gastropods were examined for presence of P. tenuis larvae. Three species of snails (Z. arboreus, Z. nitidus, and D. cronkhitei) and one slug species (Deroceras laeve) accounted for 93% of the total number of infected gastropods (i.e., 66 of 71). Significantly more (P = 0.005) infected gastropods were collected from semipermanent wetlands than from grasslands or forested habitats, suggesting that wetland habitats are important transmission sites of P. tenuis from gastropods to white-tailed deer in South Dakota.

The land snail Cepaea subsulcosa (Thomae) is described from the Miocene of Baden-Wuerttemberg. Shells are preserved as aragonite and are filled with quartz crystals. The stratigraphic setting and taphonomy are discussed. Eodiagenetic quartz formation partly broke the shells. However, it did neither solve nor
silicify them. Important prerequisites for these phenomena were: cementation at the groundwater table, seasonal rainfall in a subtropical climate, carbonatic and silica-poor pore fluids, as well as embedding with relics of soft parts in a sandy sediment.