Ancient lakes of the Sahara

As a result of climate change over the past 5000 years the Sahara changed from savannah to a desert landscape. The beds of ancient lakes are home to snail shells and the petrified roots of trees and shrubs. Examples of human occupation can also be seen in the form of fireplaces and discarded tools. Examination of the geological history of these sites can give a clearer picture of how the climate changed and how humans coped with these changes.

Ancient lakes of the Sahara

As a result of climate change over the past 5000 years the Sahara changed from savannah to a desert landscape. The beds of ancient lakes are home to snail shells and the petrified roots of trees and shrubs. Examples of human occupation can also be seen in the form of fireplaces and discarded tools. Examination of the geological history of these sites can give a clearer picture of how the climate changed and how humans coped with these changes.

The Epipalaeolithic (Iberomaurusian) at Grotte des Pigeons (Taforalt), Morocco: a preliminary study of the land Mollusca

Land snail middens occur widely throughout the circum-Mediterranean, particularly in the Maghreb and Libya, but are relatively understudied when compared with the better known coastal marine middens. The site of Taforalt (Grotte des Pigeons) in north east Morocco contains thick ashy deposits with considerable numbers of land snails, dating between 13,000 and 11,000 BP. The site has been excavated periodically since its discovery in 1908, but little attention has been paid to the land snail component. Recent excavations at the site as part of the Cemeteries and Sedentism Project has facilitated reinvestigation of the Iberomaurusian layers, including the upper ashy midden unit. This investigation addresses questions surrounding chronological variation in the lithic assemblage, subsistence strategies, population health and mortuary practices. Preliminary work on the land snails has identified a low species diversity in the grey series midden layers, characterised by the large edible species Alabastrina alabastrites, Helix cf aspersa, Dupotetia dupotetiana, Otala punctata and Cernuella sp, which appear to represent an abrupt intensification in the use of land snails as a food source. Significant quantities of associated plant material and animal bone suggest that land snails are part of a broader based diet which is adopted from around 13,000 BP.

Olfactory selection of Plantago lanceolata by snails declines with seedling age

Background and Aims Despite recent recognition that (1) plant–herbivore interactions during the establishment phase, (2) ontogenetic shifts in resource allocation and (3) herbivore response to plant volatile release are each pivotal to a comprehensive understanding of plant defence, no study has examined how herbivore olfactory response varies during seedling ontogeny. Methods Using a Y-tube olfactometer we examined snail (Helix aspersa) olfactory response to pellets derived from macerated Plantago lanceolata plants harvested at 1, 2, 3, 4, 5, 6 and 8 weeks of age to test the hypothesis that olfactory selection of plants by a generalist herbivore varies with plant age. Plant volatiles were collected for 10 min using solid-phase microextraction technique on 1- and 8-week-old P. lanceolata pellets and analysed by gas chromatography coupled with a mass spectrometer. Key Results Selection of P. lanceolata was strongly negatively correlated with increasing age; pellets derived from 1-week-old seedlings were three times more likely to be selected as those from 8-week-old plants. Comparison of plant selection experiments with plant volatile profiles from GC/MS suggests that patterns of olfactory selection may be linked to ontogenetic shifts in concentrations of green leaf volatiles and ethanol (and its hydrolysis derivatives). Conclusions Although confirmatory of predictions made by contemporary plant defence theory, this is the first study to elucidate a link between seedling age and olfactory selection by herbivores. As a consequence, this study provides a new perspective on the ontogenetic expression of seedling defence, and the role of seedling herbivores, particularly terrestrial molluscs, as selective agents in temperate plant communities.

Trochoidea elegans in Surrey, England - when did it arrive?

The introduction of the snail Trochoidea elegans to one of its three known sites in Britain has been investigated. 210Pb dating suggests that it has been present at Chaldon, Surrey, at least since the first decade of the twentieth century; it may have been deliberately translocated to this site by the Rev. Canon J. W. Horsley.