Sand armour: How it provides plants with an edge up in survival

Plants have evolved a dizzying array of morphological and biochemical defences; a deceptively simple one involves sand. Some plants actively coat themselves in sand, termed psammophory, as an ingenious adaptation for survival. While the functional significance of psammophory is understudied, experimental data from Abronia latifolia and Navarretia mellita suggests that it acts as a mechanical defence against herbivory within dune habitats. This defence stems from both the damaging and non-nutritive properties of sand and the lasting detrimental effects it has on herbivore physiology. While sand armour may seem like an unusual adaptation, it certainly can deter herbivores by giving them something to chew on.

Tonsillar outbreak infection – main clinical manifestations

The tonsill represents a natural barrier against various infectious pathogens. Around the tonsillar crypts, the tissues produce an area of mechanical defence barrier formed of granulation tissue, neoformation vascularization and leukocytes. In this region a series of complex immunological processes take place, the central role being occupied by immunoglobulin A. Tonsillar outbreak infection is a particular feature of immune response, generating numerous imunopathologic reactions.

Differential herbivore damage to calcicolous lichens by snails

A laboratory experiment was conducted to determine the damage caused by snail grazing to 35 calcicolous lichen species and cyanobacteria from the Baltic island of Oland, Sweden. Individuals of four species of land snails (Balea perversa, Chondrina cliema, Clausilia bidentata and Helicigona lapicida) were allowed to graze on identified lichen species growing on pieces of limestone. Snail grazing on thalli and ascocarps was classified into four categories ranging from no damage to completely eaten. In general, some lichen species were heavily grazed, whereas others were only slightly damaged or not injured. Aspiciha calcarea, Tephromela atra and Verrucaria nigrescens were preferred by all snail species except Chondrina cliema. In general, lichen thalli that were not immersed in the calcareous rock and cyanobacteria were preferred, whereas ascocarps were avoided by one of the snail species (C. clienta). Immersed perithecia with a carbonized outer layer were avoided by all snail species except C. bidentata. Possibilities of chemical and mechanical defence properties in calcicolous lichens are discussed.