An anatomical investigation of calcicolous endolithic lichens from the Trieste karst (NE Italy)

ABSTRACT

The anatomy of five endolithic lichens (Acrocordia conoidea, Petractis clausa, Rinodina immersa, Verrucaria baldensis, and V. marmorea) from the Trieste Karst (north-eastern Italy) was thoroughly investigated. Samples already used in previous ecophysiological studies were examined by histological and mineralogical techniques, and by SEM. Biomineralisation products were searched for by X-ray diffractometry, X-ray microdiffractometry, and Fourier Transformed Infrared spectrophotometry. The results confirm that the photobiont layer is located approximately at the same depth in the substratum, although the species occur in habitats with strongly different light regimes; the thallus development is relatively constant within populations of a single species, but differs considerably among species. Several peculiarities of each species were revealed, such as the presence of large clews of hyphae in the inner layer of P. clausa, forming large voids in the substratum, or the development of morphologically different oil-hyphae. Calcium oxalate crystals were not detected. Some terms currently used to describe the anatomy of endolithic lichens are critically discussed, and the new term “lithocortex” and “pseudo-medulla” are introduced.

KEY WORDS:

• Anatomy
• calcium oxalate
• dissolution
• endolithic lichens
• limestone