Morphological evidence for the symbiotic character of Turgidosculum complicatulum Kohlm. & Kohlm. (= Mastodia tesselata Hook.f. & Harvey)

The symbiotic nature of the association between mycobiont and photobiont in the Antarctic lichen Turgidosculum complicatulum has been questioned. Some authors consider the lichen T. complicatulum to be an alga parasitized by the fungus. The photobiont Prasiola crispa ssp. antarctica (Kutzing) Knebel also occurs free-living in adjacent microhabitats. The initial developmental stages of this Antarctic lichen or lichen-like association are described here for the first time. The aim of this study was to examine the early developmental stages of T. complicatulum in order to characterize the nature of the association between photobiont and mycobiont. SEM and light microscopy revealed a decisive role of unicellular aplanospores and other few-celled stages of the alga in the process of lichenization. There is a slight morphogenetic influence of the mycobiont on the photobiont, but no cortex differentiated. The outer layer of the thallus does not contain phenolic substances other than melanin. On the basis of morphological investigations and some physiological and chemical properties T. complicatulum fan be described as a lichen with simple organisational level, although certain features challenge usual concepts of lichen symbiosis. [KEYWORDS: development; initial stage; lichenization; Mastodia tesselata; mutualism; parasitism; Prasiola crispa; symbiosis; Turgidosculum complicatulum Antarctica; survival; fungus