HEAVILY LICHENIZED PHYSOLINUM (CHLOROPHYTA) FROM A DIMLY LIT CAVE IN MISSOURI¹

Abstract

Heavily lichenized Physolinum monile (De Wildem.) Printz from damp limestone walls in a dimly lit cave located in Missouri was studied from fresh collections and specimens fixed in situ, and from cultures. The narrow (7‐13 μm wide thallus), profusely branched plant consisted of filaments of the alga P. monile ensheathed by clear fungal cells (5‐8 in a single layer) that adhered tightly to each other and completely covered the algal cells. Cells of P. monile filaments were uninucleate, each containing a single massive chloroplast with numerous tightly packed thylakoids and lipid droplets and surrounded by a thin layer of cytoplasm. No plasmodesmata occurred in the cellulosic crosswalls between adjacent cells. The ensheathing fungal cells contained concentric bodies, produced haustoria that penetrated the algal cells, and developed hyphae (the tips of which formed clusters of conidia). Ensheathing fungal cells were well situated and constructed to concentrate light on the algal cells. Colonies of blue‐green algae were firmly attached to the surface of the fungal cells. The association was slow growing but frequently produced and released aplanospores from the algal cells. Aplanospores were single (not attached to each other) with smooth walls or united in groups of two or more. Structures resembling lichen soredia, composed of aplanospore‐like cells attached to one or more comdia‐like cells, commonly occurred among the lichenized Physolinum filaments. The single chloroplast that occupies most of the cell's volume, the numerous, tightly packed thylakoids, and light focusing by ensheathing fungus cells may enable the organism to survive in a dimly lit environment. Because the filamentous alga reproduces only by aplanospores, we propose resurrection of the genus Physolinum. The lichenized Physolinum somewhat resembles the lichens Coenogonium moniliforme Tuck. and Cystocoleus Thwaites.

Lichinodium is a new lichenized lineage in the Leotiomycetes

“…Thelebolus haustoria have been observed in Coenogonium (Meier and Chapman 1983) but they are present in Physolinum monile (Davis et al 1989).…”

“…Although two more filamentous species associated with Trentepohlia have been described, their phylogenetic and taxonomic position is not clear (i.e. Physolinum monile, Davis et al 1989 and Racoleus, the latter suggested as ''? Capnodiales (incertae sedis)'' in Hawksworth et al 2011).…”

Corticolous green algae from tropical forest remnants in the northwest region of São Paulo State, Brazil

“…The uncertainties about the real position of the species cause the possibility for use of both names and some authors, as Davis et al (1989), Davis & Rands (1993) and Bicudo & Santos (2001), refer to the species as Physolinum monilia, while others, as Akiyama (1971) and Ettl & Gärtner (1995), use the name Trentepohlia monilia.…”

Concentric Bodies in Conidia of Monodictys Anaptychiae (Hyphomycetes)

“…The earlier reports from lichens have breen summarized in several review papers (e.g. Peveling 1973;Lallemant et al 1986;Galun 1988) and more recent reports include findings in paraphyses of Chaenotheca chrysocephala (Honegger 1985) and from hyphae of a possible Coenogonium or Cystocoleus species (Davis et al 1989). Reports from several non-lichenized ascomycetes have been made, for example by Bellemere (1973; Hysterographium fraxini, Rhytisma acerinum, Tryblidiopsis pinastri, Hypoderma rubi, Heterosphaeria patella and Ostropa barbara), Tu & Colotelo (1973, Sclerotinia borealis), Granett (1974, Ventura inaequalis) and Beilharz (1985, Pseudopeziza trifolii).…”