6 pages, figures, and tables statistics.The ultrastructure of the thalloconidia (asexual propágules of the mycobiont) in
eight species of the lichen genus Umbiiicaria have been investigated. The selected species possessed
thalloconidia corresponding to the three morphological types already described for the European
flora. The study revealed for the first time the integrity of the cytoplasm in these propagules.
Groups of well-differentiated concentric bodies, mitochondria with short and parallel cristae
and vesicles coming from the endoplasmic reticulum were observed in the thalloconidia of U. decussata
and U. havaasii. In some specimens of U. polyphylla, lipidie bodies filled most of the cytoplasm
in the thalloconidia. In broad outline the ultrastructure observed in the thalloconidia was
similar to that of the other mycobiont cells.Peer reviewe

Ascaso, Carmen

Sancho, Leopoldo G.

Valladares Ros, Fernando

Digital.CSIC

Cryptogamie, Bryol. Lichénol. 1992,13 (4): 335-340 335FINE STRUCTURE OF THE THALLOCONIDIA OF THELICHEN GENUS UMB1LICARIAC. ASCASO *, L.G. SANCHO ** and F. VALLADARES** Centro de Ciencias Medioambientales. C.S.I.C. Serrano 115 bis.28006 Madrid. Spain.** Dpto. Biología Vegetal u. Fac. Farmacia. Universidad Complutensede Madrid. 28040 Madrid. Spain.ABSTRACT - The ultrastructure of the thalloconidia (asexual propágales of the mycobionl) ineight species of the lidien genus Umbiiicaria have been investigated. The selected species pos-sessed thalloconidia corresponding to the three morphological types already described for the Eu-ropean flora. The study revealed for the first time Üie integrity of the cytoplasm in these propag-ules. Groups of well-differentiated concentric bodies, mitochondria with short and parallel cristaeand vesicles coming from the endoplasmic reticulum were observed in the thalloconidia of U. de-cussata and U. havaasü. In some specimens of U. polyphylla, lipidie bodies filled most of the cy-toplasm in the thalloconidia. In broad outline the ultrastructure observed in the thalloconidia wassimilar to thai of the other mycobiont cells.INTRODUCTIONThalloconidia - mycobiont propagóles produced from the lower cortex (Frey1929) - were known until the last decade only from the genus Umbiiicaria, where theyare present in nearly half of the species. Recently, analogous structures have beenfound in crustaceous lichens belonging to other families (Poelt & Obermayer 1990).Hasenhüttl & Poelt (1978) were the first to study thoroughly the thalloconidia in Um-biiicaria. They called them "Brutkórner" and proposed a morphological classificationbased mainly on the origin and génesis of the thalloconidia and on the number of cellsthat constitute them in the marure state. Furthermore, they demonstrated the germina-tive capability of these propagules in U. nylanderiana and U. vellea. Hestmark (1990)proposed the replacement of the term "thallospore", in use at that time (Hawksworth etal. 1983, Topham et al. 1982), by the more precise "thalloconidium".Poelt & Obermayer (1990) pointed out the richness of plasma in the thalloco-nidia which were hardly stained with lactophenol cotton-blue. Hestmark (1990, 1991aand 199Ib) has used transmission electrón microscopy as a complementary method inthe morphological description of the thalloconidia to observe the type of septum andwall stmcture. Nevertheless, no information concerning the cellular fine structure ofthese propagules is available. The present work provides the first comparative dataconcerning the cytoplasmic ultrastructure of the thalloconidia in the genus Umbiiicaria.336 C. ASCASO et al. ULTRASTRUCTURE OF THALLOCONIDIA IN UMBILICARIA 337MATERIALS AND METHODSFor the present study eight species belonging to the genus Umbilicarla wereselected. The three morphological types of thalloconidia described by Hasenhüttl &Poelt (1978) for the European Umbilicariaceae were represented in these species. Theselected species and the corresponding morphological type of thalloconidium were:Vmbilicaria decussata (Vill.) Zahlbr., U. leiocarpa DC. in Lam. & DC., U. nylanderia-na (Zahlbr.) H. Magn., U. polyrrhiza (L.) Fr. and U. subglabra (Nyl.) Harm. with theAnthracina type; U. polyphylla (L.) Baumg. Fl. with the Polyphylla type and U. havaa-sü Llano and U. vellea (L.) Ach. with the Vellea type of thalloconidia. Voucher speci-mens are in MAF.The samples were collected between 1987 and 1989, and in all cases theywere processed within three days of collection. From three specimens of each species,portions of 2 mm2 from the zone halfway between the umbilicus and the margin wereobtained. These portions were embedded in Spurr's resin (Spurr 1969) after conven-tional fixation and dehydration (Ascaso et al. 1986). Ultra-thin sections were stainedwith lead citrate (Reynolds 1963) for observation with the transmission electrón micro-scope.RESULTS AND DISCUSSIONTransmission electrón microscopy revealed the remarkable cellular integrity ofthe thalloconidia of Vmbilicaria decussata and U. polyrrhiza (Anthracina type). Thesehad well-differentiated nuclei (Fig. 1), often with a lobed outline and with a folded nu-clear membrane delimiting some narro w compartments. The mitochondria had anovoid shape with internal cristae of variable length and generally with a parallel ar-rangement (Figs. 1 and 2). This parallel distribution of the cristae within the mito-chondria seems to be constant in all the cells of the mycobiont (Valladares & Ascaso1992, and unpublished results). In Fig. 2 the vacuolar apparatus can also be seen, well-developed in these thalloconidia, with vacuoles with a lobed tonoplast. The vacuoles,very similar to the most common type found by Boissiere (1979, 1982) in Peltigeracanina, are less prominent as a cellular componen! than in the hyphae of the algal lay-er of other lichens belonging to the family Umbilicariaceae (Valladares & Ascaso1992). In addition to the vacuoles, several vesiculated structures located at the end ofthe endoplasmic reticulum were also found (Fig. 3).In the thalloconidia of Vmbilicaria polyphylla two different ultrastructural ap-pearances have been observed. One group of specimens possessed a large number oflipidie bodies in the cytoplasm to the detriment of the other organdíes and structures(Figs. 4 and 5). The lipidie bodies, also called "sphaerosomes", have a homogeneousaspect with a low electrón density and occupy between 70% and 80% of the cyto-plasmic volume. As they have no external membrane and float freely within the cyto-plasm, they very often lose their individuality, forming big irregular masses withrounded outlines. The second group of specimens did not possess this unusually largenumber of lipidie bodies. The differences between these two groups could be due tothe different date of collection (the first group was collected in autumn and the secondin spring), but more data are needed in order to determine the sources of ultrastruclur-al variability.The thalloconidia of Vmbilicaria havaasii showed an aggregation of manycells (Vellea type, Figs. 6 and 7). The lipidie bodies are present, although in smallernumbers than in some thalloconidia of U. polyphylla and generally in a peripheral po-sition.Fig. 1-3 - Transmission electrón micrographs of Anthracina type thalloconidia in Umbilicaria.Fig. 1 and 2: Umbilicaria polyrrhiza. Fig. 3: Umbilicaria decussata. Symbols: c= concentric bod-ies, m= mitochondria, n= nucleus, re= endoplasmic reticulum, v= vacuole. Bar= lujn.Complexos of well-differentiated concentric bodies have been observed withinthe thalloconidia of all the species studied. These structures, which are very commonwithin all the vegetativo hyphae of lichenized fungí (Griffiths & Greenwood 1972),have also been found in ascospores (Ascaso & Calvan 1975). The presence of concen-tric bodies in the thalloconidia points to a widespread distribution of these structuresC. ASCASO et al.|íg, 4-5 - Transmission electrón micrographs of the thalloconidia of Umbilicaria polyphylla. Thesymbols used are n= nucleus and s= sphaerosomes. Bar= lum.¡Biong the mycobiont cells. They may be related to relatively high metabolic activityjfihese cells since they have been associated with growing regions of the thallus(Baissiére 1979). In broad outline however, the ultrastructure observed in the thalloco-nidia was similar to that of the other mycobiont cells.In all the species studied the cell wall of the thalloconidia consisted of several»ell-differentiated layers. The innermost layer next to the plasmalemma was stainedpoorly with lead citrate and was generally less than 0.5^m thick; the extemal layerwas thicker but irregular and was stained more intensely.In our opinión, the optimum ultrastructural state of tnany thalloconidia, incanparison with some rather necrotic or disorganized cells of the lower cortex, may¡náirectly support their potential role in the dispersal of the eight species studied.We consider highly desirable further research on the evoluüon and seasonalvaiation in the germinative capability of the thalloconidia, combining germination-ratedata with ultrastructural studies in continuation of the research bcgun by Fiechter &Honegger (1988) on the soredia of Hypogymnia physodes.fig. 6-7 - Transmission electrón micrographs of the thalloconidia of Umbilicaria havaasii. Sym-bols: m= mitochondria, n= nucleus, s= sphaerosomes. Bar= lum.ULTRASTRUCTURE OF THALLOCONIDIA IN UMBILICARIA 339340 C. ASCASO et al.ACKNOWLEDGEMENTS. - We thank Dr E. Manrique for his valuable críticisms andsuggestions. We are grateful to Ms MJ. Villoslada and Mr F. Pinto for technical assistance andto Dr W. Sanders for correcting the English manuscript. Financial support was provided byDirección General de Investigación Científica y Técnica, M.E.C. (PB 87/0229).REFERENCESASCASO C. & CALVAN J., 1975 - Concentric bodies in three lichen species. Arch. Microbio!.105: 129-130.ASCASO C., BROWN D.H., & RAPSCH S., 1986 - The ultrastructure of the phycobiont of de-siccated and hydrated lichens. Lichenologist 18: 37-46.BOISSIERE M.C., 1979 - Cytologie du Peltigera canina (L.) Willd. en microscopie électronique:le mycobionte á l'état végétatif. Rev. Mycol. 43: 1-49.BOISSIERE M.C., 1982 - Cytochemical ultrastructure of Peltigera canina: some features relatedto its symbiosis. Lichenologist 14(1): 1-27.FIECHTER E. & HONEGGER R., 1988 - Seasonal variations in the fine structure of Hypogym-nia physodes (h'chenized Ascomycetes) and its Trebouxia photobiont. Plant Syst. Evol.158:249-263.FREY E., 1929 - Beitrá'ge zur Biologie. Morphologie und Systematik der Umbilicariaceen. Hed-wigia69: 219-252.GRIFFITHS H.B. & GREENWOOD A.D., 1972 - The concentric bodies of lichenized fungi.Arch. Mikrobiol. 87: 285-302.HASENHÜTTL G. & POELT J., 1978 - Über die Brutkórner bei der Hechtengattung Umbilica-ria. Ber. Deutsch. Bot. Ges. 91: 275-296.HAWKSWORTH D.L, SUTTON B.C. & ATNSWORTH G.C., 1983 - Ainsworth & Bisby's Dic-tionary of the fungí. 7th. ed. Huddersfield: Commonwealth Mycological Institute.HESTMARK G., 1990 - Thalloconidia in the genus Umbilicaria. Nord. J. Bot. 9: 547-574.HESTMARK G., 1991 a - Teleomorph-anamorph relationships in Umbilicaria I. Making the con-nections. Lichenologist 23(4): 343-360.HESTMARK G., 1991 b - Teleomorph-anamorph relationships in Umbilicaria U Patterns in pro-pagative morph production. Lichenologist 23(4): 361-380.POELT J. & OBERMAYER W., 1990 - Über Thallosporen bei einigen Krustenflechten. Herzogia8: 273-288.REYNOLDS S., 1963 - The use of lead cúrate at high pH as an electrón-opaque stain in electrónmicroscopy. J. CellBiol. 17:200-215.SPURR A.R., 1969 - A low-viscosity epoxy resin embedding médium for electrón microscopy. J.Ultrastruct. Res. 26:31-43.TOPHAM P.B., SEAWARD M.R.D. & BYLINSKA E.A., 1982 - Umbilicaria propagulifera newto the northem hemisphere. Lichenologist 14: 47-52.VALLADARES F. & ASCASO C., 1992 - Three-dimensional quantitative description of sym-biont ultrastructure within the algal layer of two members of the lichen family Umbili-cariaceae. Lichenologist 24(3): 281-297.Cryptogamie, Bryol. Lichénol. 1992,13 (4): 341-347341NOTES ON THE LICHEN GENUS UMBILICARIAIN CORSICAGeir HESTMARKDivisión of Botany, Department of Biology, University of Oslo Box1045, Blindem, N-0316 Oslo, Norway.*%£INTRODUCTIONí * lichenol°8ist's ^am. Clean air, iarge variations in«* Ve8etation "ncs ranging from the1975> make for «" exctionall richcrozaisc,™ a//eCft!- *"? to C°rSÍCa l had the oPPortunity to sample members of theZ, Um}blllCana * a number «f tocalities. Resides adding to the number ofr yJT"ted fr°m CorSÍCa* ^  observations seem to throw some lightthe biogeographical provenance of the Corsican mountain lichen flora.Üf- PreSení. **?? l 1ÍSt ! 7 taxa which "« k"™0 also fr°m localities outsidediscuss their biogeographical affinity.generic concept adopted here is one tentatively accepting a familyÍng °f tW° genera: V"**™™ Hoffm. and LasalKa Mérat. Inaheu & Gillet (m^ 192fi) ^  ^ ^^ ^ ^ÍÍJTfoíí^ ^ ^  *' former Gyrophora, while Wemer & Deschátres} aCCept °nly a Single 8enus: Umbilicaria. The reasons for this^ *c exPlained by Frey (1933, 1949) and Poelt (1977). The, [SÍCa rePresented by L. brigantium (Zschacke) Llano and L.no bn8antium< originally described from Corsica (Monte Angelo)(1927), appears to be a Corso-Sardean endemic (Sancho & Crespo 1989).

Fine structure of the Thalloconidia of the Lichen Genus Umbilicaria

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