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Departamento Biología de Organismos, Universidad Simón Bolívar, Apartado 89000 Sartenejas, Baruta, Edo. Miranda, Venezuela
David L. Hawksworth 1
Departamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense, Plaza Ramón y Cajal, Ciudad Universitaria, ES-28404 Madrid, Spain
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ABSTRACT |
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Korfiomyces gelatinosum gen. et sp. nov. is described from resinous wood of an unidentified tree in the Venezuelan Amazon, part of the Guayana region; it is saprobic and not lichenized. The ascomata are apothecioid, arise on a brownish subiculum, are gelatinous and initially have a raised exciple. The asci are lecanoralean with a thin outer amyloid layer and occasionally a minute internal apical amyloid ring. The paraphyses are simple and capitate, and the as-cospores brownish and 1-septate. The possible affinities of the new genus are discussed; no family to accommodate it satisfactorily was found, and for the time being it is recommended that it be treated as Lecanoromycetes incertae sedis.
Key words: Amazonas, Ascomycota, Guianas, Helotiales, Lecanoromycetes, lichens, resinicolous fungi, tropical fungi
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INTRODUCTION |
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). Further, Korf (1990) estimated that at least half, and probably more than two-thirds, of the world’s discomycetes remained undescribed, and the tropics are a major source of these fungi, although the research carried out on them is meager (Zhuang and Korf 1991). It is not surprising, therefore, that unusual discomycetes that are not easily referred to already described genera or even families are discovered as areas such as the Venezuelan Amazon are explored by mycologists. Here we describe a novel discomycete from the Venezuelan Amazon in honor of Dr Richard P. Korf as he approaches his 80th year. This fungus provides another example of a fungus that cannot be confidently assigned, not only to any described genus but further to any currently accepted family, emphasizing the gaps in our knowledge of discomycetes that Dr Korf has pointed to.
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TAXONOMY |
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Apothecia scattered or gregarious, apparently non-lichenized, superficial, discoid, sessile with a basal subiculum, 150–250 µm diam and coriaceous when dry, and 300–350 µm diam and gelatinous when rehydrated in water, easily becoming detached from the substratum when wet, disk at first concave with a raised margin, becoming convex (pulvinate) when mature with the margin less distinct; when rehydrated in water becoming translucent and pale orange with a deep orange basal attachment; when rehydrated in 2% KOH the disk changes color to ochraceous, and the outermost thin receptacle layer and basal point of attachment turn dark brown; the apothecia arise from a subiculum of straight to torulose brown to dark brown hyphae, 2–3.5 µm wide, which have irregular nodular thickenings on their walls. Receptacle covered by a thin gelatinized layer with no discernible cellular structure, 3–4 µm thick. Ectal excipulum 25–30 µm thick when rehydrated, composed of globose to elongated thick-walled cells embedded in a gel, cells 3–8 µm diam, broader at the sides and narrower at the margins and the base, cell walls 2.5 µm thick. Medullary excipulum textura globulosa, the cells immersed in a gel, smaller than those of the ectal excipulum. Subhymenium textura intricata. Hymenium gelatinized, the asci and paraphyses adhering to each other. Paraphyses sparse filiform, abruptly swollen and capitate with cyanophilic granules on the swollen head, the apices to 9.5 µm diam thick, with gelatinized walls, adhering to the asci. Asci lecanoralean, saccate, arising from croziers, with a thick inner wall and an evident apical thickening 4–5 µm, with a small apical ring staining faintly blue in iodine (Melzer’s reagent), the outer layer gelatinized, 1.5–2 µm thick and staining blue in iodine (Melzer’s reagent and Lugol’s solution after pretreatment with 5% KOH), 27–38 x 8–12 µm, 8-spored. Ascospores bi-or triseriately arranged in the asci, brown-walled, rugose, broadly ellipsoid to somewhat soleiform, composed of two unequal cells, an upper larger rounded one 5–11.5 x 3.5–6 µm, and the other more elongate and narrowing towards the apices, 5.5–6.5 x 3–4 µm, overall length 10.5–17.5 µm.
HOLOTY PUS: VENEZUELA: AMAZONAS: Departamento de Rio Negro, Cerro de la Neblina, Neblina base camp on Rio Mawarinuma, 00°50'N, 66°10'W, elevation ca 140 m, terra firme forest, on resin and bark of light-weight fallen trunk, 27 Nov 1984, Coll. T. Iturriaga 615 (VEN).
Etymology. – This generic name is coined in honor of Richard P. Korf (Cornell University, Ithaca, New York), doyen of the discomycetes, who has done so much to genially inspire, challenge and improve the ways in which these fungi are studied, as well as facilitating taxonomic mycology in general through the launch of Mycotaxon, the publication of books under that imprint, and contributions to the improvement of mycological nomenclatural practices. He was also the first person to recognize that the type species of this new genus required more detailed study and might be undescribed. The specific epithet recalls the gelatinous nature of the apothecia.
Ecology. – Saprobic on resinous light-weight wood of a fallen trunk, perhaps of a balsawood tree (Ochroma lagopus) or other Bombacaeae. The wood is discolored, and no algae were found associated with the apothecia; various other fungi are present.
Distribution. – Known only from the type collection from Venezuela (Amazonas).
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DISCUSSION |
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). In Dactylospora Körb., which comprises saprobic, lichenicolous and bryophilous fungi, the asci lack any internal apical ring, have a much denser iodine-positive sheath, the exciple is carbonaceous and composed of dark brown thick-walled pseudoparenchymatous cells, and the paraphyses characteristically are branched toward the apex and dark brown capitate (Hafellner 1979). We also considered Arthonia Ach. s. lat., a genus that in the broad sense includes not only lichenized but lichenicolous and probably saprobic species, but this possibility is excluded because that genus has irregularly shaped ascomata that lack any exciple, generally branched and anastomosed paraphysoids, and asci with fisitunicate discharge and a generally distinct iodine-positive tholus (Purvis et al 1992).
The Gyalectales includes some genera with characteristically gelatinous ascomata, notably Pachyphiale Lönnr., but in that genus the exciple comprises narrow compacted hyphae, the paraphyses are filamentous and hooked at the tips, and the asci are multispored without any internal apical structure, and the ascospores acicular to fusiform (Purvis et al 1992). Gelatinopsis Rambold & Triebel (syn. Micropyxis Seeler non Duby), a fungicolous and lichenicolous genus with gelatinized fruits referred to Helotiaceae, has thin-walled asci lacking any apical structures, an exciple of conglutinate hyphae, and all tissues are unchanged with iodine (Rambold and Triebel 1990, Aptroot et al 1997).
The capitate paraphyses apices recall Orbilia Fr. to some extent, but in that genus the asci are thin-walled, do not react with iodine, are never rostrate, and the ectal excipulum comprises thin-walled globose to angular cells (Korf 1973, Baral 1994).
We also considered the genera of Agyriales, an order that includes lichenized and saprobic or facultatively lichenized fungi, some genera of which have gelatinized apothecia (Lumbsch 1997, Lumbsch et al 2001). However, the exciple in that order is generally well developed and comprises branched and anastomosing hyphae and the paraphyses are branched and anastomosed, lacking the proportionately large capitate swellings seen in Korfiomyces; in addition, septate ascospores are known in only one genus of the order (Anzina Scheid.). Skytella D. Hawksw. & R. Sant. also has waxy ascomata, but these lack an exciple and the paraphyses are inflated and branched and the asci thin-walled with no tissues turning blue in iodine (Hawksworth and Santesson 1988).
In addition to these features, the subicular hyphae, which are not aggregated into multihyphal rhizoidal strands but are separate, are especially unusual. The narrower hyphae have walls that appear in light microscopy to be unevenly thickened, but in the wider ones, which generally are closer to the excipulum, the thickenings develop a nodular form.
In summary, we failed to find any genus, family or order that could accommodate this distinctive little discomycete from the Venezuelan Amazon. We therefore introduce yet a new generic name for a fungus of uncertain affinities. In the interim, while a conclusive placement of our new genus must await molecular studies of fresh material, it seems most appropriate to refer Korfiomyces to the class Lecanoromycetes incertae sedis in the system of Eriksson et al (2003).
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Corresponding author. E-mail: myconova{at}terra.es
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LITERATURE CITED |
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Baral H-O. 1994. Comments on ‘Outline of the ascomycetes—1993’. Syst. Ascom. 13:113–128.
Eriksson OE, Baral H-O, Currah RS, Hansen K, Kurtzman CP, Læssøe T, Rambold G. 2003. Outline of Ascomycota—2003. Myconet 9:1–89.
Hafellner J. 1979. Karschia, Revision einer Sammelgattung an der Grenze von lichenisierten und nichtlichenisierten Ascomyceten. Beih. Nova Hedw. 62:1–248.
Hawksworth DL 2001. The magnitude of fungal diversity: the 1.5 million species estimate revisited. Mycol. Res. 105:1422–1432.
———, Santesson R. 1988. Skytella, a new genus for Phacopsis mulleri Willey (syn. Agyrium flavescens Rehm). Graphis Scripta 2:33–37.
———, Sherwood MA. 1981. A reassessment of three widespread resinicolous discomycetes. Can. J. Bot. 59:357–372.
Iturriaga T, Paez I, Sanabria N, Holmquist O, Bracamonte L, Urbina H. 2000. Estado Actual del Conocimiento de la Micobiota en Venezuela. Documentos Técnicos de la Estrategia Nacional Para la Diversidad Biológica, Universidad Simón Bolívar, Ministerio del Ambiente, Caracas. 147 p.
Korf RP. 1973. Discomycetes and Tuberales. In: Ainsworth GC, Sparrow FK, Sussman AS, eds. The fungi: an advanced treatise. Vol. IVA. New York: Academic Press. p 249–319.
——— 1990. Discomycete systematics today: a look at some unanswered questions in a group of unitunicate ascomycetes. Mycosystema 3:19–27.
Lumbsch HT. 1997. Systematic studies in the suborder Agyriineae (Lecanorales). J. Hattori Bot. Lab. 83:1–73.
———, Schmitt I, Döring H, Wedin M. 2001. Molecular systematics supports the recognition of an additional order of Lecanorales: Agyriales. Myco. Res. 105:16–23.
Purvis OW, Coppins BJ, Hawksworth DL, James PW, Moore DM, eds. 1992. The lichen flora of Great Britain and Ireland. Natural History Museum Publications, London.
Rambold G, Triebel D. 1990. Gelatinopsis, Geltingia and Phaeopyxis: three helotialean genera with lichenicolous taxa. Notes Roy. Bot. Gdn Edinb. 46:375–389.
Zhuang W-Y, Korf RP. 1991. Our current knowledge of the tropical non-lichnenized operculate discomycetes. Mycosystema 4:129–139.
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