Hanging in the air: A tough skin for a tough life
3
Volume 10, Part 1,February 1996 HANGING IN THE AIR: A TOUGH SKIN FOR A TOUGH LIFE MARIA NUNEZ Forestry and Forest Products Research Institute, PO. Box 16, Tsukuba, Ibaraki 305, Japan One of the most typical images of tropical forests is the curtain of hanging lianas and epiphytes which gives the touch of mystery to those experi- encing the rainforest for the first time (Fig 1). Drawing back this wooden curtain means enter- ing a magic world. For common rainforest inhab- itants such as fungi, the wooden curtain means food waiting for the toughest to use. The Cuyabeno reserve, with its almost permanent rainy season and 90% humidity in the air offers all the expectations of the mycophile. The hang- ing twigs in the understorey were a paradise for fungi. The canopy and understorey of a rainforest are hostile niches for fungi where hanging twigs, especially those found in forest gaps and along the trails, are exposed to sudden changes of humidity and temperature. During our stay in Cuyabeno, we usually enjoyed a hot, sunny morning with rain in the afternoon. It was easy to collect about twenty basidiomes on twigs 1-2 m above the ground. My aim was to have a close look at how the basidiomes on hanging twigs were constructed in order to stand drought and at the same time spread their spores efficiently. Following a simi- lar study in an African rainforest (Ryvarden & Nunez, 1992) it soon became clear that the Ecuadorian fungi followed the same trends. As for type of basidiomes, about 80% looked like whitish paint on the twigs. Some had a leathery consistency e.g. species of Heterochaete (Heterobasidiomycetes), Aleurodiscus, Dendro- the le, Laeticorticium (Corticiaceae s. str.) Scytinostroma and Vararia (Lachnocladiaceae) and Hymenochaete (Hymenochaetaceae) whilst others were cobweb-like (several species in Hyphoderma, Hyphodontia, Leptosporomyces and Trechispora (Corticiaceae s.str.). Several resupinate polypores, mainly the common cos- mopolitan species Schizopora paradoxa (Schrad.: Fr.) Donk, S. flavipora (Cke.) Ryv., Megasporoporia cavernulosa (Berk.) Ryv., and Pachykytospora papyracea (Schw.) Ryv. were also found. Even a stipitate polypore was present: Polyporus leprieurii Mont., usually with long, black rhizomorphs at the stipe-base. Two non- stipitate agarics were also abundant on hanging twigs: Favolaschia antarctica (Speg.) Sing. and Crepidotus sp. but only the Corticiaceaeand Polyporaceae s.1. are discussed here. Under the microscope, I constantly found that many of the leathery basidiomes were sterile. The typical basidial palisade was substituted by sterile, usu- ally spiny elements forming what is called a catahymenium. In Vararia species, the sterile elements were embedded in a mucilaginous, dex- trinoid matrix (Hedger & Baxter, 1993). Wetting these basidiomes was difficult. The species with cobweb-like basidiomes in contrast, were all fer- tile with small, ellipsoid to globose spores up to 6 [Lm long, and usually lacked sterile" elements among the basidia. They were easily soaked with water. Among the polypores, Schizopora species have typically thick-walled hyphae encrusted at the dissepiments. The crystal layer can sometimes block the pore-mouths (pers. obs.). Megasporoporia cavernulosa has brush-like hyphae in the pore-mouths called dendrohy- phidia. Its basidomes are leathery and usually sterile; fertile basidomes have large spores up to 16 x 7 [Lm. Pachykytospora papyracea has large echinulate spores up to 17x 8 [Lm. Both of these species, as those placed in the Lachnocladiaceae, have dextrinoid hyphae. The complex basidiomes of Polyporus lep- rieurii are so tough that they seem to have been cut from a piece of leather (Fig 2). The pores are almost invisible to the naked eye and black cuti- cle covers the stipe, from which grow black rhi- zomorphs several centimetres long; even in this species about 60% of the basidomes collected were sterile. What advantages do the characters men- tioned above confer on the species occurring on hanging twigs? Ryvarden (1993) suggested that large spores of ..
-
Upload
maria-nunez -
Category
Documents
-
view
213 -
download
1
Transcript of Hanging in the air: A tough skin for a tough life
Volume 10, Part 1, February 1996
HANGING IN THE AIR: A TOUGH SKIN FOR ATOUGH LIFE
MARIA NUNEZ
Forestry and Forest Products Research Institute, PO. Box 16, Tsukuba, Ibaraki 305, Japan
One of the most typical images of tropical forestsis the curtain of hanging lianas and epiphyteswhich gives the touch of mystery to those experi-encing the rainforest for the first time (Fig 1).Drawing back this wooden curtain means enter-ing a magic world. For common rainforest inhab-itants such as fungi, the wooden curtain meansfood waiting for the toughest to use. TheCuyabeno reserve, with its almost permanentrainy season and 90% humidity in the air offersall the expectations of the mycophile. The hang-ing twigs in the understorey were a paradise forfungi.
The canopy and understorey of a rainforestare hostile niches for fungi where hanging twigs,especially those found in forest gaps and alongthe trails, are exposed to sudden changes ofhumidity and temperature. During our stay inCuyabeno, we usually enjoyed a hot, sunnymorning with rain in the afternoon. It was easyto collect about twenty basidiomes on twigs 1-2m above the ground.
My aim was to have a close look at how thebasidiomes on hanging twigs were constructed inorder to stand drought and at the same timespread their spores efficiently. Following a simi-lar study in an African rainforest (Ryvarden &Nunez, 1992) it soon became clear that theEcuadorian fungi followed the same trends.
As for type of basidiomes, about 80% lookedlike whitish paint on the twigs. Some had aleathery consistency e.g. species of Heterochaete(Heterobasidiomycetes), Aleurodiscus, Dendro-the le, Laeticorticium (Corticiaceae s. str.)Scytinostroma and Vararia (Lachnocladiaceae)and Hymenochaete (Hymenochaetaceae) whilstothers were cobweb-like (several species inHyphoderma, Hyphodontia, Leptosporomyces andTrechispora (Corticiaceae s.str.). Severalresupinate polypores, mainly the common cos-mopolitan species Schizopora paradoxa(Schrad.: Fr.) Donk, S. flavipora (Cke.) Ryv.,Megasporoporia cavernulosa (Berk.) Ryv., andPachykytospora papyracea (Schw.) Ryv. were also
found. Even a stipitate polypore was present:Polyporus leprieurii Mont., usually with long,black rhizomorphs at the stipe-base. Two non-stipitate agarics were also abundant on hangingtwigs: Favolaschia antarctica (Speg.) Sing. andCrepidotus sp. but only the CorticiaceaeandPolyporaceae s.1. are discussed here. Under themicroscope, I constantly found that many of theleathery basidiomes were sterile. The typicalbasidial palisade was substituted by sterile, usu-ally spiny elements forming what is called acatahymenium. In Vararia species, the sterileelements were embedded in a mucilaginous, dex-trinoid matrix (Hedger & Baxter, 1993). Wettingthese basidiomes was difficult. The species withcobweb-like basidiomes in contrast, were all fer-tile with small, ellipsoid to globose spores up to 6[Lm long, and usually lacked sterile" elementsamong the basidia. They were easily soakedwith water.
Among the polypores, Schizopora species havetypically thick-walled hyphae encrusted at thedissepiments. The crystal layer can sometimesblock the pore-mouths (pers. obs.).Megasporoporia cavernulosa has brush-likehyphae in the pore-mouths called dendrohy-phidia. Its basidomes are leathery and usuallysterile; fertile basidomes have large spores up to16 x 7 [Lm. Pachykytospora papyracea has largeechinulate spores up to 17 x 8 [Lm. Both of thesespecies, as those placed in the Lachnocladiaceae,have dextrinoid hyphae.
The complex basidiomes of Polyporus lep-rieurii are so tough that they seem to have beencut from a piece of leather (Fig 2). The pores arealmost invisible to the naked eye and black cuti-cle covers the stipe, from which grow black rhi-zomorphs several centimetres long; even in thisspecies about 60% of the basidomes collectedwere sterile.
What advantages do the characters men-tioned above confer on the species occurring onhanging twigs?
Ryvarden (1993) suggested that large spores of
..
•
Volume 10, Part 1, February 1996
Fig 1 The curtain of hanging twigs in a primary rain for-est.
Aleurodiscus and Dendrothele are filled withnutrients which may allow them to germinateeffectively as soon as they hit the appropriatesubstrate. [Although species with abundantsmall spores, such as Peniophora, are very effi-cient at dispersal, they are somewhat disadvan-taged in successfully penetrating substratesunder desiccating conditions -RW]. The role ofsterile hymenial elements and of the mucilagi-nous matrix in Lachnocladiaceae to withstand
Fig 2 Polyporus leprieurii, a common species in the understorey ofCuyabeno Reserve .
drought has been discussed by Pegler & Young(1993), and Hedger & Baxter (1993) respectively.Plunkett (1956) and Hedger, Lewis & Gitay (1993)have interpreted rhizomorphs as stipes that candevelop a pileus when conditions of aeration andhumidity are optimal for spore dispersal.
In summary, species living on twigs exhibittwo different strategies to protect themselvesagainst drought, which can be termed K- and r-
strategies in basidiospore formation. (Nunez &Ryvarden, 1993). Some species expose sterilebasidiomes with waterproof surfaces (be it acatahymenium, stipe and pileal cuticles, or amucilaginous layer) during dry periods and onlyproduce basidia under conditions of high humidi-ty. The other strategy consists in only producingbasidiomes when humidity is high enough forsporulation. Basidiomes are then extremelyephemeral, mainly consisting of small basidiaand constantly releasing spores while water isavailable, but collapsing under water stress.
World distribution of species on hanging twigs.Most of the species on twigs in Cuyabeno belongto the cosmopolitan genera Aleurodiscus,Dendrothele, Hymenochaete, Megasporoporia,Pachykytospora, Schizopora, Scytinostroma, andVararia. Several biogeographical aspects areworth mentioning. The first one is the need for ataxonomic and geographical survey of fungi onhanging twigs, and of tropical corticioid fungi ingeneral. In Cuyabeno one new species ofHyphodontia (Hjortstam, pers. comm.), onespecies only previously known from Australia(Aleurodiscus australiensis Wakefield (=Acanthophyrium australiense (Wakef.) Gunn)and one only known from Borneo (Corneromyceskinabalui Ginns) were found. There are goodindications that many species of Corticiaceaehave a worldwide distribution (Boidon &Lanquetin, 1984; Hallenberg, 1987; Hallenberg,1991).
Polyporus leprieurii, the stipitate polypore inthe Ecuadorian forests, has not been found inAfrica. Even if South America and Africa shareother Polyporus species, it is Microporus affinis(Blume & Nees: Fr.) Kuntze, another stipitatespecies, that occupies the same niche in Africanrain forests as Polyporus leprieurii does in S.America. Both taxa have a leathery consistencyand minute pores invisible to the naked eye. It iswidely accepted that this is more the result of
convergence to adapt to drought than a reflec-tion of a common evolutionar y history. Thequestion of which stipita t e polypore occurs ontwigs in South East Asian tropical forests, whereboth Microporus affinis and Polyporus leprieuriioccur, remains open. [Microporus xanthop us(Beav.: Fr.) Kuntze is the equivalent in S.E. Asia- R.w.] .
I thank Kurt Hjortstam for identifying C. kin-abalui and the new Hyphodontia species, DrGordon Dickson and Dr John Hedger for suc-cessfully organizing the exp edition andVittoriano, Angelina, and all the Secoya peoplewho allowed us to disturb their environment.
References:Boidin, J. & Lanquetin, P. (1984) Le genre Amylos tereum
(Basidiomycetes). Intercornpatibilites partielles entrees peces all opatriques . Bullet in de la SocieteMycologique de France 100: 211-236.
Hall enb erg, N. (1987) Culture studies in Cort iciaceae(Basidiomycetes). Windahlia 17: 43-48.
Hall enber g, N. (1991) Pairing tests wit h species ofAphyllophorales (Basidiomycetes) from two phytogeo-graphically isolated areas. Mycotaxon 42: 335-386.
Volume 10, Part 1, February 1996
Hedger, J ., Lewis P. & Gitay, H. (1993) Litter-trapping byfungi in moist tropical forest . In Aspects of tropicalmycology, Eds. Isaac, S. Frankland, J ., Watling, R. &Whalley, A.J.S. pp 15-35. Cambridge University Press.
Hedger, J . & Baxter, R. (1993)Electron microscope stud-ies on a litt er trapping fungus from tropical forest . InAspects of tropical mycology. Ed s. Isaac, S. Frankland,J. Watlin g, R. & Whalley, A.J.S. p. 305. CambridgeUniversity Press.
Nun ez, M. & Ryvarden, L. (1993) Basidiomycetes ontwigs at ground level and in the canopy: a comparison.In Aspects of trop ical my cology . Eds. Isaac, S.Frankland , J . Watling, R. & Whalley, A.J.S. p. 307.Cambridge University Press.
Pegler, D.N. & Young, TWX (1993) Basidiome structurein Lachnocladiales sensu lato. Kew Bulletin 48: 37-52.
Plunkett, B.E. (1956)The influence of factors of the aera-tion complex and light upon fruit-body formation inpure cultures of an agaric and a polypore. Annals ofBotany, New Series 20: 563-586.
Ryvarden, L. (1993) Tropical polypores. In Aspects oftropical mycology . Eds. Isa ac, S., Frankland , J. ,Watling, R. & Whalley, A.J.8. pp. 149-170. CambridgeUniversity Press.
Ryvarden, 1. & Nunez, M. (1992) Basidiomycetes in thecanopy of an African rain forest. In Rapport de mis-sion: Radeau des cimes. Octobre-Novembre 1991: 116-118 Ed s. Halle, F. & Pascal, O. pp. 116-118. Lyon:Fondation ELF.
MYCOLOGICAL DISPATCHES
A spergillus fumigatus Fresenius and similar fila-mentous fungi are usually harmless but cancaus e havoc in immunocompromised patientswhose immune systems have been weakened orde stroyed by chemotherapy or HIV. Thesespecies are retarded, but not killed , by estab-lished antifungal drugs. The New Scientist (9December 1995, p.20) reports on a fungicide pro-duced by Streptovert icill ium fervens (De Boer,Die t z, Evans & Michaels ) Locci, Baldacci &Paetrolini Baldan, a soil actinomycete (cited as afungus) that is harmless to mammals.
Though discovered in 1989 by Fujisawa, aJapanese pharmaceutical company, it has onlynow been synthesised - by Ton y Barrett andKrista Kasdorf of Imperial College. The metabo-lite is composed of a chain of five carbon trian-gles (cyclopropy ls), caus ing it to be dubbed"jawsamycin" because of the re semblance toshark's teeth. The compound, however, has 10crural centres, points about which mirror imagesof the molecule can form for a total of 1024possi-ble isomers, only one of which is jawsamycin.
The Imperial College chemists will report howthey synthesised a precise replica of the naturalproduct in 15 chemical reactions in a future issueof Chemical Communications: a synopsis of thesynthesis is described in this report .
Vesicular arbuscular (VA) my corrhizae areassociated with most terrestri al plants, includinga number of major crop species. At present themolecular mechanisms underlying fungal-medi-ated uptake and translocation of phosphate fromsoil to plant remain unknown because t hesefungi are obligate symbionts. Reports in Nature378 (1995) 560-561; 626-629 describe how M.J .Harrison and M.L. van Buuren, studying Glomusoersi jorme (Karst. ) Berch, have begun to investi-gate this process by being the first to identifyand clone a complementary DNA that encodes atransmembrane phosphat e transport er (GvPT).Expression of GvPT was found to be localized tothe external hyphae which are the initial site ofphosphate uptake from the soil.
R.T. Moore
•
