A cephalodium (pl. cephalodia) is a small gall-like structure found in some lichens. They occur only lichens which contain both cyanobacterial and green algal partners. Cephalodia can occur within the tissues of the lichen, or on its upper or lower surface. Lichens with cephalodia can fix nitrogen, and may be an important contributor of nitrogen to the ecosystem.
Illustration showing cephalodium in relation to other parts of the lichen: 1 – Cephalodium 2 – Cyanobacteria 3 – Cortex 4 – Green algal photobiont 5 – Medulla
Lichens are complex organisms composed of a fungal partner and a photosynthetic partner. While the photosynthetic partner is most often a species of green alga, in about 10 percent of all lichens, a species of cyanobacterium is involved instead. In an even smaller number of cases – estimated at between 2 and 4 percent of all lichens – species of both a green alga and a cyanobacterium serve as photosynthetic partners.[1] There are roughly 520 species of these "tripartite" lichens, which fall into at least 21 different genera.[2] In most of these lichens, the green algae live within the lichen's medulla while the cyanobacteria are housed in specialized structures called cephalodia. These can be located on the upper or lower surface of the lichen, or within its interior.[3][4] In a few species, the cyanobacteria is the main photobiont and the green alga is housed in the cephalodia.[5]
Descriptionedit
Dark purplish-brown cephalodia on the upper surface of Peltigera venosa
Most external cephalodia are gall-like structures that are simple in shape: generally rounded, lobed or sac-like. A few are more complexly coral-like.[6] They can range in size from "minute" to several millimeters across and are typically a different color than the rest of the lichen's thallus.[4][6] In some lichens, internal cephalodia form as lumps within the lichen's medulla. These can become large enough that the swellings are visible on the lichen's surface.[7] The fungal partner forms a thick layer of cortical tissue around the outside of each internal or external cephalodium, which helps to reduce the oxygen levels in the structure's interior.[6]
Typically, only a single species of cyanobacteria is found in any single cephalodium, and that species is found in all of an individual lichen's cephalodia.[8] However some lichens, like Psoroma spinuliferum, which is known from coastal Alaska, have two different strains of cyanobacteria in two different types of cephalodia.[9] In another Arctic species, Nephroma arcticum, multiple forms of cyanobacteria have been found in the same cephalodia. Researchers have been unable to successfully culture the cyanobacteria, so cannot determine whether these were two different species or two distinct morphs of the same species.[10]
Formationedit
Many species of cyanobacteria grow epiphytically in the environment, where they may come into contact with the upper or lower surface of a lichen.[8] If the cyanobacteria species is one which is compatible with the lichen's fungal partner, the fungus's hyphae will grow towards and eventually ensnare the cyanobacteria.
Cyanobacteria are capable of fixing atmospheric nitrogen. They can take gaseous nitrogen and convert it into a form which both they and the lichen's mycobiont can use. This allows those lichens which contain cyanobacteria to survive on nitrogen-poor substrates. As a result, they are often among the early colonisers of bare rock and soil.[11] Lichens containing cyanobacteria (cyanolichens) are among the major contributors of fixed nitrogen to some ecosystems, including mature tropical highland forests.[12] Cyanobacteria in tripartite lichens (where they are confined to cephalodia) generally have higher rates of nitrogen fixation than do cyanobacteria in bipartite lichens (where they are the main photosynthetic partner).[13]
Baron, George (1999). Understanding Lichens. Slough: Richmond Publishing. ISBN978-0-85546-252-9.
Brodo, Irwin M.; Sharnoff, Sylvia Duran; Sharnoff, Stephen (2001). Lichens of North America. New Haven, CT: Yale University Press. ISBN978-0-300-08249-4.
Budel, Burkhard; Scheidegger, Christoph (2008). "Thallus morphology and anatomy". In Nash III, Thomas E. (ed.). Lichen Biology (2nd ed.). Cambridge: Cambridge University Press. ISBN978-0-521-87162-4.
Cornejo, Carolina; Scheidegger, Christoph (January 2013). "New morphological aspects of cephalodium formation in the lichen Lobaria pulmonaria (Lecanorales, Ascomycota)". The Lichenologist. 45 (6): 77–87. doi:10.1017/S0024282912000631. S2CID 85602245.
Elvebakk, Arve; Tønsberg, Tor (Summer 2018). "Psoroma spinuliferum (Pannariaceae), a new corticolous lichen species from Alaska with two different types of cephalodia". The Bryologist. 21 (2): 166–173. doi:10.1639/0007-2745-121.2.166. hdl:10037/14525. JSTOR 26774967.
Grimm, Maria; Grube, Martin; Schiefelbein, Ulf; Zühlke, Daniela; Bernhardt, Jörg; Riedel, Katharina (March 2021). "The Lichens' Microbiota, Still a Mystery?". Frontiers in Microbiology. 12: 623839. doi:10.3389/fmicb.2021.623839. PMC8042158. PMID 33859626.
Hale, Mason E. (1983). The Biology of Lichens (3rd ed.). London: Edward Arnold. ISBN978-0-7131-2867-3.
Honegger, Rosmarie (2008). "Morphogenesis". In Nash III, Thomas E. (ed.). Lichen Biology (2nd ed.). Cambridge: Cambridge University Press. ISBN978-0-521-87162-4.
Jordan, William Paul; Rickson, Fred R. (July 1971). "Cyanophyte Cephalodia in the Lichen Genus Nephroma". American Journal of Botany. 58 (6): 562–568. doi:10.1002/j.1537-2197.1971.tb10005.x. JSTOR 2441039.
Lehr, H.; Galun, M.; Ott, S.; Jahns, H.-M.; Fleminger, G. (2000). "Cephalodia of the Lichen Peltigera aphthosa (L.) Willd. Specific Recognition of the Compatible Photobiont". Symbiosis. 29: 357–365.
Markham, John; Otárola, Mauricio Fernández (February 2021). "Bryophyte and lichen biomass and nitrogen fixation in a high elevation cloud forest in Cerro de La Muerte, Costa Rica". Oecologia. 195 (2): 489–497. doi:10.1007/s00442-020-04840-4.
Rikkinen, Jouko (April 2013). "Molecular studies on cyanobacterial diversity in lichen symbioses". MycoKeys. 6: 3–23. doi:10.3897/mycokeys.6.3869.
January 01, 1970
cephalodium, cephalodium, cephalodia, small, gall, like, structure, found, some, lichens, they, occur, only, lichens, which, contain, both, cyanobacterial, green, algal, partners, cephalodia, occur, within, tissues, lichen, upper, lower, surface, lichens, with. A cephalodium pl cephalodia is a small gall like structure found in some lichens They occur only lichens which contain both cyanobacterial and green algal partners Cephalodia can occur within the tissues of the lichen or on its upper or lower surface Lichens with cephalodia can fix nitrogen and may be an important contributor of nitrogen to the ecosystem Illustration showing cephalodium in relation to other parts of the lichen 1 Cephalodium 2 Cyanobacteria 3 Cortex 4 Green algal photobiont 5 Medulla Contents 1 Context 2 Description 3 Formation 4 Nitrogen fixation 5 References 5 1 SourcesContext editLichens are complex organisms composed of a fungal partner and a photosynthetic partner While the photosynthetic partner is most often a species of green alga in about 10 percent of all lichens a species of cyanobacterium is involved instead In an even smaller number of cases estimated at between 2 and 4 percent of all lichens species of both a green alga and a cyanobacterium serve as photosynthetic partners 1 There are roughly 520 species of these tripartite lichens which fall into at least 21 different genera 2 In most of these lichens the green algae live within the lichen s medulla while the cyanobacteria are housed in specialized structures called cephalodia These can be located on the upper or lower surface of the lichen or within its interior 3 4 In a few species the cyanobacteria is the main photobiont and the green alga is housed in the cephalodia 5 Description edit nbsp Dark purplish brown cephalodia on the upper surface of Peltigera venosa Most external cephalodia are gall like structures that are simple in shape generally rounded lobed or sac like A few are more complexly coral like 6 They can range in size from minute to several millimeters across and are typically a different color than the rest of the lichen s thallus 4 6 In some lichens internal cephalodia form as lumps within the lichen s medulla These can become large enough that the swellings are visible on the lichen s surface 7 The fungal partner forms a thick layer of cortical tissue around the outside of each internal or external cephalodium which helps to reduce the oxygen levels in the structure s interior 6 Typically only a single species of cyanobacteria is found in any single cephalodium and that species is found in all of an individual lichen s cephalodia 8 However some lichens like Psoroma spinuliferum which is known from coastal Alaska have two different strains of cyanobacteria in two different types of cephalodia 9 In another Arctic species Nephroma arcticum multiple forms of cyanobacteria have been found in the same cephalodia Researchers have been unable to successfully culture the cyanobacteria so cannot determine whether these were two different species or two distinct morphs of the same species 10 Formation editMany species of cyanobacteria grow epiphytically in the environment where they may come into contact with the upper or lower surface of a lichen 8 If the cyanobacteria species is one which is compatible with the lichen s fungal partner the fungus s hyphae will grow towards and eventually ensnare the cyanobacteria Nitrogen fixation editMain article Lichens and nitrogen cycling Cyanobacteria are capable of fixing atmospheric nitrogen They can take gaseous nitrogen and convert it into a form which both they and the lichen s mycobiont can use This allows those lichens which contain cyanobacteria to survive on nitrogen poor substrates As a result they are often among the early colonisers of bare rock and soil 11 Lichens containing cyanobacteria cyanolichens are among the major contributors of fixed nitrogen to some ecosystems including mature tropical highland forests 12 Cyanobacteria in tripartite lichens where they are confined to cephalodia generally have higher rates of nitrogen fixation than do cyanobacteria in bipartite lichens where they are the main photosynthetic partner 13 References edit Grimm et al 2021 p 623839 Cornejo amp Scheidegger 2013 p 79 Hale 1983 p 26 a b Budel amp Scheidegger 2008 p 56 Baron 1999 p 22 a b c Honegger 2008 p 86 Lepp 2012 a b Lehr et al 2000 p 358 Elvebakk amp Tonsberg 2018 pp 167 8 Jordan amp Rickson 1971 p 566 Brodo Sharnoff amp Sharnoff 2001 p 22 Markham amp Otarola 2021 p 495 Rikkinen 2013 p 4 Sources edit Baron George 1999 Understanding Lichens Slough Richmond Publishing ISBN 978 0 85546 252 9 Brodo Irwin M Sharnoff Sylvia Duran Sharnoff Stephen 2001 Lichens of North America New Haven CT Yale University Press ISBN 978 0 300 08249 4 Budel Burkhard Scheidegger Christoph 2008 Thallus morphology and anatomy In Nash III Thomas E ed Lichen Biology 2nd ed Cambridge Cambridge University Press ISBN 978 0 521 87162 4 Cornejo Carolina Scheidegger Christoph January 2013 New morphological aspects of cephalodium formation in the lichen Lobaria pulmonaria Lecanorales Ascomycota The Lichenologist 45 6 77 87 doi 10 1017 S0024282912000631 S2CID 85602245 Elvebakk Arve Tonsberg Tor Summer 2018 Psoroma spinuliferum Pannariaceae a new corticolous lichen species from Alaska with two different types of cephalodia The Bryologist 21 2 166 173 doi 10 1639 0007 2745 121 2 166 hdl 10037 14525 JSTOR 26774967 Grimm Maria Grube Martin Schiefelbein Ulf Zuhlke Daniela Bernhardt Jorg Riedel Katharina March 2021 The Lichens Microbiota Still a Mystery Frontiers in Microbiology 12 623839 doi 10 3389 fmicb 2021 623839 PMC 8042158 PMID 33859626 Hale Mason E 1983 The Biology of Lichens 3rd ed London Edward Arnold ISBN 978 0 7131 2867 3 Honegger Rosmarie 2008 Morphogenesis In Nash III Thomas E ed Lichen Biology 2nd ed Cambridge Cambridge University Press ISBN 978 0 521 87162 4 Jordan William Paul Rickson Fred R July 1971 Cyanophyte Cephalodia in the Lichen Genus Nephroma American Journal of Botany 58 6 562 568 doi 10 1002 j 1537 2197 1971 tb10005 x JSTOR 2441039 Lehr H Galun M Ott S Jahns H M Fleminger G 2000 Cephalodia of the Lichen Peltigera aphthosa L Willd Specific Recognition of the Compatible Photobiont Symbiosis 29 357 365 Lepp Heino 2012 Form and structure Australian National Botanic Gardens and Australian National Herbarium Retrieved 29 October 2023 Markham John Otarola Mauricio Fernandez February 2021 Bryophyte and lichen biomass and nitrogen fixation in a high elevation cloud forest in Cerro de La Muerte Costa Rica Oecologia 195 2 489 497 doi 10 1007 s00442 020 04840 4 Rikkinen Jouko April 2013 Molecular studies on cyanobacterial diversity in lichen symbioses MycoKeys 6 3 23 doi 10 3897 mycokeys 6 3869 Retrieved from https en wikipedia org w index php title Cephalodium amp oldid 1187120690, wikipedia, wiki, book, books, library,
