Biology:Megaloblastenia
Megaloblastenia is a genus of crustose lichen-forming fungi in the family Megalosporaceae,[1] comprising three species.[2] Proposed by Dutch lichenologist Harrie Sipman in 1983, the genus is characterised by its thick, ecorticate thallus ranging from pale whitish-grey to yellowish, and its [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]-like fruiting bodies (apothecia) that can be [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] or [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]. Megaloblastenia lichens form a symbiotic relationship with Dictyochloropsis algae, produce hyaline, bicellular [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] with [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] structure, and contain chemical compounds such as zeorin, pannarin, or usnic acid. Found in Australasia and South America, these lichens typically grow as epiphytes on trees in moist forests within temperate to tropical oceanic climates.
Taxonomy
Genus Megaloblastenia was proposed by the Dutch lichenologist Harrie Sipman in 1983, with M. flavidoatra assigned as the type species.[3] This species was originally described by William Nylander in 1867 as a member of Lecidea.[4]
Description
Megaloblastenia is a lichen genus with a crustose thallus, meaning it forms a crust-like layer that adheres tightly to its [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]. The thallus is relatively thick and mostly lacks an outer protective layer ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]), and its colour ranges from pale whitish-grey to yellowish. Some specimens may have soredia—tiny structures used for reproduction—while others do not. Unlike many lichens, Megaloblastenia does not contain calcium oxalate crystals. The photosynthetic partner ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) in this lichen is Dictyochloropsis, an alga with nearly spherical cells measuring 6–12 μm in diameter.[5]
The fruiting bodies (ascomata) are [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]-like structures called apothecia, which can range from [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (with a thallus-coloured margin) to [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (with a dark margin) in form. These apothecia are [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], meaning they sit directly on the surface, and are often constricted at the base. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] of the apothecia is usually flat or slightly wavy and sometimes has a powdery coating ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]). The outer rim ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) is generally thick, glossy, and persistent, with a cup-shaped cross-section. This exciple is made of tightly packed, radiating fungal filaments (hyphae) that are branched and interconnected (anastomosed).[5]
The spore-producing layer (hymenium) is clear (hyaline) and turns blue when stained with iodine-based stains. The sterile filaments (paraphyses) within the hymenium are slender (about 1–2 μm wide), branched, and interconnected, but they do not have enlarged tips (non-[[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]).[5]
The sacs that produce spores (asci) are club-shaped ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) and usually contain eight spores, though some spores may abort before fully maturing. The asci have a distinctive blue-staining outer layer and a well-developed blue [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (a thickened region at the tip), but lack internal divisions. Some asci may also have a short, cone-shaped ocular chamber at the tip. The spores ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) are colourless (hyaline), ellipsoid, and composed of two connected cells (bicellular). The cell walls are thickened at the ends (polar) and at the septum that divides the cells, forming a [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] structure. The two cells are connected by a narrow channel, and the spore wall has two layers.[5]
In addition to sexual reproduction, Megaloblastenia produces asexual reproductive structures called pycnidia, which are embedded in the thallus. These release tiny rod-shaped (bacilliform) spores called conidia that measure 3–5 μm long and about 0.5 μm wide.[5]
The genus contains chemical compounds such as zeorin, along with either pannarin or usnic acid, which are common lichen substances.[5]
Habitat and distribution
Confined to oceanic climates in temperate to tropical regions of Australasia and South America, Megaloblastenia species typically grow as epiphytes on trees in moist forests.[5]
Species
- Megaloblastenia flavidoatra (Nyl.) Sipman (1983) – Australasia
- Megaloblastenia marginiflexa (Hook.f. & Taylor) Sipman (1983) – Australasia; South America
- Megaloblastenia sorediata Kantvilas (2022)[6] – Australia
References
- ↑ Wijayawardene, N.N.; Hyde, K.D.; Dai, D.Q.; Sánchez-García, M.; Goto, B.T.; Saxena, R.K. et al. (2022). "Outline of Fungi and fungus-like taxa – 2021". Mycosphere 13 (1): 53–453 [156]. doi:10.5943/mycosphere/13/1/2. https://www.researchgate.net/publication/358798332.
- ↑ "Megaloblastenia". Species 2000: Leiden, the Netherlands. https://www.catalogueoflife.org/data/taxon/CDL47.
- ↑ Sipman, H.J.M. (1983). A monograph of the lichen family Megalosporaceae. Bibliotheca Lichenologica. 18. p. 87. https://repository.naturalis.nl/pub/534845/MBMHU1983482001001.pdf.
- ↑ Nylander, W. (1865). "Lichenes Novae Zelandiae, quos ibi legit anno 1861 Dr. Lauder Lindsay" (in la). Journal of the Linnean Society. Botany 9 (36): 244–259. doi:10.1111/j.1095-8339.1866.tb01283.x. https://www.biodiversitylibrary.org/page/226257.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Kantvilas, G (2023). "Megaloblastenia, version 2023:1.". in de Salas, M.F.. Flora of Tasmania Online. Hobart: Tasmanian Herbarium, Tasmanian Museum and Art Gallery. https://flora.tmag.tas.gov.au/lichen-genera/megaloblastenia/.
- ↑ Kantvilas, G (2022). "A sorediate addition to the genus Megaloblastenia". Muelleria 41: 12–16. doi:10.5962/p.375322. https://rbgv-storage-prod.azureedge.net/media/hatk02pb/muelleria-41-kantvilas-megaloblastenia-12-16.pdf.
Wikidata ☰ Q21225735 entry
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