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Manna Lichens

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Manna lichens of the world
Mohammad Sohrabi
Iranian Research Organization for Science and Technology (IROST), Tehran, Iran
Last Update: 
Sat, 01/05/2013 - 21:15


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The ‘Manna lichens’

An exciting phenomenon in most of temperate arid and semiarid regions of the world is the occurrence of erratic and vagrant lichens (see I, V, VII, Kappen 1988, Rosentreter 1993, Pérez 1997a, b). Vagrant lichens are known from windswept steppes and deserts in the C and SW Asia, N Africa, S Europe and NW North America. Because of their loose growth form that varies in size from a pea to a hazel-nut, and with no attachment to the substrate, they can easily be blown around in heavy winds. These lichens have been hypothesized to be the best candidate for the “Biblical manna” (cited in Exodus 16:31) that was eaten by the Israelites when they wandered the Sinai wilderness for 40 years (Perez-Llano 1944, Richardson 1974, Brodo et al. 2001). The word “Manna” was also used in Qur'an, but no lichen species has been suspected to be Qur'anic manna (I).

The “Biblical manna” is defined as the food “miraculously” provided for the Israelites in the wilderness during their escape from Egypt. In many textbooks and popular books (see Evans et al. 2002, Kiple & Coneè Ornelas 1999, Webster & Weber 2007) it has been quoted that the “Biblical manna” might have been a lichen. In Aspicilia s.lat. (currently Circinaria) species with vagrant form (subfruticose and even with amorphous thalli), and without proper attachment to the substrate are known as ‘manna lichens’. The most widely accepted view in textbooks is that the manna of the Bible might be the “manna lichen” (Lichen esculentus Pall. ≡ Lecanora esculenta (Pall.) Eversm. or ≡ Aspicilia esculenta (Pall.) Flagey ≡ Circinaria esculenta (Pall.) Sohrabi nom. provis.) which is moved around by the wind in the Eurasian steppes and deserts, sometimes accumulating in drifts so large that people consume it as food, or use it as additive to bread (see also Nelson 1951, Crum 1993, Brodo et al. 2001). It must be noted that the ‘manna lichen’ is considered more as a famine food rather than everyday food stuff. Most lichen carbohydrates are indigestible when raw and need to be specially prepared before they are eaten (Crawford 2007).

The informal term ‘manna lichen’ has been used in publications since the 18th century by several authors (e.g., Pallas 1776, Göbel 1830, Eversman 1831, Link 1848, 1849, Berkeley 1849, Pitra 1868, Reichardt 1864, Visiani 1865, Krempelhuber 1867, Errera 1893, Elenkin 1901a, b, c, d, e, 1907, Mereschkowsky 1911a, b, 1921, Perez-Llano 1944, Donkin 1980 and Crum 1993). Donkin (1981) undertook a large literature survey on the nature and source of 'manna' as a miraculous food of biblical times. He documented an extensive number of references to manna lichens and provided some historical information and observations by European naturalists and travellers in Asian deserts (e.g., Eversmann in1820-25, Aucher-Éloy in 1825-30, Thénard in 1828 and Parrot in 1824-25). According to Aucher-Éloy (1843) falls of the ’manna lichen’ do occur in the surrounding area of [‘Reżā'iyeh’] Urmia Lake (Daryacheh-e-Orumiyeh), and in some localities in the southern Caspian to central Asia Minor. However, based on my own knowledge of Iranian literature no document of such lichen fall has been made in recent years and I have never heard about it from the local nomads, or their traditional knowledge.

Up to now, the most commonly cited ‘manna lichen’ (Lecanora esculenta or Aspicilia esculenta) has not been reported from the Sinai Desert and Egypt. The most recent publications from the entire region were provided by Temina et al. (2005) and Seaward & Sipman (2006). In their publications, it was shown that A. esculenta (Circinaria esculenta nom. provis.) does not occur in the area (see also study I). Recently, Thor & Nascimbene (2010) published the lichen checklist of Libya and the name A. esculenta was included. Based on my extensive herbarium study, I presume that the name A. esculenta in their study most probably refers to C. jussuffii nom. provis. The latter is one of the most widespread species known from Algeria (Link 1848, 1849), Libya and Morocco (see VII) and Iran (Rabenhorst 1871, see VII) recently also found from Iraq (see VII). Most of the old reports of manna lichen from Iran (Persia, western Caspian Sea region) are misidentifications and refer to saxicolous members of this group (see also Seaward et al. 2008, Sohrabi et al. 2010 and VII), or perhaps to the new species described as Circinaria gyrosa nom. provis. (VII).

According to Zohary (1982) the miraculous manna of the Sinai Desert is probably a product of a vascular plant (e.g., Hammada salicornica, Anabasis setifera, Capparis cartilaginea or Asclepias sinaica as Gomphocarpus sinaicus) rather than a lichen species. It was also hypothesized that manna is most probably sweet excretions, which in some dry areas can be produced by species of Aphididae (Al-Aswad et al. 1977).

 

Circinaria Link, in Neues J. Bot. 3: 5. 1809.

 – Type species: Urceolaria hoffmannii (Ach.) Ach., nom. illeg. [≡ Circinaria contorta (Hoffm.) A. Nordin, S. Savić & Tibell].

= Sphaerothallia Nees in Nova Acta Phys.-Med. Acad. Caes. Leop.-Carol. Nat. Cur. 15: 360. 1831 – Type species (see study I): Sphaerothallia esculenta (Pall.) Reichardt [≡ Circinaria esculenta (Pall.) Sohrabi nom. provis.].

= Chlorangium [Link in Bot. Zeitung (Berlin) 7: 731, Taf. X, figs. 1–4. 1849, nom. provis.] Link ex Rabenh., Lich. Eur. Exs. 7: No. 199. 1857 – Type species (see study I): Chlorangium jussuffii (Link) Rabenh. [≡ Circinaria jussuffii (Link) Sohrabi nom. provis.].

= Agrestia J.W. Thomson in Bryologist 63: 246. 1960 – Type species (see study I): Agrestia cyphellata J.W. Thomson [=Circinaria hispida (Mereschk.) A. Nordin, S. Savić & Tibell].

[– “Jussufia Link ex Wiegmann” in Arch. Naturgesch. (Berlin) 13: 248. 1847, nom. nud. – Based on Jussufia edulis Link ex Wiegmann, nom. nud. [=Circinaria jussuffii (Link) Sohrabi nom. provis.]].

 

Thallus crustose, subfruticose, subfoliose, or umbilicate. Subfruticose thallus forming globular masses, lump shaped, with dumpy erect branches or condensed squamulose, round or occasionally irregular, slightly concave to flat or ±convex to verrucose to verruculose. Umbilicate thallus attached with central strands to the substrate. Subfoliose thallus free (vagrant), more or less rolled up by the lobes. Crustose thallus weakly cracked to distinctly areolate, rimose, more or less scattered, sometimes radiating, contiguous, margin indistinct to distinct; some species with radiating marginal lobes. Prothallus occasionally develops when thallus in crustose form, rare, often indistinct, sometimes ± well developed, fimbriate or forming a zone or a thin rime at the margin, grey to dark olive or brown-black to dark black. Surface white to grey, brown or brownish-black, often muddy or earthy color, sometimes ochre or olive, sometimes ± reddish-orange (when ferriferous oxides present in soil), dull to ± shiny. Sufficient data on isidia or soredia lacking. Cephalodia absent. Pseudocyphellae present in some species. Cortex one or two layers, with even to uneven thickness, mainly paraplectenchymatous, in some subfruticose species forming two layers, outer part paraplectenchymatous and inner part prosoplectenchymatous, upper one usually covered with an epinecral layer or crystals. Medulla white, I–. Photobiont Trebouxia or other chlorococcoid genera; cells ± globose. Ascomata apothecial, urceolate, aspicilioid, sometimes ± sessile forming crypto-lecanorine, round to angular, sometimes elongated or irregular. Disc flat to concave, rarely convex, black to brown-black or bluish-black, sometimes white-pruinose. Thalline margin formed by the margin of the areole, flat and indistinct to ± elevated, sometimes prominent; concolorous with thallus, or sometimes darker, or in some species with a conspicuous white rim in inner part or entirely white. True exciple often thin but rather distinct in some species, sometimes visible as a dark ring or wall around the disc section, cells in the uppermost part rounded and brown to olive-brown, ± I+, partly entirely blue. Epihymenium green to olive, olive-brown or brown, rarely blue-green, N ± green to light-green ("Aspicilia-green"), K ± brown, sometimes contains crystals dissolving in N. Hymenium hyaline, rather variable in thickness in several species, often more than 90 μm thick, usually I+ blue, persistent or ± rapidly turning yellow-green, yellow-brown or rusty-red. Paraphysoids (paraphyses) moniliform, with (3–)4–7(–8) uppermost cells ± globose (3–6 μm in diam.), to submoniliform with 1–2(–3) uppermost cells ±globose to subglobose, or largely ellipsoid, very rarely non-moniliform with simply septate paraphysoids without globose apical cells. Paraphysoids often rather variable even in the same apothecium (best examined in KOH), in lower part narrow, (1–)1.5–2(–2.5) μm wide, simple to ± branched and ± anastomosing. Subhymenium and hypothecium hyaline, usually I+ blue or turning yellow-green to copper-red, sometimes muddy colour and indistinct. Asci clavate, Aspicilia type, wall and apical dome I–, outer coat I+ blue, with 1–4–(6–8) spores. Ascospores hyaline, simple, globose to ellipsoid, I– , usually 10–35 μm long. Conidiomata pycnidial, immersed, single or sometimes aggregated; wall colorless but in upper part brown or sometimes olive to green; ostiole dark, punctiform to elongated; conidiogenous cells sessile or on short conidiophores (might be particular to Circinaria and more or less of Arthonia galactites (DC.) Dufour type sensu Vobis 1980). Conidia hyaline, simple, bacilliform to filiform, straight or curved, in some species quite variable in length. Spot tests: cortex and medulla I–, K–, C–, P– or P+ orange. Secondary metabolites: aspicilin in some species, hypostictic and stictic acid in C. jussuffii, but in many species no substances found. Geography: mostly Holarctic, frequently found in temperate regions, some vagrant groups restricted to arid regions. Substrate: mainly on rocks, on pebbles and small rocks, often on calciferous or calcareous rocks, or on soil, or without substrate (vagrant). Habitat: often in open and sun exposed sites, few species in steppe-forest area.