Acaulospora colombiana

WHOLE SPORES

COLOR: Light orange-brown (0/10/20/0) to dark orange-brown (0/20/80/0) with most being orange-brown (0/20/60/0)

SHAPE: Globose to subglobose.

SIZE DISTRIBUTION (lenght x width): 100-140 µm, mean = 115 µm (n = 100).

SUBCELLULAR STRUCTURE OF SPORES

SPORE WALL: Formed by two layers (L1 and L2). L1 usually absent in mature spores because this layer is continuous with the wall of the neck of the sporiferous saccule and tend to slough off. L2 is laminated, pigmented (giving the spore its color) and shows little variation in thickness within the same spore.

L1: Outermost evanescent layer, hyaline (0-0-10-0), smooth, that tends to degrade and not be present in mature spores (even in fresh spores from single culture). Layer is 0.5-1.0 µm thick. This layer is easily detected when spores are still attached to the sporiferous saccule.

L2: A yellow-brown layer (0-30-100-0) consisting of several sublayers (lamina), ranging from 2.0-3.0 µm (mean = 2.1 µm). In some spores, L2 is 1.0-1.5 µm thick and it can reach up to 3.5 µm.

GERMINAL WALLS: Two germinal walls (GW1 and GW2) are differentiated after spore wall is formed, each formed by two layers (L1 and L2).

GW1: This wall is formed by two flexible hyaline layers that are very adherent to each other. Because of that, this wall appears to be formed by only one layer at 400x and ranges in thickness from 0.5-1.0 µm. Visualization of both layers is possible at 1000x.

GW2: A flexible wall formed by two tightly adherent layers. L1 is hyaline (0.5-1.0 µm thick) covered with granular excrescences (forming a “beaded” layer). These excrescences are visible in fresh-mounted slides and they tend to disappear within a few months of storage. L2 is hyaline with amorphous properties and its thickness varies depending on how much pressure is applied when spores are broken under the coverslip. C2 is easily observed and measured when spores are mounted in Melzer´s reagent. This layer can be 1.0 µm thick in spores broken with not much pressure applied or to expand up to 4-8 µm thick. L2 reacts strongly in Melzer´s reagent, turning red-purple (20-80-20-0) to dark red-purple (40-80-60-0).

SCAR

Two scars are observed and they represent the connection of the spore with the neck of the sporiferous saccule. The larger scar is located near the saccule, 12-30 µm diameter (mean = 24 µm), and the smaller scar is located distal to the saccule, 6-18 µm diameter (mean = 11 µm). The smaller scar can be ovoid, 10-12 x 5-8 µm diameter.

SPORIFEROUS SACCULE

COLOR: In young spores, sporiferous saccule is salmon and then changes to white during spore development. Later, it becomes hyaline as the contents disintegrate

SHAPE: Globose to subglobose

SACCULE WALL: Two layers. L1 is the outermost layer, 0.5 to 1.0 µm thick, and L2 is whitish and 2-4 µm thick

Comparison with Original Description

Color:

Description: Pale yellow to light golden brown

SCT115A: orange-brown

Shape:

Description: not informed

SCT115A: Globose to subglobose

Size:

Description: (75-) 100-115 (-135) µm

SCT115A: 100-140 µm, mean = 115 µm.

Spore Wall: Indicated in the original protologue as being formed by two walls (outer spore wall and wall two), which correspond to layers 1 and 2 of the spore wall, according to the terminology adopted herein based on ontogenetic studies.

Spore Wall: L1

Description: “the outer spore wall confluente with the wall of the hyphal stalk (referring to the neck of the sporiferous saccule), hyaline, ephemeral, 0.5-2.0 µm, firmly adhered to wall two and found only on newly-formed spores”.

SCT115A: evanescent hyaline layer, ranging from 0.5-1 µm and usually not presente in mature spores

Spore Wall: L2

Description: "wall two yellow-brown to golden-brown in color, 2-3 µm thick, with laminae".

SCT115A: laminated layer, orange-brown, ranging from 1-3.5 µm (mean = 2.1 µm).

Germinal Wall 1: GW1

Description: "wall three hyaline, 1 µm thick, separating from other walls on broken spores".

SCT115A: Hyaline, flexible wall, formed by two very thin layers that appears as a single layer. Thickness of this GW1 (both layers) is 1 µm.

Germinal Wall 2: GW2

Description: "wall four membranous, having a “beaded” appearance, 0.5 µm thick, hyaline, tightly wrinkled when broken, wall five membranous, 1 µm thick, hyaline, turning dark purple in Melzer’s reagent".

SCT115A: Hyaline, flexible wall formed by two layers. Layer 1 (L1) with granular appearance, 0.5-1.0 µm thick. Layer 2 (L2) with amorphous properties, hyaline, and reacting strongly in Melzer (turning red-purple to dark red-purple); this layer is 0.5-1.0 µm thick, but it can expand (due to its amorphous property) up to 4-8 µm depending on amount of pressure applied when spores are broken.

Taxonomic History

Reference: Schenck, N.C., J.L. Spain, E. Sieverding & R.H. Howeler (1984). Several new and unreported vesicular-arbuscular mycorrhizal fungi (Endogonaceae) from Colombia. Mycologia 76(4):685-699.

Etymology: colombiana, referring to the country (Colombia) in which this species was first observed in 1978.

Type: spores from pot cultures with Pueraria phaseoloides (culture no. C-10) at CIAT. Originally observed and collected from cassava roots and native grasses in Carimagaua. Type OSC No. 41497; Isotype FLAS No. F58675 and FH.

This species was originally described as Entrophospora colombiana by Schenck and co-workers in 1984. At that time, spore formation within the neck of a sporiferous saccule was the main characteristic to allocate AMF species in the genus Entrophospora. Reviewing the genus Entrophospora, Sieverding & Oehl (2006) transfered this species (and E. kentinensis) to the new genus Kuklospora. This proposal was based on the morphological distinction of this species compared to the type species of the genus, Entrophospora infrequens. In a phylogenetic study of Acaulospora species, Kaonongbua et al. (2010) observed that species in Kuklospora differed from other Acaulospora species only in the position of the spore within the neck of the sporiferous saccule, a convergent character that is found in other clades within Glomeromycota, and rejected the genus as a monophyletic group. As a result, the species was transferred to Acaulospora and Acaulospora colombiana proposed as a new combination.

Nomenclature: Acaulospora colombiana (Spain & Schenck) Kaonongbua, J.B. Morton & Bever

= Entrophospora colombiana Spain & Schenck

= Kuklospora colombiana (Spain & Schenck) Oehl & Sieverd.

Biogeography

Acaulospora colombiana is a cosmopolitan species, detected in all continents, except Antarctica, present in 14 countries and 7 Biogeographical realms. The species was recorded to occurr in tropical, subtropical and temperate climatic regions with two records for the boreal region (in Sweden). Acaulospora colombiana was recorded in several ecosystems like sand dunes (de Souza et al. 2011), agroecosystems (Siqueira et al. 1989) and degraded areas (Mehrotra 1998). This species was recorded for the biomes Desert and Xeromorphic Shrublands (Ganesan et al 1991), Flooded Grasslands (Gomide et al. 2014), Mangroves (Fabian et al. 2018), Temperate Broadleaf Forests (Hewins et al. 2015), Temperate Conifer Forests (Oehle et al. 2011), Tropical & Subtropical Savannas and Grasslands (Tchabi et al. 2008), Temperate Grasslands, Savannas & Shrublands (Graham et al. 1986), Tropical & Subtropical Dry Forests (Silva et al. 2014), and Tropical and Subtropical Moist Broadleaf Forests (Stürmer & Siqueira 2011).

In Brazil, this species was recorded from maritime sand dunes, Araucaria forests, pantanal, rupestrian fields, canga, restinga, degraded areas, and agroecosystems, in 14 states of all brazilian regions, in the floristic domains of Atlantic Forest, Amazon Forest, Cerrado, Caatinga, and Pantanal.

The map below shows countries (in red) where Acaulospora colombiana was detected.

References:

de Souza RG, da Silva DKA, de Mello CMA, Goto BT, da Silva FSB, Sampaio EVSB, Maia LC. 2011. Arbuscular mycorrhizal fungi in revegetated mined dunes. Land Degradation & Development DOI 10.1002/ldr.1113

de Marins JF, Carrenho R, Thomaz SM. 2009. Occurrence and coexistence of arbuscular mycorrhizal fungi and dark septate fungi in aquatic macrophytes in a tropical river-floodplain system. Aquatic Botany, 91:13-19.

Fabían D, Guadarrama P, Hernandez-Cuevas L, Ramos-Zapata JA. 2018. Arbuscular mycorrhizal fungi in a coastal wetland in Yucatan, Mexico. Botanical Sciences 96:24-34.

Ganesan V, Ragupathy S, Parthipan B, Rajini Rani DB, Mahadevan A. 1991. Distribution of vesicular-arbuscular mycorrhizal fungi in coal, lignite, and calcite mine spoils of India. Biol. Fertil. Soils, 12:131-136.

Gomide PHO, Silva MLN, Soares CRFS, Cardoso EL, Carvalho F, Leal PL, Marques RM, Stürmer SL. 2014. Fungos micorrízicos arbusculares em diferentes fitofisionomias do Pantanal da Nhecolândia, Mato Grosso do Sul. Revista Brasileira de Ciência do Solo 38:1114-1127.

Graham JH, Fardelmann D. 1986. Inoculation of citrus with root fragments containing chlamydospores of the mycorrhizal fungus Glomus intraradices. Can. J. Bot., 64:1739-1744.

Hewins CR, Carrino-Kyker SR, Burke DJ. 2015. Seasonal variation in mycorrhizal fungi colonizing roots of Allium tricoccum (wild leek) in a mature mixed hardwood forest. Mycorrhiza 25:469-483.

Mehrotra VS. 1998. Arbuscular mycorrhizal associations of plants colonizing coal mine spoil in India. J. of Agric. Sci. 130:125-133.

Kaonongbua W, Morton JB, Bever JD. 2010. Taxonomic revision transferring species in Kuklospora to Acaulospora (Glomeromycota) and a description of Acaulospora colliculosa sp. nov. from field collected spores. Mycologia 102 1497-1509.

Oehl F, D Schneider, E Sieverding, CA Burga 2011. Succession of arbuscular mycorrhizal communities in the foreland of the retreating Morteratsch glacier in the Central Alps. Pedobiologia 54:321-331.

Stürmer SL, Siqueira JO 2011. Species richness and spore abundance of arbuscular mycorrhizal fungi across distinct land uses in Western Brazilian Amazon. Mycorrhiza 21:255-267.

Siqueira J, Colozzi-Filho A, Oliveira E. 1989. Ocorrencia de micorrizas vesicular-arbusculares em agro e ecossistemas do estado de Minas Gerais. Pesquisa Agropecuaria Brasileira, 24:1499-1506.

Sieverding E, Oehl F. 2006. Revision of Entrophospora and description of Kuklospora and Intraspora, two new genera in the arbuscular mycorrhizal Glomermoycetes. J. App. Bot and Food Quality 80 69-81.

Silva IR, Mello CMA, Neto RAF, Silva DKA, Melo AL, Oehl F, Maia LC. 2014. Diversity of arbuscular mycorrhizal fungi along an environmental gradient in the Brazilian semiarid. Applied Soil Ecology 84:166-175.

Tchabi A, Coyne D, Hountondji F, Lawouin L, Wiemken A, Oehl F. 2008. Arbuscular mycorrhizal fungal communities in sub-Saharan Savannas of Benin, West Africa, as affected by agricultural land use intensity and ecological zone. Mycorrhiza 18:181-195.

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