Henssenia glaucella Ertz, R. S. Poulsen & Sochting 2017, comb. nov.
Creators: name: Ertz, Damien
name: Poulsen, Roar S.
name: Charrier, Maryvonne
name: Søchting, Ulrik
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Lecanoromycetes
Peltigerales
Koerberiaceae
Henssenia
Henssenia glaucella

description: Henssenia glaucella (Tuck.) Ertz, R.S. Poulsen & Søchting comb. nov. (Figs. 10–11)   
MycoBank: MB 822684  
 Basionym: Pannaria glaucella Tuck., Bull. Torrey Bot. Club 6: 57 (1875). Steinera glaucella (Tuck.) C.W. Dodge, B.A.N.Z. Antarct. Res. Exped. Rep., ser. B, 7: 66 (1948). Type:—KERGUELEN. 1875, J.H. Kidder (U.S. Transit of Venus Expedition) (holotype FH!, in very poor condition).   
 Epitype here selected:— KERGUELEN.Val Studer, sur les hauts de la rive droite de la rivière du Sud, 334 m elev., 49°17’49”S, 70°03’09”E, 16 November 2016, Ertz 21005 (BR!).   
 Thallus subfoliose to placodioid, to 3(–3.5) cm diam., margin distinctly and ±regularly lobate, central parts sometimes becoming ±crustose-areolate or ±squamulose; marginal lobes broadening to 1.5(–2) mm towards their ends and there occasionally notched. Upper surface smooth, rarely slightly roughened in central areas, matt, uniformly pale grey or becoming darker grey to pale brownish towards the centre, not pruinose, without isidia.Areoles derived from secondary rimose cracking between the main fissures, complete or incomplete, angular, flat to slightly convex. Apothecia discrete or sometimes 2–5(–10) contiguous, up to 0.8(–1) mm diam., immersed when young, eventually more or less level with the surface of the thallus or sessile, sometimes with a slightly constricted base at maturity when sessile, leaving characteristic white and large depression with exposed medulla when abraded; disc dull brown to reddish-brown or black, slightly concave when immature, plane or convex at maturity; thalline margin not elevated, smooth, distinct and to c. 0.06 mm wide in sessile ascomata, concolourous with thallus. Thalline anatomy: thallus c. 220–400 μm thick; upper ±algal-free layer consists of a c. 5–20 μm thick, hyaline layer of oval or slightly cuboidal cells 7–19 × 5–8 μm diam., which is overlaid by an uneven, amorphous, semi-translucent necrotic layer, c. 1–5 μm thick. Photobiont cells 8–11 μm diam., sometimes distinctly wider than long, heterocytes c. 8–10 μm diam.; hyphae in the c. 1/4–1/3 lower part closely compacted, either vertically aligned as in the central areoles, or ±horizontally radiating towards the apices of the marginal lobes, generally interspersed with simple chains of algal cells; hyphae c. 2–4 μm wide, with cells c. 10–20 μm long. Lower surface with a ±irregularly developed cortical layer composed of ±isodiametric cells c. 3–5 μm diam in cross section of the thallus lobes. Apothecial anatomy: Excipulum compound, consisting of an inner proper exciple and an outer thalline exciple; proper exciple almost inconspicuous, laterally of 2-3 hyphae arranged in parallel, c. 10–15 μm, with cells c. 5–10 × 2–3 μm and basally paraplectenchymatous, c. 20-25 μm, with isodiametric cells c. 2–4 μm diam.; thalline exciple thin, often distinct. Hymenium 80–90 μm high; epihymenium pale brown, 10–20 μm; paraphyses 1.5–3 μm wide; apical cells swollen, up to 3–5 μm wide, embedded in a gelatinous matrix that is brownish, K–. Hypothecium 70–100 μm high, of densely short-celled hyphae above with cells up to 14 × 6 μm, becoming paraplectenchymatous with cells 3–6 μm diam. below, I+ pale orange, KI+ pale orange with few dark blue spots. Asci 60–85 × 9–13 μm; ascospores (4–7)–8 per ascus, simple or appearing 1-septate (= plasma bridge), ellipsoid, 9–10 × 5–7 μm, without a gelatinous sheath, I– (except internal cytoplasm becoming dark orange), KI–. Pycnidia observed one time (Ertz 18735), immersed in the thallus near an apothecia, pear-shaped, wall hyaline, c. 10–15 μm thick, of isodiametric cells 3–4 μm diam.; conidia bacilliform, 4–5 × 1 μm.   
 Distribution and ecology: Henssenia glaucella is known only from Kerguelen (including type locality) and Crozet (this paper). Records from other archipelagos should be checked against Steinera molybdoplaca. The species grows on exposed basaltic rock and pebbles sometimes in relatively damp situations from low to high elevation.   
 Notes:   
1) ‘J.P. Kidder’ is written on the label of the holotype (FH), but the correct name is ‘J.H. Kidder’.  
 2) Henssenia glaucella has apothecia often leaving characteristic white and large depressions with exposed medulla when abraded (Fig. 10). Steinera molybdoplaca differs by having a thallus that might reach 6 cm diam., by ±urceolate apothecia that never become sessile and by mainly 3-septate ascospores. The species is very close to Henssenia subglaucella, but that species differs notably by a smaller thallus usually having a brownish tinge. H. werthii differs by distinctly smaller and brown thallus having distinct striae on the thallus lobes and slightly longer ascospores.   
 3) The holotype specimen is in poor condition but clearly belongs to the genus Henssenia and not to Steinera s. str. (e.g. simple small ascospores, ascus type, etc.; Fig. 11). Because of the fragmentary nature of the holotype, doubts remain to which species of Henssenia the name glaucella should be applied. As the thallus was originally described as being “glauco-cinerascente” and the main thallus appears to be two centimeter in diameter (but it is unclear if two thalli might have been contiguous, as most of the specimen is abraded), the name is epitypified on a specimen of the species of Henssenia having a pale greyish thallus and occurring in Kerguelen, despite the fact that thalli are often larger than stated in the original description (“Specimens scarcely half an inch across”). Material described here as H. subglaucella could thus also be a possibility because of the rather small thalli, but the thalli of this species mainly have a brownish tinge.   
 Examined specimens: CROZET. Île de La Possession, tout près de la base Alfred Faure, c. 125 m, 46°26’02”S, 51°51’34”E, 16 November 2012, D. Ertz 17670 (BR); vallon du ruisseau du barrage, au sud de la base Alfred Faure, c. 70 m, 46°26’18”S, 51°51’35”E, sur un bloc rocheux près du ruisseau, 17 November 2012, D. Ertz 17741 (BR); ibidem, crête rocheuse située juste au nord de la Baie Américaine et à l’ouest du Rocher Pyramidal, lieu-dit ‘ Crête Alouette’, c. 230 m, 46°22’44”S, 51°47’36”E, 25 November 2015, D. Ertz 20673 (BR); ibidem, Mont du Mischief, près du sommet, c. 900 m, 46°24’59”S, 51°41’37”E, 08 December 2015, D. Ertz 20865 (BR); ibidem, Mont Branca, versant sud-ouest, 270 m, 46°26’23”S, 51°49’39”E, 11 November 2016, D. Ertz 20962 (BR). KERGUELEN. Péninsule Courbet, La Grande Muraille, 150 m, 49°17’0”S, 70°08’5”E, 15 December 1998, R. S. Poulsen 159 p. p. (C); Val Studer, vallon encaissé s’ouvrant dans le versant droit de la Rivière du Sud un peu en aval du Lac Supérieur, 105 m, 49°17’27”S, 70°03’11”E, 16 Novermber 2016, D. Ertz 20997, 21000 (BR); ibidem, versant droit de la Rivière du Sud, 113 m, 49°17’20”S, 70°02’55”E, 16 Novermber 2016, D. Ertz 20974 (BR); ibidem, 90 m, 49°17’22”S, 70°02’59”E, 16 Novermber 2016, D. Ertz 20980, 20984 (BR). La Mortadelle, SE part (at the foot) of La Mortadelle, c. 0.5 km W of Lac Ampère, c. 100 m from cabin/shelter, 150 m, 49°25’4”S, 69°10’8”E, 20 January 1999, R. S. Poulsen 597 (C); ibidem, 28 January 1999, R.S. Poulsen 677 (C, H); c. 0.5 km SE of summit of La Mortadelle on upper S-exposed side of the mountain, c. 650 m, 49°24’3”S, 69°08’7”E, 31 January 1999, R. S. Poulsen 723 (C). Golfe du Morbihan, Île Australia, 123 m, 49°27’56”S, 69°52’32”E, 21 December 2013, D. Ertz 18735 (BR).
description: Published as part of Ertz, Damien, Poulsen, Roar S., Charrier, Maryvonne & Søchting, Ulrik, 2017, Taxonomy and phylogeny of the genus Steinera (Arctomiales, Arctomiaceae) in the subantarctic islands of Crozet and Kerguelen, pp. 201-238 in Phytotaxa 324 (3) on pages 224-227, DOI: 10.11646/phytotaxa.324.3.1, http://zenodo.org/record/13698300