Search on : Taxa descriptions

 


   
Remarks (public):The new species is characterised by a combination of very pale areolate thallus, very numerous and largely immersed perithecia, each with a spreading involucrellum, and comparatively large asci and ascospores. The aquatic and semi-aquatic V. praetermissa (Trevis.) Anzi occurs, among other places, in south-eastern and north-eastern Queensland (including the Atherton Tableland). However, while the thallus is outwardly and anatomically quite similar to that of V. pluviosilvestris, it is subtended by a thick brownish black basal layer. In addition, the ascospores are considerably smaller [15-24 — 6.5-9.5 µm; McCarthy (2001)]. The newly described lichen does not grow in creeks or on seasonally inundated rocks.
Verrucaria pluviospora was collected from shaded, fine- and coarse-grained siliceous rock outcrops, boulders and cliff faces in rainforest at ten localities between Wallaman Falls (18°35Â’S) and Mossman Gorge (16°28Â’S) and at elevations of 55-980 m. It is likely to be as common in similar habitats further south in Queensland.
 
Description type:Original description 
Description:Thallus crustose, epilithic, sometimes coalescing to form colonies to 5(-10) cm wide, usually off-white to pale grey when dry, occasionally darker, richly rimose to areolate (less rimose in deep shade), with a smooth to rugulose or irregularly and minutely uneven surface, matt, 30-60 µm thick in the absence of ascomata, to 100(-120) µm thick between ascomata in richly fertile thalli; moist thalli pale greenish (when ascomata are sparse) to medium greenish grey (when ascomata are numerous and densely aggregated); areolae angular to irregular, separated by thin cracks. True cortex lacking, but the uppermost 10-20 µm of the thallus without algae; cells rounded to angular and vertically elongate, 3-8 — 3-5 µm, hyaline, thin-walled. Algae chlorococcoid, dominating the rest of the thallus (vertical section), bright green, globose, subglobose or ellipsoidal, 5-10(-12) — 4-8(-10) µm; interstitial cells similar to those of the alga-free layer. Prothallus not apparent. Basal layer absent; however, overlapping involucrellum bases in abundantly fertile thalli can give the misleading impression of a thick continuous layer of blackish basal hyphae. Perithecia usually very numerous, almost entirely immersed in the thallus, with only the upper part of the involucrellum exposed; wetting the thallus often shows the full extent of the immersed involucrellum; perithecia less commonly semi-immersed in the thallus. Involucrellum black, (0.2-)0.38(-0.55) mm diam. [25 measured], usually exposed only towards the apex, c. 40-60 µm thick, contiguous with the excipulum but also speading laterally into the thallus and towards the substratum. Perithecial apex usually plane to convex, (0.08-)0.15-0.22(-0.35) mm diam. [50 measured], with a central, hyaline to grey-brown plane shallowly depressed or, occasionally, crateriform ostiole (40-)80(-100) µm diam. Excipulum hyaline to greyish brown in thin section, 20-25(-30) µm thick. Centrum subglobose to obpyriform, 0.15-0.28 mm diam. Periphyses 15-30(-40) — (1.5-)2-2.5 µm, simple to sparingly branched. Paraphyses absent at maturity. Hymenial gel IKI+ orange-brown. Asci fissitunicate, 8-spored, narrowly to broadly clavate to cylindroclavate or obclavate, occasionally almost subglobose, 65-115 — 24-40 µm. Ascospores simple, hyaline, narrowly to broadly ellipsoidal, occasionally subcylindrical or broadly clavate, biseriate or irregularly massed in the asci, (22-)31(-39) — (9-)12(-15) µm [80 measured]; wall usually 0.7-1 µm thick, occasionally to 2 µm (due to environmental stress?); contents granulose and, frequently, large-guttulate. 
Taxon name: