Freshwater Ascomycetes - Species Monograph

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Genus	Species	Author
Jahnula	seychellensis	K. D. Hyde and S. W. Wong
Class	Order	Family
Dothideomycetes	Jahnulales	Inc. sed.

Genbank ID: 435393 MycoBank ID: 460479

Synonymy:

Description

Habit:

Ascomata on submberged wood.

Ascomata:

Ascomata 272–300 x 365–380 µm, pale reddish brown, globose, flattened at the base, sessile, superficial, with subtending broad, brown, septate, stoloniferous hyphae, ostiolate, short papillate.

Peridium:

Peridium 30 µm wide; in longitudinal section 4-5 cell layers thick, comprised of an inner layer of elongated moderately thick-walled hyaline cells, and an outer layer of large, moderately thick-walled, pigmented cells.

Beak:

Neck 32–35 x 80–85 µm, apex of the neck lined by elongated subglobose cells.

Hamathecium:

Pseudoparaphyses 3–4 µm wide, hyaline, septate, slightly constricted at the septa, anastomosing above the asci.

Ascus:

Asci 158–268 x 26–32 µm, fissitunicate, obclavate, sessile, with an apical chamber, and eight, 2–3 seriate ascospores.

Ascospore:

Ascospores 38–44 x 12–20 µm, (mean = 39 x 15 µm, n =20), broadly ellipsoidal, one-septate, slightly constricted at the septum, light brown, multiguttulate; apical cell of the ascospore broader than basal cell and mammiform, lower cell tapering and rounded towards the base; with gelatinous pads on the ascospore apices; gelatinous pads stain blue in aqueous nigrosin.

Sheath:

None observed.

Appendage:

Gelatinous pads on the ascospore apices.

Culture:

None observed.

Anamorph:

None observed.

Other info

Type & Location:

The Seychelles, LÕniole, Riviere St. Louis, on submerged wood, Aug. 1996, K.D. Hyde (HKU(M) 3239, holotypus.

Other Specimens:

Costa Rica: La Selva Biological Station, Sura 60, 10°25'48''N, 84°1'32''W, UTM Zone 16, 825685mE, 1154486mN, on submerged, corticated wood, CMP, A492-1.

Substratum:

Submerged wood.

Habitat:

Lotic habitats in the tropics.

Distribution:

Costa Rica, The Seychelles, Philippines, Thailand. (See World Records Database)

Pertinent Literature:

Hyde, K.D. 1992. Tropical Australian Freshwater Fungi. I. Some Ascomycetes. Aust. Syst. Bot., 5: 109–116. Raja, H.A. and C.A. Shearer. 2006. Jahnula species from North and Central America, including three new species. Mycologia 98: 319–332.

Comments:

The specimen from Costa Rica is conspecific with J. seychellensis K. D. Hyde and S. W. Wong (Hyde and Wong 1999) from The Seychelles. Hyde and Wong (1999) in their original description of J. seychellensis described the ascospores as being dimorphic, with large light brown and small dark brown ascospores. In our collections, we did not find distinctly dimorphic ascospores, however, there were some minor differences in color and size of ascospores (FIGS. 71–74) but possibly due to differences in developmental stage. Jahnula seychellensis is similar to J. bipolaris in many respects, including ascospore appendage and ascus morphology. They differ, however, in ascomal and ascospore shape.

Additional Pictures

Ascospore appendages.
Ascospore at 100X
Ascospore without appendages.
Immature ascus.
Endoascus apex.
Endoascus apex.

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