Otospora gen. nov. Oehl, J. Palenzuela & N. Ferrol
MycoBank number: MB 506746; Index Fungorum number: IF 506746; Facesoffungi number: FoF;
Type species: Otospora bareai J. Palenzuela, N. Ferrol & Oehl
Sporae singulatim lateraliterque efformatae in distantia ad sacculum sporiferum terminalem vel intercalarem. Sporae globosae vel subglobosae cum tunicis duabus: tunica exterior et tunica interior. Pauciores strata exteriores sporarum coniuncta tunica hyphae et sacculi. Strata interiores tunicae exterioris persistentes. Tunica interior sporae subtiliter laminata et perpetua, sine strato granulato. Formation of sporocarps unknown. Spores formed in a short distance to a terminal or intercalary formed sporiferous saccule by swelling laterally on the hyphal stalk (5neck) of the saccule with two spore walls, an outer and an inner wall. Most layers of the outer wall are continuous with the wall of the sporiferous saccule. The inner layers of the outer wall are persistent. One to several septa are formed in the hyphal stalk during spore formation; at the beginning of spore formation, the content of the sporiferous saccule is separated from the hypha by septa at some distance of the terminus and the not yet developed spore; at later developmental stages additional septa in the stalk, positioned between the saccule terminus and the developing spore, may separate the collapsing saccule terminus from the spore. A final plug-like septum usually closes the pore at the spore base. The inner wall forms de novo during spore formation and consists of a thick, finely laminate layer that might have each one thin layer adherent on its outer and its inner surface. None of the layers of the inner wall have a beaded appearance. Formation of vesiculararbuscular mycorrhizae unknown.
Etymology. Greek: oto– (vtoz 5 ear), –spora (spora 5 seed, spore) referring to the pigmented, tangentiallateral ear-like stalk at the spore base that persists on the spore of the type species after the terminus of the sporiferous saccule has collapsed and detached from the saccule stalk.
Commentary. The principal characters that differentiate Otospora from all other species in the Glomeromycetes forming spores laterally on (i.e. acaulosporoid) or within (i.e. entrophosporoid) a stalk of a sporiferous saccule are summarized (TABLE I). In brief the new genus shares acaulosporoid type of spore formation with the genera Acaulospora Gerd. & Trappe (Gerdemann and Trappe 1974) and with the bimorphic genera Archaeospora J.B. Morton & D. Redecker emend. Spain (Morton and Redecker 2001, Spain 2003) and Appendicispora Spain, Oehl & Sieverd. (Spain et al 2006). However acaulosporoid spores of Acaulospora and Appendicispora species have a more complex spore wall structure than Otospora; that is they have three walls (Stu¨ rmer and Morton 1999, Oehl et al 2006, Spain et al 2006). Furthermore acaulosporoid spores of Acaulospora have a ‘‘beaded’’ ornamentation on the surface of the inner wall (Morton and Benny 1990) and acaulosporoid spores of Appendicispora spp. do not directly arise laterally on the hyphal stalk of the sporiferous saccule but form on a pedicel, which branches laterally from the stalk. Only acaulosporoid spores of Archaeospora have two walls as in Otospora. However Archaeospora spores have a simply structured outer wall being thin, only bilayered, hyaline and sometimes evanescent (TABLE I; Spain 2003, Hafeel 2004, Spain et al 2006).