Morphological and ultrastructural studies of Nostoc foliaceum MOUGEOT ex BORN. et FLAH. (Cyanophyceae) growing on soil MAR��A SUSANA VIGNA1,2 and MAR��A TERESA WENZEL1 1 Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biolog��a Experimental, Buenos Aires, Argentina 2 Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Buenos Aires, Argentina With 12 figures and 1 table Abstract: Nostoc foliaceum MOUGEOT ex BORN. et FLAH. (Nostocales, Nostoca- ceae) is restricted to North America and Europe, and its description was limited to MOUGEOT���s original illustrations (1854). This report extends the geographic distri- bution to South America and on the basis of material collected from the field and cultured (Buenos Aires Province, Argentina), provides taxonomical characters by which this species can be compared with Nostoc commune VAUCHER ex BORN. et FLAH. In addition, an exhaustive morphological and ultrastructural study, particu- larly of the development and ultrastructure of the akinetes, is provided. Resumen: La distribuci��n de Nostoc foliaceum MOUGEOT ex BORN. et FLAH. (Nos- tocales, Nostocaceae) est�� restringida a Am��rica del Norte y Europa, este trabajo extender��a la misma a Am��rica del Sur. Sobre la base de material de campo (Pro- vincia de Buenos Aires, Argentina) y de cultivo se realiz�� un exhaustivo estudio morfol��gico y ultraestructural, con especial menci��n al desarrollo y ultraestructura de las acinetas. Adem��s se analizaron similitudes y diferencias entre Nostoc folia- ceum y Nostoc commune VAUCHER ex BORN. et FLAH. respecto del h��bitat, talo y caracteres taxon��micos. Se considera en el futuro realizar un estudio filogen��tico molecular con el prop��sito de dilucidar la posible sinonimia entre ambas especies. Key words: cultures, Cyanoprokaryota, Cyanophyceae, morphology, Nostoc fo- liaceum, soil algae, taxonomy, ultrastructure Introduction The genus Nostoc VAUCHER ex BORN. et FLAH. is included in the family Nostocaceae, order Nostocales (KOM��REK & ANAGNOSTIDIS 1989). Many species of this genus have been reported from different types of aquatic and terrestrial environments. Some of the species most frequently Algological Studies 126 103���112 Stuttgart, April 2008 DOI: 10.1127/1864-1318/2008/0126-0103 1864-1318/08/0126-103 $ 2.50 �� 2008 E. Schweizerbart���scheVerlagsbuchhandlung, D-70176 Stuttgart 09_Vigna_K.indd 103 09_Vigna_K.indd 103 30.04.2008 11:14:55 Uhr 30.04.2008 11:14:55 Uhr

104 M. S. VIGNA and M. T. WENZEL observed growing on soil are Nostoc commune VAUCHER ex BORN. et FLAH., N. muscorum AG. ex BORN. et FLAH., N. elliposporum (DESM.) RA- BENH. ex BORN. et FLAH., N. humifusum (CARM.) ex BORN. et FLAH., N. pas- serianum BORN. et THUR., N. foliaceum MOUGEOT ex BORN. et FLAH. and N. verrucosum VAUCHER ex BORN. et FLAH. According to BORNET & FLAHAULT (1888), Nostoc foliaceum was first described by MOUGEOT in 1854. TILDEN (1910) reproduced the original il- lustrations by MOUGEOT, and since then this species has only been cited in the general monographs by FORTI (1907), GEITLER (1932) and STARMACH (1966), with no new contributions to the original description and illustra- tions. Nostoc foliaceum has previously been recorded in North America (TIL- DEN 1910) and Europe (BORNET & FLAHAULT 1888, FORTI 1907, GEITLER 1932, SKUJA 1964, STARMACH 1966). The objectives of the present work are to provide a detailed description of N. foliaceum using light and electron microscopy, and to compare it with N. commune. Materials and methods The material was collected at the beginning of December 1999 from garden soil of a sandy loam type, in the locality of San Clemente del Tuy�� (36�� 22' S, 56�� 44' W), Buenos Aires Province, Argentina. The soil sample was taken from the surface layer to a depth of 5 cm, and then transferred to a sterile container. Part of the sample was air-dried before being deposited in the Crypto- gamic Collection (BAc N�� 45691) of the Museo Argentino de Ciencias Nat- urales Bernardino Rivadavia, Argentina. The remaining part of the sample was rehydrated for further observations, specific identification, isolation and culture. Unialgal cultures were grown on soil-water medium (PRINGS- HEIM 1946), and liquid and agarised BBM (ARCHIBALD & BOLD 1970). They were kept under controlled conditions of temperature (25 ��C �� 1 ��C) and photoperiod (12:12), and at a light intensity of 23 ��mol m���2 s���1. Taxonomic studies were based on the works by BORNET & FLAHAULT (1888), FORTI (1907), TILDEN (1910), FR��MY (1930), GEITLER (1932), DESIKACHARY (1959), STARMACH (1966) and KOM��REK & ANAGNOSTIDIS (1989). The light microscopes used for photographs and illustration were a Zeiss Standard 14 with a M35 digital camera and a Wild M20, both equipped with a drawing tub. For transmission electron microscopy (TEM) examination, the material was fixed in 1 % glutaraldehyde and 2 % osmium tetroxide, after which it was dehydrated in a graded acetone series and embedded in Spurr resin. 09_Vigna_K.indd 104 09_Vigna_K.indd 104 21.04.2008 22:35:09 Uhr 21.04.2008 22:35:09 Uhr