An account of the red algal genus Sporolithon (Sporolithaceae, Corallinales) in southern Australia

Abstract

Sporolithon (Sporolithaceae, Corallinales) is represented in southern Australia by S. durum (Foslie) Townsend et Woelkerling, comb. nov. The species and the development of male and female-carposporangial conceptacles and tetrasporangial compartments and sori are described in detail for the first time. Information on etymology, collections examined, distribution, seasonality and habit and comparisons with other species is also included. Published records of S. erythraeum from southern Australia have not been substantiated. Two further species have been reported under the generic name Archaeolithothamnion. Archaeolithothamnion australasicum is a species of uncertain status, while A. mirabile is conspecific with Lithothamnion muelleri Lenorrnand ex Rosanoff. Differences between the Sporolithaceae and the Corallinaceae, and the delimitation of genera within the Sporolithaceae, are reconsidered in relation to new data on S. durum. The Sporolithaceae is characterised by tetrasporangia that produce cruciately arranged spores and develop within calcified sporangial compartments, while the Corallinaceae is characterised by tetrasporangia that produce zonately arranged spores that do not develop in calcified sporangial compartments. Two genera of Sporolithaceae are recognised: Heydrichia, in which tetrasporangial compartments are enclosed by modified filaments to form sporangial complexes; and Sporolithon, in which tetrasporangial compartments are not enclosed by modified filaments and sporangial complexes are absent. The concepts of conceptacle and sorus also are reconsidered.

Taxonomic study of crustose coralline algae off the northeastern Brazilian coast

“…In S. episporum, the opposite is the case. However, the use of this feature has been contested by some authors (Townsend et al 1995, Harvey et al 2002. Harvey et al (2002) reported that the proportion of secondary pitconnections and cell fusion varies in specimens of S. durum found in Australia, and that this feature should not be used to separate the two species.…”

“…The specimens in this study were identified as S. episporum by satisfying the criteria set by Keats & Chamberlain (1993) and Nunes et al (2008) (Table 1). There have been few descriptions of the structure and development of the carposporangial conceptacles in Sporolithon, being restricted to S. durum (Foslie) Townsend & Woelkerling (1995: 86-91) (Townsend et al 1995, Woelkerling 1996, Harvey et al 2002 and S. episoredion (Adey, Townsend & Boykins) Verheij (1992: 501). S. episoredion has carposporangial conceptacles much larger than those found in the present study (Verheij 1992, Table 2).…”

Three deep water species of Sporolithon (Sporolithales, Rhodophyta) from the Brazilian continental shelf, with the description of Sporolithon elevatum sp. nov.

“…According to modern concepts of coralline red algal taxonomy, these characters are no longer sufficient for precise identification because they are too variable (Verheij 1993;Bahia et al 2011). The most important characters currently used in Sporolithon taxonomy are: 1) diameter/length of the tetrasporangial compartment, 2) fate of old sporangial cases, 3) number of cells in the paraphyses, 4) Presence of a basal layer of elongated cells in areas where sporangia develop, (5) number of cells by which sorus is raised above surrounding thallus surface and (6) soral organization (Verheij 1993;Keats & Chamberlain 1993;Townsend et al 1995;Alongi et al 1996;Bahia et al 2011;Bahia et al 2013). In the present work we compared Sporolithon species for which recent (since 1990) detailed descriptions are available (Table 1).…”

“…Moreover, diagnostic features used in many taxonomic reviews (Verheij 1993;Keats & Chamberlain 1993;Townsend et al 1995;Alongi et al 1996;Bahia et al 2011;Bahia et al 2013) were used: 1) diameter/length of the tetrasporangial compartment, 2) fate of old sporangial cases, 3) number of cells in the paraphyses, 4) Presence of a basal layer of elongated cells in areas where sporangia develop, (5) number of cells by which sorus is raised above surrounding thallus surface and (6) soral organization. Identified samples were incorporated into the herbarium collection of the Botanical Garden of Rio de Janeiro (RB) and Museu Nacional (R).…”

Heydrichia homalopasta sp. nov. (Sporolithaceae, Rhodophyta) from Australia

“…The terminology used in this paper is that used by Townsend and Adey (1990) and Townsend et al (1994Townsend et al ( , 1995 except that the term sorus is replaced by nemathecium. A nemathecium is defined as an area of thallus where the vegetative structure has been modified concurrent with the differentiation of reproductive cells.…”