Sporolithon indopacificum Maneveldt & P. W. Gabrielson 2017, sp. nov.
Creators: name: Maneveldt, G. W.
name: Gabrielson, P. W.
name: Kangwe, J.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Plantae
Rhodophyta
Florideophyceae
Corallinales
Sporolithaceae
Sporolithon
Sporolithon indopacificum

description: Sporolithon indopacificum Maneveldt & P.W.Gabrielson sp. nov. (Figs 3–15)   
 Holotype:— L 3964509!, 06.vi.2016, leg. J. S. Kangwe, J. Nene & K. Mohammed, collection number T16 /01 (Fig. 3), free-living rhodolith occurring intertidally (and exposed at low water of spring tide) in a mixed rocky/muddy substrate, variably also dominated by seagrasses and algal turfs. Fragments of the holotype are in UWC and NCU.   
Isotypes:— L 3964510!, L 3964511! and UWC T 16/01. Fragments of the isotypes housed in L are also in NCU.  
 Type Locality:— Tanzania. Zanzibar Island, Chwaka Bay, Mapopwe Creek (06°10 ’ 38.24 ” S; 39°25 ’ 41.27 ” E).   
 Etymology:— ‘ indopacificum ’ in reference to the species’ distribution in both the tropical western Indian and Pacific oceans.   
 Description   
 DNA Sequences:—Three rbc L sequences were obtained, one from the holotype, L 3964509, 1384 bp long (GenBank MG051266) and one from each isotype L 3964510 (GenBank MG051267) and L 3964511 (GenBank MG051268), both 691 bp long, and from the holotype a psb A sequence (GenBank MG051270), 850 bp long (Table 1). Over comparable lengths the rbc L sequences were identical to each other. Both the rbc L sequences and the psb A sequence are diagnostic for S. indopacificum.   
Habit and morphology:—Plants non-geniculate, free-living as spherical rhodoliths measuring roughly 35–50 mm in diameter (Fig. 3). Thalli lumpy with crowded, mostly contiguous, swollen protuberances (Figs 3, 4). Surface texture matt with freshly collected, living plants brownish pink to maroon in colour. Individual rhodoliths comprise solely this species overgrowing itself in a superimposed manner of variably thin (60 μm) to thick (> 1200 μm) crusts (Fig. 5).  
 1 Based on molecular data, Richards et al. (2017) showed that S. dimotum is not a synonym of S. ptychoides; the authors have subsequently resurrected the name S. dimotum.   
 2 Verheij (1993) examined the lectotype and isolectotype specimens but did not differentiate between the type specimens and other morpho-anatomically representative specimens in the description of the species.   
 3 Verheij (1993) examined the lectotype specimen but did not differentiate between the type specimen and other morpho-anatomically representative specimens in the description of the species.   
 4 See Richards et al. (2017).   
 5 Richards et al. (2017) confirmed that all sequenced specimens reported as S. ptychoides from other parts of the world are not this species.   
 6 See figure 12 in Bahia et al. (2011).   
 7 See figure 7B in Richards et al. (2017).   
 8 See figure 31 in Keats and Chamberlain (1993).   
 9 Verheij (1993) reported secondary pit connections to cell fusion in a ratio of 4-5:1, but did not distinguish between type and morpho-anatomically assigned representative specimens. Keats & Chamberlain (1993) did confirm the presence of both secondary pit connections and cell fusions (rare) for the type specimen.   
 10 Observed from figure 6D in Henriques et al. (2014).   
 11 Observed from figure 4 in Verheij (1992).   
 12 See figures 40 and 41 in Keats & Chamberlain (1993).   
 13 Observed from figures 10 and 12 in Bahia et al. (2014b).   
 14 While Verheij (1993) reported the absence of a layer of elongate cells at base of tetra/bisporangial chambers for the lectotype specimen, Richards et al. (2017) showed them to exist in representative specimens confirmed by molecular analyses.   
 15 Observed from figure 6 in Richards et al. (2017).   
Anatomy:—Thallus dorsiventrally organised, monomerous and haustoria absent (Figs 6, 7). Medulla extremely thin and plumose (non-coaxial) (Figs 6, 7), composed of 3–10 filaments aligned more or less parallel to substratum, measuring no more than 50 μm thick. Medullary filaments comprise square to elongate cells, measuring 10–37 μm in length and 5–8 μm in diameter. Cortex comprises the bulk of the thallus (Fig. 6). Cortical filaments comprise square to elongate cells, measuring 5–30 μm in length and 4–12 μm in diameter. Contiguous medullary and cortical filaments joined primarily by secondary pit connections; cell fusions absent to rare. Subepithallial initials square to rectangular, measure 5–15 μm in length and 5–12 μm in diameter, and are similar in size to subtending cells. Epithallial cells single layered (2 layers when shedding), flattened with flared upper corners (Fig. 8), and measure 3–5 μm in length and 4–12 μm in diameter. Trichocytes absent (thus far not observed in any species of Sporolithales).  
Reproduction:—No gametangial material observed. Tetra/bisporangial chambers clustered in sori in a superficially raised layer(Figs4, 9,11–13),3–5cells(incl.epithallial cell)above surrounding thallus surface.Individual tetra/bisporangial chambers uniporate (Figs 10, 14), clustered in large groups (Figs 9, 11), and have floors flush with (Fig. 12) to sunken (Fig. 13) 4 cell layers below surrounding vegetative surface. Chambers longitudinally elliptical, measuring 30–45 μm in diameter and 85–110 μm high, separated by 0–4 sterile paraphyses (mostly 0–1) comprised of 3–5 elongate cells each (Figs 14, 15) that are no different to immediately surrounding vegetative filaments. Chambers possess a basal layer of elongate cells (Fig. 15). Chamber pores measure 8–17 μm in diameter and surrounded by 8–13 rosette cells (Fig. 10) that are no different from the surrounding sorus surface cells. Entire tetra/bisporangial sori appear to be sloughed off from the outer thallus (Fig. 4); no buried chambers observed. Chambers bear only one tetra/bisporangium (Figs 14, 15) measuring 65–90 μm in length and 25–40 μm in diameter. Most sporangia not cleaved (Fig. 14). Other sporangia either zonately arranged bisporangia (Fig. 15) or incompletely divided tetrasporangia with ‘T’-shaped pattern of division (Fig. 14). Tetra/bisporangia bear apical pore plugs (Figs 10, 14, 15) and borne on a single stalk cell (Fig. 14).  
Distribution:— Fiji and Tanzania based on DNA sequences.
description: Published as part of Maneveldt, G. W., Gabrielson, P. W. & Kangwe, J., 2017, Sporolithon indopacificum sp. nov. (Sporolithales, Rhodophyta) from tropical western Indian and western Pacific oceans: First report, confirmed by DNA sequence data, of a widely distributed species of Sporolithon, pp. 115-128 in Phytotaxa 326 (2) on pages 118-123, DOI: 10.11646/phytotaxa.326.2.3, http://zenodo.org/record/13699776