Sporolithon sinusmexicanum J. Richards & Fredericq 2018, sp. nov.
Creators: name: Richards, Joseph L.
name: Fredericq, Suzanne
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Rhodophyta
Florideophyceae
Corallinales
Sporolithaceae
Sporolithon
Sporolithon sinusmexicanum

description: Sporolithon sinusmexicanum J.Richards & Fredericq sp. nov. (Figs. 3–23)
Holotype: LAF 6956A (Figs. 3–17), Sackett Bank, NWGMx (28° 38.0’ N; 89° 33.028’ W), 65–68 m deep, leg. J. L. Richards & S. Fredericq, 7.ix.2014.
Additional material examined: LAF 6970B (Figs. 18–23), Dry Tortugas Vicinity, SEGMx (24° 31.494’N; 83° 19.793’W), 69 m deep, leg. J. L. Richards & S. Fredericq, 10.ix.2014 (collected from site in field), 15.xii.2014 (collected from microcosm).
Etymology: The specific epithet refers to the Gulf of Mexico, the locality of the holotype and Florida specimen.
Description
DNA sequences: DNA sequences from the holotype: rbc L (GB accession = KY994126), psb A (GB accession = MF034549), LSU (GB accession = KY980437), and UPA (GB accession = KY980429); and from the Florida specimen: LSU (GB accession = KY980438), rbc L (GB accession = KY994127), and psb A (GB accession = MF034550).
Morphology and Habit: Thallus non-geniculate, forming biogenic rhodoliths that are smooth to warty (Fig. 3) or with numerous protuberances (Fig. 18). Found growing in benthic rhodolith beds at a depth of 65– 69 m.
Vegetative Anatomy: It was not determined with certainty if thallus construction is dimerous or monomerous, though some areas of the thallus appeared putatively monomerous. New vegetative layers (Fig. 4) formed by a secondary hypothallium with one to two layers of basal filaments (Fig. 5). Hypothallial cells rectangular in shape, 11.5–20 μm long x 3–7 μm wide. Perithallium with abundant cell fusions (Figs. 6, 20); secondary pit connections not observed. Perithallial cells 6.6–19 μm long x 7–10.6 μm wide. Meristematic cells 4.2–12 μm long x 7.8–15.3 μm wide (Figs. 7, 8, 20, 21). Epithallium (Figs. 7, 8, 20, 21) a single layer of armored epithallial cells that are 2–3 μm long x 4–7.8 μm wide, with thick, heavily calcified cell walls and a trapezoidal-shaped lumen.
Reproduction: Tetrasporangial sori are sloughed off after spore release. Sori were observed in the process of sloughing off the surface of the rhodoliths (Figs. 9–13, 22). Pores with rosette cells that remained intact (n=5) showed 10–12 rosette cells surrounding each tetrasporangial compartment pore (Fig. 14). Sections showed tetrasporangial compartments at the protuberance tip (Figs. 15–17) and no buried tetrasporangial structures embedded in the perithallium (Figs. 15, 19). Intact tetrasporangial compartment measured 83 μm long x 59 μm wide (n=1), subtended by a stalk cell 14 μm long x 28 μm wide (n=1) (Fig. 16). Tetrasporangial compartments surrounded by paraphyses with non-elongated cells at the base of tetrasporangial compartments (Figs. 16, 17). Female and male structures were not observed.
Distribution: Sackett Bank, NWGMx, and the vicinity of the Dry Tortugas, SEGMx.
Comments: Unidentified spherical inclusions were observed in the perithallium of specimen LAF 6970B, which may be unidentified life history stages of microalgal organisms (Fig. 23), as reported in Krayesky-Self et al. (2017).
description: Published as part of Richards, Joseph L. & Fredericq, Suzanne, 2018, Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico, pp. 135-146 in Phytotaxa 350 (2) on pages 136-137, DOI: 10.11646/phytotaxa.350.2.2, http://zenodo.org/record/13702410