Roseolithon littorale, Kato & Adachi & Iryu & Baba, 2024

Kato, Aki, Adachi, Kenta, Iryu, Yasufumi & Baba, Masasuke, 2024, Coralline red algal species diversity at a shallow rhodolith bed in warm-temperate Japan, including two new species of Roseolithon (Hapalidiales, Corallinophycidae), Phycologia 63 (6), pp. 520-533 : 526

publication ID	https://doi.org/10.1080/00318884.2024.2421269
DOI	https://doi.org/10.5281/zenodo.15537247
persistent identifier	https://treatment.plazi.org/id/03DD87C1-FFD2-FF8E-D2E4-B3DADFDE3EF1
treatment provided by	Felipe
scientific name	Roseolithon littorale
status	sp. nov.

Treatment

Roseolithon littorale Min-Khant-Kyaw, A.Kato & M.Baba sp. nov.

Figures 4–12 View Figs

DESCRIPTION: Thalli were non-geniculate, warty and epilithic on pebbles or forming entirely free-living rhodoliths with sub-spheroidal to sub-elliptical shapes, c. 2 cm wide. Colour of living thalli was rose pink ( Fig. 4 View Figs ). Thallus construction was monomerous with a multistratose non-coaxial (plumose) hypothallus composed of filaments running parallel to the substratum. Cells of perithallial filaments arose from hypothallial filaments and were composed of approximately square to elongate cells ( Fig. 5 View Figs ). Cells of contiguous hypothallial and perithallial filaments were frequently joined by cell fusions; secondary pit connections were not observed. Subepithallial initials (intercalary meristematic cells) were composed of square to elongate cells, shorter than or approximately equal to their immediate inward derivatives ( Fig. 6 View Figs ). A single layer of epithallial cells was flattened with flared outer cell walls (trapezoidal; Fig. 6 View Figs , inset). Trichocytes were not observed. Tetra/bisporangial conceptacles were multiporate, raised above the surrounding thallus surface without differentiation into a peripheral rim and pore plate ( Figs 7–9 View Figs ). Each pore opening was surrounded by 5–6 rosette cells in depressions giving a pitted appearance in surface view ( Fig. 8 View Figs ). Conceptacle roofs were composed of 3–6 cell layers including epithallial cells. Pore canals were blocked by apical plugs before releasing spores and lined by 2–5 celled filaments ( Fig. 10 View Figs ). Pore canal filaments include rosette cells with slightly sunken roofs and the underlying squarish, elongate and/or wedge-shaped cells ( Fig. 11 View Figs ). Pore canal cells were generally longer than and/or approximately equal to other roof cells ( Figs 10, 11 View Figs ). Tetrasporangia were zonately divided. Conceptacles appeared to be buried ( Fig. 12 View Figs ), but also appeared to be shed. Gametangial thalli were not observed. Data on vegetative and reproductive features are summarized in Table 1 View Table 1 .

HOLOTYPE: SAP 115684 About SAP (tetrasporophyte), collected on 20 April 2023 by Min-Khant-Kyaw & A. Kato, deposited in the Herbarium of the Graduate School of Science ( SAP), Hokkaido University, Sapporo, Japan ( Fig. 4 View Figs ).

HOLOTYPE GENBANK ACCESSION NUMBERS: psb A, LC822410 View Materials ; rbc L-3P, LC822433 View Materials ; COI-5P, LC822444 View Materials .

GoogleMaps

TYPE LOCALITY: 32°33.08'N, 130°06.38'E; intertidal; Tsujishima Island GoogleMaps , Amakusa City, Kumamoto Prefecture, Japan.

ETYMOLOGY: ‘ littorale ’ in reference to the shallow water habitat of the species in the intertidal zone.

ADDITIONAL SPECIMEN EXAMINED: In addition to the holotype sequences, six psb A sequences, two rbc L-3P sequences and two COI-5P sequences were generated from Japanese specimens ( Table S1 View Table 1 ).

DISTRIBUTION: Based on DNA sequences, R. littorale is currently known only from the type locality ( Tsujishima Island ) and Shirasu in Japan.

HABITAT: Occurring as free-living rhodoliths or as attached epilithic plants on pebbles in the intertidal zone.

Figures

Figs. 4–12. Habit, vegetative, and tetra/bisporangial conceptacle characters of Roseolithon littorale sp. nov. Fig. 4. Warty holotype specimen (SAP 115684, tetrasporophyte). Scale bar = 1 cm. Fig. 5. Vertical fracture through the inner thallus showing the monomerous construction with multistratose non-coaxial hypothallial filaments (h) giving rise to perithallial filaments (p) (SAP 115686). Scale bar = 100 μm. Fig. 6. Vertical fracture of the outer thallus showing a single-layered epithallus (arrows), subepithallial initials (i) and cell fusions (f) between adjacent perithallial filaments (SAP 115687). Scale bar = 10 μm. Inset: Detail of epithallus showing flattened epithallial cells with flared outer walls (trapezoidal) (arrowheads) (SAP 115684). Scale bar = 10 μm. Fig. 7. Surface view showing raised tetra/bisporangial conceptacle without differentiation into a peripheral rim and pore plate (arrow) (SAP 115684). Scale bar = 1 mm. Fig. 8. Surface view of a multiporate tetra/bisporangial conceptacle with rosette cells in depressions giving the central pore plate a pitted appearance (arrowheads) (SAP 115684). Scale bar = 100 μm. Inset: Detail of a pore (asterisk) opening bordered by six rosette cells (1–6) (SAP 115684). Scale bar = 10 μm. Fig. 9. Vertical fracture through a raised multiporate tetra/bisporangial conceptacle (SAP 115687). Scale bar = 100 μm. Fig. 10. Vertical section through a multiporate tetra/bisporangial conceptacle roof showing apical plugs (asterisks) occluding the pore canals (SAP 115684). Scale bar = 50 μm. Fig. 11. Vertical fracture through a tetrasporangial conceptacle pore canal (asterisk) lined by slightly sunken rosette cells (arrows) followed by squarish (sq) and elongate (e) pore canal cells (SAP 115684). Scale bar = 10 μm. Fig. 12. Vertical section through the thallus showing a buried tetrasporangial conceptacle with a zonately divided tetrasporangium (t) (SAP 115684). Scale bar = 50 μm.