Croisettea ohelouliuli F.P. Cabrera & A.R. Sherwood, 2022

Cabrera, Feresa P., Huisman, John M., Spalding, Heather L., Kosaki, Randall K., Smith, Celia M. & Sherwood, Alison R., 2022, Cryptic diversity in the genus Croisettea (Kallymeniaceae, Rhodophyta) from Hawaiian mesophotic reefs, Phycologia 61 (6), pp. 572-583 : 577-578

Croisettea ohelouliuli F.P. Cabrera & A.R. Sherwood sp. nov.

Figs 17–21

DESCRIPTION: Blades foliose, magenta pink to rose red, blades sometimes wider than high, 5–9 cm in height and 0.5–7 cm wide. Blades are smooth-surfaced, irregularly lobed, membranous, and attached with a short stipe to the substratum by a small discoid holdfast. Blades uniformly 40–80 µm thick, the medulla composed primarily of sparse filaments and stellate cells with central bodies 5–9 µm wide by 7–13 µm high, and elongate, slender arms (4–6 in number), 2–4 µm wide by 30– 100 µm long. The outer cortical layer subtending 1–2 layers of refractive isodiametric cells, 3–7 µm wide by 5–12 µm high.

HOLOTYPE: ARS 09953/ BISH 780920 , ‘ Au‘Au Channel , Maui, Hawai‘i, USA (113 m depth), collected 29 September 2006 by H. Spalding and T. Kerby. GenBank accessions: rbc L, OM621861 ; COI, OM509723 .

ISOTYPE: ARS 09954/ BISH 780921 , ‘ Au‘Au Channel , Maui, Hawai‘i, USA (94 m depth), collected 29 September 2006 by H. Spalding and T. Kerby .

ETYMOLOGY: The species epithet ohelouliuli refers to “the dark and vibrant ‘ōhelo” (or algae with no known species attached to it). ‘Ōhelo also describes the colour of the limu in its reference to a mauka (land) plant, Vaccinium reticulatum Smith, and its deep, red-coloured berries and endemicity to Hawai‘i (see Table S3 for more details on how the species name was developed by the CWG).

DISTRIBUTION: Two specimens collected from the ‘ Au‘Au Channel , Maui, Hawai‘i, USA; depth range of 94–113 m.

Morphology and ecology

Thalli are bright fuchsia to dark red, soft and fleshy, irregularly lobed or with smooth margins, 1.5–9 cm in length and 0.5–7 cm in width ( Figs 17, 18 ). Blades emerge from a short stipe with a small discoid holdfast that attaches to the substratum, beset with numerous perforations and small protuberances, and are uniformly 40–80 µm thick ( Fig. 19 ). The medulla is composed primarily of sparse filaments with darkly staining stellate cells with large central bodies 5–9 µm wide by 7–13 µm, bearing high and elongate, slender, radiating arms (4–6 in number), 2–4 µm wide by 30–100 µm long ( Fig. 20 ). Cortex compact with 1–2 layers of isodiametric cells, 3–7 µm wide by 5–12 µm high ( Fig. 21 ). Tetrasporangial and gametangial reproduction not observed.

Blades found growing attached either to dense assemblages of Halimeda spp or coral rubble. Numerous perforations and small protuberances on blades either ontogenetic or marks of grazing pressure from mesophotic herbivores. So far, this species has only been documented in the MHI, ‘Au‘Au Channel, Maui at a depth range of 94– 113 m.

Figures

Figs 17–21. Morphology and anatomy of Croisettea ohelouliuli sp. nov. Fig. 17. Pressed voucher for BISH 780920 (holotype, vegetative). Scale bar = 5 cm. Fig. 18. Pressed voucher for BISH 780921 (paratype, vegetative). Scale bar = 5 cm. Fig. 19. Cross section through blade, BISH 780920. Scale bar = 50 μm. Fig. 20. Detail of a stellate cells in a squash preparation. BISH 780920. Scale bar = 50 μm. Fig. 21. Cortical cells in surface view, BISH 780921. Scale bar = 50 μm.