Croisettea haukoaweo 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

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

Figs 14–16

DESCRIPTION: Blades typically flabellate, single or clustered, 1–6 cm long by 1–8 cm wide and 40–80 µm thick, lobed with broadly crenate margin, magenta pink to rose red, with a soft, slippery consistency. One or more blades developing and producing in turn several to many marginal, subdichotomously highly lobed blades, often overtopping one another. Medulla uniform throughout with a sparse arrangement of elongated filamentous stellate cells with 4–6 arms; cortex 1–2 layers of ovoid cells, 1–3 µm wide by 5–10 µm high.

HOLOTYPE: ARS 09989/ BISH 780919 , ‘ Au‘Au Channel , Maui, Hawai‘i, USA (104 m depth), collected 29 September 2006 by H. Spalding and T. Kerby. GenBank accession: rbc L, OM621863 .

ETYMOLOGY: The species epithet haukoaweo refers to “the vibrant limu entwined with pūko’ako’a ( Halimeda sp. ) found in the cool deep waters”. The term ‘hau’ in the name also honours Mr. Skippy Hau, conservationist and retired State of Hawai‘i Division of Aquatic Resources staff on Maui, for his lifetime dedication to the ocean and his community (see Table S3 for more details on how the CWG developed the species name).

DISTRIBUTION: A single collection, from ‘ Au‘Au Channel , Maui, Hawai‘i, USA; mesophotic depth of 104 m.

Morphology and ecology

Blades single or clustered, 1–6 cm in height, 1–8 cm wide, lobed with broadly crenate margins ( Fig. 14 ). Blades in cross section uniformly 40–80 µm thick. Stipe and mode of attachment to substrate not observed. The medulla consisting primarily of sparse filaments and stellate cells with central bodies ranging from 5– 10 µm wide by 1–3 µm high, and elongate, slender arms (4–6 in number) that are 2–3 µm wide by 15–50 µm long ( Fig. 15 ). Surface view of outer cortical ovoid cells 1–3 µm wide by 5–10 µm high ( Fig. 16 ). Tetrasporangial and gametangial reproduction not observed.

Although mode of attachment of blades was not identified, parts of blades were found entwined with species of mounding, prostrate species of Halimeda J.V. Lamouroux , which are abundant in the ‘Au‘Au Channel, Maui (see Spalding et al. 2019, fig. 29.1b). Blades of C. haukoaweo are only documented in the MHI in the ‘Au‘Au Channel, Maui at 104 m depth.

Figures

Figs 14–16. Morphology and anatomy of Croisettea haukoaweo sp. nov. Fig. 14. Pressed voucher for BISH 780919 (holotype, vegetative). Scale bar = 5 cm. Fig. 15. Cross section through apical portion of the blade showing inner cortical cells and medullary stellate cells, BISH 780919. Scale bar = 25 μm. Fig. 16. Cortical cells in surface view, BISH 780919. Scale bar = 50 μm.