Gloiocladia laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, 2025

Allsopp, Kazumi R., Cabrera, Feresa P., Fumo, James T., Spalding, Heather L., Williams, Taylor M., Kosaki, Randall K., Leonard, Jason, Hauk, Brian, Pyle, Richard L., Wagner, Daniel, Smith, Celia M. & Sherwood, Alison R., 2025, New species in the cryptic genus Gloiocladia J. Agardh (Faucheaceae, Rhodophyta) from Hawaiian Mesophotic Coral Ecosystems, Cryptogamie, Algologie 20 (5), pp. 67-80 : 73

Gloiocladia laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood , sp. nov.

( Fig. 3 A-I)

TYPE MATERIAL. — Hawai‘i • Kapou ( Lisianski), Papahānaumokuākea Marine National Monument ; 26°2’13”N, 173°47’31”W; 59 m a.s.l.; 14.IX.2014; collected by J. Leonard (NWHI-246); BISH 789091 (ARS 10279); GenBank accessions OR881954 ( rbc L) and OR881946 (COI).

ETYMOLOGY. — Laukuamo‘o (noun in apposition, and hence nondeclinable) is derived from multiple Hawaiian nouns. The name was developed using traditional Hawaiian naming practices in collaboration with the Nomenclature Subcommittee of the Papahānaumokuākea Native Hawaiian Cultural Working Group (CWG) ( Appendix 1). “Lau” refers to a leaf or blade of a plant and can also refer to multiplicity. “Kua” refers to the back or the shape of a human spine, while “mo‘o” refers to the mourning gecko species found in Hawai‘i ( Lepidodactylus lugubris Duméril & Bibron ), which exhibits a similar sawtooth-like pattern on its back. By connecting all three terms, the name accentuates the intertwined sawtooth-like body plan and the biogeography of the species found in the “geological backbone” of the Hawaiian Archipelago, the Northwestern Hawaiian Islands or Papahānaumokuākea Marine National Monument.

MATERIAL EXAMINED. — BISH 789092 (ARS 10164), BISH 789093 (ARS 10286), BISH 789094 (ARS 11120), BISH 789095 (ARS 11147), BISH 789096 (ARS 11148), BISH 789097 (ARS 11390) .

SUBSTRATE / HOST. — Small pebbles (epilithic), or other larger macroalgae such as Amansia sp. (epiphytic).

HABIT AND VEGETATIVE MORPHOLOGY. — Thalli are thin and elongated, oval in cross section, rounded at tips and exhibiting a distinctive construction of the blades with sawtooth-like branchlets, although a few specimens lack branchlets. Plants prostrate, and can be epiphytic on other macroalgae such as Amansia , by entangling their sawtooth-like branchlets with host thalli. Plants appear brownyellow in situ when compared to Amansia ( Fig. 3A). The alga exhibits a deep wine-red color when living ( Fig. 3B). Generally, thalli are irregularly-dichotomously branched. A single branch can extend up to 20 mm in length and 4 mm in width, including branchlets ( Fig. 3C). Sawtooth-like branchlets are positioned c. 300 µm apart and can extend into full branches ( Fig. 3D). A gelatinous layer surrounds the outermost cortical layer of apices ( Fig. 3E). Blades are up to 350 µm thick in cross section, and are composed of multiple layers of small, densely packed cortical cells, and larger medullary cells ( Fig. 3F). Outer cortical cells are loosely arranged, 5 µm in diameter and visible from the surface ( Fig. 3G). Laterally arranged subcortical cells connected via secondary pit connections ( Fig. 3H). Tightly arranged medullary cells have dimensions of 40-80 × 30- 50 µm in cross section ( Fig. 3I). Primary pit connections can be observed between individual medullary cells, subcortical cells, and cortical cells ( Fig. 3I). No reproductive features were observed.

DISTRIBUTION. — Exclusive to MCE depths of 55-104 m throughout the Hawaiian Islands, including Kapou (Lisianski), Manawai (Pearl and Hermes), Lalo (French Frigate Shoals), and Maui.

DESCRIPTION

Plants epiphytic on other algae or lithophytic on rubble via rhizoidal attachment or entanglement. Thallus decumbent, up to 60 mm long. Stipes appear oval to circular in cross section, holdfasts not present in collected specimens. Plants irregularly dichotomously branched, deep wine red when alive, and pale pink when dried. Vegetative axes are narrow, up to 2 mm wide excluding sawtooth branchlets, with branchlets extending up to an additional 2 mm on either side of the axis. Branchlets can extend in opposite or alternating distichous patterns. Axes are flattened except in basal regions, 300-400 µm thick, and covered in a gelatinous layer that is seemingly thin and delicate at apices to allow the cell division of loosely-arranged cortical cells. Thallus multiaxial with 1-3 layers of loosely arranged rounded outer cortical cells, 5 µm in diameter from the surface view of the thallus. No lateral secondary pit connections observed between cortical filaments. Subcortical cells appear elongated and triangular, up to 16 × 9 µm in cross section, connected via primary pit connections to the medullary and cortical cells. Laterally arranged subcortical cells connected via secondary pit connections, forming a network. Medulla cellular and compact, consisting of large hyaline cells that decrease in size toward the cortex. Medullary cells forming 5-9 layers, axially elongated, ranging in size up to 80 × 50 µm in cross-section, forming frequent pit connections to adjacent medullary cells. Gametophytic and tetrasporic reproductive structures not observed.