Centroceras clavulatum
Rhodophyta, Ceramiaceae
Authority: (C. Agardh) Montagne
Hawaiian name: none
Characteristic feature: Y-shaped branches, with the final two branches curving inwards creating a claw-like appearance.
Description: Plants filamentous, in entangled unialgal mats or within mixed turf communities; delicate, colourless, unicellular hairs often present on young segments and tips, and in plants from deep water; erect axes to 4 cm long, to 300 mm diam., unbranched or subdichotomously branched (rarely unilateral), successive branches 8-12 segments apart, apices slightly to moderately forcipate, rarely without terminal pair; adventitious branches often present, formed abaxially from first periaxial cells; single layer of small cuboidal corticating cells covering each internode, underlying axial cells reaching 750 mm long; 14 periaxial cells, each giving rise to 3 corticating filaments: 2 acropetal (distal) filaments and 1 longer basipetal (proximal) filament; acropetal filaments 2-3 cells long, sometimes forming 2-layered cortex at node; first acropetal filament on any periaxial cell often terminating in 1-3-celled spine; basal cell of second acropetal filament also forming a basipetal filament which, with single basipetal filament on periaxial cell, contributes to the 28 major individual basipetal corticating filaments covering each internode. Multicellular rhizoids forming in clusters from periaxial cells in contact with substrata. Tetrasporangia emergent, usually surrounding nodes of main axis but occasionally also on lateral branches, ca. 50 mm long, sometimes subtended by a spine, loosely jacketed by 3-4-celled colourless involucral filaments. Spermatangial bearing cells the terminal cells partly immersed clusters of branchlets around nodes. Cystocarps lateral on continuously growing branches, surrounded by 1-2 short, usually curved involucral filaments.
Habitat: Intertidal to shallow subtidal; epiphytic or saxicolous, common in mats or turf communities.
Hawaiian distribution: All main Hawaiian Islands, including the Northwestern Hawaiian Islands.
Other: Indigenous to Hawai‘i.