Hydroclathrus clathratus

Phaeophyta, Scytosiphonaceae

Authority: (C. Agardh) Howe

Hawaiian name: none

Characteristic feature: Net-like yellowish-brown alga.

Description: Plants irregularly shaped, thick, often lobed, forming perforated netlike masses, often 15-25 cm in diameter (exceptionally to 1 m), sometimes spongy or slippery; light tan or yellow to medium brown; in development approximately spherical and hollow, becoming highly convoluted , with numerous irregularly shaped and sized perforations; plants usually broadly attached over most of lower surface by groups of rhizoids. Cortex 1-2 layers of small irregularly shaped, pigmented cells, each about 7.5 µm in diameter; medulla 3-6 layers of inwardly progressively larger and colorless cells around hollow center; margins of perforations often inrolled and sometimes coalescing by short rhizoids to form hollow sections. Plurilocular organs in sori, together with hairs, often covering much of outer surface, sporangia about 7.5 by 10 µm ; paraphyses absent.

Habitat: Usually in mid- to low intertidal pools and shallow reef flats. Occasionally in intertidal upper pools; rarely to 33m depth. Often epiphytic, often in multispecies turf, or growing on rocks.

Hawaiian distribution: All main Hawaiian Islands, including the Northwestern Hawaiian Islands.

Other: Indigenous to Hawai‘i.